Quality Changes of Large Yellow Croaker Meat with Different Cooked Degrees during Frozen Storage and Reheating Process

This study investigated the quality changes of large yellow croaker meat during the frozen storage and reheating processes at different cooking degrees (total cooked, TC: center temperature of fish meat reaches 90 ℃, medium-cooked, MC: center temperature of fish meat reaches 50 ℃, and uncooked group: NC) by measurements of moisture loss, color difference, total viable count (TVC), thiobarbituric acid reactive substances (TBARs), carbonyl content, and microstructure. Results indicated that after freezing and reheating, the moisture loss, TBARs, and carbonyl content of TC group were 24.46%, 0.62 mg/kg, and 0.96 nmol/mgprot (0 week), respectively, which were 2.63%, 6.8% and 15% higher than the samples in MC group, and 10%, 19% and 16.7% higher than the samples in NC group, respectively. The same trend was observed in increasing of storage time, indicating that the higher the degree of maturation, the greater the loss of moisture and oxidation of lipid and proteins after freezing and reheating. The changes of L* and W values of the MC and TC groups were lower than those of the NC group after freezing-reheating, b* of the MC and TC groups were significantly greater than those of NC group (P<0.05) due to lipid oxidation caused by the preheating treatment. The total viable count (TVC) and total volatile basic nitrogen (TVB-N) increased more slowly in pre-heated samples (TC and MC) during frozen storage, TVB-N in the NC, MC, and TC groups increased by 51.6%, 41%, and 36%, respectively, indicating that the higher the degree of heating, lead to slower spoilage. The myofibril fragmentation index (MFI) and microstructure showed that the muscle fiber structure of pre-heated samples could be better preserved during frozen storage, and there was no significant differences between pre-heating groups. In summary, thermal processing can effectively lower the quality deterioration of large yellow croaker during the frozen storage and reheating process. The protein and oil oxidation in MC and TC groups are greater than those of NC group due to pre-heating treatment. These findings provide theoretical references for the further development of large yellow croaker.