Progress 02/01/11 to 01/31/16
Outputs
Target Audience:The target audiences for this project include: (1) corporations manufacturing consumer food products, (2) suppliers of equipment, ingredients, and services to that industry, (3) individual professionals responsible for designing, operating, analyzing, and/or validating processing systems, in terms of product microbial safety, and (4) regulatory agencies responsible for promulgating and enforcing rules related to food product safety. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The entire research team (including 9 undergraduates and 5 graduate students) previously was trained in advanced laboratory techniques necessary for conducting experiments with biosafety level-2 pathogens in low-moisture powders, which present specific challenges in ensuring worker safety, due to risk of airborne particles during sample preparation and handling. Additionally, 9 members of the project team attended the annual meeting of the International Association for Food Protection, where they presented project results and participated in various Professional Development Groups. How have the results been disseminated to communities of interest?Project results have been shared with key stakeholders (beyond scientific conferences) by the following means in the past year: (1) Presentations at the Low-Moisture Task Force pre-meeting at the Institute for Food Safety and Health (IFSH) spring meeting in Chicago, IL and (2) A nationally distributed webinar. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The overall project entails four types of activities: (1) lab-scale studies generating microbial response data for the multiple pathogens, products, and processes, (2) development of mathematical models to describe bacteria inactivation and/or transfer, (3) pilot-scale studies to validate those models, and (4) utilization of the models to develop and deploy tools and training directly applicable to commercial applications. By working directly at the interface of food microbiology and engineering, this project is generating unique contributions toward improving the safety of ready-to-eat products, primarily by improving the ability of food processors and food safety regulators to reliably evaluate and validate the efficacy of pathogen reduction processes. A few example accomplishments from the past year are highlighted below. In one study, we tested the impact of moisture equilibration rate on adaptive bacterial resistance to heat. Two dynamic moisture treatments were compared to two static moisture treatments to determine the effect of time-at-moisture on thermal resistance of Salmonella Enteritidis PT 30 in wheat flour. Inoculated samples were subjected to isothermal (80°C) heat treatments after slow (4-7 d) or rapid (2-4 min) equilibration to target water activities (aw), and Salmonella thermal resistance was compared via decimal reduction times (i.e., D80°C values). The D80°C value in flour that was rapidly desiccated from 0.6 to 0.3 aw was statistically equivalent (P > 0.05) to the D80°C value in flour previously equilibrated to 0.3 aw, but both were greater (P < 0.05) than the D80°C value in flour previously equilibrated to 0.6 aw. Similarly, the D80°C value in flour rapidly hydrated from 0.3 to 0.6 aw was statistically equivalent (P > 0.05) to the D80°C value in flour previously equilibrated to 0.6 aw, and both were less than the D80°C value in flour previously equilibrated to 0.3 aw. Therefore, Salmonella in the rapidly desiccated flour (0.3 aw) was as thermally resistant as that which previously had been equilibrated to 0.3 aw, and Salmonella in the rapidly hydrated flour (0.6 aw) responded similarly to that in the flour previously equilibrated to 0.6 aw. These results suggest that the response period to new aw is negligible, which is critically important in applying thermal resistance data or parameters to industrial pasteurization validations. We also have evaluated Salmonella thermal resistance on inoculated almonds stored for long periods. To date, Salmonella-inoculated almonds (~0.45 water activity) have been stored at room temperature for 12 mos, with the thermal resistance (D80°C) quantified five times during the storage period. Salmonella thermal resistance was unchanged (P > 0.05) during the storage study, further indicating the significant challenge of managing a pathogen that is both persistent and highly thermally resistance even after long periods of desiccated storage. Several aspects of this project have continued to develop, test, and report on alternative approaches to modeling the effect of product and process variables on Salmonella resistance to lethal treatments in low-moisture foods. In one study, multiple secondary models were tested for the effect of product (wheat flour) aw on Salmonella Enteritidis PT30 thermal resistance. A full-factorial experimental design included three temperatures (75, 80, and 85°C) and four water activities (~0.30, 0.45, 0.60, and 0.70 at 24ºC). Prior to isothermal treatment, sample aw was achieved by equilibrating samples within a humidity-controlled conditioning chamber. Two primary models (log-linear and Weibull-type) and three secondary models (second-order response surface, modified Bigelow-type, and combined-effects) were evaluated using the corrected Aikake Information Criterion (AICc) and root mean squared errors (RMSE). Statistical analyses of the primary models favored the log-linear model. Incorporating the three secondary models into the log-linear primary model yielded RMSE values of 2.1, 0.78, and 0.96 log CFU/g and AICc values of 460, -145, and -19 for the response surface, modified Bigelow, and combined-effects models, respectively. The modified Bigelow-type model, which exponentially scaled both temperature and aw effects on thermal inactivation rates, predicted Salmonella lethality significantly better (P < 0.05) than did the other secondary models examined. Overall, aw is a critical factor affecting thermal inactivation of Salmonella in low-moisture products, and should be appropriately included in thermal inactivation models for these types of systems. Although water activity has been the primary variable used in prior studies when quantifying the effect of moisture on Salmonella thermal resistance, our results have demonstrated that this approach is not likely to work as a generalized metric across all low-moisture products. In one aggregate analysis, D80°C values for Salmonella Enteritidis PT30 were calculated by linear regression of isothermal inactivation data from multiple studies (wheat flour, almonds, dates; 0.25, 0.45, 0.65 aw; 70-90°C). Water activity and %mc were measured and/or calculated from moisture isotherms (sorption and desorption, accordingly). Linearity of inactivation curves was confirmed, and correlation coefficients were estimated between logD and aw and %mc. The D80°C values for the different products exhibited a log-linear trend with aw, as well as with %mc. The correlation coefficients varied less than 5% when comparing aw and %mc vs. logD (e.g., -0.96 and -0.95, respectively, for wheat flour). The results suggest that %mc may be a suitable, or even preferable, metric for the effect of water on inactivation process. When comparing the utility of aw vs. %mc for inactivation modeling or process validation, %mc has the advantage of being measurable (potentially real-time in dynamic processes), and this study shows a consistent correlation with logD. This is critically important to both monitoring and modeling inactivation processes in low-moisture foods. The results from this past year have continued to support the premise that low-moisture pasteurization processes need to be validated for different types of products, given that efficacy can be affected by product structure, water activity, etc. Therefore, it is extremely important to use product-specific inactivation parameters, as developed in this project, when validating pasteurization processes.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Benoit AN, Marks BP, Ryser ET, Jeong S, Crandall PG. 2015. Image analysis of a fluorescent physical surrogate for quantifying Listeria monocytogenes transfer between delicatessen meats and product contact surfaces. Applied Engineering in Agriculture. 31(6):939-948.
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Progress 10/01/14 to 09/30/15
Outputs
Target Audience:The target audiences for this project include: (1) corporations manufacturing consumer food products, (2) suppliers of equipment, ingredients, and services to that industry, (3) individual professionals responsible for designing, operating, analyzing, and/or validating processing systems, in terms of product microbial safety, and (4) regulatory agencies responsible for promulgating and enforcing rules related to food product safety. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The entire research team (including 7 undergraduates and 5 graduate students) previously was trained in advanced laboratory techniques necessary for conducting experiments with biosafety level-2 pathogens in low-moisture powders, which present specific challenges in ensuring worker safety, due to risk of airborne particles during sample preparation and handling. Additionally, 7 members of the project team attended the annual meeting of the International Association for Food Protection, where they presented project results and participated in various Professional Development Groups. How have the results been disseminated to communities of interest?Project results have been shared with key stakeholders (beyond scientific conferences) by the following means in the past year: (1) A presentation at the Low-Moisture Task Force pre-meeting at the Institute for Food Safety and Health (IFSH) spring meeting in Chicago, IL and (2) A workshop presentation at the Process Expo in Chicago, IL in September 2015. What do you plan to do during the next reporting period to accomplish the goals?Overall, during the next reporting period, the project will focus on the following activities: Low-Moisture Products: During the next reporting period, the project will focus on: (1) continuing to test product factors affecting bacterial resistance to lethal treatments for a matrix of additional products, (2) testing novel approaches to modeling the product-process effects on thermal inactivation of Salmonella on/in low-moisture products, and (3) conducting additional pilot-scale validation trials. First, experimental studies currently are focused on generating additional lab-based data quantifying the impact of product structure and composition on bacterial resistance to multiple lethal treatments (i.e., dry- and moist-air heating, RF, and x-ray) for wheat products (whole kernels, meal, and flour) and dried fruit (whole dates and date paste). Samples are being inoculated, and subjected to a range of lethal treatments. Second, the data from bench-scale studies are being used to quantify proposed improvements in inactivation models for these classes of products and processes. Statistical measures of model uncertainty resulting from model development will be applied to pilot-scale validation trials, in order to experimentally verify the reliability of those predictions of model performance, which is essential information when applying inactivation models to real-world process validation. Fresh Produce: A database of bacterial transfer data has been compiled in the previous year, and an analysis of the aggregated data has been started to elucidate commonality in the characteristics of the response curves across product types, transfer event types, contact surfaces, etc. Using these and new laboratory-scale data, initial parameters for a dimensional analysis-based model will be estimated.
Impacts
What was accomplished under these goals?
The overall project entails four types of activities: (1) lab-scale studies generating microbial response data for the multiple pathogens, products, and processes, (2) development of mathematical models to describe bacteria inactivation and/or transfer, (3) pilot-scale studies to validate those models, and (4) utilization of the models to develop and deploy tools and training directly applicable to commercial applications. By working directly at the interface of food microbiology and engineering, this project is generating unique contributions toward improving the safety of ready-to-eat products, primarily by improving the ability of food processors and food safety regulators to reliably evaluate and validate the efficacy of pathogen reduction processes. A few example accomplishments from the past year are highlighted below. In one study on low-moisture products, the effect of product water activity on the temperature dependency of Salmonella inactivation kinetics was demonstrated by evaluating commonalities and differences within and across product categories with differing equilibrium isotherm characteristics. We recovered decimal reduction time values (D-values) reported for multiple low-moisture products (including wheat flour, whey protein, and multiple peanut butter products. Those D-values were plotted and analyzed as functions of temperature and water activity. Then the temperature changes required to reduce the D-value by 90% (ZT) were calculated and analyzed in relation to water activity. The observed D-values showed a reasonable log-linear decrease with temperature, but the relationship with water activity varied among products. In peanut butter, a positive correlation (p < 0.05) was observed between ZT and water activity (i.e., ZT increasing >60% with room-temperature water activity increasing from 0.2 to 0.8), while for low-fat peanut butter, whey protein, and wheat flour, a negative correlation was observed (p < 0.3, < 0.15, and < 0.05, respectively), with a very similar pattern across these three product. These results reinforce the need for a better understanding of the role of water activity in inactivation processes. The results are consistent with previously reported tendencies for low-moisture products and support the possibility that a significant part of the differences observed across products might be related to physicochemical aspects of moisture equilibrium, parallel to the biological explanations previously proposed. Additionally, we further demonstrated that product structure can affect these physicochemical relationships and thereby impact thermal resistance, testing thermal resistance of Salmonella Enteritidis PT30 on/in multiple almond and wheat products. Raw almonds, surface-damaged almonds, blanched almonds, and whole wheat kernels were surface-inoculated with Salmonella Enteritidis PT30. Almond meal, almond butter, wheat meal, and wheat flour were fabricated by grinding the same raw almonds or wheat kernels in a food processor, and inoculated with the same Salmonella. All inoculated products were equilibrated to ~0.4 water activity in computer controlled-humidity chambers. The inoculated whole almond and wheat kernels (vacuum-packaged in thin layer plastic bags) and fabricated samples (in aluminum test cells, sample thickness < 1 mm) were heated (in triplicate) in an isothermal water bath (80C), pulled at multiple intervals, cooled in an ice bath, diluted in peptone water, and plated on modified tryptic soy agar to enumerate survivors. Salmonella thermal resistance (D80C) was greater (P < 0.05) on/in all the almond products than on/in the wheat products. The D80C values on raw, damaged, and blanched almonds were statistically equivalent, but significantly less (P < 0.05) than in almond meal and butter of equivalent composition. Moreover, the D80C value in wheat meal was significantly higher (P < 0.05) than on/in whole wheat surface and flour. The net effect was to show that product structure can affect Salmonella thermal resistance; however that effect differs by product. The high oil content in the almond products may have caused the difference, as compared to the wheat products. In either case, knowledge of structure effects on thermal resistance is important to ensure accurate validation of pathogen intervention processes. Broadly, in evaluating the common characteristics of pathogen inactivation data in low-moisture products, we also quantitatively evaluated the fit of primary and secondary models on the survival/inactivation kinetics of Salmonella in multiple low-moisture foods. Isothermal and iso-moisture survival/inactivation data for Salmonella in low-moisture foods (> 1,000 data series; 8 different products; temperatures -20 - 120°C; water activity 0.11 - 0.95) were collected from prior studies and categorized. Log-linear, Weibull, Cerf, and Modified Gompertz primary models were fit to single and grouped replicate data series and were statistically compared using the Akaike Information Criteria (AIC). Secondary models describing the effects of temperature and aw were similarly analyzed. Based on AIC, primary regression on single data series resulted in a 95% likelihood of the log-linear and Weibull models being the correct model in ~1 and 32% of the cases, respectively. Similarly, primary regression on grouped replicate series resulted in a 95% likelihood of the log-linear and Weibull models being the correct model in ~0.5 and 29% of the cases, respectively. When additional criteria was considered (for example, parameter significance testing), a 95% likelihood of the log-linear, Weibull, Cerf, and Modified Gompertz models being the correct model in ~39, 33, 5, and 4% of the cases, respectively. Based on the primary model regression results, the Weibull model best described the survival/inactivation kinetics of Salmonella during isothermal and iso-moisture conditions. However, careful consideration is required for the development or application of secondary models for dynamic temperature or moisture processes. In a related study, the impact of parameter estimation techniques on the uncertainty of inactivation parameters was demonstrated, using a case study of Salmonella reduction during moist-air heating of almonds. Model fitting was performed using the NonLinearModel.Fit algorithm (MatLab). The root mean square error (RMSE), RSEP, variance-covariance matrix (VCM) and scaled sensitivity coefficients (SSC) were used to evaluate general identifiability and performance of the model. Results indicated a reasonable performance of the model (RMSE=1.6), with RSEP below 7.5%. However, VCM and SSC indicated some correlation among the parameters. To improve model performance, a multivariate optimization was applied to minimize the correlation, in that the sum of the RSEP was used as the objective function. The improved fitting yielded similar results as the initial one. However, two of the elements on the VCM were reduced from around -0.5 to < 0.10, and the RSEP of the associated parameter also reduced from ~7.5% to < 3.5%. The remaining element on the matrix did not change, which indicated that a larger correlation among those parameters exists (0.91) and may be intrinsic to the model form. Post-fitting analysis of estimated parameters and optimization of reference values for inactivation models can be a useful tool to improve the performance and reliability of models, particularly given complex process-product interactions that occur low-moisture product pasteurization. The results from this past year have continued to support the premise that low-moisture pasteurization processes need to be validated for different types of products, given that efficacy can be affected by product structure, water activity, etc. Therefore, it is extremely important to use product-specific inactivation parameters, as developed in this project, when validating pasteurization processes.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Smith DF, Marks BP. 2015. Effect of rapid product desiccation or hydration on thermal resistance of Salmonella enterica serovar Enteritidis PT 30 in wheat flour. Journal of Food Protection 78(2):281-6.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Garc�s-Vega F, Marks BP. 2014. Use of simulation tools to illustrate the effect of data management practices for low and negative plate counts on the estimated parameters of microbial reduction models. Journal of Food Protection. 77(8):1372-1379.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Breslin TJ, Tenorio-Bernal MI, Marks BP, Booren AM, Ryser ET, Hall NO. 2014. Evaluation of Salmonella Thermal Inactivation Model Validity for Slow Cooking of Whole-Muscle Meat Roasts in a Pilot-Scale Oven. Journal of Food Protection 77(11):1897-1903.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2015
