Progress 07/01/03 to 06/30/08
Outputs
OUTPUTS: Listeria monocytogenes is a gram-positive pathogen frequently involved in outbreaks of foodborne disease. The natural (generally recognized as safe) and inexpensive qualities of lysozyme make it a widely used food preservative for controlling foodborne pathogens. However, its efficacy against pathogens may be reduced by the undesirable interactions with food components and non-target bacteria. Nanoparticles functionalized with pathogen-specific antibodies (immunonanoparticles) may serve as a carrier of natural antimicrobials to target the specific pathogen and improve the stability of antimicrobials in foods. The objective of this research was to study the antimicrobial activity of lysozyme absorbed on immunonanoparticles against L. monocytogenes Scott A. Polystyrene nanoparticles with active carboxyl groups were conjugated with anti-L. monocytogenes through covalent bounding. Immunonanoparticles were then coated with lysozyme by direct adsorption. The antimicrobial activity of lysozyme adsorbed on immunonanoparticles was compared to that of free lysozyme in phosphate buffered saline. Several factors, such as the amount of anti-L. monocytogenes and lysozyme, and the adsorption time, were optimized for the most efficient inhibition. A modified Lowry method was used to quantify the lysozyme adsorbed on immunonanoparticles. Nanoparticles were conjugated with 0.04 ug anti-L. monocytogenes per ml, and at that concentration, immunonanoparticles demonstrated enhanced antimicrobial activities of lysozyme. Lysozyme 350 ug adsorbed on immunonanoparticles reduced the L. monocytogenes Scott A population from 5.2 log CFU/ml to below the detection limit in 3 h. However, when free lysozyme 500 ug/ml was used, ca. 2.2 log CFU/ml of the L. monocytogenes Scott A remained culturable after 5 h treatment. Our study revealed that the use of immunonanoparticles coated with lysozyme is a more efficient method than direct addition of lysozyme in inhibiting L. monocytogenes. Antimicrobial coatings were developed using gelatin and commercial nisin mixtures. In the liquid system, all square nisin films showed 3 log reduction by one hour except control. At 4 hours, there was no detected L. monocytogenes in the peptone solution containing 4.5mg, 9.2mg, 16.3mg and 24.4mg of nisin. At 6 and 8 hours, every nisin film inhibited L. monocytogenes completely. In the solid system, each circular nisin films included 0.04mg, 0.09mg, 0.16mg and 0.23mg of nisin showed positive effect against L. monocytogenes. However, the activity of 0.04mg circular nisin film was very weak compared to other positive films. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The objective of this research was the development of active films to enhance the safety and quality of food. Peer reviewed publications, trade journal articles, book chapters and presentation have contributed to the goals of this project.
Publications
- Mangalassary, S., I. Han, and P. Dawson. 2005. Effect of nisin carry over into the plating medium on Listeria monocytogenes enumeration and efficacy of chymotrypsin for inactivation of nisin on ready-to-eat meat surfaces. Poultry Science Association Meeting, Auburn University, Auburn, AL.
- Dawson, Paul L., Lina Ramirez-Lopez, and Inyee Han,. 2006.Thermal Process Preliminary Calculations: Enumeration of Thermally Resistant Bacteria in Raw Rendering Materials, Animal Co-Products Research Conference, Clemson University
- Crane, E., B. Ballieu, K. Horm, H. Johnson, A. Spokowski, J. Trevino, R. Yost, P. Dawson. 2006. The Effect of Cleaning on Survival of E. coli on Common Food Preparation Surfaces. Focus on Creative Inquiry, April 2006, Clemson University.
- Min, B.J., I.Y. Han and P.L. Dawson. 2006 Effects of antimicrobial edible films against Listeria monocytogenes in a liquid and solid system. Institute of Food Technologists Meeting in Orlando, FL.
- Mangalassary, Sunil, Inyee Han, and Paul Dawson. 2006. Carry-over effect of nisin in antimicrobial treatment of ready-to-eat meat. Institute of Food Technologists Meeting in Orlando, FL.
