Abstract: In this paper, the effect of different freezing methods including slow fridge freezing at ?20 ℃, and rapid freezing at ?20, ?40 and ?60 ℃ and in liquid nitrogen, on biochemical characteristics of freshwater crabs were evaluated in terms of muscle pH and malondialdehyde (MDA) content, and Ca2+-ATPase activity, total sulfhydryl content, and surface hydrophobicity of myofibrillar protein. The results showed that during storage at ?20 ℃, pH, Ca2+-ATPase activity and total sulfhydryl content decreased, MDA content increased firstly and then decreased, and surface hydrophobicity increased continuously. All tested parameters changed more slowly or less significantly in rapidly frozen group than in the slowly frozen one. Freezing at ?60 ℃ and in liquid nitrogen were significantly better than at ?20 ℃ and ?40 ℃. Moreover, there was no significant difference in freezing between ?60 ℃ and in liquid nitrogen.

Key words: crab, freezing rate, protein, lipid, oxidation