Citation:
Benoit AN, Marks BP, Ryser ET, Jeong S, Crandall PG. 2015. Image analysis of a fluorescent physical surrogate for quantifying Listeria monocytogenes transfer between delicatessen meats and product contact surfaces. Applied Engineering in Agriculture. Accepted for publication.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2015
Citation:
Bruin JM, Marks BP, Bourquin LD. 2015. Food safety training and assessment with diverse workers new to muscle foods processing. Food Protection Trends. In review.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Otwell J, Hall NO, Bornhorst GM, Marks BP. 2015. Effects of initial product water activity and time-varying pH on Salmonella survival during simulated gastric digestion of almond meal. IFT Abstract. Presented at the Annual Meeting of the Institute of Food Technologists. July 16-19, 2015. Chicago, IL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Syamaladevi R, Tadapaneni RK, Garces-Vega F, Tang J, Marks B, Carter B, Sablani S. 2015. Water activity variation at elevated temperatures and thermal resistance of Salmonella in selected low-moisture foods. IAFP Abstract P1-62. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Liu S, Zhong Q, Smith D, Villa-Rojas R, Tang J, Zhu M, Marks B. 2015. Validation of Enterococcus faecium NRRL B2354 as a surrogate for Salmonella in thermal treatment of wheat flour at different water activities. IAFP Abstract P-63. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Steinbrunner P, Jeong S, Suehr Q, Marks B. 2015. Factors affecting x-ray inactivation of Salmonella in low-moisture foods. IAFP Abstract P1-66. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Garces-Vega F, Marks B. 2015. Re-interpretation of water activity effects on temperature dependency of Salmonella inactivation in low-moisture foods. IAFP Abstract P1-77. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Carroll J, Jeong S, Suehr Q, Marks B. 2015. Factors affecting dry cross-contamination of Salmonella during almond processing. IAFP Abstract P1-79. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Suehr Q, Jeong S, Marks B. 2015. Modeling of cross-contamination of Salmonella during almond processing. IAFP Abstract P1-80. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Limcharoenchat P, Marks B, Ryser E, James M, Hall N. 2015. Comparing the effect of product structure on thermal resistance of Salmonella Enteritidis PT30 on/in almond and wheat products. IAFP Abstract P1-82. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Hildebrandt I, Marks B. 2015. Meta-analysis of Salmonella survival/inactivation kinetics in low-moisture foods. IAFP Abstract P1-95. Presented at the Annual Meeting of the International Association for Food Protection. July 25-28. Portland, OR.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Garces-Vegas F, Jeong S, Dolan KD, Marks BP. 2015. Modeling Salmonella inactivation in low moisture foods: Using parameter estimation to improve model performance. Abstract P.090. Presented at the 9th International Conference on Predictive Modelling in Foods. Rio de Janeiro, Brazil. September 8-12, 2015.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2015
Citation:
Hildebrandt IM. 2015. Quantifying sources of error in Salmonella thermal inactivation models in meats and low-moisture foods. M.S. thesis. Biosystems Engineering. Michigan State University. East Lansing, MI.
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: The target audiences for this project include: (1) corporations manufacturing consumer food products, (2) suppliers of equipment, ingredients, and services to that industry, (3) individual professionals responsible for designing, operating, analyzing, and/or validating processing systems, in terms of product microbial safety, and (4) regulatory agencies responsible for promulgating and enforcing rules related to food product safety. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The entire research team (including ~4 undergraduates and ~4 graduate students) previously was trained in advanced laboratory techniques necessary for conducting experiments with biosafety level-2 pathogens in low-moisture powders, which present specific challenges in ensuring worker safety, due to risk of airborne particles during sample preparation and handling. Additionally, 10 members of the project team attended the annual meeting of the International Association for Food Protection, where they presented project results, participated in the Low Water Activity Professional Development Group, and taught or attended a full-day workshop on pasteurization of low-moisture products. How have the results been disseminated to communities of interest? Project results have been shared with key stakeholders (beyond scientific conferences) by the following means in the past year: (1) A nationally-broadcast webinar with over 170 live attendees and over 400 registered attendees (with access to the recorded webinar), (2) A presentation at the Low-Moisture Task Force pre-meeting at the Institute for Food Safety and Health (IFSH) spring meeting in Chicago, and (3) A portion of the content in a one-day workshop at the International Association for Food Protection (IAFP) annual meeting. What do you plan to do during the next reporting period to accomplish the goals? Overall, during the next reporting period, the project will focus on the following activities: Low-Moisture Products: During the next reporting period, the project will focus on: (1) testing product factors affecting bacterial resistance to lethal treatments for a matrix of additional products, (2) aggregating new and shared inactivation data for quantifying uncertainty in candidate inactivation models, and (3) conducting additional pilot-scale validation trials. First, experimental studies currently are focused on generating additional lab-based data quantifying the impact of product structure and composition on bacterial resistance to multiple lethal treatments (i.e., dry- and moist-air heating, RF, and x-ray) for wheat products (whole kernels, meal, and flour) and dried fruit (whole dates and date paste). Samples are being inoculated and equilibrated at MSU, and subsequently shipped to WSU, in order to enable direct comparisons of results across technologies and laboratories. Second, the data from bench-scale studies are being used to quantify the impact of the product characteristics on primary and secondary models for Salmonella inactivation. In particular, the inactivation models developed via isothermal inactivation tests at MSU (across all product types) will be applied to predict the lethality outcomes during RF treatments at WSU, in order to quantify the validity and robustness of those models across technologies, location, and scale. Lastly, the statistical measures of model uncertainty resulting from model development will be applied to pilot-scale validation trials, in order to experimentally verify the reliability of those predictions of model performance, which is essential information when applying inactivation models to real-world process validation. Fresh Produce: A database of bacterial transfer data will be compiled, and an analysis of the aggregated data will be conducted to elucidate commonality in the characteristics of the response curves across product types, transfer event types, contact surfaces, etc. Using these and new laboratory-scale data, initial parameters for a dimensional analysis-based model will be estimated. Multiple Products: A quantitative analysis of prior microbial inactivation studies is being conducted. The impact of experimental and statistical methods on the resulting models, in terms of validity and utility, will be quantified.
Impacts
What was accomplished under these goals?
The overall project entails four types of activities: (1) lab-scale studies generating microbial response data for the multiple pathogens, products, and processes, (2) development of mathematical models to describe bacteria inactivation, transfer, survival, and/or growth, (3) pilot-scale studies to validate those models, and (4) utilization of the models to develop and deploy tools and training directly applicable to commercial applications. By working directly at the interface of food microbiology and engineering, this project is generating unique contributions toward improving the safety of ready-to-eat products. Example accomplishments from the past year are highlighted below. Low-Moisture Foods: The effects of product characteristics on the resistance of Salmonella to lethal treatments have been quantified, and inactivation models and parameters reported. One study evaluated the impact of product structure and inoculation protocol on the thermal resistance of Salmonella on whole almonds, blanched almonds, almond meal, and almond butter, all of the same composition and water activity (~0.4 a­w­). Almonds were inoculated with Salmonella Enteritidis PT30 and equilibrated to ~0.4 aw, and almond meal and butter were fabricated from the inoculated/equilibrated almonds. Small samples were heated for a range of durations in an isothermal water bath (~80°C). Initial Salmonella populations and sample aw were not different (P > 0.05) after grinding and milling. However, D80°C values were greater (P < 0.05) in almond meal (60.7 min) and almond butter (66.0 min) than on the whole almonds (19.1 min). Similarly, a separate test series tested the effects of the product structures described above on the resistance of Salmonella to low-energy x-ray treatment. For almond kernels, meal, and butter, the aw at the time of irradiation was 0.333, 0.339, and 0.315, and the radiation D-values were 0.430, 0.363, and 0.318 kGy for kernels, meal, and butter, respectively, again revealing a significant (P < 0.05) effect of product structure on the Salmonella resistance to the lethal treatment. A related study evaluated the effect of rapid desiccation on the thermal resistance of Salmonella. Wheat flour was inoculated with Salmonella Enteritidis PT30 (~8.0 log CFU/g), then divided into three treatment groups. Groups A and B were equilibrated over ~4 d to 0.6 and 0.3 aw, respectively. Group C was equilibrated to 0.6 aw, then rapidly dried to 0.3 aw (< 4 min), using desiccated room temperature air in a small fluidized bed drying system. Samples then immediately were isothermally treated (80°C) in aluminum test cells for varying durations. The mean D values for groups A, B, and C were 1.3, 7.3, and 5.7 min, respectively. The rapidly desiccated group (C) and the group initially equilibrated to 0.3 aw (B) were not significantly different (P > 0.05), but both were significantly greater than for the group initially equilibrated to 0.6 aw (P < 0.05). Salmonella in the rapidly desiccated flour (0.3 aw) was as thermally resistant as that which previously had been equilibrated to 0.3 aw. These results suggest that the observed enhanced thermal resistance of Salmonella at lower aw is a state function that requires negligible adaption time. The results from this past year have demonstrated that pasteurization processes need to be validated for different types of products, given that efficacy can be affected by product structure, even at identical composition and aw. Therefore, it is extremely important to use product-specific inactivation parameters, as developed in this project, when validating pasteurization processes. Fresh Produce: Additional experiments were conducted to evaluate the impact of fundamental physical variables on bacterial transfer to/from fresh produce and equipment contact surfaces and/or water. Potatoes were cut into 3-cm cubes, spot-inoculated with Salmonella, and then pulled across a stainless steel plate with variations in surface roughness (brushed vs. mirror finish), sliding speed (2, 5, 8 mm/s), total contact distance (20, 30, 180 cm), and additional mass placed on the product (30, 60, 90 g) to obtain different normal forces. Greater transfer (P < 0.05) was seen to mirror-finished stainless steel. Overall, normal force did not significantly affect transfer, except at long contact distances; however, contact speed and distance impacted cumulative transfer (P < 0.05) for certain cases. For example, greater cumulative transfer (P < 0.05) occurred over 30 cm of contact at 5 mm/s than at 2 mm/s (420,000 vs. 190,000 CFU total). The results have shown that quantifying the effects of individual physical variables is critical to the future development of bacterial transfer models and the refabricating/redesigning of fresh-cut processing equipment and related produce-handling operations to minimize cross-contamination. Multiple Products: Additional activities in the past year have focused on quantifying the impact of data management and model development methods on the subsequent accuracy and uncertainty of microbial inactivation models. One study was conducted to quantify the effect of data management practices on confidence interval sizes for resulting model parameters. Simulated experimental microbial reduction data sets (n = 100), with random errors, were synthesized (Yobs). Five low-count data management practices were applied, log-linear and Weibull models were fit to the resulting data, and the size of the resulting confidence intervals (CI) were compared. The ranking of CI sizes among data management practices varied among data and model types. The Y+ approach (i.e., omitting any data associated with negative plate countes), previously shown to be the most accurate (smallest RMSE, P < 0.05), nevertheless most often had the largest CI sizes, as much as double (P < 0.05) those for Yobs (i.e., the original “true” data). For most of the other approaches, the magnitude of the CI size fell between those of Yobs and Y+; 22 out of 30 cases yielded average CI sizes larger (P < 0.05) than those for Yobs. These results suggest that the application of low-count data management practices significantly affects both the accuracy and uncertainty of the model parameters. The fact that the CI sizes for Y+ were most often the largest indicated that predictions based on these results, even if more accurate, are also more uncertain. This could influence model selection and utility in risk assessments and food safety management. In another study, a quantitative meta-analysis of experimental inactivation data reported in the Combined Database for Predictive Microbiology (ComBase) was conducted to examine factors affecting replication errors. The entire collection of data in ComBase (current as of March 2013) was acquired and consisted of ~45,000 data records, ~30,000 which contained time series data, and ~3,500 which were classified as thermal inactivation trials. A data mining and analysis program was coded to identify and extract data from experiments reporting replicate data records, and then calculate replication error as a function of time, temperature, and source categorization. Data were discriminated by organism, product, product experimental conditions, methodology specifications, and temperature. Of the ~3,500 records, the median replication errors for experiments using poultry or pork were 0.058 and 0.078 log(CFU/g), respectively, while experiments using beef or produce were closer to the median global replication error across all inactivation records (0.358, 0.293 and 0.429 log(CFU/g)). Based on the analysis, there is a significant impact of test medium on replication errors in thermal inactivation studies. Additionally, there is a critical underrepresentation of key food categories in inactivation trials within the database.
