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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
To reduce the risk of food borne illness associated with the consumption of meat and poultry, seafood and aquaculture, and complex ready-to-eat foods while maintaining product quality and extending shelf-life. The specific objectives of the research program are as follows: .
1)Utilize microbiological and molecular techniques to determine the effect of intervention technologies on microbial physiology, virulence and injury in order to assist in the design of effective process interventions;.
2)Develop and validate nonthermal and advanced thermal intervention technologies such as ionizing and UV radiation, radio-frequency and microwave heating, vacuum-steam-vacuum processing and ozonation to inactivate pathogens and spoilage microorganisms in raw and ready-to-eat meat and poultry, seafood and aquaculture products, and related complex solid foods, in combination with GRAS food additives;.
3)Define the impact of non-thermal and advanced thermal intervention technologies on food quality and chemistry.

1b.Approach (from AD-416)
D-values and the growth potential in shelf-life studies will be determined for foodborne pathogens using inoculated products following application of non-thermal and advanced thermal technologies. Particular attention will be focused on the use of multiple technologies, commonly known as the hurdle approach, to inactivate pathogens in foods. The effects of intrinsic and extrinsic factors such as processing variables, and product composition (temperature, dose, atmosphere, GRAS additives, pH, moisture, etc.) will be determined. Effects of interventions on the chemistry of foods and the formation and biological effect of toxicological markers will be determined using GC and GC-MS based technologies and bioassays.

3.Progress Report
There has been significant progress in the development, validation and commercialization of nonthermal and thermal process interventions that specifically address Plan Component(s) 1.2.4 Processing Intervention Strategies. One significant development is the initiation of research which can improve the safety of fish and seafood products. Per capita consumption of fish and seafood, including aquaculture raised products, has been increasing in the U.S. In 2008 the Farm Bill transferred responsibility for inspection of farmed catfish from the U.S. Food and Drug Administration to the USDA Food Safety Inspection Service (USDA FSIS), to begin in 2010. As part of the transfer USDA FSIS has invited a Project scientist to serve on the USDA-FSIS Ad-Hoc Panel for Catfish Safety and Risk Analysis. In the last 2 years the Project has focused an increasing fraction of its resources on improving the post-harvest safety of finfish which has included determination of proper cooking parameters for inactivation of pathogens in finfish, the use of Generally Recognized as Safe (GRAS) antimicrobials to control pathogens in raw finfish, the use of ultraviolet and ionizing radiation to control pathogens in farm raised catfish and tilapia, and the use of bacteriophages to control Listeria monocytogenes in farm raised catfish. Research collaborators and stakeholders include the National Fisheries Institute, the Cold Water Institute, the USDA FSIS, and the USDA-ARS Catfish Genetics Group located in Mississippi, and the fish processing industry. Other research has included the use of ultraviolet light (UV) to control pathogenic bacteria on food and food contact surfaces. Research results on the use of UV light to control L. monocytogenes, in combination with Flash Pasteurization or GRAS antimicrobials, has been transferred to the meat processing industry, Health Canada, the USDA FSIS and the U.S. Food and Drug Administration. Research on the use of Flash Pasteurization (FP), in cooperation with our CRADA partner, to control Listeria on precooked sausages has continued. FP has now been adopted by at least four major meat processors in the U.S., Central America, and South America with an estimated $1 billion in product treated using the FP process in 2009. Research on the use of microwave with automatic-feedback for power and temperature control has continued.

1. Thermal death time of foodborne pathogens on fish: Consumption of seafood, per capita, is increasing in the U.S. Foodborne illnesses can sometimes be contributed to consumption of improperly cooked fish and seafood products. Thermal inactivation kinetics, D and Z value determinations, which are the cooking time and temperature requirements to kill bacteria, were determined for Salmonella and Escherichia coli O157:H7 inoculated onto catfish and tilapia. The results of this study will provide federal action agencies, fish processing industries and consumer proper cooking temperature and time required to kill these pathogens in two of the most popular fish consumed in the U.S.

2. New approach developed for inactivation of Listeria monocytogenes in raw catfish: Consumption of fish, per capita, is increasing in the U.S. Foodborne illnesses can sometimes be contributed to consumption of improperly cooked fish and seafood products. Bacteriophages are viruses that infect only bacteria, and are considered a green or organic intervention technology. Bacteriophages applied to catfish were able to inactivate 2 log (99%) of the foodborne pathogen L. monocytogenes on catfish fillets stored for 6 days at 10C. This technology may help catfish industry provide safer food for consumers and assist regulatory agencies in the formation of science-based food safety policy.