- Crane, E., B. Ballieu, K. Horm, H. Johnson, A. Spokowski, J. Trevino, R. Yost, P. Dawson. 2006. The Effect of Cleaning on Survival of E. coli on Common Food Preparation Surfaces. Institute of Food Technologists Meeting in Orlando, FL. 6/2006/
- Dawson, P.L., Acton, J.C., Han, I.Y., and Dhananjayan, R. 2007. CO2 injection during grinding maintains color quality and retards microbial growth in ground turkey breast meat. CIGR Section VI International Symposium on FOOD AND AGRICULTURAL PRODUCTS: PROCESSING AND INNOVATIONS, Naples, Italy. 24-26 September 2007.
- Acton, J.C, Dawson, P.L. Kalleda, R.K., Han, I.Y., Toler, J.E., Chen, F. and Kim, H.J. 2008. Shelf life extension of shrimp (white) using modified atmosphere packaging. 59th Pacific Fisheries Technologist Meeting. February 3-6, 2008 Hotel Whitcomb, San Francisco, California USA
- Greene, A.K., P. L. Dawson, editors A.K. Greene, P.L. Dawson, D. Nixon, and J.R. Atkins. 2005. Safety of Animal Fats for Biodiesel Production: A Critical Review of Literature. Published by Advanced Technologies for Fuels Canada. Mr. Rodney Semotiuk, President & CEO, ATF Advanced Technologies and Fuels Canada, Inc., 80 Aberdeen Street, Suite 400, Ottawa, ON K1S 5R5.
- Dawson, P.L. 2005. Post Processing Treatments for Ready-to-Eat Meats: High Pressure and Surface Thermal Processing. Symposium manuscript based on presentation given at the USDA Food Safety Conference, Myrtle Beach, SC. Journal of the Association of Food and Drug Officials. (AFDO) 69(4): 9-21.
- Seydim, A., Guzel-Seydim, Z., Acton, J.C., and Dawson, P.L. 2006. Effects of Rosemary Extract and Sodium Lactate on Quality of Vacuum Packaged Ground Ostrich Meat. J. Food Science 71(1): S71-S76.
- Seydim, A.C., Acton, J.C., Hall, M.S., and Dawson, P.L. 2006. Effects of packaging atmospheres on shelf-life quality of ground ostrich meat. Meat Science 73(3): 503-510
- Antony, S., J.R. Rieck, J.C. Acton, I.Y. Han, E.L. Halpin, and P.L. Dawson. 2006. Effect of dry honey on the shelf life of packaged turkey roll slices. Poultry Science 85:1811-1820
- Min, B.J., I.Y. Han and P.L. Dawson. 2005. Antibacterial Effect of Nisin-adsorbed Silica and Corn Starch Powder against Listeria monocytogenes, International Association of Food Protection Meeting in Baltimore, MD, 9/2005.
- Chen, Anita, Sunil Mangalassary, Inyee.Y. Han, and Paul L.Dawson. 2005. Eliminating Listeria monocytogenes in packaged, ready to eat (RTE) turkey bologna by combining in-package pasteurization with antimicrobial agents. Governors School for Science and Mathematics Research Forum.
- Ellis,M; Cooksey,-K; Dawson,-P; Han,-I; Vergano,-P, 2006. Quality of fresh chicken breasts using a combination of modified atmosphere packaging and chlorine dioxide sachets. Journal of Food Protection. 69(8): 1991-1996.
- Min, B.J., Dawson, P.L. and Shetty, K. 2005. Antioxidant and bioactive films to enhance food quality and phytochemical production during ripening. Korean Journal of Food Science and Animal Resources. 25:60-65.
- Dhananjayan, R., I.Y. Han, J.C. Acton, and P.L. Dawson. 2006. Growth depth effects of bacteria on ground turkey meat patties subjected to high carbon dioxide or high oxygen atmosphere. Poultry Science 85:1821-1828.
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Progress 01/01/07 to 12/31/07
Outputs
The reduction of overall pathogen load in meat was addressed both in handling of poultry offal some of which returns to the food chain as meal for chicken feed and in the preparation of ready-to-eat meat products. Working through the industry-funded Animal Co-Products Research and Education Center, thermally-resistant bacteria isolated from raw poultry offal were evaluated for their resistance to inactivation. Ready-to-eat meat products were treated with in-package pasteurization coupled with antimicrobials to inactivate Listeria monocytogenes.