Publications
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2014
Citation:
Breslin TJ, Tenorio-Bernal MI, Marks BP, Booren AM, Ryser ET, Hall NO. 2014. Evaluation of Salmonella thermal inactivation model validity for slow cooking of whole-muscle meat roasts in a pilot-scale oven. Journal of Food Protection. In press.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Buchholz AL, Davidson GR, Marks BP, Ryser ET. 2014. Tracking an Escherichia coli O157:H7 contaminated batch of leafy greens through a pilot-scale fresh-cut processing line. Journal of Food Protection. 77(9):1487-1494.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Garc�s-Vega F, Marks BP. 2014. Use of simulation tools to illustrate the effect of data management practices for low and negative plate counts on the estimated parameters of microbial reduction models. Journal of Food Protection. 77(8):1372-1379.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2014
Citation:
Smith DF, Marks BP. 2014. Effect of rapid product desiccation or hydration on thermal resistance of Salmonella Enteritidis PT 30 in wheat flour. Journal of Food Protection. Accepted for publication.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Zeng W, Vorst K, Brown W, Marks BP, Jeong S, Perez-Rodriguez F, Ryser ET. 2014. Growth of Escherichia coli O157:H7 and Listeria monocytogenes in packaged fresh-cut romaine mix at fluctuating temperatures during commercial transport, retail storage, and display. Journal of Food Protection. 77(2):197-206.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2014
Citation:
Smith DF. 2014 Modeling the Effect of Water Activity on Thermal Resistance of Salmonella in Wheat Flour. M.S. thesis. Biosystems Engineering. Michigan State University. East Lansing, MI.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Garces-Vega F, Marks B. 2014. Data management practices for low and negative plate counts affect the confidence intervals of the estimated parameters of microbial reduction models. Abstract P3-157. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Hildebrandt I, Marks B, Ryser E, Villa-Rojas R, Tang J, Buchholz S. 2014. Impact of inoculation procedures on thermal resistance of Salmonella in wheat flour and associated repeatability of results. Abstract P1-162. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Hildebrandt I, Marks B. 2014. Meta-analysis of microbial thermal inactivation response data and experimental replication errors via ComBase. Abstract P3-158. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
James M, Walch M, Tuncan E, Belete T, Jeong S, Marks B. 2014. Efficacy of dry and moist heat on the inactivation of Salmonella in a low-moisture powder residue attached to stainless steel surfaces. Abstract P1-177. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Limcharoenchat P, Marks BP, Jeong S. 2014. The effect of changing almond water activity on thermal inactivation of Salmonella Enteritidis PT30 during dry heating. ASABE Paper 1913989. Presented at the Annual International Meeting of the American Society of Agricultural and Biological Engineers. July 13-16, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Marks BP. 2014. Salmonella inactivation parameters for low-moisture foods pasteurization: finding them, compiling them and making them accessible. S34. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Maz�n B, Marks B, Ren L, Ryser E. 2014. Effects of physical variables on Salmonella transfer from produce to stainless steel. Abstract P1-158. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Ren L, Maz�n B, Marks B, Ryser E. 2014. The effect of water velocity on Escherichia coli O157:H7 transfer from inoculated lettuce to wash water in a closed pipe system. Abstract P1-144. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Smith D, Marks B. 2014. Effect of rapid desiccation on thermal resistance of Salmonella in wheat flour. Abstract P1-179. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Suehr QJ, Jeong S, Marks BP, Ryser ET. 2014. Discrete element modeling of bacterial cross contamination during almond processing. ASABE Paper 1900582. Presented at the Annual International Meeting of the American Society of Agricultural and Biological Engineers. July 13-16, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Villa-Rojas R, Tang J, Zhu M, Liu S, Tadapaneni R, Syamaladevi R, Marks B. 2014. Inactivation of Salmonella in low-moisture products at relatively high temperatures using radiofrequency-assisted heat treatments (RFHT). Abstract P1-176. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Jeong S, Marks B, Ryser E. 2014. Effect of almond product structure on x-ray inactivation kinetics of Salmonella. Abstract P1-174. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Jeong S, Marks B, Ryser E. 2014. Minimizing Salmonella attachment to dry surfaces through use of high-frequency mechanical vibration. Abstract P3-132. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Limcharoenchat P, Marks B, Hildebrandt I, Hall N. 2014. Effect of product structure on thermal resistance of Salmonella Enteritidis PT30 on whole almonds, in almond meal and in almond butter. Abstract P1-175. Presented at the Annual Meeting of the International Association for Food Protection, Indianapolis, IN. Aug 3-6, 2014.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: The target audiences for this project include: (1) corporations manufacturing consumer food products, (2) suppliers of equipment, ingredients, and services to that industry, (3) individual professionals responsible for designing, operating, analyzing, and/or validating processing systems, in terms of product microbial safety, and (4) regulatory agencies responsible for promulgating and enforcing rules related to food product safety. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The entire research team was trained in advanced laboratory techniques necessary for conducting experiments with biosafety level-2 pathogens in low-moisture powders, which present specific challenges in ensuring worker safety, due to risk of airborne particles during sample preparation and handling. How have the results been disseminated to communities of interest? Project results have been shared with key stakeholders (beyond scientific conferences) by the following means: (1) A web-based presentation to the Product Safety Solutions Group (PSSG, a PMMI and GMA supported consortium of major corporations working in in low-moisture foods), (2) An onsite presentation at the annual meeting of the PSSG, (3) A half-day meeting with FDA personnel in Chicago, and (4) A presentation at the Low-Moisture Task Force pre-meeting at the IFSH annual meeting in Chicago. What do you plan to do during the next reporting period to accomplish the goals? Overall, during the next reporting period, the project will focus on the following activities: LOW-MOISTURE PRODUCTS: Experimental studies will focus on: (a) a multi-laboratory study quantifying the contribution of sample preparation, inoculation, and thermal treatment methods on the variability and uncertainty in the resulting inactivation data and models, (b) the impact of post-contamination storage conditions and duration on subsequent bacterial resistance, and (c) the impact of product structure and composition on bacterial resistance to multiple lethal treatments (i.e., traditional thermal, RF, and x-ray). Data from the bench-scale studies and additional pilot-scale, Salmonella-inoculated challenge studies will be utilized to develop and test alternative secondary models for the impact of product characteristics (i.e., composition and structure) and process conditions on Salmonella inactivation. Multiple model forms will be proposed and tested, in terms of model accuracy. Additionally, sources of uncertainty in process validation will be quantified, based on results from the aforementioned multi-laboratory study, bench-scale experiments, and pilot-scale validation trials. Improved methods for reliably applying microbial inactivation models, in terms of honest estimates of uncertainty in process lethality, will be tested and demonstrated. MEAT AND POULTRY: The previously described global inactivation model for Salmonella in meat and poultry products will be incorporated in a next-generation tool for pilot-testing with industry partners. FRESH PRODUCE: Parameters for the previously mentioned model, based on dimensional analysis principles, will be estimated based on laboratory-scale transfer tests. Additionally, a preliminary, first-principle model for bacterial transfer to/from fresh produce will be developed, based on the underlying physical mechanisms. In a separate study, transient product temperature data, collected (by a collaborator) from actual transportation and retail settings, will be used to predict pathogen growth in fresh-cut products. MULTIPLE PROJECTS: A quantitative analysis of prior microbial inactivation studies is being conducted. The impact of experimental and statistical methods on the resulting models, in terms of validity and utility, will be quantified.
Impacts
What was accomplished under these goals?
The overall project entails four types of activities: (1) laboratory-scale studies generating microbial response data for the multiple pathogens, products, and processes described in the specific objectives, (2) development of mathematical models to describe bacteria inactivation, transfer, survival, and/or growth, based on those laboratory-scale data, (3) pilot-scale studies to validate those models under commercially relevant processing conditions, and (4) utilization of the validated models to develop and deploy tools and training directly applicable to commercial applications. By working directly at the interface of food microbiology and food process engineering, this project is generating unique contributions toward improving the safety of ready-to-eat food products. Within each group of objectives, example accomplishments from the past year are highlighted below. LOW-MOISTURE PRODUCTS: The impact of inoculation methods on Salmonella thermal resistance in wheat flour has been demonstrated to be significant, which is critically important to the design and execution of any process validation study. The thermal resistance of Salmonella in wheat flour also was shown to be significantly affected by water activity, even when the water activity was changed nearly instantaneously prior to the thermal treatment, suggesting combined physicochemical/biological factors affecting thermal resistance in low-moisture foods. Additionally, with inoculated almonds, modified models for water effects on Salmonella thermal resistance were demonstrated for dry air heating at multiple initial water activities; initial results imply that dynamic product water activity and process humidity both affect thermal resistance and that model error is reducing by accounting for both factors. MEAT AND POULTRY: Salmonella’s response to sublethal heating was quantified in terms of six stress genes; only one of those genes (ibpA) displayed significant changes in transcript level over time, with a significant increase followed by a significant decrease to a level above the initial level. These results, in addition to concurrent culture-based analyses of injury, will significantly inform previously-reported/published improvements in inactivation models accounting for the impact of sublethal history (e.g., as can occur during slow roasting processes) on subsequent thermal resistance of Salmonella in meat and poultry products. In a separate study, three candidate empirical models for bacterial transfer meat slicing were compared across multiple data sets, in order to elucidate phenomenological differences attributed to contact or product type. Based on the Akaike Information Criterion, the selection of the most likely correct model was affected by product type and the contact type (e.g., mechanical slicing vs. sequential surface contacts), which reveals underlying transfer characteristics not previously evident individual studies. FRESH PRODUCE: A dimensional analysis approach was used to develop a generic model for bacterial transfer to/from product subjected to solid-surface or water contact events. Experiments are underway to develop the data necessary to estimate the model parameters. MULTIPLE PRODUCTS: The impact of experimental methods and data handling protocols on microbial reduction models was analyzed and quantified in two studies. In the first, two different experimental methods were applied to determine thermal inactivation kinetics of Salmonella in meat products, with both conducted at two different collaborating laboratories (MSU and USDA-ARS-ERRC), and with two different inactivation models tested against the data. The results showed significant impact of method, laboratory, and model choice on the resulting model characteristics and statistics, which is critically important to the utilization of published inactivation data for process validation. In the second study, the procedure for handling low plate counts in microbial reduction studies was evaluated, in terms of the impact on model selection and accuracy. Five different, previously-published data management practices were applied for handling plate counts below the limit of detection, and the resulting model selection and accuracy were significantly affected. For example, when negative plate counts were replaced by the limit of detection for a truly log-linear process, the Weibull model was erroneously selected as the most likely correct model.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Benoit A, Marks B, Ryser E, Crandall P. 2013. Multiple Models for Aggregated Foodborne Pathogen Transfer Data between Meat Products and Contact Surfaces. Abstract P1-55. Presented at the Annual Meeting of the International Association for Food Protection. July 28-31. Charlotte, NC.
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2013
Citation:
Benoit A. 2013. Experimental and mathematical models for Listeria monocytogenes transfer between delicatessen meats and contact surfaces. M.S. thesis. Biosystems Engineering. Michigan State University. East Lansing, MI
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Bruin JM, Marks BP, Bourquin LD. 2013. Food safety training and assessment with diverse workers new to muscle foods processing. Abstract 298-01. Presented at the Institute of Food Technologists Annual Meeting. July 13-16, 2013. Chicago, IL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Carroll L, Bergholz T, Marks B. 2013. Modeling the Physiological Response of Salmonella to Heat Shock during Slow Cooking Processes. Abstract P2-05. Presented at the Annual Meeting of the International Association for Food Protection. July 28-31. Charlotte, NC.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Limcharoenchat P, Marks B, Jeong S. 2013. The effect of initial almond water activity on thermal inactivation of Enterococcus faecium during dry heating. Abstract P3-82. Presented at the Annual Meeting of the International Association for Food Protection. July 28-31. Charlotte, NC.
- Type:
Other
Status:
Published
Year Published:
2013
Citation:
Marks BP, Hildebrandt I. 2013. Salmonella inactivation parameters for low-moisture food pasteurization. Presented to the Product Safety Solutions Group. July 17, 2013. Chicago, IL.
- Type:
Other
Status:
Published
Year Published:
2013
Citation:
Marks BP. 2013. Improving pasteurization validation methods for Salmonella in low-moisture foods. Invited presentation. Institute for Food Safety and Health, Low-Moisture Food Safety Task Force Meeting. September 17, 2013. Bedford Park, IL.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Maz�n B, Marks B. 2013. A dimensional analysis approach to modeling bacterial pathogen transfer during conveying, washing, and slicing of fresh cut produce. Abstract P3-101. Presented at the Annual Meeting of the International Association for Food Protection. July 28-31. Charlotte, NC.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Smith D, Hildebrandt I, Marks B. 2013. Neta-analysis of Salmonella inactivation parameters and data for thermal pasteurization of low moisture foods. Abstract P2-09. Presented at the Annual Meeting of the International Association for Food Protection. July 28-31. Charlotte, NC.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Tenorio-Bernal M, Marks BP, Ryser ET, Booren AM. 2013. Evaluating the predictive ability of a path-dependent thermal inactivation model for Salmonella subjected to prior sublethal heating in ground turkey, beef, and pork. Journal of Food Protection. 76(2):220-226.
