Progress 09/01/11 to 08/31/15
Outputs
Target Audience:The target audiences for this project are: (1) individuals who are responsible for designing, validating, and documenting the safety of pasteurization processes for low-moisture foods (in industry or regulatory roles), but who lack specific formal education or training specifically aimed at this unique challenge, and (2) corporations that manufacture low-moisture food products or pasteurization equipment designed for these products. The results from this project will improve the ability of these groups to ensure the safety of low-moisture food products, by providing training resources, scientific data, and tools that uniquely support the needs of these professionals and the low-moisture food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The entire research team (including ~5 undergraduates, and 7 graduate students) 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 nationally broadcast webinar, (4) A half-day meeting with FDA personnel in Chicago, (5) Multiple presentations at the Low-Moisture Task Force pre-meeting at the IFSH annual meeting in Chicago, and (6) A full-day, onsite pre-meeting at the 2014 IAFP Annual Meeting. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Overall, this collaborative project has resulted in significant contributions to low-moisture food safety. In particular, an enhanced understanding of the interactions between food product moisture content, water activity (aw), temperature, and thermal resistance of Salmonella is fundamentally altering modeling methods for inactivation of Salmonella in these systems and the approach to applying such tools to process validation. Collaborative work between Washington State University (WSU) and Michigan State University (MSU) has applied that new information in demonstrating how these interactions may partially explain the extremely high thermal resistance of Salmonella in products like peanut butter, which is improving approaches to inactivation modeling. Related work at MSU also has altered the understanding of how product aw and pathogen acclimation to low-moisture systems may or may not affect lethality outcomes in real, dynamic processes. This project has shown that dynamic processing conditions can potentially alter or override the aw effect. These results, and others generated in this project, are important in helping the industry understand critical process and product variables that must be quantified and monitored to ensure reliable process validations and safe products. Lastly, these and other findings were included in a publicly-available database of low-moisture inactivation data, in a nationally attended webinar, and in an in-person, hands-on workshop serving practicing professionals responsible for this type of work in industry. OBJECTIVE 1: The effects of inoculation methodologies on stability and thermal resistance of Salmonella in wheat flour, and the repeatability of those results, were quantified via a cross-laboratory (MSU and WSU) study. Inoculation method impacted repeatability, population stability, and inactivation kinetics (α=0.05), regardless of laboratory, demonstrating the importance of thoroughly documenting (and standardizing) methods used in pathogen inactivation studies. The relationships between aw, temperature, product characteristics, and Salmonella thermal resistance also were quantified in collaborative tests between MSU and WSU. Analyses of new and prior data demonstrated that the relationship between Salmonella D-values and aw varied significantly among products. An improved understanding of temperature-induced changes in aw of low-moisture products is critical in designing and validating pasteurization processes. In another study, two primary models and three secondary models were compared for predicting the impact of aw and temperature on Salmonella thermal inactivation in wheat flour. In all cases, the incorporation of an aw term was essential for accurate lethality predictions. The inactivation of Salmonella in wheat flour subjected to alternative technologies also was quantified in lab-scale tests. Isothermal inactivation kinetics study showed a more conservative inactivation rate than radiofrequency-assisted heat treatments (RFHT), meaning that the kinetic parameters may be used as guidelines to design RFHT process conditions. In a low-energy X-ray study (wheat kernels, meal, and flour), product characteristics were shown to affect X-ray inactivation of Salmonella in low-moisture products, which is important to consider in developing future novel processes. OBJECTIVE 2: In the area of radio-frequency (RF) heating, results addressed basic heating behaviors and strategies for improving heating uniformity, a key factor in scaling-up to commercial applications. Results indicated that heating rate can be predicted by mathematical modeling, with varying dielectric properties in a large range and various RF conditions. Subsequently, a new strategy to improve RF heating uniformity in low-moisture foods for pathogen control was demonstrated. Polyetherimide (PEI) cylindrical blocks on the top and bottom of peanut butter samples in a cylindrical jar were evaluated to improve RF heating uniformity; a computer simulation was developed and tested; a new temperature uniformity index was proposed to evaluate