Characterization of Endogenous Protease and the Changes in Proteolytic Activity ofAcetes vulgarisandMacrobrachium lanchesteriDuringKapiProduction

Abstract

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.

Microbiological and chemical changes of shrimp Acetes vulgaris during Kapi production

“…These changes in free amino acid during processing might be influenced by endogenous proteases in raw material and microbial proteases proliferated during processes. Our previous study revealed that proteolytic activity of fresh shrimp was decreased after being salted and dried, but continuously increased during fermentation up to 30 days (Pongsetkul et al 2016). Those proteases more likely played a profound role in protein degradation, thus contributing to the liberation of free amino acids throughout Kapi production.…”

Effect of amla and ginger powders on quality criteria of African catfish (Clarias gariepinus) fingers

“…Highly unsaturated fatty acids are more likely to oxidise, which lowers their nutritional value and produces a disagreeable taste and odor (Chotphruethipong and Benjakul, 2019). Proteolytic enzymes and gut bacteria break down a significant amount of proteins, resulting in the production of ammonia and nitrogenous substances, which compromises the safety and sensory qualities of the proteins (Olatunde et al, 2019;Pongsetkul et al, 2017).…”

Recent developments of natural antimicrobials and antioxidants on fish and fishery food products

“…Highly unsaturated fats are more susceptible to oxidation, thus reducing their nutritive value and generating unpleasant odor and taste (Chotphruethipong & Benjakul, 2019; Maqsood et al., 2014). Large proportions of proteins are degraded by proteolytic enzymes and gut microflora to produce ammonia and nitrogenous compounds, affecting their safety and sensory attributes (Hsieh & Kinsella, 1989; Olatunde et al., 2019b; Pongsetkul et al., 2017).…”