Characteristics of silver carp surimi gel under high temperature (100 C): quality changes, water distribution and protein pattern

The effects of high-temperature treatments (100-125 degrees C) on the properties of silver carp surimi gel were studied. The results showed that the gel strength and water holding capacity (WHC) of surimi gel decreased significantly (P < 0.05), with the increase of heating temperature and the prolongation of heating time, and the higher the temperature, the greater the decrease trend. Hydrophobic interaction and disulphide bonds decreased significantly, while ionic bonds increased significantly (P < 0.05), as well as beta-sheet increased while beta-turn and coil decreased significantly, which confirmed the changes of protein secondary structure caused by high-temperature treatments. Myosin heavy chain (MHC) and actin bands gradually narrowed, and the production of new bands larger than 250 kDa by SDS-PAGE showed the aggregation and cross-linking reaction of proteins. However, the increased band intensity of 50-75 kDa and the increase of trichloroacetic acid (TCA) soluble peptides showed the degradation of proteins. The decrease of PT22 and the increase of PT23 indicated the conversion of immobilised water to free water in the gel matrix. In conclusion, high-temperature heating caused the changes of protein secondary structure as well as chemical forces and water conversion, resulting in protein denaturation, aggregation, cross-linking and degradation, forming a loosen and irregular gel network.