pasteurization process heating uniformity; and experimental validation tests were conducted. PEI assistance reduced temperature differences and has potential as a pasteurization intervention for low-moisture foods after process optimization by industry. In the area of thermal processing, the impacts of dynamic heating/moisture-changing conditions were evaluated for thermal processing of wheat flour and almond kernels. Salmonella in rapidly desiccated flour had the same thermal resistance as that which previously had been equilibrated to 0.3 aw over a week, and Salmonella in rapidly hydrated flour had the same thermal resistance as that in flour previously equilibrated to 0.6 aw over a week. The results suggest that response period to new aw is negligible, which is critically important in applying thermal resistance data or parameters to industrial pasteurization validations. In the case of almond processing, Salmonella-inoculated almonds were equilibrated to ~0.25, 0.5, or 0.7 aw and subjected to high-velocity, dry-air heating approximating commercial roasting conditions. Although aw is known to significantly affect Salmonella thermal resistance, aw did not significantly affect endpoint lethality in this process. These results show that it is possible for process conditions (i.e., temperature, humidity, and air velocity) to essentially override the aw effect on thermal resistance. This is extremely important in providing guidance to the industry and regulators, regarding critical factors to monitor and control in validating pasteurization processes. OBJECTIVE 3: The outreach and training component of this project entailed direct translation of research results, dissemination of a low-moisture inactivation database, webinar-based training, and an in-person workshop offered via the International Association for Food Protection (IAFP). The project PD gave presentations of project activities at three different meetings of the Low-Moisture Food Safety Task Force within the Institute for Food Safety and Health (IFSH), in partnership with an FDA collaborator. This group, comprised of ~80 individual representing the low-moisture food industry, also provided input on project priorities. In terms of the database, over 1,400 individual inactivation datasets have been collected from ~50 published studies and publicly disseminated (www.egr.msu.edu/~marksbp/drydata) to provide a repository for stakeholder access. A meta-analysis of these data demonstrated that the Weibull model generally was the preferred primary model; however, careful consideration is required for the development or application of secondary models for dynamic processes. An in-person workshop (Validating Pasteurization Processes for Low-Water Activity Products) was conducted as an IAFP pre-meeting event in 2014. The workshop presenters included the project PD and industry and FDA collaborators. Over 50 attendees represented all sectors of the low-moisture industry (e.g., nuts, cereal products, confectionary, baked goods, pet foods, spices, etc.), with 92% reporting medium, high, or very-high responsibility level for process validations. Content encompassed regulatory considerations, validation guidelines, model utilization, non-pathogenic surrogates, and statistical uncertainty. The workshop was designed to achieve six objectives with 26 learning outcomes. In surveys asking how well the workshop achieved the stated outcomes and provided useful content, 98% of the attendees responded "good" to "excellent," with a mean score of 4.2 on a 5-point scale. Overall, the workshop was extremely successful in reaching and positively impacting the primary target audience for this project - individuals responsible for designing and validating pasteurization processes.
Publications
- 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:
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.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Jiao Y, Shi H, Tang J, Li F, Wang S. 2015. Improvement of radio frequency (RF) heating uniformity on low moisture foods with Polyetherimide (PEI) blocks. Food Research International. 74:106-114.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2016
Citation:
Hildebrandt IM, Marks BP, Ryser ET, Villa-Rojas R, Tang J, Garces-Vega FJ, Buchholz SE. 2016. Effects of inoculation procedures on variability and repeatability of thermal resistance of Salmonella in wheat flour. Journal of Food Protection. Submitted.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2016
Citation:
Smith DF, Hildebrandt IM, Casulli KE, Dolan KD, Marks BP. 2016. Modeling the effect of temperature and water activity on the thermal resistance of Salmonella Enteritidis PT30 in wheat flour. Journal of Food Protection. Submitted.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2016
Citation:
Syamaladevi RM, Tadapaneni RK, Xu J, Villa-Rojas R, Tang J, Carter B, Sablani SS, Marks B. 2016. Relationship between water activity variation at elevated temperatures and thermal resistance of Salmonella in selected low-moisture foods. Food Research International. Submitted.
- Type:
Journal Articles
Status:
Under Review
Year Published:
2016
Citation:
Jeong S, Marks BP, James MK. 2016. Comparing thermal process validation methods for Salmonella inactivation on almonds. Journal of Food Protection. Reviewed, resubmission pending.
