Fig. 4 showed the changes in the salt-soluble protein (SSP) in frozen shrimps during multiple freeze–thaw cycles.Figs. 2 and 3 indicated that only the number of freeze–thaw
cycle affected the cutting force and the SSP for each freezing method. Fig. 5 showed the changes of the SSP in shrimps frozen under the selected conditions of both freezing
methods during multiple freeze–thaw cycles when we observed only the effect of freeze–thaw cycles. The denaturation of muscle proteins may occur during multiple freeze–
thaw cycles and a decrease in SSP could be due to the denaturation of proteins caused by the interaction of free fatty acid with SSP and the consequent lower solubility of proteins. In addition, the toughness of frozen shrimp was attributed to myosin denaturation,as well as cross-linking and aggregation of myofibrillar proteins. As the SSP in shrimps decreased when the freeze–thaw cycles increased, the cutting force of
the shrimp muscle also increased. The cutting force increased up to two freeze–thaw cycles and then leveled off after that for both freezing methods (Fig. 5). An
increase in the cutting force indicated that the samples became toughen which might be due to the fiber shrinkage and drip loss