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Title: Determination of 5-log pathogen reduction times for heat-processed, acidified vegetable brines

item Breidt, Frederick
item Hayes, Janet
item McFeeters, Roger

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2004
Publication Date: 2/1/2005
Citation: Breidt, F., Hayes, J.S., Osborne, J.A., McFeeters, R.F. 2005. Determination of 5-log pathogen reduction times for heat-processed, acidified vegetable brines. Journal of Food Protection. 68:305-310.

Interpretive Summary: Data is presented that shows the minimum times and temperatures of heating needed to ensure that disease-causing microorganisms are destroyed in commercial, acidified vegetable products (including pickles, peppers, and others). We know of no record in the scientific literature of bacteria causing disease outbreaks from these products. However, previous laboratory research with acidified vegetable brines has shown that some acid-resistant microbes can survive for extended periods (two weeks or longer) in acidified vegetable products. Our results indicate that current commercial heat processes kill microbial pathogens with a large margin of safety.

Technical Abstract: Recent outbreaks of acid-resistant food pathogens in acid foods, including apple cider and orange juice, have raised concerns about the safety of acidified vegetable products. We determined pasteurization times and temperatures needed to assure a 5-log reduction in the numbers of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella strains in acidified cucumber pickle brines. Cocktails of five strains of each pathogen were (separately) used for heat-inactivation studies between 50 and 60 deg C in brines which had an equilibrated pH value of 4.1. Salmonella strains were found to be less heat-resistant than E. coli O157:H7 or L. monocytogenes strains. The non-linear killing curves generated during these studies were modeled using a Weibull function. We found no significant difference in the heat-killing data for E. coli O157:H7 and L. monocytogenes (p = 0.9709). The predicted 5-log reduction times for E. coli O157:H7 and L. monocytogenes were found to fit an exponential decay function. These data were used to estimate minimum pasteurization times and temperatures needed to ensure safe processing of acidified pickle products and show that current industry pasteurization practices offer a significant margin of safety.