Impacts
Thermal inactivation of bacteria in raw poultry offal (SC) Raw poultry offal was recovered from a poultry processing plant and separate samples were subjected to increasingly more severe heat treatments after which samples were plated on BHI. Isolated cells were recovered from the highest temperature (most severe heat) treatment and subjected to thermal inactivation studies. Staining of cells revealed the presence of spores which were subsequently found to be aerobic in nature. A heat resistant isolate was subjected to thermal inactivation tests and three statistical models were used to predict the inactivation pattern. Heat inactivation of Listeria on RTE meats (SC, NC) The objective of this study was to evaluate the effect of nisin and/or lysozyme in combination with in-package pasteurization of a ready-to-eat (RTE) low fat turkey bologna on the inactivation of L. monocytogenes. Sterile bologna samples were initially treated with solutions of nisin (2mg/ml = 5000
AU/ml = 31.25 AU/cm2), lysozyme (10mg/ml = 80 AU/ml = 0.5 AU/cm2), and a mixture of nisin and lysozyme (2mg nisin + 10 mg lysozyme/ml = 31.75AU/cm2). Bologna surfaces were uniformly inoculated with a Listeria suspension resulting in a population of ~ 0.5 log CFU/cm2. Samples were vacuum-packaged and subjected to heat treatment (60, 62.5 or 65C). Two non-linear models (Weibull and log-logistic) were used to analyze the data and then from the model parameters, the time needed to achieve a 4 log reduction was calculated. Nisin-lysozyme combination and nisin treatments were effective in reducing the time required for 4 log reductions at 62.5 and 65C, but not at 60C. At 62.5C, nisin-lysozyme treatment required 23% less time than the control sample to achieve a 4 log reduction and 31% less time at 65C. Lysozyme alone did not show enhanced antilisterial activity with heat. Results from this study can be useful to the industry in developing an efficient intervention strategy against
contamination of RTE meat products by L. monocytogenes.
Publications
- Dawson, P.L., Cooksey, K., and Mangalassary, S. 2008. Environmentally-friendly meat packaging. In Environmentally-friendly packaging for food. Editor, Chiellini, C. Woodhead Publishing Limited. Cambridge, England.
- Dawson, P.L., S. Mangalassary, and B.W. Sheldon, 2007. Thermal Processing of Poultry Products. In: Thermal Food Processing: New Technologies and Quality Issues. D. Sun, ed. CRC Press, Boca Raton, FL (Ch. 7, p. 197-233).
- Dawson, P.L. 2006. Avian Influenza. World Food Logistics Organization and International Association of Refrigerated Warehousemen. Orlando, FL.
- D. Thorpe, BJ. Min, I.Y. Han, and P. Dawson. 2006. Testing Tea Tree Oil as an Antibiotic Agent in Gelatin Films. Summer Research Eureka Program, Clemson University.
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Progress 01/01/06 to 12/31/06
Outputs
Project 1 In-package pasteurization effects to inhibit Listeria monocytogenes on ready-to-eat meats. Thickness effects The surface heating rate and final surface temperature during in-package pasteurization were determined for different thickness levels of two types of bologna having different 13% and 18% fat content. Three different thickness levels 4, 12, and 20 mm corresponding to 1, 3, and 5 slices of bologna were each vacuum-packaged separately in a clear polymer pouch after placing thermocouples on the surface. Refrigerated samples were immersed into a water bath set to one of four pre-determined temperatures 60, 70, 80, and 90 C and time and temperature data were recorded for 10 min. Surface- heating rate was fastest in the thinnest 4 mm and slowest in the thickest 20mm samples for all four pasteurization temperatures. Surface- heating rate was slower in bologna with higher fat content compared to lower fat bologna. Final surface temperature attained after 3
min was lower with increased thickness levels for all pasteurization temperatures. Thus meat sample thickness and fat content significantly affect surface heating rate and final surface temperature during in-package pasteurization of bologna. Project 2 Nisin carry-over into the enumeration media Concern as to the effect of antimicrobial carry-over into the enumeration media has been expressed in clinical and food-related studies since this can affect the resulting predicted populations of bacteria exposed to inactivation experiments. The objective of this study was to evaluate the carry over effect of nisin on the survival of Listeria monocytogenes and to study the efficacy of α-chymotrypsin for inactivation of nisin on ready to eat low fat turkey bologna. In the current study, the enumerating media was dosed with 0 to 1000 AU/ml of nisin and 4.5 AU/ml was found to be the critical level for nisin activity in the media to affect L. monocytogenes growth. Furthermore,
α-chymotrypsin was found to be effective in inactivating nisin against L. monocytogenes while not affecting bacterial growth in the medium.
