37-3 |
|
J. F. FRANK, Dept. of Food Science & Technology, Univ. of Georgia, 211 Food Science Bldg., Athens, GA 30602-7610 Under most circumstances in the food industry biofilm control can be achieved by proper cleaning followed by chemical sanitation of the surface. However, in some cases, usually due to poor equipment design, the biofilm may not be accessible to cleaning agents and the best control strategy may be heat inactivation. Pathogens attached to surfaces or imbedded in biofilms may have greater heat resistance then their planktonic counterparts, so heat inactivation of pathogens in biofilms cannot be predicted using data from cell suspensions. Kinetic models that require CFU data are not readily applied to biofilm cells because quantitative removal of cells from the surface is difficult, and because detached cells are clumped resulting in an underestimation of cell numbers and a tailing of the heat inactivation curve. To avoid these difficulties, we developed models for the heat inactivation of Listeria monocytogenes in biofilms using fraction negative data. This data was obtained by total immersion of biofilm-containing coupons in hot water and then testing treated coupons for the presence/absence of L. monocytogenes by incubation of the coupon in enrichment broth (trypticase soy broth with yeast extract). The models provide for the prediction of L. monocytogenes inactivation in biofilms formed on stainless steel or rubber, in mixed culture with Pseudomonas sp. and with a coating of chicken fat/protein emulsion. The models can be used to adjust heating time and temperature conditions to reduce the risk of L. monocytogenes survival to a desired level. For example heat treatment at 80 °C for 16.2 minutes is required to achieve a 90% probability of complete inactivation of L. monocytogenes on stainless steel in the presence of Pseudomonas biofilm and poultry soil.
Session 37, Biofilms in the food industry: Problems and solutions
|