Antioxidant and functional properties of protein hydrolysates obtained from starry triggerfish muscle using trypsin from albacore tuna liver

Protein hydrolysates from starry triggerfish (Abalistes stellaris) muscle with a degree of hydrolysis (DH) of 60% were prepared using trypsin from albacore tuna (Thunnus alalunga) liver. The hydrolysates were investigated for antioxidant activity and functional properties. Antioxidant activities including DPPH (2,2-diphynyl-1-picrylhydrazyl) radical scavenging activity, ABTS (2,2-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging activity, ferric reducing antioxidant power (FRAP) and metal chelating activity of hydrolysate samples were dose dependent. After being subjected to gastrointestinal model systems, the DPPH radical scavenging activity and metal chelating activity of the hydrolysates increased, especially in the duodenal condition, suggesting the enhancement of those activities of hydrolysates after ingestion. For functional properties, hydrolysis by the trypsin increased the solubility of hydrolysates to above 72.8% over a wide pH range. The hydrolysates possessed interfacial properties, which were governed by their concentrations. An increase in concentration of up to 2.0% (w/v) favoured the emulsifying activity index (EAI) and emulsion stability index (ESI), while a further increase to 3.0% (w/v) diminished emulsifying properties. Foam expansion and foam stability increased as the protein concentration increased. Therefore, the results of the present study suggest that starry triggerfish muscle can effectively be converted to protein hydrolysates, and the hydrolysates could be a potential ingredient in functional food as well as natural antioxidants in lipid food systems.