Fate of selected food-borne pathogens during the fermentation of squid shiokara

Abstract

Shiokara, a traditional fermented seafood in Japan, has never been reported to cause bacterial food poisoning. In this study, shiokara products were inoculated with Staphylococcus aureus, Vibrio parahaemolyticus, and Clostridium botulinum type E and the fates of these pathogens were determined during the fermentation of squid shiokara. V. parahaemolyticus declined rapidly and was not detectable after 12 days of fermentation. When shiokara was inoculated with mixtures of vegetative cells and spores of C. botulinum type E, the number of vegetative cells declined rapidly within 2 days, though the viable spores remained. S. aureus survived but did not grow or produce enterotoxin during the fermentation. These results confirmed the safety of traditional shiokara with respect to bacterial food hygiene. However, strict control of contamination by S. aureus throughout the manufacturing process is necessary, because the organism remained viable during fermentation.