Process optimisation and physicochemical characterisation of enzymatic hydrolysates of proteins from co-products of Atlantic Salmon (Salmo salar) and Yellowtail Kingfish (Seriola lalandi)

The aim of this study was to develop an enzymatic hydrolysis process of protein co-products for two major commercial fish species in Australia: Atlantic salmon (AS) and Yellowtail kingfish (YTK). The outcomes are to produce high protein recovery of fish protein hydrolysates within controlled molecular weight ranges that display enhanced physicochemical properties of oil binding and emulsification. Three enzymes (Flavourzyme, Neutrase and Alcalase) were applied to processing co-products. Protein recovery and physicochemical properties were evaluated with increasing hydrolysis time from 30 min to 180 min and ratio of enzyme to substrate (E/S) from 0.5% to 3.0%. In order to achieve a product with optimum emulsifying capacity (50 +/- 0.6 m2 g-1), an E/S ratio of 0.61.3% Flavourzyme was applied for 30111 min with a protein recovery of 55%; in order to achieve a product with optimum oil-binding capacity (8.3 +/- 0.3 g oil g hydrolysates-1), an E/S ratio of 2.33.0% Flavourzyme was applied for 2564 min with a protein recovery of 70%. YTK protein hydrolysates were further membrane-fractionated into five fractions (>100 kDa, 50100 kDa, 3050 kDa, 1030 kDa and <10 kDa), and of these, the 1030 kDa exhibited the best properties of oil binding (19 +/- 0.3 g oil g hydrolysates-1) and emulsification (57 +/- 0.7 m2 g-1). These results demonstrate the importance of enzymatic hydrolysis of seafood co-products into high-value ingredients for food products and processing.