Inactivation of Vibrio parahaemolyticus and retardation of quality loss in oyster (Crassostrea gigas) by ultrasound processing during storage

The health problems caused by foodborne pathogens of raw oysters have been widely concerned. Traditional heating methods tend to lead the loss of the original nutrients and flavors, in this study, the nonthermal ultra-sound technology was applied to inactivate Vibrio parahaemolyticus on raw oysters, and the retardation effects on microbial growth and quality loss of oysters stored at 4 celcius after ultrasonic treatment were also investigated. After treated by 7.5 W/mL ultrasound for 12.5 min, the Vibrio parahaemolyticus in oysters was reduced by 3.13 log CFU/g. By measuring total aerobic bacteria and total volatile base nitrogen, the growth trend after ultrasonic treatment was delayed compared with heat treatment, and the shelf life of oysters was prolonged. At the same time, ultrasonic treatment delayed the changes of color difference and lipid oxidation of oysters during cold storage. Texture analysis showed that ultrasonic treatment helped maintain the good textural structure of oys-ters. Histological section analysis also demonstrated that muscle fibers were still tightly packed after ultrasonic treatment. Low-field nuclear magnetic resonance (LF-NMR) illustrated that the water in the oysters was well maintained after ultrasonic treatment. In addition, gas chromatograph - ion mobility spectrometer (GC-IMS) showed that ultrasound treatment could better preserve the flavor of oysters during cold storage. Therefore, it is believed that ultrasound can inactivate foodborne pathogens of raw oysters and keep its freshness and original taste better during storage.

Automated summary

In this study, nonthermal ultrasonic technology was used to inactivate Vibrio parahaemolyticus on raw oysters, and the effects on microbial growth and quality loss of oysters during storage were investigated. The results showed that ultrasonic treatment reduced the number of Vibrio parahaemolyticus in oysters and delayed the growth trend of microorganisms. It also prolonged the shelf life of oysters and maintained their freshness and flavor better during storage.