Chemical wash targets Salmonella

Reducing bacterial contamination in food products poses many problems for the food industry. While it is quite obviously important to protect against food-borne pathogens such as Salmonella, e. coli, and Listeria, equally important is the effective preservation of taste. To date, this has been a puzzle difficult to resolve. Recently, University of Georgia (U.S.) scientists, led by Dr. Mike Doyle, developed a chemical wash for poultry and produce that might solve the conundrum that has baffled many.

Doyle is an internationally recognized authority on food safety whose research focuses on developing methods to detect and control food-borne bacterial pathogens at all levels of the food continuum, from the farm to the table. He has served as a scientific advisor to many groups, including the World Health Organization, the Food and Drug Administration, the U.S. Department of Agriculture, the U.S. Department of Defense and the U.S. Environmental Protection Agency.

Scientist Live spoke with Dr. Doyle about his research.

How did you first get involved in developing a chemical wash for Salmonella?

One of our primary missions at the Center for Food Safety is to develop practical approaches for reducing and controlling harmful bacteria in foods. That is our primary driving force - developing better methods that consumers, producers, or processors can use to reduce pathogen contamination and increase detection. We have a project through the state of Georgia to reduce Salmonella contamination on poultry. As part of that project, our goal is to evaluate different chemical treatments that can potentially inactivate Salmonella.

At the beginning, we always start out with a pure system then move into more complicated ones like water with poultry feces. What we learned from our research was that a particular combination of chemicals - specifically an organic acid that is not frequently used in foods and a detergent - had a dramatic effect on reducing Salmonella populations, not only in water but also on food products like vegetables and poultry meat.


What are the shortcomings of current washes widely used in the food industry?

Presently, chlorine is used in poultry and fresh-cut produce antimicrobial washes. Chlorine is not entirely effective as an antimicrobial in the presence of organic loads which includes protein materials like blood. In the presence of protein, chlorine also produces by-products of which some are carcinogenic. So there is an interest in coming up with alternatives. There are some alternatives but they are not fully effective and don't kill as many bacteria as our treatment does. Moreover, they may damage tissue of particularly sensitive foods like leafy greens - lettuce and spinach, for example - that are very sensitive to certain treatments.


Does the wash you developed fight other forms of bacteria?

We tested against E. coli O157:H7, Salmonella, and Listeria. It's effective against all three.


Would food producers be able to use the wash on a wide range of products?

That is yet to be determined. For produce, we have concentrated on lettuce and tomatoes. There is considerably more to be evaluated. From past experience, lettuce has been very difficult to treat and keep from browning over a short period of time. For example, when we use combinations of lactic acid and acetic acid at levels needed to kill bacteria, we find that leafy green tissue begins to brown within a few days. That is why we are excited about this treatment. The tissue does not brown in a few days after treatment. Rather it retains its green color for several weeks.

Is the wash effective against non-bacterial microbes?

That is what we plan to test. We want to evaluate its efficacy on parasites like Cryptosporidium and Cyclospora as well as some viruses.

Many chemical washes are known to produce slightly altered tastes. How does your wash perform?

The wash treatment performs well in this regard. I tasted treated products and don't detect any off flavor or odor or discoloration.

What is the next step for your lab in terms of this project?

One of our priorities for the wash is to reduce Salmonella contamination on poultry and we have some additional approaches we would like to apply, including pre-harvest. By that I mean as chickens are loaded onto the truck there may be an opportunity to apply the wash to feathers and reduce the Salmonella contamination on the feathers. The outer surface of chickens is often the source of Salmonella on the meat. Also, we are looking at the scald water tanks which are another source of contamination to determine if we can successfully apply the treatment in the scald water. Finally, we want to apply the treatment with electrostatic spraying - especially to feathers - to see if we can reduce contamination using less treatment solution.

 

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