- 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 Enteritidis PT 30 in wheat flour. Journal of Food Protection. 78:281-286.
|
Progress 09/01/13 to 08/31/14
Outputs
Target Audience:The target audiences for this project are: (1) individuals who are responsible for designing, validating, and documenting the safety of pasteurization processes for low-moisture foods (in industry or regulatory roles), but who lack specific formal education or training specifically aimed at this unique challenge, and (2) corporations that manufacture low-moisture food products or pasteurization equipment designed for these products. The results from this project will improve the ability of these groups to ensure the safety of low-moisture food products, by providing training resources, scientific data, and tools that uniquely support the needs of these professionals and the low-moisture food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The entire research team (including ~5 undergraduates, and 7 graduate students) 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 nationally broadcast webinar, (4) A half-day meeting with FDA personnel in Chicago, (5) A presentation at the Low-Moisture Task Force pre-meeting at the IFSH annual meeting in Chicago, and (6) A full-day, onsite pre-meeting at the 2014 IAFP Annual Meeting. What do you plan to do during the next reporting period to accomplish the goals?For objective 1, additional dynamic moisture thermal inactivation trials will be conducted with the remaining product categories, including pastes. Additionally, parallel tests will be conducted with the same products equilibrated to multiple water activities and subjected to x-ray and RF treatments. All of the resulting data will be used to test multiple alternative secondary models for incorporating water effects (i.e., product water activity and/or process humidity) into Salmonella inactivation models. For objective 2, additional tests will be conducted to quantify the impact of RF processes on heating uniformity and lethality outcomes, and to quantify the impact of thermal process conditions on the relative importance of product water activity on Salmonella thermal resistance. For objective 3, the results of the onsite workshop will be analyzed. Additionally, a needs assessment will be conducted (via industry partners in the Low-Moisture Task Force of the Institute for Food Safety and Health) to identify remaining gaps in knowledge and tools needed to improve the ability of the industry to validate low-moisture pasteurization processes.
Impacts
What was accomplished under these goals?
Overall, this collaborative project continues to focus on enhancing the ability of the low-moisture food industry to design, analyze, and validate pasteurization processes. This entails improving the understanding of how low-moisture product characteristics, particularly water activity (aw), impacts resistance of Salmonella to lethal treatments. Results from these studies are advancing approaches to modeling Salmonella inactivation and improving the use of such models for process validation. Project results are being translated via a publicly-available databased, webinars, talks with industry stakeholder groups, and an in-person all-day workshop on low-moisture pasteurization validation methods. Within each of the various project objectives, a few key example accomplishments are highlighted below. OBJECTIVE 1: The effects of inoculation methodologies on stability and thermal resistance of Salmonella in wheat flour, and the repeatability of those results, were quantified via a cross-laboratory (MSU and WSU) study. The experimental design consisted of a cross-laboratory comparison (MSU and WSU), both conducting isothermal Salmonella inactivation studies in wheat flour (~0.45 aw, 80°C), utilizing five different inoculation methods: (A) high-concentration, low liquid volume (HCLV) broth culture, (B) HCLV lawn culture, (C) pelletized lawn culture, (D) direct harvest of lawn culture with wheat flour, and (E) fomite transfer of a lawn culture. Inoculated wheat flour was equilibrated ~5 days to ~0.45 aw, and then subjected to isothermal treatment (80ºC) in aluminum test cells in a water bath. Results indicated that inoculation method impacted repeatability, population stability, and inactivation kinetics (α=0.05), regardless of laboratory. Salmonella inoculated with methods A and E exhibited instability during equilibration. Lawn-based cultures resulted in stable populations prior to thermal treatment; however, method D yielded different D-values across the two laboratories (α=0.05), which was attributed to a larger potential impact of operator variability on this method. Methods B and C yielded stable inoculation levels and repeatable D-values of ~250 and ~285 s, respectively. Overall, the results demonstrate that inoculation methods have a significant effect on Salmonella population kinetics and the subsequent interpretation of isothermal inactivation experiments in low-moisture foods, which reinforces the critical importance of thoroughly documenting (and standardizing) methods used in pathogen inactivation studies. OBJECTIVE 2: In a test of dynamic thermal/moisture process conditions, 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. After inoculation, two