Deterioration in quality of quick-frozen pork patties induced by changes in protein structure and lipid and protein oxidation during frozen storage

Changes in quality, protein structure and oxidative reactions of quick-frozen pork patties (after -30 degrees C, 30 min), which were frozen at -8 degrees C, -18 degrees C, -25 degrees C,-8/-18 degrees C (stored at -8 degrees C for 5 days, then stored at -18 degrees C for 5 days, storage cycle continue until the end of storage period), -18/-25 degrees C (the same process as -8/-18 degrees C, temperature is -18 degrees C and -25 degrees C) for 0, 1, 2, 3, and 6 months were investigated. The a*-value, pH, water holding capacity and texture properties of pork patties were significantly changed (P < 0.05) at -8 degrees C, -8/ -18 degrees C, - 18/-25 degrees C after 1 month of frozen storage. The water redistribution within the patties was detected by LF-NMR analyses. After 6 months of frozen storage, the TBARS and carbonyl content of samples frozen at -8/ -18 degrees C increased by 444% and 239%, respectively. Meanwhile, a decrease in fluorescence intensity reflected a decline in protein structure integrity. The association among quality, oxidative reactions and protein structure were elucidated by principal component analysis. The quality deterioration of the pork patties may be induced by the oxidative reaction and destruction of protein structural integrity during frozen storage.