Bacterial Flora in Pasteurized Oysters after Refrigerated Storage

Abstract

ABSTRACTFreshly shucked oysters (Crassostrea virgtnica) were chlorinated, sealed in pouches and pasteurized. Chlorination reduced the total plate count by a range of 40% to 90%; pasteurization further reduced the population by 99.9%. During refrigerated storage, the organisms that survived pasteurization were all Gram‐positive. By comparison, the predominant organisms found in fresh oysters were Gram‐negative. Some organisms survived after heating at 80°C for 10 min, but all were killed after heating at this temperature for 15 min. The facultatively anaerobic plate count gradually increased during storage. The major bacteria surviving after pasteurization and cold‐storage were Bacillus, Clostridium, Corynebacterium, Listeria, Peptostreptococcus and Staphylococcus.