Biochemical changes in non-thermally processed red snow crab meat during refrigerated storage

Red snow crab (Chionoecetes japonicus) is the most industrially processed into cooked-frozen meat. However, the conventional boiling process causes notable loss of flavor and nutrients. A non-thermal separation method based on freezing and sequential thawing was previously developed to enhance crab meat quality. This study aimed to elucidate biochemical changes in non-thermally processed crab leg meat during refrigerated storage, focusing on enzymatic activity and metabolite accumulation. Samples were stored at 4°C (Raw group), and changes in pH, volatile basic nitrogen (VBN), bacterial counts, enzyme activities (arginase, tyrosinase, and alkaline phosphatase), and related metabolites were monitored. To better understand the biochemical changes, frozen (F) and microwave-heated (M) samples were included as reference groups with reduced enzymatic and microbial activities. In the Raw group, pH, VBN, and bacterial counts increased markedly after day 3. Enzyme activities also rose, while arginase activity declined after day 3, matching a sharp decrease in arginine and an increase in ornithine and urea. Inosine monophosphate and inosine decreased, while hypoxanthine accumulated, indicating quality loss. By day 8, melanosis and tissue disruption were evident in the Raw group, whereas the F and M groups remained visually and biochemically stable. These findings provide insight into spoilage mechanisms in refrigerated, non-thermally processed crab meat.