Effects of High-Pressure Treatment on Microbial Inactivation and the Quality of Oyster (Crassostrea gigas)

Abstract:

Oyster (Crassostrea gigas) is popular seafood with delicious taste and rich nutrients. The produce of oyster in China was as large as 4,352,000 tons in 2014. In this study we investigated the effects of high pressure processing (HPP) and cold storage on microbial inactivation, the total volatile basic nitrogen (TVB-N), and the pH of oysters. Tastes of oysters after HPP and heat processing were compared. It was found that there was an over 2-lg reduction in the total number of bacterial colonies after 300 MPa processing for 15 min. Similar results were observed under conditions such as 400 MPa for 10 min or 15 min, and 500 MPa for 5 min, 10 min or 15 min. Particularly when treated at 500 MPa for 10 min, no colony in oysters could be detected. The results above indicated that HPP treatment could effectively suppress the microorganisms in oysters. The shelf life of raw-eaten oysters could be extended to 15 days when stored at 4℃ after HPP treatments such as 300 MPa for 15 min, 400 MPa for 10 min, and 500 MPa for 5 min. TVB-N was also effectively inhibited by HPP treatments. The TVB-N level remained <10 mg/100 g in 20 days when stored at 4℃ after HPP at 300 MPa for 15 min. Oysters treated with HPP had significantly higher pH value and hardness compared to the untreated (P<0.05), and the springiness was also increased. The electric nose test detected no significant difference in taste between HPP-treated and the untreated oysters. However, the taste of heat-treated oysters was apparently different from those of HPP-treated and the untreated. These results indicated that HPP treatment might be an effective non-thermal processing technology. HPP with proper conditions could efficiently extend the shelf life of raw-eaten oysters and improve their quality.