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2013
Citation:
Zeng W, Vorst K, Brown W, Marks BP, Jeong S, Perez-Rodriguez F, Ryser ET. 2013. Growth of Escherchia coli O157:H7 and Listeria monocytogenes in packaged fresh-cut Romaine mix at fluctuating temperatures during commercial transport, retail storage, and display. Journal of Food Protection. In press.
|
Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: The overall mission of this project is to develop improved methods for the design and operation of processing systems for commercially-produced food products, based on the criteria of microbial safety, processing yield, and product quality. Significant activities occurred in the areas of low-moisture foods, meat and poultry, and fresh produce. Low-moisture foods: The focus this year has been on both bench-scale and pilot-scale inactivation trials with almonds. Non-isothermal inactivation trials focused on the impact of initial water activity and process humidity on Salmonella inactivation. Current tests are quantifying the relationship between the rate of moisture loss and bacterial adaptation during thermal pasteurization processes. Meat and poultry: Project activities focused on two key areas: (1) completion and dissemination of a global thermal inactivation model for Salmonella in meat and poultry products, and (2) quantifying sources of error and uncertainty underlying the development and utilization of such a model. The global inactivation model was parameterized using two regression methods and previously published inactivation data for Salmonella in turkey, beef, and pork. The models were validated against industry-relevant data from Salmonella-inoculated, pilot-scale challenge studies with steaks/fillets and patties cooked in an impingement oven, and whole-muscle roasts and hot dogs cooked in a moist-air convection oven. The uncertainty analysis encompassed two parts. The first was a direct analysis of human error in positioning temperature probes during cooking validations, and the resulting impact on lethality calculations. This was achieved by enlisting two groups of human subjects (n = 32) to position temperature probes into the center of meat patties, and then quantifying the positioning error via computed tomography (CT) scans of the subsequently frozen patties. The statistical distribution of those errors was input into a bacterial inactivation model to generate a probability function quantifying the contribution of probe positioning error to predicted lethality error. The second part of the uncertainty analysis encompassed a collaborative study between two laboratories (MSU and USDA-ARS-ERRC), in which both laboratories used the same irradiated ground beef, the same 8-serovar Salmonella cocktail, two different methods each for conducting isothermal inactivation trials, and two different methods for estimating the resulting thermal inactivation parameters. This method enabled a quantitative comparison of the degree to which the laboratory, the experimental method, and the data analysis method impacted the resulting inactivation parameters. Fresh produce: The main focus has been on developing a phenomenological model for transfer of bacterial pathogens to/from fresh produce during processing. Data are being acquired (via a collaborator) from multiple bench- and pilot-scale trials with washing and slicing of lettuce, tomatoes, celery, and onions. These data will be used to test a transfer model that has been constructed using dimensional analysis methods. PARTICIPANTS: The following are the individuals who worked on this project during the reporting period, and a brief description of their roles on the project: Bradley Marks - PI. Managing overall experimental plans, data management and analysis strategies, and project team meetings and progress. Supervising all of the research staff and undergraduate students on the project. Elliot Ryser - co-PI. Supervising the overall microbiological testing conducted as part of the inoculated challenge studies, including method development and validation. Kirk Dolan - co-PI. Provided significant consultation in design and application of statistical modeling methodologies, particularly in parameter estimation and quantification of uncertainty. Sanghyup Jeong - research assistant professor. Designing and maintaining data acquisition systems and custom software for real-time monitoring of process lethality in pilot-scale, inoculated validation tests. Nicole Hall - laboratory manager. Supervising undergraduate students working on the experimental microbiology activities on this project (sample prep, media prep, enumeration, etc.). Michael James - BSL-2 pilot plant manager. Setting-up and managing pilot-scale, inoculated challenge studies in the biosafety level-2 pilot processing facility. Pichamon Limcharoenchat, Ph.D. student. Running bench-scale trials evaluating the impact of changing water activity on bacterial resistance during non-isothermal heating processes. Six undergraduate students (MSU, biosystems engineering, food science, microbiology, physics) worked on both the experimental and modeling aspects of this project. TARGET AUDIENCES: The target audience for this project is industry professionals responsible for designing, validating, and documenting the safety of processes for manufactured food products, particularly low-moisture foods, meat and poultry, and fresh produce. The results from this project will improve the ability of this group to ensure the safety of these products. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Low-moisture foods: The thermal inactivation work has confirmed the significant effect of product water activity on the thermal resistance of Salmonella on almonds and powders. In non-isothermal heat treatments, a modified thermal inactivation model, accounting for the impact process humidity, significantly improved prediction accuracy over traditional (D, z) model forms; however, there is a small, but statistically significant, impact of initial water activity on the prediction bias, indicating a need (as expected) to further refine the inactivation model. Current tests are addressing this issue, in addition to the previously unaddressed issue of dynamic moisture changes, and the impact of change rate on the resistance of Salmonella to the lethal treatment, which will be critical in validation of industrial processes. Meat and poultry: The global thermal inactivation model for Salmonella in meat and poultry products performed satisfactorily when accounting for fat content, sublethal injury, and muscle structure, improving accuracy and bias against temperature-only models. Additionally, actual outcomes from the pilot-scale validation trials reflected a significantly higher degree of uncertainty than predicted using prediction intervals based on laboratory-scale data. In terms of the uncertainty source analyses, human error in probe placement can yield significant errors in computed lethality for rapidly cooked products. For example, a probe positioning error of 1.5 mm from the product center corresponded to an approximately 3 log over-prediction of process lethality. In terms of the cross-laboratory comparisons, the two different experimental methodologies (although both well-published) yielded significantly different (P < 0.05) inactivation parameters, and the data processing and regression methods also affected these results. Ultimately, there is a significant need for standardized methods for generating pathogen inactivation data, models, and parameters, in order to consolidate information across studies and maximize the potential utility of such models to the industry. Nevertheless, a global thermal inactivation model was demonstrated as feasible and successful, and incorporation of such a model into an industry-ready tool (underway) will have significant positive impact on the ability of the industry to generate reliable and valid thermal process validations. Fresh produce: No prior research in bacterial transfer during produce processing has resulted in a phenomenologically satisfactory or mechanistic model for the transport processes (other than probabilistic models). The current attempt at a generalized model will be critical in determining whether data from multiple studies can be aggregated for a meta-analysis of factors affecting bacterial cross-contamination during produce processing.
Publications
- Benoit A, Marks B, Ryser E. 2012. A quantitative meta-analysis of existing foodborne pathogen transfer data. IAFP Abstract P1-174. Presented at the International Association for Food Protection Annual Meeting. Providence, RI. July 22-25, 2012.
- Benoit AN, Marks BP, Ryser ET, Jeong S. 2012. GloGerm powder as a surrogate to assess Listeria monocytogenes transfer between delicatessen turkey and a stainless steel surface. IFT Abstract 043-14. Presented at the Institute of Food Technologists Annual Meeting. Las Vegas, NV. June 25-28, 2012.
- Henriques J, Suehr Q, Marks B, Jeong S, Limcharoenchat P. 2012. Statistical distribution of human error in positioning temperature probes in meat patties for thermal process validation. IAFP Abstract P3-11. Presented at the International Association for Food Protection Annual Meeting. Providence, RI. July 22-25, 2012.
- Hildebrandt I, Marks B, Juneja V, Osoria A, Hall N. 2012. Cross-laboratory comparative study on the impact of experimental and regression methodologies on Salmonella thermal inactivation parameters. IAFT Abstract P3-29. Presented at the International Association for Food Protection Annual Meeting. Providence, RI. July 22-25, 2012.
- James M, Jeong S, Marks B, Ryser E. 2012. Impact of product water activity on the validity of thermal inactivation models for Salmonella on almonds. IAFP Abstract P1-170. Presented at the International Association for Food Protection Annual Meeting. Providence, RI. July 2012.
- Jiao Y, Tang J, Wang S. 2012. Dielectric, physical, and thermal properties of low moisture model food for dielectric heating process. IFT Abstract 079-24. Presented at the Institute of Food Technologists Annual Meeting. Las Vegas, NV. June 2012.
- Marks B. 2012. Improved process validation strategies for Salmonella inactivation on low-moisture food products subjected to thermal pasteurization processes. IAFP Symposium S11. Presented at the International Association for Food Protection Annual Meeting. Providence, RI. July 22-25, 2012.
- Zeng W, Vorst K, Brown W, Marks B, Perez-Rodriguez F, Ryser E. 2012. Monte Carlo simulation of Escherichia coli O157:H7 and Listeria monocytogenes growth in bagged salad greens during commercial transport, retail storage and display. IAFP Abstract T4-12. Presented at the International Association for Food Protection Annual Meeting. Providence, RI. July 22-25, 2012.
- Tenorio-Bernal M, Marks B, Dolan K. 2012. Uncertainty estimations and validation of a universal Salmonella thermal inactivation model for ground- and whole-muscle meat and poultry product. 2012. IFT Abstract 043-11. Presented at the Institute of Food Technologists Annual Meeting. Las Vegas, NV. June 25-28, 2012.
- Tenorio-Bernal MI, Marks BP, Ryser ET, Booren AM. 2013. Evaluating the predictive ability of a path-dependent thermal inactivation model for Salmonella subjected to prior sublethal heating in ground turkey, beef, and pork. Journal of Food Protection. 76: in press.
- Tenorio-Bernal MI. 2012. A multi-product, multi-factor thermal inactivation model for salmonella in meat and poultry products. M.S. thesis. Department of Biosystems and Agricultural Engineering. Michigan State University. East Lansing, MI.
- Villa-Rojas R, Tang J, Wang S, Gao M, Kang D, Mah J, Gray P, Sosa-Morales ME, Malo AL. 2012. Thermal inactivation of Salmonella Enteritidis PT30 in almond kernels as influenced by water activity. IFT Abstract 035-130. Presented at the Institute of Food Technologists Annual Meeting. Las Vegas, NV. June 2012.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: The overall mission of this project, which is to develop improved methods for the design and operation of processing systems for commercially-produced food products, based on the criteria of microbial safety, processing yield, and product quality, focuses on three product categories: low-moisture foods, meat and poultry, and fresh produce. Significant activities occurred in all three of these areas during the past year. Low-moisture foods: Activity in this area focused pilot-scale thermal inactivation trials with Salmonella-inoculated and moisture-equilibrated almonds in the MSU BSL-2 Pilot Plant. These tests have yielded quantitative measures of the underlying and inherent uncertainty associated with multiple methods of process validation, including use of a non-pathogenic surrogate or inactivation models applied to product temperature data collected using various methods. Additionally, these data are being used to test the accuracy of these various validation methods, including traditional and improved inactivation models. Meat and poultry: Project activity focused on completion of additional pilot-scale cooking trials, synthesis of Salmonella inactivation data sets from multiple laboratories, validation of thermal inactivation models using those data, and development and testing of multiple forms of a universal thermal inactivation model for Salmonella in meat and poultry products. In the most recent round of pilot-scale challenge studies, beef and turkey hot dogs were inoculated with Salmonella, prior to stuffing in the casings, and subjected to a range of cooking treatments in a pilot-scale, moist-air convection oven. In each case, the actual Salmonella lethality was compared to the computed lethality, which further augments our significant set of pilot-scale validation data. Fresh produce: This is the newest portion of this overall project. X-ray irradiation work continues to focus on quantifying the inactivation kinetics for key bacterial pathogens in high priority products (e.g., leafy greens). Additionally, the framework for developing a conceptual model for bacterial transfer to/from food surfaces and associated processing surfaces and media has been developed and will be a focus in the coming year. Specific outputs from this project during 2011 included 2 journal articles published in peer-reviewed journals and 6 papers presented at national meetings. In the coming year, major activities on this project will include on-going pilot-scale inactivation trials with low-moisture products, development and testing of improved inactivation models for pasteurization of additional low-moisture product categories (i.e., large particulates, powders, and pastes), testing of the universal thermal inactivation model for Salmonella in meat and poultry products, and initial development of a database of transfer data and models for foodborne pathogens on fresh produce and other products. PARTICIPANTS: This project is directed by Dr. Bradley Marks, with close collaboration with Drs. Elliot Ryser, Kirk Dolan, and Ik Soon Kang. In 2011, three graduate students, one post-doctoral researcher, two post-graduate research assistants, and eight undergraduate students (in biosystems engineering, food science, microbial genomics, and physics) worked on various aspects of this project. TARGET AUDIENCES: The target audience of this project is corporations and professionals who are responsible for manufacturing ready-to-eat food products, equipment companies that support those processors, and the regulators responsible for ensuring the microbial safety of those products. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Overall, this project has generated a variety of outcomes that contribute to the overall program mission, a few of which are highlighted here as examples. Over a wide range of processes/products, our results continue to show that the relationships between food product characteristics (e.g., water activity), processing conditions (e.g., heating rate, humidity), and pathogen inactivation are complex and require a thorough validation before models of these processes can be reliably applied to commercial systems. For example, our work on thermal pasteurization of low-moisture products (i.e., almonds) has demonstrated that well-validated thermal inactivation models, based on well-measured product surface temperature, can actually be more reliable (i.e., lower uncertainty) than biologically-based validations utilizing a non-pathogenic surrogate. This is significant, relative to quantitatively understanding the reliability of a pasteurization validation, and the desired margin of safety. In the case of Salmonella inactivation in meat and poultry products, we similarly found that laboratory methodologies significantly impact reported thermal inactivation parameters, which, in turn, significantly impacts the utility of the results when applied to actual process validations. Our pilot-scale validation of thermal inactivation models fills a critical scientific gap, as there is negligible data in the literature addressing the validity of these types of models. Overall, the various components of this project have shown that the validity and underlying uncertainty associated with pathogen inactivation models has previously been considerably underreported; however, processors of fully-cooked meat and poultry products must fully understand these measures of model utility, in order to ensure the statistical reliability of process design and validation. Additionally, in applying such data to the development of a universal thermal inactivation model for Salmonella in meat and poultry products, we have shown that variability in experimental methods across multiple studies causes significant, unexplained variability in lethality results, which subsequently results in very large prediction intervals when applying resulting models to future data. The models that we are currently testing account for meat product species, structure (whole-muscle vs. ground), fat content, product temperature, and sublethal thermal history in predicting Salmonella inactivation, which will be the first generalized, but application-specific model of its kind in this sector.
