Characterization of structural and functional properties of fish protein hydrolysates from surimi processing by-products

• Protamex and Alcalase were effective to hydrolyze surimi processing by-products.
• Structures of hydrolysates were affected by DH and enzyme type employed.
• Functionalities were also determined by DH and enzymes.
• Present study obtained the structure–functionality relationship of hydrolysates.

Structural and functional properties of fish protein hydrolysates with different degrees of hydrolysis (DH) from surimi processing by-products, prepared by Protamex and Alcalase, were evaluated. As the DH increased, the zeta potentials of the hydrolysates increased (p > 0.05). The surface hydrophobicity of the hydrolysates was significantly affected by DH (p < 0.05). A wide variety of peptides were obtained after hydrolysis by Protamex and Alcalase. The hydrolysate with DH 10%, prepared by Protamex, contained more large protein molecules than did the others. Hydrolysis by both enzymes increased solubility to more than 65% over a wide pH range (pH 2–10). The interfacial activities of hydrolysates decreased with increasing DH (p < 0.05). The hydrolysate with DH 10%, prepared by Protamex, exhibited the best interfacial properties among all of the samples. Thermal properties were also affected by the hydrolysis. The results reveal that structures and functionalities of the hydrolysates were determined both by DH and enzyme type employed.