Impacts
Quantitating the synergism between pasteurization and antimicrobials in ready-to-eat meat will assist the meat industry in reducing the incidence of L. monocytogenes in these products. Also, determination of the heat-inactivation models will allow a clearer understanding the patterns of how these bacteria are destroyed by heat will result in better treatments to ensure consumer safety.
Publications
- Dawson, P.L., Mangalassary, S., and Sheldon, B.W. 2005. Thermal Processing of Poultry Products. In Thermal Food Processing: Modeling, Quality assurance, and Innovations. Da-Wen Sun, Editor. Marcel Dekker, NY.
- Min, B.J., I.Y. Han and P.L. Dawson. 2006. Effects of antimicrobial edible films against Listeria monocytogenes in a liquid and solid system. Institute of Food Technologists Meeting in Orlando, FL. 6/2006/
- Mangalassary, S., Inyee Han, and Paul Dawson. Carry-over effect of nisin in antimicrobial treatment of ready-to-eat meat. 2006. Institute of Food Technologists Meeting in Orlando, FL. 6/2006/
- Dawson, P.L. and Spinelli, N. 2005. Poultry Flavors. In Food Flavor. Feng Chen, Editor, Wadsworth Publishing.
- Antony, S., J.R. Rieck, J.C. Acton, I.Y. Han, E.L. Halpin, and P.L. Dawson. 2006. Effect of dry honey on the shelf life of packaged turkey roll slices. Poultry Science (85 1821-1828).
- Dhananjayan, R., I.Y. Han J.C. Acton and P.L. Dawson. 2006. Growth depth effects of bacteria on ground turkey meat patties subjected to high carbon dioxide or high oxygen atmosphere. Poultry Science (85:1811-1820)
- Dawson, P.L, Lina Ramirez-Lopez, and Inyee Han,. 2006. Thermal Process Preliminary Calculations Enumeration of Thermally Resistant Bacteria in Raw Rendering Materials, Animal Co-Products Research Conference, Clemson University 4/2006.
- Crane, E., B. Ballieu, K. Horm, H. Johnson, A. Spokowski, J. Trevino, R. Yost, P. Dawson. 2006. The Effect of Cleaning on Survival of E. coli on Common Food Preparation Surfaces Focus on Creative Inquiry, April 2006, Clemson University.
- Crane, E., B. Ballieu, K. Horm, H. Johnson, A. Spokowski, J. Trevino, R. Yost, P. Dawson. 2006. The Effect of Cleaning on Survival of E. coli on Common Food Preparation Surfaces. Institute of Food Technologists Meeting in Orlando, FL. 6/2006/
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Progress 01/01/05 to 12/31/05
Outputs
Different concentrations of lysozyme (1.25, 2.5,5 and 10 mg/ml) into the plating medium after initial serial dilution techniques were made to act directly on the organism then plated for enumeration. The concentrations used did not cause any reduction in Listeria indicating that only a very high initial lysozyme concentration would cause in a carry over effect. Bologna samples were subjected to 3 treatments, - control (no antimicrobial agent, only organism), nisin (500 IU/ml), and lysozyme (100mg/ml) and then inoculated. Meat samples were then vacuum-packaged. Thermal processing of the bologna samples were carried out in a water bath pre-set (65 and 60C were used in this study). Meat surface temperature was measured using K type Teflon insulated thermocouples oriented on the meat surface inside the vacuum bag. All samples were submerged in the hot water bath simultaneously and were removed at timed intervals after the target temperature was reached. Each sample was
