Cryoprotective Effect of Hydrolysate ofTilapia Skin on Tilapia Fillets

Taking tilapia skin as the research object, the cryoprotective activity of its enzymatic hydrolysate was evaluated to provide basic data for the development of new safe and efficient non-phosphorus antifreeze agent.【Method】 With degree of hydrolysis as the index, a single factor experiment was conducted on the alkaline protease enzyme solution temperature, pH value and the addition amount of enzyme, and the index was optimized by orthogonal experiment, to determine the optimal hydrolysis time.The molecular weight of enzymatic hydrolysate product obtained under the condition of optimization was determined by using high performance size exclusion chromatography.And the cryoprotective effect of enzymatic hydrolysis product was explored with thawing water loss rate, salt soluble protein content, Ca2+-ATPase activity and sulfhydryl content as indexes of antifreeze activity.【Result】The tilapia skin was hydrolyzed by alkaline protease, and the optimal hydrolysis conditions were obtained by orthogonal test：reaction temperature at 55 ℃, pH of 7.5, with an enzyme dose of 0.7% and enzymatic hydrolysis time of 3h.Under the optimal conditions, the molecular weight of enzymatic hydrolysates mainly ranged from 367.05 u to 6264.80 u. At a dosage of 5%, the biochemical indexes(thawing water loss rate, salt-soluble protein content, Ca2+-ATPase activity and total sulfhydryl) of freezing protection effect of enzymatic hydrolysate group during 6 weeks of freezing storage were similar to or better than those of phosphorus-containing antifreeze group, and were significantly better than those of blank control group.【Conclusion】The enzymatic hydrolysate of tilapia skin hydrolyzed by alkaline protease could significantly inhibit the freezing denaturation of tilapia fillets.