Title: Physiochemical changes in frozen herring

The objective of this study was to investigate the effects of different frozen storage temperature (-25°C and fluctuant -12°C) on lipid degradation and protein conformation changes of frozen herring and compare the physicochemical changes of herring frozen at different post-mortem period (frozen on board and frozen on land). Analysis of herring stored at fluctuant -12±3°C for 4 weeks and constant -25°C for two weeks were performed after 0, 2, 4 and 6 weeks of frozen storage. While the stable -25°C samples were analyzed only after 0 and 6 weeks of frozen storage. The effect of the physicochemical parameters were studied by measuring liquid holding capacity (LHC), drip loss, peroxide value(PV), TBARS, free fatty acids (FFA), lipid content, water content, pH value, disulfide bonds content, available and total SH groups. The results showed that lower temperature -25°C can effectively reduce drip loss, especially inhibit the lipid degradation including PV, TBARS and FFA of herring, compare with fluctuant -12°C. Freezing herring during pre-rigor period can slow down lipid oxidation including PV and TBARS, and reduce conformational changes of protein caused by freezing process compare with post-rigor frozen herring.