Abstract:Due to the rapid development of Tilapia exportation in China, a large number of fish processing by-products have been generated which are rich in collagen. Proper extraction of the collagen from the by-products could help alleviate environmental pollutions as well as improve the added value of the fish processing by-products. In this study we used Tilapia skin as the material and applied the orthogonal design and the single factor test to exam the efficiency of alkali method, acid method and enzyme method in the pretreatment of Tilapia skin, according to the skin yield, viscosity and gel strength. Through a set of experiments we first identified the best method among the three and then optimized the bleaching and extraction process, and at last we made a discussion about this study to provide guidance on the gelatin production using fish skin. The results showed that the enzyme method was the best for gelatin extraction. The process was as below: the fish skin was treated with 0.2% mixed enzyme solution at pH 3.5, and underwent enzymatic hydrolysis at 40℃ for 1 h; the skin was then blanched with 6% potassium permanganate solution for 3 h followed by further blanching with 1.5% oxalic acid solution for 45 min; the skin was then degelatinized at pH 5−6. The gelatin extraction process includes 3 heating steps: 60℃ for 2 h, 65℃ for 2 h, and 70℃ for 2 h before the final filtrated product was pooled. The filtrate was then concentrated to around 20% in the vacuum (≥500 mmHg) at the temperature ≤60℃. The concentrate was dried (water content <14%) at 60℃ and the final gelatin product was obtained after crushing. The yield of gelatin was 19.93% (wet basis), and the viscosity was 13.1 mPa•s, and the gel strength was 1034.3 g/cm2.
