Validation of an Individual Quick Freezing (IQF) Process to Reduce Vibrio vulnificus Numbers to \u3c30MPN/g in Raw Oysters

This validation study was conducted during the months of July, August and Sept., 2003. The Food and Drug Administration and the Interstate Shellfish Sanitation Conference require that oysters used for a validation study are collected during the same processing day, are from the same lot of shellfish, and have an adjusted geometric mean (AGM) MPN of at least I 00,000/g of Vibrio vulnificus as an initial load. The oysters were removed from refrigerated storage and held at 71 °F (21 °C) for 40-45 hours prior to freezing in order to achieve a minimum AGM of 100,000/g Vibrio vulnificus . After quick freezing the oysters at -70°F (-57°C) for nine minutes, approximately 8-10 weeks of frozen storage at 0°F (-l 8°C) were required to reduce V. vulnificus levels from 105 MPN/g to less than 30MPN/g. Initial V. vulnificus numbers in excess of 1,000,000/g, required prolonged frozen storage (\u3e20 weeks) of the oysters at 0°F (-18°C) to reduce V. vulnificus numbers to less than 30MPN/g