| Tilapia, which is recommended by Food and Agriculture Organization of the United Nations, has a huge production in our country. Nearly half of the production would be processed before exportation each year. During the process, tons of by-products including fish scale, fish skin and internal organs were discharged. The main ingredient of the scales is collagen, by reasonable use can not only solve the environmental problem, but also improve the comprehensive utilization of tilapia.In this study, tilapia scales were used as raw material, from which the collagen and collagen oligopeptides were extracted. The main research results are as follow:To make sure that the collagen content can be accurately measured in follow-up experiments, the collagen hydrolysis process and some details in determination were optimized and evaluated. When the conditions were as follow:vacuum,127℃ and for 5 hours, the collagen of Tilapia scale can be completely hydrolyzed without compromising the hydroxyproline. Compared with the traditional methods, the improved one was much time-saving and acid-saving.Based on the single-factor experiments, the response surface method using SAS 9.2 software was adopted to establish a quadratic polynomial mathematical model to optimize the process of tilapia scale collagen extraction. Research the effect to collagen extraction rate with different water extraction temperatures, times and liquid-solid ratios. Results showed that:the main factor that influence the extraction rate was in turn as: extraction temperature> time> liquid-solid ratio. By solving the corresponding regression equation, the optimal extract conditions could be obtained under the following conditions:extract temperature 120℃, optimal liquid-solid ratio 46:1, reacting for 5 h 39 min, the yield of collagen would be 44.58%,44.89% and 44.16%. UV scan showed the collagen extracted from tilapia scales had a maximum absorption at the wavelength of 225 nm. Amino acid composition analysis showed that the most abundant amino acid was glycine, while tryptophan, tyrosine and phenylalanine barely existed.The single-factor tests were conducted, using hydrolysis degree as an indicator, respectively by different kinds of proteases to find out their effects on enzymolysis of tilapia scales collagen. It turned out that Flavourzyme was the most efficient one. The main factors influencing the efficiency of enzymatic hydrolysis were screened by Plackett-Burman test among 5 independent parameters which were temperature, substrate concentration, solution pH, enzymatic addition and hydrolysis time. The solution temperature, solution pH and enzymatic addition were chosen to optimize the process of collagen hydrolysis using hydrolysis degree as an indicator in the response surface method test. The optimal hydrolysis could be obtained under the following conditions: temperature 49℃, pH value 7.2, the amount of Flavourzyme addition 16700 U/g, the degree of hydrolysis would be 10.85%,10.98% and 10.76%.Three different Tilapia-scale-collagen-peptide components were obtained after membrane separation:component Ⅰ (larger than 5000 Da),component Ⅱ (between 500-5000 Da) and component Ⅲ (smaller than 500 Da). By three kinds of in vitro experiments, their antioxidant abilities were evaluated respectively. The results showed that the antioxidant abilities were concentration related and varied with different components, among which the component Ⅲ (smaller than 500 Da) had the strongest antioxidant abilities, a, b, c, d four components were obtained when component Ⅲ purified by Sephadex G15. Antioxidation experiments showed that component b and component c had higher antioxidant capacity in those four, also the antioxidant abilities had certain ascent compared with component Ⅲ. |
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