Hydrolysates from rainbow trout (Oncorhynchus mykiss) processing by-product with different pretreatments: Antioxidant activity and their effect on lipid and protein oxidation of raw fish emulsion

Rainbow trout by-product was minced and subjected to different preparing methods including simple distilled water washing, calcium chloride + citric acid washing or their combinations, prior to hydrolysis. Particle diameter and zeta potential of the homogenized by-product were similar to 45 nm and similar to 23 mV, respectively. Less thiobarbituric acid-reactive substances (TBARS) and protein carbonyls were formed during hydrolysis when minces were washed with distilled water (BPW-FPI) or distilled water prior to calcium chloride + citric acid washing (W-CaCi-BPFPI) (P < 0.05). The extent of oxidation was reduced by addition of pistachio green hull extract (P < 0.05). BPW-FPI showed high ABTS radical cation scavenging activity, metal chelating activity and ferric reducing antioxidant power (FRAP). The addition of BPW-FPI (1-3 g/100g) also decreased the oxidation of raw fish emulsion during 6 days of refrigerated storage in a dose dependent manner (P < 0.05). Thus, BPW-FPI could serve as the alternative antioxidant in raw fish emulsion.