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­­UW scientists team with meat industry to provide food safety solution

Foodborne pathogens are often difficult to control during food production. Salmonella, which causes over 1 million illnesses in the U.S. each year, is particularly nefarious. It can cleverly adapt to its environment to survive under extreme circumstances. In low-moisture conditions, for instance, Salmonella becomes even better at withstanding heat, creating a food safety hazard for meat and poultry products cooked in dry-heat conditions.

To help mitigate this issue, the U.S. Department of Agriculture in 2017 updated its industry guidance in Appendix A. According to the new guidance, a 90% humidity level must be maintained during meat and poultry cooking processes that take less than one hour to ensure product safety.

Meeting this new guideline presented a problem for many processors: Smaller-sized meat and poultry products like chicken nuggets and beef patties often are cooked for short times at high temperatures using an impingement oven, a continuous cooking system driven via conveyor belt. When Salmonella are exposed to these dry-heat methods, the bacteria dessicate, or dry out, which makes them more heat tolerant and better able to survive the high temperatures. Processors needed a way to ensure the inactivation of Salmonella in their products without having to replace their existing impingement ovens, which are large and expensive pieces of equipment.

A team of UW–Madison researchers, including Jeff Sindelar, professor and extension specialist in the Department of Animal and Dairy Sciences, and Kathy Glass, distinguished scientist and associate director of the Food Research Institute (FRI), set out to help solve this problem, collaborating with meat industry advisor Bob Hanson and representatives from numerous FRI industry partners, including Hormel Foods, Johnsonville Sausage, Jones Dairy Farm, SugarCreek Packing, Tyson Foods, and ConAgra.

In a study recently published in Meat and Muscle Biology, the group shared the results of their collaborative effort to design, test, and validate a new processing method known as hydrated surface lethality (HSL) – that involves steam injection – that satisfies the new USDA guideline without requiring any major equipment modifications to existing impingement ovens.

“The team designed an extensive series of experiments that tested this hypothesis for a range of chicken, pork, and beef products using many different process conditions, and conducted these experiments in FRI’s labs over several months,” explains Hanson.

Reasoning that pathogens lurking inside meat products were already continuously hydrated, the scientists decided to focus on the surface pathogens. They hypothesized that maintaining hydration on product surfaces for a sufficient time was key to killing the pathogens. By incorporating HSL steps during cooking to achieve wet-bulb temperatures of 160°F or higher, the researchers were able to successfully inactivate Salmonella in finished products. The research paper includes information about how to modify equipment to implement HSL, as well as simple parameters that can be used to validate the food safety of industrial cooking processes using newly-modified equipment.

“From my perspective, I was so impressed with the effectiveness of the FRI group,” says Hanson. “This group worked together as a high-performing team that thrived on collaboration. Everyone contributed to the success of the project, and it was completed in a timely and cost-effective manner.”

The research provides a workable solution that benefits not only processors but also ensures consumer safety, demonstrating the positive outreach of the university throughout Wisconsin and beyond.

“This was a great project where we brought together academic and industry experts to find science-based, government-supported, and industry-applicable solutions,” says Sindelar.

The Food Research Institute (FRI), a part of the College of Agricultural and Life Sciences at the University of Wisconsin–Madison, operates its own laboratories and administers its own research and service programs. The mission of FRI is to catalyze multidisciplinary and collaborative research on microbial foodborne pathogens and toxins and to provide training, outreach, and service to enhance the safety of the food supply. To fulfill this mission, FRI conducts fundamental and applied research, provides accurate and useful information and expertise, delivers quality education and training, and provides leadership in identifying and resolving food safety issues to meet community, government, and industry needs.