subsequently homogenized and plated after serial dilution. Plates were incubated at 37C for 48 h before enumerating colonies. D values were determined from the linear portion of the survivor plots using linear regression analysis. The z- values were determined by constructing decimal reduction time curves (mean log D-values versus temperature) and then taking the inverse slope of the curve. Antimicrobial film preparation Each film was made by casting method. Gelatin was used as a carrier and glycerol was used as a plasticizer. Gelatin and glycerol were dissolved in boiling water. To remove the heat denaturation of antimicrobials at high temperature, antimicrobial was mixed at lower temperature. Nisin (Nisaplin) and Guardian (CS-150) were used as a antimicrobials in this study. The antimicrobial mixture was cast and dried on the plate (25cmx25cm) at room temperature for 20 hours. After drying for 20 hours, peeled films were used for the experiment. Antimicrobial activity Liquid system
L. monocytogenes ATCC15313 was used as a test organism to determine antimicrobial activity via the peptone solution (0.1%) system. Each square antimicrobial film (5.5cmx5.5cm) is submerged into 15 ml peptone solution containing L. monocytogenes at the level of 106, and each sample was continuously mixed by orbit shaker at 50 rpm. Antimicrobial activity of Nisin (Nisaplin) was tested at 0, 1, 2, 4, 6, 8 hours respectively and Guardian (CS-150) was tested at 0, 2, 4, 8, 12, 24 hours respectively. After incubation of each sample in the BHI media at 37C for 48 hours, a number of L. monocytogenes was counted. Solid system L. monocytogenes ATCC15313 was used as a test organism to determine antimicrobial activity via the agar diffusion technique. Small circular film (6mm diameter) was placed on the surface of L. monocytogenes at the level of 107. After incubation at 37C for 48 hours, clear zone was measured by micro caliper. Significant reductions of Listeria were observed with
nisin-impregnated gelatin films.
Impacts
The development of antimicrobial films for meat products will add a possible hurdle for the meat industry to use to reduce the presence and risk from Listeria contamination. The determination of the carry-over effect of antimcrobials during the enumeration of bacteria will allow the accurate determination of the effect of antimicrobial in food. Prevention of Listeria in meats will have a significant ecnomic impact for the meat industry by reducing the number of recalls due to Listeria.
Publications
- P. Dawson, I. Han, B. Cox, C. Black and L. Simmons. 2005. Residence time and food contact time effects on transfer of Salmonella Typhimurium from tile, wood and carpet: Testing the five-second rule. International Journal of Food Microbiology (accepted).
- Courtenay. M., Ramirez, L., Cox, B., Han, I., Jiang, X. and Dawson, P. 2005. ServSafe handwashing methodology compared to rinsing and alcohol-based sanitizers. Food Service Technology (accepted).
- Min, B.J., Dawson, P.L. and Shetty, K. 2005. Antioxidant and bioacitve films to enhance food quality. Korean Journal of Food Science and Animal Resources. 25:60-65.
- Dawson, P.L. 2005. Post Processing Treatments for Ready-to-Eat Meats: High Pressure and Surface Thermal Processing. Symposium manuscript based on presentation given at the USDA Food Safety Conference, Myrtle Beach, SC. Journal of the Association of Food and Drug Officials. (AFDO) 69(4): 9-21.
