EFFECT OF SQUID LIVER EXTRACT ON PROTEINS AND ON THE TEXTURE OF COOKED SQUID MANTLE

The liver extract of squid Illex argentinus has a proteolytic activity at pH 2-8, with optimum at pH 2.6-3.1. At pH 6 the enzymes retain about 30 and 55% of the maximum proteolytic activity towards hemoglobin and casein, respectively. In squid mantle meat treated with the extract 24 h at 4C and 20C, the sarcoplasmic and myofibrillar proteins were hydrolyzed to low molecular fractions, as was shown by SDS-PAGE. Soaking isolated collagen fibers in the liver extract resulted after 24 h in almost complete solubilization of the fibers in buffered SDS/urea solutions. The solubilized product contained only low molecular weight components. A significant hydrolysis of the proteins in the squid mantle, treated with the liver extract at 20 or 4C, was accompanied by a decrease in toughness of the cooked product by about 65 and 40%, respectively, as compared to the toughness of untreated cooked samples. Cooking of the mantle directly in the liver extract had practically no tenderizing effect.