Tri-component edible film inhibits bacterial contamination.

To inhibit the advance of C. jejuni on raw chicken, Food Safety Consortium scientists found that applying an edible film on the chicken's surface significantly reduces the level of contamination. The edible film is most effective when it consists of a combination of three antimicrobial agents: two proteins--zein and nisin--and the compound EDTA, which does most of the work involved in killing pathogens.

EDTA (ethylene diaamine tetraacetate) is a chelating agent. It binds to many different metal ions and prevents them from reacting with any other chemical that might be present. Zein by itself, EDTA by itself and nisin by itself each has some benefit. But when the three compounds are combined, you have your most effective pathogen treatment at refrigeration temperatures.

Experiments showed that EDTA delivered the most pathogen-killing power to the mixture. Zein on its own doesn't have much killing power, but adding zein to the mix provided the way to deliver the antimicrobial agent. As a coating, zein has prolonged contact with the food surface. So, the scientists are using edible films to deliver antimicrobial treatments.

Raw poultry is susceptible to bacterial contamination when it is processed. This contamination can persist when poultry products are refrigerated at temperatures just above freezing, at about 2 C to 4 C. Unfortunately, C. jejuni, the leading cause of bacterial diarrhea, is a leading source of contamination in these circumstances.

Individual companies that want to use the mixture's ingredients, which are already approved for use in other products, can receive approval to extend their use to raw poultry by filing a petition with the USDA Food Safety and Inspection Service. Companies are looking at this approach as a pathogen control measure.

Much of the poultry on the market consists of value-added chicken that only needs to be heated in the oven. Adequately cooking the product will kill pathogens. Raw poultry, however, is still a relatively popular item. If it comes out of the refrigerator with C. jejuni on its surface, heat will kill the bacteria in the oven. But there remains the danger of cross-contamination while the uncooked product is being prepared.

Previous research by the scientists led to the use of similar antimicrobial coatings containing zein and nisin to protect ready-to-eat cooked poultry from L. monocytogenes contamination. But Listeria isn't as great a threat on raw poultry as it is on ready-to-eat products.

Further information. Michael Johnson, University of Arkansas, Department of Food Science, 2650 N. Young Ave. Fayetteville, AR 72704; phone: [phone]; fax: [phone]; email: [e-mail].