3. Combining antimicrobials and ultraviolet light to inactivate bacteria on Frankfurters: Frankfurters can occasionally become contaminated by bacteria following cooking and prior to packaging, leading to product recalls and foodborne illness outbreaks. Ultraviolet light (UV) or the FDA approved antimicrobial lauric arginate ester (LAE) was used to inactivate Salmonellae, Listeria monocytogenes, Staphylococcus aureus on the surfaces of frankfurters. UV and LAE each inactivated 99 percent of Listeria on the frankfurters. The use of UV, followed by addition of LAE to the frankfurter packages immediately prior to sealing, inactivated over 99.9 percent of the three pathogens on frankfurters and inhibited Listeria growth during 3 months refrigerated storage at 10C. The use of UV, LAE, or the combination of UV and LAE had no effect on frankfurter color or texture. The research provides precooked sausage manufacturers a very inexpensive method for controlling pathogens on frankfurters, and may help manufacturers provide safer precooked sausages to consumers.

4. Development of a Microwave oven with automatic control improves food safety: Improper cooking of raw or partially cooked microwavable foods has led to occasional foodborne illness outbreaks and product recalls. A new microwave heating control mechanism was developed for in-package pasteurization of foods. Modified from a commercial inverter-based microwave oven (2245 MHz, 1.25 KW) by addition of an infrared sensor and a data acquisition system, a power control program was developed to control the power output of the microwave oven. A TV-dinner type product, made from mechanically tenderized beef and inoculated with E. coli O157:H7, was tested using this new microwave heating system. Experiments showed complete inactivation of E. coli O157:H7 and background flora by proper selection of heating temperature and heating time. A reliable microwave technology which monitors and controls food temperature will help food processors, restaurants and consumer to ensure food safety.

5. Defining the growth and destruction of E. coli in tenderized beef: Non-intact tenderized beef has become a potential source for contamination of E. coli O157:H7. In order to understand the impact of contaminated non-intact beef on food safety, a storage study on the fate of E. coli in non-intact beef was conducted. The study also investigated the use of rifampicin resistant strains for growth modeling. The results showed the growth rate of E. coli cells in tenderized beef is a linear function of temperature (<37C), and the minimum growth temperature is about 12C. The rifampicin-resistant strains of E. coli O157:H7 grow 10-20 percent slower than the wild type strains of E. coli. This work will assist the USDA Food Safety Inspection Service in the formation of science-based policies for production and cooking of tenderized beef. This work was conducted as part of project 1935-42000-054-01R.

6.Technology Transfer

Number of New CRADAS1
Number of Active CRADAs1

Review Publications
Sommers, C.H., Cooke, P.H., Fan, X., Sites, J.E. 2009. Ultraviolet Light (254 nm) Inactivation of Listeria monocytogenes on frankfurters that contain potassium lactate and sodium diacetate. Journal of Food Science. 74(3):M114-M119.

Sommers, C.H., Cooke, P.H. 2009. Inactivation of avirulent Yersinia pestis in butterfield's phosphate buffer and frankfurters by UVC (254 nm) and gamma irradiation. Journal of Food Protection. 72(4):755-759.

Fan, X., Kays, S.E. 2008. Formation of trans Fatty Acids in Ground Beef and Frankfurters due to Irradiation. Journal of Food Science. 74(2):C79-C84.

Jin, Z.T., Liu, L.S., Sommers, C.H., Boyd, G., Zhang, H.Q. 2009. Radiation resistance and post-irradiation proliferation of Listeria monocytogenes on ready-to-eat deli meat in the presence of pectin/nisin films. Journal of Food Protection. 72(3):644-649.

Sommers, C.H., Geveke, D.J., Pulsfus, S., Lemmenes, B. 2009. Inactivation of Listeria innocua on frankfurters by ultraviolet light and flash pasteurization. Journal of Food Science. 74(3):M138-M141.

Huang, L., Liu, L.S. 2009. Simultaneous Determination of Thermal Conductivity and Thermal Diffusivity of Food and Agricultural Materials Using a Transient Plane-Source Method. Journal of Food Engineering. 95:179-185.

Rajkowski, K.T. 2008. Radiation D10-Values on Thawed and Frozen Catfish and Tilapia for Finfish Isolates of Listeria Monocytogenes. Journal of Food Protection. 71(11):2278-2282.

Last Modified: 8/27/2015
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