Effect of multiple freeze–thaw cycles on myoglobin and lipid oxidations of grass carp surimi with different pork back fat content

Fresh grass carp was used to produce surimi and 50 g kg^-1, 100 g kg^-1, or 150 g kg^-1 pork back fat was added. The water distribution, TBARS, myoglobin oxidation, color parameter (L^*, a^*, b^*), heme and non-heme iron content of samples were determined to analyze the effects of different fat content on the oxidation of myoglobin and lipids during multiple freeze-thaw cycles of grass carp surimi. Both multiple freeze-thaw cycles and increased fat content lead to an increase in TBARS, a blue shift in the absorption peak of myoglobin porphyrin, a decrease in heme iron content, and an increase of non-heme iron content. Repeated freeze-thaw caused a decrease in immobilised water content and L^*, and caused an increase in a^* and b^*. Increased fat content caused an increase in immobilised water content, L^* and a^*, and caused a decrease in b^*.