Protein hydrolysis and proteinase activity during the ripening of salted anchovy (Engraulis encrasicholus L.). A microassay method for determining the protein hydrolysis

The protein hydrolysis and proteinase activity during the ripening of salted anchovy were studied. A rapid, simple, and inexpensive microassay method for determining the protein hydrolysis by trinitrobenzenesulfonic acid (TNBS) has been developed. A linear relationship was observed between proteolysis determination by the TNBS method and ripening time in the fish muscle and in the brine (r = 0.99). A linear relationship was also observed between the ratio nonprotein nitrogen and total nitrogen (NPN/TN) and ripening time (r = 0.98). Proteolysis by the TNBS method and NPN/ TN determination could be considered as objective methods to follow and assess the ripening process of an anchovy. A value of proteolysis by the TNBS method of 240 mM leucine in the fish muscle and/or 200 mM leucine in the brine would indicate the ripening point. The crude enzyme prepared of fish muscle and brine showed that alkaline proteinases-dominate.