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Progress 01/01/04 to 12/31/04
Outputs
In-Package Pasteurization Coupled with Additional Antimicrobial Treatments The goal was to combine pasteurization with use of an antimicrobial bio-based film and determine the effects on pathogen outgrowth. The inhibitory effects of in-package pasteurization (3-5D, decimal reduction times) combined with a nisin (7%, w/w) containing wheat gluten film were tested over an eight week storage period against Listeria monocytogenes and Salmonella Typhimurium populations inoculated on refrigerated bologna. Bologna slices subjected to the in-package pasteurization process yielded final L. monocytogenes populations that fluctuated between 1.2 and 3.8 log cfu/g (3.8 to 7.0 log reduction) and S. Typhimurium populations that progressively declined from 100 to <10 cfu/g over the 2-month refrigerated storage period (5.7 to 7.3 log reduction). The wheat gluten film containing nisin was effective in reducing the population of L. monocytogenes (2.75 log reduction with pasteurization; 1
log reduction without pasteurization), but was not effective against S. Typhimurium (<1 log reduction). Nisin Retention and Activity Evaluation with food-grade powders The goal was to determine the ability of various food-grade powders to adsorb and release nisin activity. The antimicrobial peptide nisin is an effective bacterial inhibitor and has been adsorbed onto various surfaces and added to packaging films. In the present study, nisin was adsorbed onto food-grade powders then evaluated for nisin activity in a series of three experiments. Adsorbent powders used were calcined diatomaceous earth, synthetic calcium silicate, hydrate, 2 diatomaceous earth, and corn starch powders. Adsorption was conducted by placing the powders in agitated nisin solutions, followed by dehydration of the powder pellet after centrifugation. The dehydrated powders were then tested for inhibitory activity against either Lactobacillus plantarum or Listeria monocytogenes. Activity was measured by placing
the nisin-adsorbed powders in solutions of 0.1% peptone water inoculated with one of the test bacterial strains. Cel-pure 65 adsorbed then released from 74.7 to 94.7% of the nisin activity contained in the original solution (500 to 800 IU/ml) in which the powders were agitated. Corn starch adsorbed then released from 45.4 to 60.5% of nisin activity when from 300 to 700 IU/ml nisin activity adsorbing solutions were utilized. 1% of nisin-absorbed Celpure 100 and Celpure 65 powders in 30 ml of log 4.5 cfu/ml Listeria monocytogenes inoculum reduced populations to below detection levels (<101 cfu/ml) within 24 and 6 hours, respectively. Thus, nisin-adsorbed powders were highly efficient at both adsorption and release of antimicrobial activity. Filter-Cel, CP-1000, CP-65 and corn starch did not differ in % adsorption themselves, ranging from 54.2 to 76% adsorption efficiency (Figure 2). Micro-Cel-E adsorbed and released the least nisin (16.7% efficiency) among the powders tested. These
adsorption/release efficiencies are 10-100 times higher than those calculated for packaging films having nisin incorporated into their structure when tested under the same conditions.
Impacts
In-package pasteurization parameters will be useful for meat processors in developing rapid thermal treatments to reduce pathogens in RTE meats. Antimicrobial film development for RTE meat products can also be furthered by these results. The results from the nanoparticle study will be useful in designing the biosensor that improves the sensitivity and specificity of pathogen or toxin detection.
Publications
- Min, B.J., Shetty, K., and Dawson, P.L. 2003. Antioxidant and Bioactive films to enhance food quality and phytochemicals production during ripening. Poster presentation at the Nutrition Summit in Columbia, SC, October 17.
- Harmon, L., Dawson, P.L., and Han, I.Y. 2003. Nisin absorption onto food-gade coating agents to inhibit bacterial growth. 14th annual South Carolina Governors School for Science and Mathematics Undergraduate Research Colloquium. Columbia, SC.
- Black, C.L., Dawson, P.L., and Han, I.Y. 2004. Surface adhesion of S. Typhimurium from household surface to bologna: testing the 5-second rule. 15th annual South Carolina Governors School for Science and Mathematics Undergraduate Research Colloquium.
- Courtenay, M., Dawson, P.L. and Han I.Y. 2004. The efficacy of hand washing and sanitizers on microbial contamination. South Carolina Governors School for Science and Mathematics Undergraduate Research Colloquium.
- Pan, Lisa, Han, Inyee, and Dawson, Paul. 2003. NSF Undergraduate Research Program in Nanotechnology in the Food Sciences.
- Pan, Lisa, Han, Inyee, and Dawson, Paul. 2004. NSF Undergraduate Research Program in Nanotechnology in the Food Sciences.
- Dawson, P.L. and Stephens, C. 2004. Packaging of Poultry Products, In Poultry Meat Processing and Qualtiy Mead, ed. Woodhead Publishing Limited, Cambridge, England.
- Dawson, P.L., Mangalassary, S., and Sheldon, B.W. 2004. Thermal Processing of Poultry Products. In Thermal Food Processing: Modeling, Quality assurance, and Innovations. Da-Wen Sun, Editor. Marcel Dekker, NY.
