TitleEffects of flash freezing, followed by frozen storage, on reducing Vibrio parahaemolyticus in Pacific raw oysters (Crassostrea gigas).
Publication TypeJournal Article
Year of Publication2009
AuthorsLiu, C, Lu, J, Su, Y-C
JournalJ Food Prot
Volume72
Issue1
Pagination174-7
Date Published2009 Jan
ISSN0362-028X
KeywordsAnimals, Colony Count, Microbial, Consumer Product Safety, Crassostrea, Food Contamination, Food Handling, Food Preservation, Freezing, Humans, Shellfish, Time Factors, Vibrio parahaemolyticus
Abstract

This study investigated the effects of flash freezing, followed by frozen storage, on reducing Vibrio parahaemolyticus in Pacific raw oysters. Raw Pacific oysters were inoculated with a five-strain cocktail of V. parahaemolyticus at a total level of approximately 3.5 x 10(5) most probable number (MPN) per gram. Inoculated oysters were subjected to an ultralow flash-freezing process (-95.5 degrees C for 12 min) and stored at -10, -20, and -30 degrees C for 6 months. Populations of V. parahaemolyticus in the oysters declined slightly by 0.22 log MPN/g after the freezing process. Subsequent storage of frozen oysters at - 10, -20, and -30 degrees C resulted in considerable reductions of V. parahaemolyticus in the oysters. Storing oysters at -10 degrees C was more effective in inactivating V. parahaemolyticus than was storage at -20 or -30 degrees C. Populations of V. parahaemolyticus in the oysters declined by 2.45, 1.71, and 1.45 log MPN/g after 1 month of storage at -10, -20, and -30 degrees C, respectively, and continued to decline during the storage. The levels of V. parahaemolyticus in oysters were reduced by 4.55, 4.13, and 2.53 log MPN/g after 6 months of storage at -10, -20, and -30 degrees C, respectively. Three process validations, each separated by 1 week and conducted according to the National Shellfish Sanitation Program's postharvest processing validation-verification interim guidance for Vibrio vulnificus and Vibrio parahaemolyticus, confirmed that a process of flash freezing, followed by storage at -21 +/- 2 degrees C for 5 months, was capable of achieving greater than 3.52-log (MPN/g) reductions of V. parahaemolyticus in half-shell Pacific oysters.

Alternate JournalJ. Food Prot.
PubMed ID19205481