static moisture groups were equilibrated to 0.3 and 0.6 aw over 4-7 days, and two dynamic moisture groups then were rapidly (< 4 min) desiccated from 0.6 to 0.3 aw or hydrated from 0.3 to 0.6 aw. Samples then were subjected to isothermal (80°C) heat treatments, 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. OBJECTIVE 3: In terms of webinar-based outreach, project PD Marks presented a portion of a 2014 webinar entitled "Tools for Validating Key Components of a Low-Moisture Food Safety Plan." The webinar had >400 registrants, with 174 live attendees, which was the largest webinar hosted by the sponsor (Food Eng. magazine) in recent years, indicating a high demand for training in this area. In evaluations, 100% of the attendees responded that they had learned something new, with very high scores for usefulness and effectiveness. Additionally, an in-person workshop (Validating Pasteurization Processes for Low-Water Activity Products) was conducted as an IAFP pre-meeting event in August 2014. The workshop presenters included the project PD and industry and FDA collaborators. Over 50 attendees represented all sectors of the low-moisture industry (e.g., nuts, cereal products, confectionary, baked goods, pet foods, spices, etc.), with 92% reporting medium, high, or very-high responsibility level for process validations. Content encompassed regulatory considerations, validation guidelines, model utilization, non-pathogenic surrogates, and statistical uncertainty. The outcomes are currently being evaluated.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Jiao Y, Tang J, Wang S. 2014. A new strategy to improve heating uniformity of low moisture foods in radio frequency treatment for pathogen control. Journal of Food Engineering. 141: 128-138.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Jiao Y, Tang J, Wang S, Koral T. 2014. Influence of dielectric properties on the heating rate in free-running oscillator radio frequency systems. Journal of Food Engineering, 120: 197-203.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Villa-Rojas R, Tang J, Wang S, Gao M, Kang D-H, Mah J-H, Gray P, Sosa-Morales ME, Lopez-Malo A. 2013. Thermal inactivation of Salmonella Enteritidis PT 30 in almond kernels as influenced by water activity. Journal of Food Protection, 76(1): 26-32.
- 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:
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:
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:
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:
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.
|
Progress 09/01/12 to 08/31/13
Outputs
Target Audience: The target audiences for this project are: (1) individuals who are responsible for designing, validating, and documenting the safety of pasteurization processes for low-moisture foods (in industry or regulatory roles), but who lack specific formal education or training specifically aimed at this unique challenge, and (2) corporations that manufacture low-moisture food products or pasteurization equipment designed for these products. The results from this project will improve the ability of these groups to ensure the safety of low-moisture food products, by providing training resources, scientific data, and tools that uniquely support the needs of these professionals and the low-moisture food industry. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The entire research team (including ~4 undergraduates, and 3 graduate students) 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: (1) additional experiments to quantify the rate of change in Salmonella thermal resistance when subjected to rapidly changing moisture conditions, (2) further development and testing of modified secondary inactivation models accounting for product and process moisture, (3) development of specific training materials to be used for the 2014 IAFP pre-meeting workshop, and (4) pre- and post-assessment of the knowledge and behaviors of individuals attending the workshop. For objective 1, additional dynamic moisture thermal inactivation trials will be conducted with the remaining product categories, including pastes. Additionally, parallel tests will be conducted with the same products equilibrated to multiple water activities and subjected to x-ray and RF treatments. All of the resulting data will be used to test multiple alternative secondary models for incorporating water effects (i.e., product water activity and/or process humidity) into Salmonella inactivation models. For objective 2, pilot-scale inoculated challenge studies will be initiated. The first trials will focus on thermal pasteurization of particulates (i.e., almonds) at different initial water activities and dynamic process conditions. For objective 3, detailed training resources will be developed for the pending workshop. A pre-assessment instrument will be developed, tested, and administered to the workshop participants. Three post-assessments will be developed, tested, and administered – testing reaction to the training at one point (immediately after the workshop), knowledge at three times (at the end of the workshop, one-month post-workshop, and six months post-workshop), and assessing impact on behaviors one and six months post-workshop.
Impacts
What was accomplished under these goals?
