Effects of high hydrostatic pressure (HHP) and storage temperature on bacterial counts, color change, fatty acids and non-volatile taste active compounds of oysters (Crassostrea ariakensis)

The effects of HHP and storage temperature on bacterial counts, color, fatty acids and flavor compounds of oysters Crassostrea ariakensis were investigated. Counts of Vibrio vulnificus and Vibrio parahaemolyticus decreased to undetectable levels in ≥ 400 MPa-treated oysters. Storage at -20 °C significantly restrained microbial growth compared to 4 °C (P < 0.05). L* values of HHP-treated oysters significantly increased compared to raw oysters (P < 0.05). Storage slightly affected the color according to total color difference (ΔE*) values. Fatty acid profiles and betaine contents in 400 and 600 MPa-treated oysters at 0 and 15 d were almost the same as raw samples. Contents of total free amino acids (FAAs), Na+ and Ca2+ were significantly higher in 400 and 600 MPa-treated oysters than those in raw oysters at 0 d (P < 0.05), while the opposite results were observed in 5'-adenosine monophosphate (AMP), 5'-guanosine monophosphate (GMP), citric acid, succinic acid, K+ and PO43- (P < 0.05). At 400 and 600 MPa, FAAs significantly decreased after 15-d storage at 4 °C and -20 °C (P < 0.05), while no significant changes were observed in nucleotides, organic acids and inorganic ions.