- Dawson, P.L. and Spinelli, N. 2004. Poultry Flavors. In Food Flavors. Feng Chen, Editor.
- Mangalassary, S., Dawson, P.L., Rieck, J., and Han, I.Y. 2004. Thickness and compositional effects on surface heating rate of bologna during in-package pasteurization. Poultry Science 83:1456-1461.
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Progress 01/01/03 to 12/31/03
Outputs
The inhibitory effects of in-package pasteurization (3-5D, decimal reduction times) combined with a nisin (7%, w/w) containing wheat gluten film were tested over an eight week storage period against Listeria monocytogenes and Salmonella Typhimurium populations inoculated on refrigerated bologna. Bologna slices subjected to the in-package pasteurization process yielded final L. monocytogenes populations that fluctuated between 1.2 and 3.8 log cfu/g (3.8 to 7.0 log reduction) and S. Typhimurium populations that progressively declined from 100 to <10 cfu/g over the 2-month refrigerated storage period (5.7 to 7.3 log reduction). The wheat gluten film containing nisin was effective in reducing the population of L. monocytogenes (2.75 log reduction with pasteurization; 1 log reduction without pasteurization), but was not effective against S. Typhimurium (<1 log reduction). Combining both treatments significantly reduced the L. monocytogenes populations and prevented
outgrowth over the two month storage period but provided no added inhibitory effect against S. Typhimurium compared to only pasteurization. Rapid pathogen detection using nanomaterials: The recent advances in nanotechnology have created exciting opportunities for microbiologists in the development of new tools and methodologies for ensuring food safety and security. We are working on to integrate nanotechnology with molecular biological techniques to develop rapid and sensitive immunoassays for the detection and analysis of priority pathogens. Bioactive nanomaterials were conjugated with the affinity-purified antibody goat anti-Escherichia coli O157:H7 by Dr. Xiuping Jiang. The ability of these nanoparticles to be used effectively in water, milk, and food products such as hamburger samples to detect and/or remove unwanted pathogenic bacteria were studied and preliminary data inticate a strong affinity for the bioactive nanoparticles for the targeted bacterium.
Impacts
In-package pasteurization parameters will be useful for meat processors in developing rapid thermal treatments to reduce pathogens in RTE meats. Antimicrobial film development for RTE meat products can also be furthered by these results. The results from the nanoparticle study will be useful in designing the biosensor that improves the sensitivity and specificity of pathogen or toxin detection.
Publications
- Dawson, P.L. and Acton J.C. 2003. Examining the technical performance of anti-microbial additive to food packaging. Anti-Microbials 2003. Brussels, Belgium. November 5-6.
- McCormick, K., Han, I.Y., Sheldon, B.W., Acton, J.C., and Dawson, P.L. 2004. In package pasteurization combined with nisin-impregnated films to inhibit Listeria monocytogenes and Salmonella Typhimurium in turkey bologna. J. Food Sci. (Submitted).
- Dawson, P, Han I., Cox, E., Black, C. and Simmons, L. 2004. Food contact time effects on pick-up of Salmonella Typhimurium from tile, wood, and carpet. Testing the five-second rule. The 2nd Global Congress dedicated to Hygienic Coatings & Surfaces, Proceedings. Orlando, FL January 26-28.
- McCormick, K., Han, I.Y., Sheldon, B.W., Acton, J.C., and Dawson, P.L. 2003. D- and Z-values for Listeria monocytogenes and Salmonella Typhimurium in packaged low-fat ready-to-eat turkey bologna subjected to a surface pasteurization treatment. Poultry Sci. 82:1337-1342.
- Dawson, P.L., Hirt, D.E., Rieck, J.R., Acton, J.C., and Sotthibandhu, A. 2003. Nisin release from films is affected by both protein type and film-forming method. Food Research International. 36(9-10):959-968, 2003
- Dawson, P.L. 2003. Antimicrobial Films. Carolina Section meeting of the American Society of Microbiology. Athens, GA. October 31st.
- Dawson, P.L., Harmon, L., Sotthibandhu, A., and Han, I.Y. 2004. Antimicrobial activity of nisin adsorbed silica and corn starch powders. Food Microbiology. (Responding to first review).
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