Microbial contamination of low-moisture foods and ingredients is an emerging and particularly vexing food safety challenge, as reflected in recent nationwide Salmonella outbreaks and/or recalls involving a diverse set of such products. Unfortunately, even the best hygiene practices cannot sufficiently ensure the safety of dry foods; therefore, processing interventions are urgently needed to reduce the risk of Salmonella in final products, particularly given pending rules pertaining to the Food Safety Modernization Act. To meet this challenge, this project is using a multidisciplinary, integrated approach to generate data, knowledge, and tools needed by the industry, and to put those resources directly in the hands of the professionals who bear the responsibility for process validations. The overall project entails: (1) bench-scale inactivation trials with Salmonella on three classes of products (powders, large particulates, and pastes) habituated to a range of water activities and subjected to multiple intervention processes (fluid-based heating, radio frequency energy, and low-energy X-ray), (2) development of novel inactivation models, (3) pilot-scale validation trials, and (4) development, delivery, and assessment of training programs in venues selected to specifically reach professionals responsible for validating interventions for low-moisture foods, but who generally lack information and tools needed to meet this specific challenge. Several specific activities/studies have been completed or initiated in these areas over the past year, with several examples highlighted below. Overall, these activities and accomplishments involve direct interactions (e.g., virtual team meetings, sample sharing, culture sharing, custom equipment fabrication and sharing) amongst the core project team (i.e., Michigan State University and Washington State University) and close collaborations with the project partners (i.e., the FDA/IFSH, the Product Safety Solutions Group, and Decagon Devices, Inc.) One completed study during the past year quantified the effect of initial and dynamic product water activity on the thermal inactivation rate of Enterococcus faecium (a non-pathogenic surrogate for Salmonella) and Salmonella Enteritidis PT30 inoculated on the surface of almonds subjected to dry air heating, and the predictive ability of a modified thermal inactivation model. Almonds were inoculated (~108 CFU/g), equilibrated to three water activities (~0.35, 0.55, 0.85), heated in a computer controlled oven (149oC dry air, ~11oC dew point) for 0 to 15 min (1 min intervals; triplicate runs), then immediately cooled in peptone water (~4oC), and plated to enumerate survivors. A previously published, modified inactivation model, accounting for process dew point, was used to predict inactivation based on measured almond surface temperature and process dew point. Given the dry heat environment, the water activity of all samples asymptotically approached a minimum value (~0.10) during heating, and the dynamic water activity was included when developing a preliminary alternative secondary model. The accuracy of the model prediction was reasonably good (RMSE < 0.6 log), and the addition of a water activity term (in addition to the process humidity terms) improved model accuracy. These results indicate that model-based validations of thermal pasteurization processes can be improved by incorporating both process humidity and product water activity into thermal inactivation models. However, a significant limitation involves the capability of measuring or monitoring product activity real-time in commercial processes. Given the critical importance of water activity to this project, another study within this project has begun to quantify the effect of elevated temperatures, above 100ºC, on the water activity of low-moisture powders (e.g., wheat flour) and pastes (e.g., peanut butter). Very few data exist in this domain, because of experimental challenges impeding such measurements. As a result, the water activity of food products used in research or process validations typically is quantified in a laboratory, at room temperature. However, given the results on dynamic water activity mentioned above, it is critically important that process validation methods accurately account for this key product property at the temperatures relevant to the actual commercial process. Consequently, two approaches have been implemented in parallel. First, a custom-built water activity system has been developed, which is capable of measuring water activity at temperatures above 100ºC. Data have been collected, and shared with collaborators, demonstrating that the relationship between temperature and water activity at these elevated temperatures, for high-fat, low-moisture products, is the opposite of that typically reported at lower temperatures. This is important, because these results might partially explain the previously reported protective effect of fat in bacterial inactivation, in terms of both physicochemical changes and biological factors. The second approach to this challenge has been via a partnership with a corporate collaborator that is a supplier of water activity meters, which is testing a modified meter at elevated temperatures. Ultimately, these results will be a critical piece of integrating water-dependent inactivation models into process analyses and validations for low-moisture food safety. Additional work in the past year has been directed at the training objective of the project. In one area, the project director and two graduate students have been directly involved with the Product Safety Solutions Group, a consortium (supported by PMMI and GMA) of companies that produce low-moisture food products. This collaboration has entailed multiple web-based meetings and one on-site meeting, in which the PD has communicated the project results the industry practitioners, and collected feedback on industry needs. One outcome of this collaboration has been the initiation of a database component of the overall project, in which a database has been constructed for compilation of all available inactivation data and parameters for Salmonella in low-moisture food products. Data have been solicited from the original sources (i.e., corresponding authors of previously published studies), and are being compiled in a format consistent with ComBase (www.combase.cc), a publicly-available database of microbial response data in foods. These data will be contributed to ComBase and separately published as a freely available data source for low-moisture food stakeholders, which will be a significant contribution to equipping the industry for improved process validations. Additionally, the PD and FDA partners have co-developed a one-day workshop entitled “Validating Pasteurization Processes for Low Water Activity Products,” which will be offered as a pre-meeting workshop at the 2014 Annual Meeting of the International Association for Food Protection (IAFP), and which will target industry personnel responsible for low-moisture process validations.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Smith D, Hildebrandt I, Marks B. 2013. Meta-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:
Conference Papers and Presentations
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:
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.
