LIQUEFYING COD FISH FRAMES UNDER ACIDIC CONDITIONS WITH A FUNGAL ENZYME

An acidic protease (Newlase A from Rhizopus niveus, Amano) was evaluat ed as to its ability to reduce viscosity of ground cod fish frames wit hout excessive hydrolysis. Newlase A had an optimal pH of 3.5 and an o ptimal temperature of 60C with Azocoll as substrate. The enzyme was mo re stable in the ground fish mixture at pH 3.5 than it was in citrate: phosphate buffer of the same pH. The enzyme hydrolyzed the fish protei ns more extensively and decreased the viscosity of the ground fish mor e between 40-50C over an extended time period than at its optimal temp erature of 60C. It is likely that the lower optimal temperature under these conditions is related to its greater stability at the lower temp eratures. The energy of activation of the deactivation of the enzyme w as 44.5 Kcal per mol-degree. Over a period of 75 min at 45C there was a decrease in viscosity of the groundfish with added enzyme of some tw o orders of magnitude. After a 3-h incubation, total soluble protein i ncreased from 30% to 48%; the amount of each molecular size fraction p roduced decreased in the following order: 1-3, > 10, < 1, and 3-10 kda ltons.