Publications
- Emery J, Marks BP, Hall N, James M, Booren AM, Ryser ET. 2011. Pilot-scale validation of a Salmonella thermal inactivation model in ground meat patties. IFT Abstract 037-40. Institute of Food Technologists Annual Meeting. New Orleans, LA. July 2010.
- Hildebrandt IM, Marks BP, Hall NO, James M, Booren AM, Ryser ET. 2011. Pilot-scale validation of a Salmonella thermal inactivation model applied to whole-muscle meat and poultry products cooked in a moist-air impingement oven. IAFP Abstract P3-155. International Association for Food Protection Annual Meeting. Milwaukee, WI. August 2011.
- James M, Marks BP, Ryser ET, Jeong S. 2011. Evaluation of critical process parameters for Salmonella inactivation on almonds subjected to thermal pasteurization. IAFP Abstract P3-117. International Association for Food Protection Annual Meeting. Milwaukee, WI. August 2011.
- Jeong S, Marks BP, Ryser ET. 2011. P1-51 Low-Energy x-ray irradiation against Escherichia coli O157:H7 in ground beef of different fat contents and product temperatures. IAFP Abstract P1-51. International Association for Food Protection Annual Meeting. Milwaukee, WI. August 2011.
- Jeong S, Marks BP, Ryser ET. 2011. Quantifying the performance of Pediococcus sp. (NRRL B-2354: Enterococcus faecium) as a nonpathogenic surrogate for Salmonella Enteritidis PT30 during moist-air convection heating of almonds. Journal of Food Protection. 74(4):603-609.
- Perez-Rodriguez F, Campos D, Ryser ET, Buchholz AL, Posada-Izquierdo GD, Marks BP, Zurera G, Todd E. 2011. A mathematical risk model for Escherichia coli O157:H7 cross-contamination of lettuce during processing. Food Microbiology. 28(4):694-701.
- Tenorio-Bernal MI, Marks BP, Booren AM, Ryser ET. 2011. A universal thermal inactivation model for Salmonella in meat and poultry products. IAFP Abstract P3-156. International Association for Food Protection Annual Meeting. Milwaukee, WI. August 2011.
- Zeng W, Vorst K, Marks BP, Jeong S, Ryser ET. 2011. Growth of Escherichia coli O157:H7 and Listeria monocytogenes in packaged fresh-cut romaine lettuce at fluctuating temperatures during commercial transport and distribution. IAFP Abstract T4-03. International Association for Food Protection Annual Meeting. Milwaukee, WI. August 2011.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation and optimization. Nearly all of the progress in this past year was in the second area (predictive microbiology). We continued to test our previously-published, novel path-dependent thermal inactivation model for the effect of prior sublethal thermal history on subsequent inactivation rates, via cooking trials with inoculated whole-muscle beef, pork, and chicken products, and ground-and-formed beef, pork, and turkey products in a pilot-scale, moist-air impingement oven. The model validity was quantified in terms of error against experimental outcomes of lethality, and the impact of scaling up the model application from laboratory to pilot-scale data also was quantified. We are utilizing these data, in combination with data from other sources, to develop a universal thermal inactivation model for Salmonella in meat and poultry products and to incorporate that model into an industry tool for process validation. We also have begun development and testing of several approaches for physical surrogates for bacterial pathogen transfer in food handling environments. Additionally, we have reported the impact of product water activity on the efficacy of low-energy x-ray irradiation for pasteurization of tree nuts, and reported novel data for x-ray inactivation of Escherichia coli O157:H7 on leafy greens. Lastly, we have conducted pilot-scale studies, in which we are quantitatively comparing five different methods (two biological and three physical) for validating thermal pasteurization processes for low-moisture products (e.g., almonds), in terms of accuracy and repeatability. Specific outputs from this project included 2 journal articles published in peer-reviewed journals and 5 papers presented at national meetings. PARTICIPANTS: This project is directed by Dr. Bradley Marks, with close collaboration with Drs. Elliot Ryser and Alden Booren. In 2010, two graduate students, one post-doctoral researcher, two post-graduate research assistants, and eight undergraduate students (in biosystems engineering, food science, and animal science) worked on various aspects of this project. TARGET AUDIENCES: The target audience of this project is corporations and professionals who are responsible for manufacturing ready-to-eat food products, particularly in the domain of protein products, and the regulators responsible for ensuring the microbial safety of those products. PROJECT MODIFICATIONS: None.
Impacts
Overall, this project has generated a variety of outcomes that contribute to the overall program mission, a few of which are highlighted here as examples. Over a wide range of processes/products, our results have shown that traditional models for thermal inactivation (e.g., D and z) over-predict actual Salmonella lethality (P<0.05) during slow meat cooking, but our recent results show that this is not necessarily true for high-speed cooking, such as occurs in commercial impingement ovens. These new results (with meat patties, steaks, and fillets) also have confirmed that the variability in Salmonella lethality increases significantly when scaling-up from laboratory- to pilot-scale (from ~0.1 to >1.0 log CFU/g). We also reported significant sensitivity of process lethality calculations to experimental parameters, such as temperature probe placement. Each of these factors need to be considered when applied pathogen inactivation models to real world pasteurization processes. In the x-ray studies, it was demonstrated that the effect of water activity on inactivation rate is not monotonic, and there is a point of maximum resistance. We also reported significant differences between the efficacy of low-energy x-ray and previously published data from gamma irradiation, relative to inactivation of Escherichia coli O157:H7 on leafy greens. All of the outcomes above are being integrated into improved simulations and methods for validating pasteurization processes. Additionally, the validation of the improved lethality models will enable the industry and regulators to more accurately evaluate the efficacy of pasteurization processes in ensuring microbial safety of ready-to-eat meat and poultry products. Ultimately, implementation of these tools will simultaneously improve the assurance of product safety and potentially generate hundreds of millions of dollars in additional product value, via improved processing yields.
Publications
- Jeong S, Marks BP. 2010. Inactivating Salmonella on almonds and walnuts using low-energy X-ray. IFT Abstract 042-07. Institute of Food Technologists Annual Meeting. Chicago, IL. July 2010.
- Jeong S, Marks BP, Ryser ET. 2010. Pediococcus spp. NRRL B-2354 (Enterococcus faecium) as a non-pathogenic surrogate for Salmonella Enteritidis PT30 during moist-air convection heating of almonds. IAFP Abstract. International Association for Food Protection Annual Meeting. Anaheim, CA. August 2010.
- Marks BP. 2010. Variability and uncertainty in pasteurization validation methods for low moisture foods. Abstract M3-D.4. Society for Risk Analysis Annual Meeting. Salt Lake City, UT. December 2010.
- Marks BP, Karthik KS, James MK. 2010. Comparing multiple methods for validating dry air pasteurization of almonds. IAFP Abstract. International Association for Food Protection Annual Meeting. Anaheim, CA. August 2010.
- Wiederoder MS, Marks BP. 2010. Error in pathogen thermal inactivation calculations in meat products due to inaccurate temperature probe placement. IFT Abstract 085-07. Institute of Food Technologists Annual Meeting. Chicago, IL. July 2010.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation and optimization. In the first area (properties), a paper was presented on kinetic modeling of surface color development during moist-air impingement cooking of meat patties, based on results activities/results described in the prior annual report. Additionally, laboratory-scale marination tests were completed to quantify the effects of marination conditions, product species, freeze-thaw cycles, and exposure time on the rate of marinade uptake and retention (i.e., holding capacity) in whole-muscle meat products. In the second area (predictive microbiology), we continued to test our previously-published, novel path-dependent thermal inactivation model for the effect of prior sublethal thermal history on subsequent inactivation rates, via laboratory- and pilot-scale cooking trials with inoculated whole-muscle beef, pork, and turkey roasts. The model validity was quantified in terms of error against experimental outcomes of lethality and predictions based on a traditional, state-dependent model for lethality. We have also begun development and testing of several approaches for modeling the transfer of bacterial pathogens between: (1) contaminated products (e.g., meat or leafy greens), (2) processing equipment (e.g., conveyor surfaces, slicers), and (3) processing water. A dimensional analysis approach was taken initially, and laboratory- and pilot-scale data from multiple experimental studies are being analyzed to test the validity of the modeling approach. Additionally, we have tested the impact of product water activity on the efficacy of low-energy x-ray irradiation for pasteurization of tree nuts, with the aim of developing an inactivation model that accounts for this effect. In the third area of this project (process simulation and optimization), inoculated validation studies were completed with Salmonella-inoculated turkey, beef, and pork roasts processed in a pilot-scale, moist-air convection oven in a biosafety level-2 pilot-processing facility at Michigan State University, in order to test existing inactivation models and generate data needed to develop a generalized process lethality model for Salmonella in meat and poultry products. Additionally, the previously-reported results on Salmonella migration into whole-muscle meat products during marination was integrated with associated thermal resistance models to develop an quantitative comparison of the risk of surviving salmonellae at the center of whole-muscle or ground products of equivalent size and thermal treatment. Lastly, we have conducted preliminary studies, at the pilot-scale, in which we are quantitatively comparing five different methods for validating thermal pasteurization processes for low-moisture products (e.g., almonds), in terms of accuracy and repeatability. Specific outputs from this project included: (1) 3 journal articles published in peer-reviewed journals, (2) 15 papers presented at national meetings, (3) 1 M.S. thesis completed, and (4) 1 M.S. food science student graduated. PARTICIPANTS: This project is directed by Dr. Bradley Marks, with close collaboration with Drs. Elliot Ryser and Alden Booren. In 2009, two graduate students, two post-doctoral researchers, two post-graduate research assistants, and eight undergraduate students (in biosystems engineering, food science, chemical engineering, and animal science) worked on various aspects of this project. TARGET AUDIENCES: The target audience of this project is corporations and professionals who are responsible for manufacturing ready-to-eat food products, particularly in the domain of protein products, and the regulators responsible for ensuring the microbial safety of those products. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Overall, this project has generated a variety of outcomes that contribute to the overall program mission, a few of which are highlighted here as examples. PROPERTIES: Tests to develop surface browning models have shown that surface moisture is the most important factor in these predictions. Marination tests have shown that marination uptake rate and retention (for whole muscle products) is significantly affected by marinade composition, product species, and freeze-thaw cycles. PREDICTIVE MICROBIOLOGY: Over a wide range of processes/products, our results have shown that traditional models for thermal inactivation (e.g., D and z) over-predict actual Salmonella lethality (P<0.05) during meat cooking. A new, path-dependent inactivation model eliminated this systematic over-prediction at the laboratory scale; however, new pilot-scale results do not statistically support that conclusion. Nevertheless, the new, path-dependent inactivation model reduced the mean lethality error by 2.6 and 1.0 log CFU/g for turkey and beef products, respectively, and reduced the corresponding root mean squared errors by 2.2 and 0.9 log CFU/g, which was a significant improvement, relative to process validation methodologies. However, variability in Salmonella lethality increases significantly when scaling-up from laboratory- to pilot-scale (from ~0.15 to ~1.4 log CFU/g), which needs to be considered when validating processes. For inoculated whole-muscle roasts cooked to a core temperature of 71.1C (160F) during slow cooking processes mimicking commercial schedules in the pilot-scale oven, salmonellae were very rarely recovered, indicating that there was no significant under-processing of those products. However, for slow-cooked roasts cooked to a target computed lethality (e.g., 6.5 log reductions), the results indicate that there is significant risk of not meeting the lethality performance standards. Therefore, particular caution should be exercised for marginally-processed products. In the x-ray studies, it was demonstrated that the effect of water activity on inactivation rate is not monotonic, and there appears to be a point of maximum resistance. In the bacterial transfer studies, the rate of transfer in a product-water system was found to be sufficiently fast to eliminate the time variable in the dimensional analysis. In a meat-surface system, the accumulation of product residue was found to affect the rate of bacterial transfer, so that this phenomenon needs to be considered in future modeling. PROCESS SIMULATION: All of the outcomes above are being integrated into improve cooking simulations and optimization efforts for those systems. Additionally, the validation of the improved lethality models will enable the industry and regulators to more accurately evaluate the efficacy of thermal processes in ensuring microbial safety of ready-to-eat meat and poultry products. Ultimately, implementation of these tools will simultaneously improve the assurance of product safety and potentially generate hundreds of millions of dollars in additional product value, via improved processing yields.
Publications
- Breslin TJ, Marks BP, Booren AM, Ryser ET, Hall N. 2009. Pilot-scale validation of Salmonella thermal inactivation in whole muscle turkey breast. IFT Abstract 027-07. Institute of Food Technologists Annual Meeting. Anaheim, CA. June 2009.
- Breslin TJ, Marks BP, Booren AM, Ryser ET, Hall NO. 2009. Scaling-up Salmonella lethality calculations from laboratory to pilot-scale slow-cooking processes. RMC Abstract. American Meat Science Association. Reciprocal Meats Conference. June 2009.
- Buchholz AL, Davidson GR, Marks BP, Todd EC, Ryser ET. 2009. Quantification of Escherichia coli O157:H7 transfer to equipment during commercial production of fresh-cut leafy greens. IAFP Abstract P3-22. International Association for Food Protection Annual Meeting. Grapevine, TX. July 2009.
- Buchholz AL, Davidson GR, Marks BP, Todd EC, Ryser ET. 2009. Transfer of Escherichia coli O157:H7 from equipment surfaces to iceberg and romaine lettuce during simulated commercial processing. IAFP Abstract T5-04. International Association for Food Protection Annual Meeting. Grapevine, TX. July 2009.