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Progress 09/01/11 to 08/31/12
Outputs
OUTPUTS: This is the first annual report for this project. As planned, the first year has focused on bench-scale inactivation trials at two sites (Michigan State University and Washington State University), initial model development, and outreach/training planning. In the first case, isothermal inactivation trials (WSU) focused on Salmonella in ground almond powder, and non-isothermal inactivation trials (MSU) focused on almonds and the impact of initial water activity and process humidity on the resulting Salmonella inactivation. Current tests are quantifying the relationship between the rate of moisture loss and bacterial adaptation during thermal pasteurization processes. Additionally, bench-scale experiments and modeling began for quantifying the effects of low-moisture product properties (peanut butter) on dielectric heating processes (WSU) and low-energy x-ray treatments (MSU). For future, larger-scale trials, a custom moisture equilibration system has been designed and built (MSU) to enable equilibration of larger (on the order of multiple kg) Salmonella-inoculated samples of almonds and flour to be shared across multiple tests within the project team. In terms of outreach activities, the PI has been actively engaged with the key industry partner, the Product Safety Solutions Group, which is a GMA/PMMI-affiliated group of industry practitioners in the area of low-moisture food safety. In this capacity, the PI has given one presentation, participated in more than six virtual group meetings, and contributed to planning discussions associated with a webinar series and future outreach activities aimed at helping industry implement improved practices for validating low-moisture food pasteurization processes. 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 (MSU) - 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 (MSU) - co-PI. Supervising the overall microbiological testing conducted as part of the inoculated challenge studies, including method development and validation. Sanghyup Jeong (MSU) - 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 (MSU) - laboratory manager. Supervising undergraduate students working on the experimental microbiology activities on this project (sample prep, media prep, enumeration, etc.). Michael James (MSU) - BSL-2 pilot plant manager. Setting-up and managing pilot-scale, inoculated challenge studies in the biosafety level-2 pilot processing facility. Pichamon Limcharoenchat (MSU), Ph.D. student. Running bench-scale trials evaluating the impact of changing water activity on bacterial resistance during non-isothermal heating processes. Juming Tang (WSU) - co-PI. Managed overall WSU portion of project, including work planning, reporting, etc. Shaojing Wang (WSU) - co-PI. Managing RF component of projct. Rossanna Villa-Rojas (WSU), Ph.D. student. Working on thermal inactivation trials. Yang Jiao (WSU), Ph.D. student. Working on radio-frequency treatments. Four undergraduate students (MSU, biosystems engineering, food science, microbiology) 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 pasteurization processes for low-moisture foods. 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
The thermal inactivation work to date has confirmed the significant effect of product water activity on the thermal resistance of Salmonella on almonds and powders. In the case of isothermal heat treatments (WSU), a Weibull model was used to describe the inactivation results. In non-isothermal heat treatments, a modified thermal inactivation model (MSU), 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. In terms of the dielectric heating work, both dielectric constant and loss factor showed an evident increasing trend with increasing moisture content and temperature, and decreasing frequency. Samples with higher moisture content (10, 16, and 22% wb) were more sensitive to temperature changes than those with low moisture content (1.3 and 4% wb). Power penetration depths were calculated at several representative frequencies, which decreased with increasing moisture content, frequency, and temperature. Overall, the project is progressing as planned, and work in the coming year will focus on cross-validation of bench- and pilot-scale inactivation results, model development and validation, and execution of outreach training activities.
Publications
- 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.
- 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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