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Characterization of Endogenous Protease and the Changes in Proteolytic Activity of Acetes vulgaris and Macrobrachium lanchesteri During Kapi Production

Pongsetkul, Jaksuma, Benjakul, Soottawat, Sumpavapol, Punnanee, Osako, Kazufumi, Faithong, Nandhsha
Journal of food biochemistry 2017 v.41 no.1
Acetes, Macrobrachium, actin, bacteria, chymotrypsin, condiments, fermentation, fluorides, hydrolysis, myosin heavy chains, oligopeptides, pH, palatability, proteolysis, raw materials, salting, shrimp, sodium chloride, soybeans, trypsin, trypsin inhibitors
Characteristics of endogenous proteases of shrimp, Acetes vulgaris (AP) and Macrobrachium lanchesteri (MP) as well as the changes in proteolytic activity during Kapi production were investigated. Maximal activity of AP and MP was found at pH 7, 60C and pH 8, 60C, respectively. Activity of both proteases decreased with increasing NaCl concentration (0–30%). Both extracts were strongly inhibited by N‐ethylmaleimide‐phenylmethane‐sulfonyl fluoride (PMSF) and soybean trypsin inhibitor (SBTI), suggesting that major proteases belonged to serine proteases. This was coincidental with high trypsin activity toward BAPNA and chymotrypsin activity toward BTEE. Proteolytic activity, trypsin and chymotrypsin were detectable throughout Kapi fermentation. The activity was decreased when salting was implemented. Nevertheless, activities increased continuously with increasing fermentation time. During Kapi production, proteins underwent degradation as indicated by the formation of oligopeptides and disappearance of myosin heavy chain and actin. Therefore, both endogenous and microbial proteases were more likely involved in proteolysis of shrimp during Kapi production. PRACTICAL APPLICATIONS: Kapi, traditional salted shrimp paste, is usually used as a condiment to enhance the palatability of many Thai foods. Recently, small shrimp Acetes Vulgaris and Macrobrachium lanchesteri have become the new alternative raw materials for Kapi production because of their availability. During fermentation, protein hydrolysis is induced by endogenous proteases in shrimp as well as those produced by halophilic bacteria. Those changes medicated by proteolysis can be associated with the final characteristics of Kapi.