Inactivation of Vibrio vulnificus and Vibrio parahaemolyticus in cryogenically frozen oyster meat using steam venting technology

A combination of steam-venting packaging and microwave cooking may be used to inactivate Vibrio vulnificus and Vibrio parahaemolyticus in oyster meat. This study investigated temperature and pressure profiles in the headspace of a steam venting package with the steam-generated inside of the package resulting from microwave heating. To determine steam venting time to inactivate pathogens, fresh oyster meat (Crassostrea virginica) was inoculated with either Vibrio vulnificus or Vibrio parahaemolyticus, cryogenically frozen (−20 °C), and packaged in microwavable trays in 50 and 100 g portions. Trays were film sealed with nitrogen in the headspace and stored in a freezer for 12 h. The film acted as a barrier against rapid moisture loss and promoted even temperature distribution in the oyster meat. Steam venting occurred due to steam pressure generated inside the package. Venting was used to prevent overheating. Data collection of temperature and pressure inside the package during microwaving was performed in a Microwave Workstation using fiber optic temperature and fiber optic pressure sensors. Temperature and pressure profiles showed that after 10 s of heating, the temperature of the oyster meat was the same both internally and upon the surface. The venting time in the 100 g package took 1.53 times longer than in the 50 g package, while the venting pressure was 52% lower than in the 50 g package. After 50 s and 60 s of microwave cooking at 100% power on 50 g and 100 g of oyster meat, respectively, total inactivation of both pathogens was achieved. The study demonstrated the steam venting package, and microwave heating could provide even heating, prevent overheating, and inactivate pathogens.