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ABSTRACT

Two Listeria monocytogenes strains stressed with sodium hypochlorite sanitizers for 5 min were inoculated in broth or onto crabmeat and stored at 4, 10 or 25C. Lag time (LT) and specific growth rate (SGR) of unstressed and stressed L. monocytogenes were compared along with those of L. monocytogenes in pathogen modeling program. Compared with L. monocytogenes ATCC 15313, more rapid growth was observed in the stressed L. monocytogenes isolated from pork bulgogi (Korean marinated steak), regardless of the storage temperature. Overall, the effect of stress response on the growth kinetics was more obvious at 4C, where LT of stressed L. monocytogenes with 75 ppm sanitizer was extended up to four times compared with the unstressed sample. Although the overall growth rate of unstressed and stressed L. monocytogenes increased with the increase of temperature, sanitizer stress mainly affected LT in the growth curve, which varied with the strength of sanitizer, storage temperature and strain.

PRACTICAL APPLICATIONS

This research can help us to understand the behavior of stressed Listeria monocytogenes with sanitizer and the risk of stressed L. monocytogenes in the RTE foods, such as cooked crabmeat or shrimp at the retail market. Therefore, strict attention must be emphasized on the use of lethal concentration of sanitizer for optimal exposure times to avoid the incidence of sublethal-injured L. monocytogenes in food processing plants, and thus additional hurdle technology must be considered for the potential growth of stressed L. monocytogenes in foods at the retail markets and home. The results of this study also indicate that the United States Department of Agriculture pathogen modeling program needs to be continuously expanded to include growth kinetics of stressed pathogen, especially L. monocytogenes as this is a psychrotrophic microorganism, which is resistant to various stresses in a food processing environment.