- Campos DT, Marks BP, Vorst KL, Keskinen LA, Ryser ET. 2009. Accounting for product residue effects when modeling bacterial transfer between processing equipment and meat products. IAFP Abstract P1-01. International Association for Food Protection Annual Meeting. Grapevine, TX. July 2009.
- Jeong S, Marks BP & Orta-Ramirez A. 2009. Thermal inactivation kinetics for Salmonella Enteritidis PT30 on almonds subjected to moist-air convection heating. Journal of Food Protection: 72 (8) 1602-1609.
- Jeong S, Marks BP, Moosekian SR, Hall NO, Ryser ET. 2009. Efficacy of low-energy X-ray for inactivating Escherichia coli O157:H7 on the surface of lettuce. IFT Abstract 125-13. Institute of Food Technologists Annual Meeting. Anaheim, CA. June 2009.
- Jeong S, Marks BP. 2009. Kinetics of surface color change during moist-air impingement processing of meat patties. ASABE Paper 096802. American Society of Agricultural and Biological Engineers Annual Meeting. Reno, NV. June 2009.
- Jones SL, Marks BP, Booren AM, Ryser ET, Hall NO. 2009. Effect of sub-lethal heating on Salmonella lethality during slow-cooking of turkey and beef products. IFT Abstract 027-07. Institute of Food Technologists Annual Meeting. Anaheim, CA. June 2009.
- Marks BP, Rochowiak JA, Tuntivanich V, Ryser ET, Booren AM. 2009. Modeling the transport of Salmonella into whole-muscle meat products during marination and the subsequent lethality during thermal processing. ICPMF Poster Abstract. 6th International Conference on Predictive Modeling in Food. Washington, DC. September 2009.
- Perez Rodriguez F, Ryser ET, Buchholz AL, Marks BP, Campos D, Todd E. 2009. A mathematical risk model for Escherichia coli O157:H7 cross-contamination of lettuce during processing. IAFP Abstract T7-04. International Association for Food Protection Annual Meeting. Grapevine, TX. July 2009.
- Tenorio-Bernal IM, Marks BP. 2009. Applying a path-dependent model for Salmonella thermal inactivation in slow-cooked turkey and beef products. Inverse Problems Symposium 2009. East Lansing, MI. 2 June 2009.
- Tenorio-Bernal MI, Marks BP, Jones SL. 2009. Applying a path-dependent model for Salmonella thermal inactivation in slow-cooked turkey and beef products. IAFP Abstract P1-07. International Association for Food Protection Annual Meeting. Grapevine, TX. July 2009.
- Wesche AM, Gurtler JB, Marks BP & Ryser ET. 2009. Stress, sublethal injury, resuscitation, and virulence of bacterial foodborne pathogens. Journal of Food Protection: 72 (5) 1121-1138.
- Marks BP, Tenorio-Bernal MI, Breslin TJ, Ryser ET, Booren AM. 2009. Validating a Salmonella thermal lethality model that accounts for prior sublethal injury during commercial meat and poultry cooking processes. ASABE Paper 096722. American Society of Agricultural and Biological Engineers Annual Meeting. Reno, NV. June 2009.
- Marks BP. 2009. Impact of experimental errors in post-process enumeration of surviving microorganisms on inactivation models. IFT Abstract 214-02. Institute of Food Technologists Annual Meeting. Anaheim, CA. June 2009.
- Mogollon MA, Marks BP, Booren AM, Orta-Ramirez A & Ryser ET. 2009. Effect of beef product physical structure on Salmonella thermal inactivation. Journal of Food Science: 74 (7) M347-M351.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation and optimization. In the first area (properties), a second study was conducted to test the feasibility of modeling surface color browning of chicken breasts, as a function of surface temperature and moisture during cooking. Tests were conducted in a pilot-scale, moist-air impingement oven. Surface temperature was logged real-time during cooking, surface color was measured via a Hunter colorimeter (using steamed chicken as a color baseline), and surface moisture content was measured at the exit from the oven. Both 0th-order and 1st-order kinetic models were tested, and model parameters were estimated using non-linear regression. Additionally, laboratory-scale tests were conducted to quantify the effects of marination conditions, product species, freeze-thaw cycles, and exposure time on the rate of marinade uptake into whole-muscle meat products. In the second area (predictive microbiology), our previously-developed model for the effect of prior sublethal thermal history on subsequent inactivation rates was tested in laboratory- and pilot-scale cooking trials with inoculated, whole-muscle beef and turkey roasts. The model validity was quantified in terms of error against experimental outcomes of lethality and predictions based on a traditional, state-dependent model for lethality. Additionally, tests have quantified the efficacy of low-energy x-ray irradiation for pasteurization of ground beef patties, almonds, and leafy greens. In the third area of this project (process simulation and optimization), validation studies were completed with Salmonella-inoculated turkey and beef roasts processed in a pilot-scale, moist-air convection oven in a biosafety level-2 pilot-processing facility at Michigan State University, in order to test existing inactivation models and generate data needed to develop a generalized process lethality model for Salmonella in meat and poultry products. PARTICIPANTS: This project is directed by Dr. Bradley Marks, with close collaboration with Drs. Elliot Ryser and Alden Booren. In 2008, two graduate students, three post-doctoral researchers, two post-graduate research assistants, and nine undergraduate students (in biosystems engineering, food science, chemical engineering, and animal science) worked on various aspects of this project. TARGET AUDIENCES: The target audience of this project is corporations and professionals who are responsible for manufacturing ready-to-eat food products, particularly in the domain of meat and poultry products, and the regulators responsible for ensuring the microbial safety of those products. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Overall, this project has generated a variety of outcomes that contribute to the overall program mission, a few of which are highlighted here as examples. PROPERTIES: Tests to develop surface browning models have shown that surface moisture is the most important factor in these predictions; however, the variability in spot measurements of color (using the Hunter colorimeter) was too high for sufficient accurate model development. Future work will incorporate image-based assessment of product quality. Marination tests have shown that marination time, marinade composition, and freeze-thaw cycles all significantly affect the rate of marinade uptake into whole-muscle meat products and the retention of mass during subsequent cooking. PREDICTIVE MICROBIOLOGY: Results to date showed that traditional inactivation parameters (D and z, previously determined via isothermal laboratory studies) over-predicted actual mean Salmonella lethality (P<0.05) during meat cooking, with over-prediction errors as high as ~5 log. Additionally, the error increased with increasing sub-lethal heating. A new secondary inactivation model eliminated (alpha=0.05) this systematic over-prediction error due to sub-lethal injury. Pilot-scale inactivation tests also revealed two other significant results. First, variability and uncertainty in Salmonella lethality increases significantly when scaling-up inactivation results from laboratory to pilot-scale, which needs to be considered when computing process lethalities. Secondly, for inoculated whole-muscle roasts cooked to a core temperature of 71.1degC (160degF) during slow cooking processes that mimicked commercial schedules in the pilot-scale oven, no salmonellae were recovered via standard plate counts, indicating that there was no significant under-processing of those products. However, for slow-cooked roasts cooked to a target computed lethality (e.g., 6.5 log reductions), the results indicate that there is significant risk of not meeting the lethality performance standards. Therefore, particular caution (and/or improved modeling methods) should be exercised for marginally-processed products. In the x-ray studies, it was demonstrated that low-energy x-ray was an effective technology for pasteurizing ground beef patties, almonds, and leafy greens. In each case, the D10rad values appear to be less than those previously reported for gamma irradiation. Additionally, the water activity of the product appears to affect D10rad. PROCESS SIMULATION: All of the outcomes above are being integrated into improve cooking simulations and optimization efforts for those systems. Additionally, the validation of the improved microbial lethality model will enable the industry and regulators to more accurately evaluate the efficacy of thermal processes in ensuring microbial safety of ready-to-eat meat and poultry products. Ultimately, implementation of these tools will simultaneously improve the assurance of product safety and generate hundreds of millions of dollars in additional product value/revenue, via improved processing yields.
Publications
- Campos DT, Marks BP, Ryser ET, Todd ECD. 2008. Modeling the growth of Listeria monocytogenes in delicatessen turkey and ham. IAFP Abstract P5-03. Presented at the International Association for Food Protection Annual Meeting. Columbus, OH. Aug 3-6, 2008.
- Hall NO, Marks BP, Campos DT, Booren AM. 2008. Effects of marination treatments on uptake rate and cooking yield of whole-muscle beef, pork, and turkey. IFT Abstract 134-13. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA.
- Jeong S, Marks BP, Ryser ET. 2008. Inactivation of Salmonella Enteritidis PT30 by low-energy x-ray irradiation on almonds at different water activities. IAFP Abstract P1-31. Presented at the International Association for Food Protection Annual Meeting. Columbus, OH. Aug 3-6, 2008.
- Jeong S, Marks BP. 2008. Efficacy of low-energy X-ray for inactivating Salmonella Enteritidis PT30 on the surface of almonds. IFT Abstract 135-18. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA.
- Marks BP. 2008. Challenges in microbial modeling for food safety engineering. Invited presentation. AIChE Midwest Regional Conference. Chicago, IL. Sept 22-23, 2008.
- Marks BP. 2008. Factors to Consider in Modeling Thermal Inactivation. Invited presentation. IAFP Symposium. Presented at the International Association for Food Protection Annual Meeting. Columbus, OH. Aug 3-6, 2008.
- Marks BP. 2008. Status of microbial modeling in food process models. Comprehensive Reviews in Food Science and Food Safety. 7(1):137-143.
- Stasiewicz MJ, Marks BP, Orta-Ramirez A, Smith DM. 2008. Modeling the effect of prior sublethal thermal history on the thermal inactivation rate of Salmonella in ground turkey. Journal of Food Protection. 71(2):279-285.
- Tuntivanich V, Orta-Ramirez A, Marks BP, Ryser ET, Booren AM. 2008. Thermal inactivation of Salmonella in whole muscle and ground turkey breast. Journal of Food Protection. 71(12):2548-2551.
- Warsow CR, Orta-Ramirez A, Marks BP, Ryser ET, Booren AM. 2008. Single directional migration of Salmonella into marinated whole muscle turkey breast. Journal of Food Protection. 71(1):153-156.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation and optimization. In the first area (properties), a preliminary study was conducted to test the feasibility of modeling surface color browning of chicken breasts, as a function of surface temperature and moisture during cooking. Tests were conducted in a commercial-scale, combination spiral/impingement oven on-site at an industrial collaborator. Surface temperature was logged real-time during cooking, surface color was measured via a Hunter colorimeter (using steamed chicken as a color baseline), and surface moisture content was measured at a transition point and exit point from the oven. A 0th-order kinetic model was applied, and model parameters were estimated using non-linear regression. In the second area (predictive microbiology), our previously-developed model for the effect of prior sublethal thermal
history on subsequent inactivation rates was tested in pre-pilot-scale cooking trials with inoculated, whole-muscle beef. The model validity was quantified in terms of error against experimental outcomes of lethality and predictions based on a traditional, state-dependent model for lethality. Additionally, tests have quantified the efficacy of low-energy x-ray irradiation for pasteurization of ground beef patties. In the third area of this project (process simulation and optimization), pilot-scale validation studies have recently begun; inoculated products are being processed in commercial equipment, in a newly-constructed, biosafety level-2 pilot-processing facility at Michigan State University to validate many of the secondary inactivation models that we have developed over the past five years, and to develop a novel and much-needed general tool for thermal process validation in the meat and poultry industry.
PARTICIPANTS: This project is directed by Dr. Bradley Marks, with close collaboration with Drs. Elliot Ryser and Alden Booren. In 2007, three graduate students, three post-doctoral researchers, one post-graduate research assistant, and six undergraduate students (in biosystems engineering and food science) worked on various aspects of this project. In 2007, Dr. Marks and one undergraduate student conducted a set of preliminary tests, related to color development, on-site at FMC FoodTech (Sandusky, OH), an industrial collaborator and leading manufacturer of commercial oven systems.
TARGET AUDIENCES: The target audience of this project is corporations and professionals who are responsible for manufacturing ready-to-eat food products, particularly in the domain of meat and poultry products, and the regulators responsible for ensuring the microbial safety of those products.
Impacts
Overall, this project has generated a variety of outcomes that contribute to the overall program mission, a few of which are highlighted here as examples. PROPERTIES: Preliminary tests have indicated that surface browning of chicken breasts during commercial processing can be mathematically models as a function of the dynamic process conditions, and that surface moisture is the most important factor in these predictions. PREDICTIVE MICROBIOLOGY: It has been shown that Salmonella in relatively slow cooked product (cooking time ~120 min) can develop significantly increased heat resistance. In these cases, traditional calculations of lethality, based on previous isothermal tests, over-predicted Salmonella inactivation by as much as ~4 logs. However our improved, path-dependent model, which accounts for the effect of prior sub-lethal history, successfully predicted the inactivation outcome for a wide range of thermal histories (i.e., cooking rates) when validated in
whole-muscle beef steaks cooked in a convection oven. Additional tests also confirmed and reported that Salmonella can migrate into the interior of intact, marinated turkey breasts and are more resistant to heat than in ground product of equivalent composition and thermal history (as we previously reported for beef and pork). In the x-ray studies, it was demonstrated that low-energy x-ray was an effective technology for pasteurizing ground beef patties, achieving a 5 log reduction of Escherichia coli O157:H7 after a dose of ~1 kGy. PROCESS SIMULATION: All of the outcomes above are being integrated into improve cooking simulations and optimization efforts for those systems. For example, the surface browning model will contribute to the improvement of previous optimization outcomes, in order to generate commercially-relevant predictions of optimal operating conditions for oven cooking systems. Additionally, the validation of the improved microbial lethality model will enable the
industry and regulators to more accurately evaluate the efficacy of thermal processes in ensuring microbial safety of ready-to-eat meat and poultry products. Ultimately, implementation of these tools will simultaneously improve the assurance of product safety and generate hundreds of millions of dollars in additional product value/revenue, via improved processing yields.
