Study On Preparation Of Gelatin From Tilapia Fish Skin With Enzyme

Gelatin is a production of collagen by moderate decomposition and denaturalization, which has a wide molecular weight distribution from several ten thousand to several hundred thousand. It is widely used in food, biomedicine and other fields. Compared with traditional methods, the Enzyme method of extracting gelatin is comparatively perfect method, which has short production cycle, less pollution and is prone to refine the quality of gelatin.This paper studied the process of preparation of gelatin from Tilapia fish skin by the enzyme method, and its physicochemical property.Fat content of tilapia fish skin as high as 13.6%, in order to improve the quality of gelatin, tilapia fish skin was degreased by lipase, the optimal conditions were determined by orthogonal test, as followings: the pH value of lipase treatment 9, the temperature 40℃, reactive time 3h, the dosage of lipase 2%,.In the optimal condition the defatted ratio could reach 67.5%.Secondly, further investigations on the fish skin enzyme-degrading reaction with four proteases were undergone in detail. The influences of the dosage of enzyme, the treatment time and temperature on the properties of gelatin such as yield, whiteness, viscosity, gel strength were researched and discussed. The optimize process of every protease for preparing gelatin from tilapia fish skin was established. The results of the optimization were as followings: the dosage of trypsin 0.2%, the pH value of enzyme treatment 5, the temperature 40℃, and the treatment time 1h; the dosage of papain 0.2%, the pH value of enzyme treatment 6, the temperature 40℃, and the treatment time 1h; the dosage of neutral proteinase 0.8%, the pH value of enzyme treatment 7, the temperature 40℃, and the treatment time 2h; the dosage of pepsin 0.2%, the pH value of enzyme treatment 3.5, the temperature 40℃, and the treatment time 1h. By comparing the quality of gelatin, Papain was established in the preparation of gelatin.Thirdly, chloros-oxalic acid combination method was used for bleaching skin, the fitting bleaching condition was established by orthogonal test as following: the dosage of chloros 15ml/100g, the oxidation bleaching time 3h, the deoxidization bleaching time 30 minutes with 1.5% oxalic acid. Finally, the optimum extracting condition was established by the investigation of gelatin extracting by ultrasonic and the experiments of the original pH value, the temperature and time. It was as following: the temperature 50℃→55℃→60℃,Ultrasonic power 60w,extracting gelatin 3 times ,2 hours every time., the process of gelatin extracting by ultrasonic was better than the traditional craft.In the optimal condition the gelatin yield could reach 23.15%, whiteness value could reach 40.5, viscosity could reach 7.52 mPa·S and the gel strength could reach 252 Bloom g, all of these reach the national standards for the edible gelatin(GB6783-94).