ARTICLE FEED & ADDITIVE MAGAZINE January 2023 63 PRODUCTION OF FPH There are four methods that can be used to prepare protein hydrolysates from fish processing waste: enzymatic, acid, alkali and microbial fermentation. The most popular techniques among these are enzymatic hydrolysis and chemical hydrolysis (acid and alkali hydrolysis). Even though the chemical hydrolysis method is yields a large amount of recovered protein, it lacks some essential amino acids. The action of endogenous digestive enzymes in the fish controls the autolysis process used to make FPH. In bacterial fermentation the growth of lactic acid bacteria which produce acid and antimicrobial substances which inhibit competing bacteria but the removal of lipid is not possible. ENZYMATIC HYDROLYSIS Enzymatic hydrolysis of proteins is the most frequently opted and most promising compared to other processes as it results in products with high nutritive value and intestinal absorption characteristics. Further, this method requires comparatively small quantity of enzymes at mild hydrolytic condition that can be deactivated easily. The use of enzymes does not destroy amino acids and resulting mixtures of peptides can be easily purified. Proteolytic enzymes are commercially available from several sources like animal, plant and microbes. Common enzymes used for FPH production are pepsins, papain, bromelain, alcalase, neutrase and flavourzyme. Enzymes of microbial origin are considered as having greater pH and temperature stability. ACID HYDROLYSIS The complete fish protein hydrolysis using hydrochloric acid or sulfuric acid has been performed at elevated temperatures and also at high pressures. The solution is neutralised to pH 6.0 to 7.0 after hydrolysis, condensed and dried further. Absolute hydrolysis process can be accomplished in 18 hours Source: Fractions of soluble FPH produced from Australasian snapper Pagrus auratus by-products using alcalase enzyme (Kristinsson & Rasco, 2000)
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