Publications
- Mogollon MA, Marks BP, Jeong S, Stasiewicz MJ, Booren AM. 2007. Effect of cooking profiles and sub-lethal history on Salmonella thermal inactivation in whole-muscle beef. IFT Abstract 098-09. Presented at the Institute of Food Technologists Annual Meeting. Chicago, IL . July 2007.
- Mogollon MA. 2007. Effect of beef product structure and sublethal cooking history on Salmonella thermal inactivation. M.S. thesis. Michigan State University. East Lansing, MI.
- Tuntivanich V, Orta-Ramirez A, Marks B, Booren A. 2007. The effect of marinade on Salmonella migration into turkey breast. IFT Abstract 098-07. Presented at the Institute of Food Technologists Annual Meeting. Chicago, IL . July 2007.
- Velasquez A. 2006. Thermal resistance and migration of Salmonella spp. into marinated pork products. M.S. thesis. Michigan State University. East Lansing, MI.
- Breslin TJ, Hall NO, Marks BP, Booren AM, Orta-Ramirez A. 2007. Migration of Salmonella into intact turkey breast muscle without intervention of external factors. IFT Abstract 098-06. Presented at the Institute of Food Technologists Annual Meeting. Chicago, IL . July 2007.
- Hall NO, Keskinen LA, Yan Z, Marks BP, Ryser ET, Booren AM, Orta-Ramirez A. 2007. Quantitative transfer of Escherichia coli O157:H7 between beef and equipment surfaces. IFT Abstract 098-08. Presented at the Institute of Food Technologists Annual Meeting. Chicago, IL . July 2007.
- Jeong S, Marks BP, Ryser ET, Booren AM. 2007. Efficacy of low-energy x-ray for eliminating Escherichia coli O157:H7 in ground beef. IFT Abstract 189-50. Presented at the Institute of Food Technologists Annual Meeting. Chicago, IL . July 2007.
- Martino KG, Marks BP. 2007. Comparing uncertainty resulting from two-step and global regression procedures applied to microbial growth models. Journal of Food Protection. 70:2811-2818.
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Progress 01/01/06 to 12/31/06
Outputs
The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation and optimization. In the first area (properties), the permeability, hydraulic conductivity, and lipid conductivity of ground beef patties were measured and quantified as a function of cooking treatment. Additionally, thermally-induced shrinkage and mass loss from whole-muscle beef tissue have been modeled via n<sup>th</sup>-order kinetics. In the second area (predictive microbiology), regression method were shown to significantly impact the uncertainty of <i>Listeria monocytogenes</i> growth models applied to data from meat and poultry products. Additionally, a first-principle model was developed for the migration of <i>Salmonella</i> into whole-muscle meat products during marination; preliminary results showed that the model was stable; however, systematic errors against experimental data indicate a need
to refine the sub-model for bacterial movement within the muscle structure. Additionally, although our previous work had shown that <i>Salmonella</i> is significantly more heat resistant in whole-muscle than in ground meat products, new results showed that the degree-of-grinding did not impact resistance; in other words, there was still a difference between whole-muscle and ground product, but not between coarsely ground, finely ground, and pureed product. In the third area of this project (process simulation and optimization), pilot-scale validation studies will be conducted in the coming year; inoculated products will be processed in commercial equipment, in a newly-constructed, biosafety level-2 pilot-processing facility at Michigan State University to validate many of the secondary inactivation models that we have developed over the past five years.
Impacts
The basic, physical properties quantified in this study will enable more fundamentally correct, and therefore more robust, mathematical models for commercial cooking systems, which will enable more reliable process designs and improved economic returns. The enhanced models for thermal inactivation of <i>Salmonella</i> will enable processors and regulators to more accurately predict process lethality, which will result in better assurance of product safety. Lastly, the process optimization tools developed and tested in this project have the potential to: (1) result in incremental improvements in process design, which will translate into better margins for product safety and yield, and (2) result in significant improvements in the design of cooking equipment, to take advantage of the opportunities revealed by the optimization process.
Publications
- Martino, K.G., Marks. B.P. 2006. Comparing two different modeling approaches for growth prediction of Listeria monocytogenes applied to meat and poultry products. IFT Abstract 036-03. Presented at the Institute of Food Technologists Annual Meeting. Orlando, FL. June, 2006.
- Mogollon, M., Marks, B.P., Orta-Ramirez, A., Booren, A.M., Ryser, E.T. 2006. Effect of beef physical structure on Salmonella thermal inactivation. IAFP Abstract P2-25. Presented at the International Association for Food Protection (IAFP) Annual Meeting. Aug. 2006. Calgary, Alberta
- Tripuraneni, M., Marks, B.P. 2006. Pore-size distributions in whole muscle and ground meat cooked to different endpoint temperatures. IFT Abstract 078D-40. Presented at the Institute of Food Technologists Annual Meeting. Orlando, FL. June, 2006.
- Tuntivanich, V., Orta-Ramirez, A., Booren, A., Marks, B.P. 2006. The migration pattern of Salmonella spp. into whole-muscle turkey breast during marination. IFT Abstract 039H-13. Presented at the Institute of Food Technologists Annual Meeting. Orlando, FL. June, 2006.
- Bornhorst, G.M., Marks, B.P., Orta-Ramirez, A. 2006. Modeling the kinetics of thermally-induced shrinkage of beef muscle during cooking. IFT Abstract 039I-07. Presented at the Institute of Food Technologists Annual Meeting. Orlando, FL. June, 2006.
- Campos, D.T., Marks, B.P., Ryser, E.T. 2006. Quantifying the distribution of sub-lethal injury in thermally heated Salmonella population. IAFP Abstract P1-57. Presented at the International Association for Food Protection (IAFP) Annual Meeting. Aug. 2006. Calgary, Alberta
- Jeong, S., Marks, B.P. 2006. Application of process optimization techniques to cooking of meat patties in industrial, moist-air impingement ovens. IFT Abstract 078D-11. Presented at the Institute of Food Technologists Annual Meeting. Orlando, FL. June, 2006.
- Jeong, S., Marks, B.P. 2006. Evaluation of strategies using neural networks, global optimization algorithms, and control parameterization for multivariable dynamic process optimization. IFT Abstract 078E-07. Presented at the Institute of Food Technologists Annual Meeting. Orlando, FL. June, 2006.
- Velasquez, A., Orta-Ramirez, A., Booren, A.M., Marks, B.P., Ryser, E.T. 2006. Migration of Salmonella spp. into Whole-muscle Pork Roasts During Marination. IAFP Abstract P2-24. Presented at the International Association for Food Protection (IAFP) Annual Meeting. Aug. 2006. Calgary, Alberta
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Progress 01/01/05 to 12/31/05
Outputs
The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation and optimization. In the first area (properties), the microstructure of ground beef patties were quantified, in terms of pore size distributions. Species, fat content, and degree of cooking all significantly (P<0.05) affected pore size distribution, which in turn will affect mass transfer properties that are important determinants of cooking yield. Currently, the relative permeabilities of water and fat are being directly measured and related to those changes in microstructure. Additionally, dimensional changes (shrinkage) of whole-muscle beef tissue have been measured via isothermal heating tests and modeled as a function of both time and temperature. In the second area (predictive microbiology), the errors inherent in existing broth-based growth models for Listeria monocytogenes and Escherichia coli
O157:H7 were deconstructed; these errors were not random, but instead were functions of various experimental parameters. These preliminary results are currently being used to develop models for accurately predicting the uncertainty (error) around model predicted values of microbial counts. Additionally, the effects of meat product structure and prior thermal history on thermal resistance of Salmonella have been further documented. Secondary models accounting for these effects have been developed and are being refined. Additionally, we are continuing to incorporate those models into a new version of the American Meat Institute Process Lethality Spreadsheet. In the coming year, pilot-scale validation studies will be conducted with inoculated products in commercial equipment, in a newly-constructed, biosafety level-2 pilot-processing facility at Michigan State University. In the third area of this project (process simulation and optimization), a fully-integrated process modeling
(including heat transfer, water transport, fat transport, Salmonella inactivation, surface color changes, and center color changes) was utilized to test and apply a variety of optimization strategies for the complex, multi-variable process of moist-air cooking. The results showed that certain global optimization methods could identify optimal dynamic control profiles; however, those profiles might be highly dependent on critical variables, such as product properties. Nevertheless, these strategies were applied to commercially relevant case studies (e.g., single and double-stage oven systems) to determine the operating conditions to achieve maximum yield while satisfying the safety and quality constraints.
Impacts
The basic, physical properties quantified in this study will enable more fundamentally correct, and therefore more robust, mathematical models for commercial cooking systems, which will enable more reliable process designs and improved economic returns. The enhanced models for thermal inactivation of Salmonella will enable processors and regulators to more accurately predict process lethality, which will result in better assurance of product safety. Lastly, the process optimization tools developed and tested in this project have the potential to: (1) result in incremental improvements in process design, which will translate into better margins for product safety and yield, and (2) result in significant improvements in the design of cooking equipment, to take advantage of the opportunities revealed by the optimization process.
Publications
- Martino, K.G., Marks, B.P., Campos, D.T., and Tamplin, M.L. 2005. Quantifying the robustness of a broth-based model for predicting Listeria monocytogenes growth in meat and poultry products. Journal of Food Protection. 68:2310-2316.
- Millsap, S.C., and Marks, B.P. 2005. Condensing-convective boundary conditions in moist air impingement ovens. Journal of Food Engineering. 70:101-108
- Carlson, T.R., Marks, B.P., Booren, A.M., Ryser, E.T., and Orta-Ramirez, A. 2005. Effect of water activity on thermal inactivation of Salmonella in ground turkey. Journal of Food Science. 70:363-366.
- Orta-Ramirez, A., Marks, B.P., Warsow, C.R., Booren, A.M., and Ryser, E.T. 2005. Enhanced thermal resistance of Salmonella in whole muscle vs. ground beef. Journal of Food Science. 70:359-362.
- Islam, M.T., Marks, B.P., and Bakker-Arkema, F.W. 2005. Modeling an Ear-Corn Dryer. Transactions of the ASAE. 48:243-249.
- Wesche, A.M., Marks, B.P., and Ryser, E.T. 2005. Thermal resistance of heat-, cold- and starvation-stressed Salmonella in irradiated comminuted turkey. Journal of Food Protection. 68:942-948.
- Guo, B. and Marks, B.P. 2005. Generalized modeling for thermal inactivation of Salmonella in meat and enhancement of the AMI process lethality spreadsheet. Abstract T86. Presented at the 51st International Congress of Meat Science and Technology. August 7-12, 2005. Baltimore, MD.
- Orta-Ramirez, A., Marks, B., Owens, S., Whalon, J., and Booren, A. 2005. Development of a method to monitor real-time thermal inactivation of pathogens in meat and poultry products. Abstract T122. Presented at the 51st International Congress of Meat Science and Technology. August 7-12, 2005. Baltimore, MD.
- Jeong, S., Marks, B.P., Dolan, K.D., Ryser, E.T., and Orta-Ramirez, A. 2005. Thermal inactivation kinetics for Salmonella on almonds subjected to moist-air convection heating. IFT Abstract 108-8. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA. July, 2005.
- Campos, D.T., Marks, B.P., Powell, M.R., and Tamplin, M.L. 2005. Quantifying the robustness of a broth-based, Escherichia coli O157:H7 growth model in ground beef. Journal of Food Protection. 68:2301-2309.
- Stasiewicz, M.J., Marks, B.P., and Orta-Ramirez, A. 2005. Modeling the effect of prior thermal history on the thermal inactivation rate of Salmonella in turkey. IFT Abstract 108-7. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA. July, 2005.
- Tripuraneni, M., Marks, B.P., and Watkins, A.E. 2005. Fat holding capacity of ground beef during cooking. IFT Abstract 89F-18. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA. July, 2005.
- Velasquez, A., Tuntivanich, V., Orta-Ramirez, A., Booren, A.M., Marks, B.P., and Ryser, E.T. 2005. Enhanced thermal resistance of Salmonella in marinated whole-muscle vs. ground pork. IFT Abstract 89E-14. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA. July, 2005.
- Tuntivanich, V., Velasquez, A., Orta-Ramirez, A., Ryser, E.T., Marks, B.P., and Booren, A.M. 2005. Enhanced thermal resistance of Salmonella and microstructure observations in marinated whole-muscle turkey. IFT Abstract 89F-34. Presented at the Institute of Food Technologists Annual Meeting. New Orleans, LA. July, 2005.
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Progress 01/01/04 to 12/31/04
Outputs
The specific objectives of this project are grouped into three areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation. In the first area (properties), the fat holding capacity (FHC) of ground beef was determined in isothermal heating tests. FHC was affected by the initial fat content and temperature, but not by heating duration. Currently, the micro-structure of ground meat matrices is being tested via mercury porosimetry, and the flow properties of the melting fat is being quantified; these results will be integrated to describe the fundamentals of fat transport during meat cooking. In the second area (predictive microbiology), significant progress was made on several objectives. A novel method for quantifying the robustness of predictive microbial models was developed and used to test broth-based models against growth data for Escherichia coli O157:H7 and Listeria monocytogenes in various meat products. The robustness
index (RI) is novel in that it quantifies the predictive accuracy of a model relative to the expected accuracy, and does so in terms of the microbial counts. Additionally, the errors inherent in predictive microbial models have been deconstructed, quantifying the relative contributions of experimental errors, primary models, and secondary models. In terms of path-dependent modeling, we have shown that prior thermal history impacts (P<0.05) the subsequent thermal resistance of Salmonella in that product, with slow heating rates increasing subsequent resistance. Therefore, a modified, Arrhenius-type model was developed and shown to accurately account for the history effect on instantaneous inactivation rates of Salmonella in ground turkey. In terms of applying predictive microbial models to real applications, a preliminary "universal" model for the decimal reduction time (D value) of Salmonella in meat and poultry products has been developed (using data from ComBase) and integrated into
a new version of the American Meat Institute Process Lethality Spreadsheet. Whereas a user previously needed to know the D value for a specific product, the new tool allows the user to enter the product type, pH, moisture, and fat content, and the model generates an estimate of the D value (with confidence interval) to use in a thermal process validation. This preliminary version of the model is currently being expanded with new data and prepared for testing. In the third area of this project (process simulation/optimization), a complete coupled heat and mass transfer model was integrated with a Salmonella inactivation model and validated for moist-air impingement cooking of ground meat patties. Additionally, a neural network was developed, based on output from that model, and used in preliminary optimization programming, which indicated that it is possible to determine the optimal operating parameters for single, double, and multi-stage oven systems. Current work is aimed at
integrated product quality constraints into the optimization protocol, in order to generate results that will help ensure product safety, quality, and maximize cooking yield and economic returns.
