Response of Vibrio parahaemolyticus 03:K6 to a hot water/cold shock pasteurization process

Vibrio vulnificus and V. parahaemolyticus are natural inhabitants of estuarine environments world wide. Pathogenic strains of these bacteria are often transmitted to humans through consumption of raw oysters, which flourish in the same estuaries. Previous studies reported the effective use of hot water pasteurization followed by cold shock to eliminate from raw oysters naturally and artificially incurred environmental strains of V. vulnificus and V. parahaemolyticus common to the Gulf of Mexico. The present study focused on the use of the same pasteurization method to reduce a highly process resistant Vibrio strain, V. parahaemolyticus O3:K6 to non-detectable levels. Oysters were artificially contaminated with 10⁴ and 10⁶ V. parahaemolyticus 03:K6 cfu g⁻¹ oyster meat. Contaminated oysters were pasteurized between 50 and 52°C for up to 22 min. Samples of processed oysters were enumerated for V. parahaemolyticus O3:K6 at 2-min intervals beginning after the 'come-up time' to achieve an oyster internal temperature of at least 50°C. The D value (D₅₂°C) was 1.3-1.6 min. V. parahaemolyticus O3:K6 proved more process resistant than non-pathogenic environmental strains found in Gulf of Mexico waters. A total processing time of at least 22 min at 52°C was recommended to reduce this bacterium to non-detectable levels (<3 g⁻¹ oyster meat).