Since equilibrium water content (We) was considered to decrease with the denaturation of fish muscle protein, critical water contents (Wc), which were obtained on the characteristic dehydration curve during dehydration with a low osmotic sheet, were measured to investigate the relationships between the denaturation of myofibrillar (Mf) protein and Wc in tilapia surimi during storage for 0, 2, 4, 6, 8, and 10 days at 0℃. An inflection point was obtained in the falling rate period of logarithmic dehydration curve for the surimi, and it was named the second critical water content (Wc2). The Wc2 decreased with decreases in MfCa2+-ATPase total activity and Mf solubility during storage. Positive high correlations between Wc2 and MfCa2+-ATPase total activity, and between Wc2 and Mf solubility were obtained.
As a result, Wc2 could be useful as an index for evaluating protein denaturation.