Antioxidant properties of aqueous and methanol soy extracts in minced trout muscle

Antioxidant capacity of freeze-dried aqueous and methanolic extracts of soy protein isolate (SPI) and soybean meal (SBM) were assessed by 2, 2′-Diphenyl-1-picrylhydrazyl (DPPH) assay and total phenolic content (TPC). Caffeic and chlorogenic acids in liquid aqueous extracts, and genistein and daidzein in liquid methanolic extracts were measured by HPLC. Freeze-dried extracts were applied (1000 and 4000 μg/g) to trout mince and TBARS formation monitored during 14 days refrigerated storage. SBM aqueous extracts-treated mince (4000 μg/g) had significantly lower (P < 0.05) TBARS than all other treatments. SPI methanolic extract had the highest TPC (100 mg chlorogenic acid equivalents/100 g extract) and genistein and daidzein contents. SPI aqueous extracts had the highest chlorogenic acid (280 μg/g) while SBM aqueous extracts had the highest caffeic acids content (484 μg/g). SPI had the best in vivo antioxidant profile. SBM extracts were most effective at retarding lipid oxidation in refrigerated trout mince.