Studies On Anchovy Endogenous Proteases And Biochemical Characterizations During The Production Of Fish Sauce Made From Low-valued Fish

Along with the upgrading of people's living standard, low-value fish are low edible value. In the fish processing, a large number of by-products, such as offal, skin, eye and eye socket, have been abandoned, which causes environmental pollution. On the other hand, the worldwide lack of protein resource becomes a serious problem. Comprehensive utilization of protein resources, Deep Processing of low-value fish and by-products has important practical significance.The biochemical characterizations during the production of fish sauce by anchovy and by-products of squid are explored. And anchovy endogenous protease is preliminarily studied.1. The biochemical characterizations of anchovy endogenous protease are studied briefly. And the appropriate anchovy autolysis conditions are explored for fish sauce production.Anchovy is rich in endogenous protease, the endogenous protease from digestive tract of anchovy has been characterized by biochemical techniques. The result shows that the anchovy crude endogenous protease is mainly composed of four proteases. Their most favorable pHs are 2.5, 5.5, 9.0, 12.5 respectively. At pH 5.5-12.5, PMSF (phenylmethyl sulfonyl fluoride) and SBTi (strontium bismuth titanate) inhibit the crude enzymes obviously. That suggests the existence of serine protease in the crude anchovy enzyme. The experiment illustrates that calcium plays a significant role in stabilizing the enzyme structure and improving the stability of the enzyme at pH6.5-9.0 and pH12.5-14.0.A study for verifying anchovy autolysis is made for the optimum conditions. The autolysis is performed under these conditions. Then the hydrolysis of anchovy autolysis with three exogenous proteases, i.e., flavor protease, alkaline protease and trypsin, is explored. The changes ofα-amino nitrogen, soluble nitrogen, total acid, TVB-N, protein and amino acid conversion rate of recovery are determined in the process. The change trends are discussed. The result shows that after hydrolysis in the initial pH9.0, at 50℃, theα-amino nitrogen concentration is 0.4962 g/100ml. At the same time, the concentration of the soluble nitrogen, recovery rate of protein and conversion rate of amino acid have all improved.2. The changes of biochemical characterizations in the production of fish sauce with by-products of squid processing.Fish sauce is generated from by-products of squid processing, including head, viscera, skin and fins. After thawed, three methods are used. Salt, soy sauce koji, distilled water and mixed proteases are added to the material in method A. Method B is the same as A except mixed protease. And in method C, the material has autolyzed 48 hours, then salt, soy sauce koji, distilled water and mixed proteases are added into it. After above-mentioned treatments, each of these materials continues to ferment 30 days at 48°C, respectively. The total soluble nitrogen, conversion rate of nitrogen, pH, amino nitrogen, total acid, total volatile basic nitrogen (TVB-N) and protease activity are assayed during the process. The results show that total soluble nitrogen, conversion rate of nitrogen, amino nitrogen and TVB-N increase in the fermentation. But the pH, total acid and protease activity exhibit different trend in different stages.