Impacts
The tools for evaluating robustness of predictive microbial models will be useful for risk assessors, who need to know the uncertainty associated with models used in overall risk assessments. The new model accounting for the effect of thermal history on inactivation rates of pathogens will enable more accurate validation of the microbial safety of slow cooking processes in the meat and poultry industry. The new version of a process lethality spreadsheet will improve the capacity of meat and poultry processors to generate more accurate, product-specific calculations for thermal process validations. Lastly, the improved cooking/lethality model for air impingement cooking of meat and poultry products will directly affect oven manufacturers, and ultimately food processors, by enabling evaluation of cooking equipment, food products, and/or food manufacturing processes prior to the full-scale development of each of these elements. This will result in improved process
design, which will translate into better margins of product safety and improved processing yields.
Publications
- Campos, D.T., Marks, B.P., Ryser, E.T., Wesche, A.M. 2004. Application of the Weibull population distribution to describe the thermal inactivation kinetics of sub-lethally injured Salmonella in ground turkey. Institute of Food Technologists Abstract 30-9.
- Jeong, S., Marks B.P. 2004. Optimizing multi-stage air impingement cooking of meat patties. American Society of Agricultural Engineers Paper 04-3022. Martino, K., Marks, B.P., Campos, D.T., Tamplin, M.L. 2004. Quantifying the robustness of a broth-based model for predicting Listeria monocytogenes growth in meat and poultry products. Institute of Food Technologists Abstract 67E-19.
- Martino, K.G., Marks, B.P., Campos, D.T., Tamplin, M.L. 2004. Contributions of primary and secondary model uncertainty to the robustness of a broth-based microbial growth model for Listeria monocytogenes and Escherichia coli O157:H7 in meat and poultry products. International Association of Food Protection Abstract P100.
- Orta-Ramirez, A., Marks, B.P., Stasiewicz, M., Ryser, E.T., Booren, A.M. 2004. Thermal inactivation of Salmonella in turkey meat depends on the heating rate of the thermal process. Institute of Food Technologists Abstract 30-6.
- Watkins, A.E. 2004. A combined convection cooking and Salmonella inactivation model for ground meat and poultry products. Ph.D. Dissertation. Michigan State University. East Lansing, MI.
- Watkins, A.E., Marks, B.P., Booren, A.M., Ryser, E.T., Orta-Ramirez, A. 2004. A model for predicting yield, temperature profile, and Salmonella inactivation during moist-air impingement cooking of ground beef patties. Institute of Food Technologists Abstract 17H-10.
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Progress 01/01/03 to 12/31/03
Outputs
The specific objectives of this project are grouped into three general areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation. Progress was made in each of these areas during the past year. The most significant accomplishments in the first area were related to quantifying and modeling transport properties of ground and formed meat products. Several theoretical models for predicting thermal conductivity of a porous material were tested against experimental data from meat samples processed in a convection oven to a variety of different conditions (temperature, moisture content, porosity). Results showed that neglecting the porosity of products cooked in an air-convection system can result in significant errors in predictions of thermal conductivity, which is a critical parameter in accurately modeling cooking processes. Additionally, two different studies investigated fat transport and holding capacity in cooked meat
products. The results showed that the fraction of fat bound in a processed product is a function of the initial fat content, process conditions, and the product species, which affects the lipid composition. These results on transport properties are currently being integrated into an improved cooking model that will enable processors and equipment manufacturers to more accurately predict dynamic oven performance characteristics prior to running any actual tests. In the second project area, the most significant accomplishments were related the effects of meat product structure and microbial culture history on the thermal resistance of Salmonella in meat products. Conclusive results have shown that pathogenic bacteria can migrate into the interior of intact, vacuum-tumbled, marinated whole-muscle products, and that vacuum and tumbling both increase bacterial migration into the product. Additionally, we have shown (and submitted for publication) conclusive evidence that bacteria that
migrate into the interior of a whole-muscle product are significantly more resistant to thermal inactivation than bacteria in ground product, even when the product composition and thermal history are equal. We also have shown that a heat shock treatment (54 C for 30 min) and even slow heating rates (<1 C/min) significantly increase the thermal resistance of Salmonella inoculated into ground meat. In the third area of this project, the improved cooking model being developed with results from the first objective is being used to conduct an optimization process for single and multi-stage, air-impingement cooking systems. In the initial stages, the optimization routine is being operated with a simplified cooking model. Once the protocol is established, the complete cooking model, which integrates heat transfer, moisture transfer, fat transport, and pathogen inactivation will be used to train an artificial neural network, which will in turn be used in an optimization program to determine
the global optimum operating conditions to simultaneously ensure pathogen inactivation and maximize processing yield for any given product and process.
Impacts
The novel results showing the potential risk of pathogen migration into marinated, whole-muscle products, and their greater thermal resistance in those products, reveal the importance of process validations being carried out for specific products and processes and not extrapolating results from different classes of products. This information will be incorporated into improvements of a publicly-available tool that is used by much of the meat and poultry industry in ensuring and documenting process lethality. The improved cooking model for air impingement cooking of meat and poultry products will directly affect oven manufacturers, and ultimately food processors, by enabling evaluation of cooking equipment, food products, and/or food manufacturing processes prior to the full-scale development of each of these elements. Coupled with the cooking/lethality model under development, this could result in improved process design, which will translate into better margins of
product safety and improved processing yields.
Publications
- Friant, N.R. Marks, B.P. Bakker-Arkema, F.W. 2003. Drying rate of individual ears of corn. ASAE Paper 03-6006. American Society of Agricultural Engineers. St. Joseph, MI.
- Islam, M.T. Marks, B.P. Bakker-Arkema, F.W.. 2003. Modeling of an ear-corn dryer. ASAE Paper 03-6007. American Society of Agricultural Engineers. St. Joseph, MI.
- Jeong, S. Marks, B.P. 2003. Modeling thermal conductivity of meat patties as a function of porosity, temperature, and composition in high temperature and humidity processes. ASAE Paper 03-6105. American Society of Agricultural Engineers. St. Joseph, MI.
- Marks, B.P. 2003. Mapping a new road to food safety. Meat Marketing and Technology. 10(10):65-72.
- Orta-Ramirez, A. Warsow, C.R. Ryser, E.T. Booren, A.M. Marks, B.P. 2003. Enhanced thermal resistance of Salmonella in whole-muscle vs. ground beef. Institute of Food Technologists Abstract 60C-7.
- Warsow, C.R. Marks, B.P. Ryser, E.T. Orta-Ramirez, A. Booren, A.M. 2003. Effects of vacuum tumbling on Salmonella migration into the interior of intact, marinated turkey breasts. Institute of Food Technologists Abstract 76F-22.
- Watkins, A.E. Marks, B.P. 2003. Effect of fat transport on cooking losses for ground meat and poultry patties. Institute of Food Technologists Abstract 87-4.
- Wesche, A.M. 2003. Thermal resistance of sublethally injured Salmonella. M.S. thesis. Michigan State University. East Lansing, MI.
- Wesche, A.M. Marks, B.P. Ryser, E.T. 2003. Thermal resistance of heat-, cold-, and starve-injured Salmonella in ground turkey. Institute of Food Technologists Abstract 29G-29.
- Wesche, A.M. Marks, B.P. Ryser, E.T. 2003. Efficacy of Oxyrase(R) and sodium pyruvate for recovering heat-, cold-, and starve-injured Salmonella. Institute of Food Technologists Abstract 76E-14.
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Progress 01/01/02 to 12/31/02
Outputs
The specific objectives of this project are grouped into three general areas: (1) product properties and processing, (2) predictive microbiology, and (3) process simulation. Progress was made in each of these areas during the past year. The most significant accomplishment in the first area was the development and commercial-scale validation of a model to predict the convective heat and mass transfer coefficients for condensing-convective conditions in moist air impingement ovens. This model now enables food processors and equipment manufacturers to predict dynamic oven performance characteristics prior to running any actual tests. In the second project area, the most significant accomplishments were related to water effects on thermal resistance and to pathogen migration into whole muscle products. In the area of water effects, tests were designed and executed to isolate the effects of water activity (an intrinsic property of the product) and air humidity (an
extrinsic property of the process) on thermal resistance of Salmonella in ground turkey. The rate of thermal inactivation significantly decreased with decreasing meat water activity (0.996 to 0.950); however, no effects were observed for a corresponding decrease in relative humidity. Secondary inactivation models were used to demonstrate that water activity can and should be included in inactivation models that are used for process lethality calculations. In the area of whole muscle products, several different experiments were conducted to test the effects of vacuum and mechanical tumbling on the migration of Salmonella into intact, marinated whole-muscle meat products. Conclusive results have shown significant potential for pathogens to migrate into the interior regions of these products and that vacuum and tumbling both increase that potential. Preliminary results have also shown significantly greater heat resistance for Salmonella that has migrated into whole-muscle product, as
compared to Salmonella mixed into ground products. In the third area of this project, boundary condition models (from the first project area) and pathogen inactivation models have been incorporated into a coupled heat and mass transfer model for convection cooking of meat and poultry products. Commercial-scale validation trials were conducted with beef patties at a corporate partner, in order to test the heat and mass transfer portions of the model. The heat transfer model was reasonably accurate (5 C standard error of prediction for transient center temperature); however, the validation data revealed some weakness in the mass transfer model, which is attributable to simplifying assumptions regarding fat transport. The model is currently being refined to remove these assumptions. Lastly, an optimization protocol is being developed, in order to use the final cooking/lethality model to optimize multi-stage convection cooking systems.
Impacts
The model for condensing-convective boundary conditions in moist air impingement ovens directly affects oven manufacturers and ultimately food processors, by enabling evaluation of cooking equipment, food products, and/or food manufacturing processes prior to the full-scale development of each of these elements. Coupled with the cooking/lethality model under development, this could result in improved process design, which can translate into better margins of product safety and improved processing yields.
Publications
- Burns, T.R. 2002. Effect of water activity and humidity on the thermal inactivation of Salmonella during heating of meat. M.S. thesis. Michigan State University. East Lansing, MI.
- Burns, T.R., Marks, B.P., Ryser, E.T., Booren, A.M. 2002. Effect of humidity on the thermal inactivation of Salmonella during air heating of meat. Institute of Food Technologists Annual Meeting. Abstract 97-3.
- Harris, K.L. 2002. Assessment of line-level training needs related to commercial production of fully-cooked meat and poultry products. M.S. thesis. Michigan State University. East Lansing, MI
- Harris, K.L., Marks, B.P., TenEyck, T.A., Booren, A.M., Ryser, E.T. 2002. Development of training materials for oven operators in the cooked meat and poultry industry. Institute of Food Technologists Annual Meeting. Abstract 57-2.
- Millsap, S.C. 2002. Modeling the condensing-convective boundary conditions in moist air impingement ovens. M.S. thesis. Michigan State University. East Lansing, MI.
- Millsap, S.C., Marks, B.P. 2002. Modeling convective/condensing heat transfer to food products in moist air impingement ovens. American Society of Agricultural Engineers. ASAE Paper No. 026045.
- Warsow, C.R., Orta-Ramirez, A., Booren, A.M., Ryser, E.T., Marks, B.P. 2002. Salmonella penetration into whole-muscle turkey during vacuum marination. Institute of Food Technologists Annual Meeting. Abstract 88-4.
- Watkins, A.E., Marks, B.P. 2002. A combined convection cooking and Salmonella inactivation model for ground meat and poultry patties. American Society of Agricultural Engineers. ASAE Paper No. 026046.
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Progress 01/01/01 to 12/31/01
Outputs
The specific objectives of this project are grouped into three general areas: product properties, predictive microbiology, and process simulation. Progress was made in each of these areas during the past year. In terms of product properties, the water-holding capacity of processed meat has been shown to be a function of both temperature and cooking time, which is a novel result. Additional data are currently being collected in order to develop a first-principle model for this relationship, which should positively affect the accuracy of future cooking models. An analytical model has also been formulated to quantify the condensing-convective boundary condition during air-impingement cooking of meat and poultry products. This model will be parameterized during the first half of 2001 via experimental trials in a commercial impingement oven, in cooperation with a corporate partner on this project. In terms of predictive microbiology, the effect of meat moisture content on
thermal inactivation of Salmonella has been tested. No significant effect was found in a limited range (plus or minus 3% from the native state); however, additional tests are currently being conducted, in which inoculated, exposed meat samples are being heated in a laboratory oven system, in order to isolate the effects of process humidity from sample moisture content. In terms of process simulation, a coupled heat and mass transfer model has been formulated for convection cooking of ground and formed meat and poultry products, and a functional computer solution completed. The accuracy of temperature and yield predictions will be tested via commercial-scale validation trials during 2001, and the pathogen inactivation models will be incorporated.
Impacts
The technical information and tools being developed in the project will provide the meat and poultry industry with the means to more accurately predict the microbial safety of ready-to-eat products, while simultaneously improving the yield, and therefore economic value, of those products.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
This is a new project (started 09/01/2000). Graduate research assistants have been hired, and research activities are being initiated. These include preliminary tests of water effects on microbial lethality in meat and initial development of a computer model for convection cooking of meat products.
Impacts
This is a new project (09/01/2000).
Publications
- No publications reported this period
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