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

Abstract

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 ultrasound 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 ℃ 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 oysters. 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.

Keywords: Oysters; Storage quality; Total volatile basic nitrogen; Ultrasound; Vibrio parahaemolyticus; Volatile flavor compounds.