Summary:
Lipid oxidation and fishy odor development in protein hydrolyzate from fresh and ice-stored Nile tilapia (Oreochromis niloticus) were investigated. During iced storage of 18 days, heme iron content decreased with a concomitant increase in non-heme iron content (P <0.05). Peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) values increased. Phospholipid content decreased with a corresponding increase in free fatty acid content. The results suggested that lipid hydrolysis and oxidation took place during storage. When protein hydrolysates were produced from fresh and 18 days ice-stored Nile tilapia muscle, higher lipid oxidation and fishy odor / flavor along with higher amount volatile compounds were obtained in hydrolysate for unfresh sample (P <0.05). However, the addition of mixed antioxidants during hydrolysis process markedly lowered lipid oxidation, b∗, ΔC∗, ΔE∗ values, fishy odor / flavor as well as the formation of volatile compounds in the resulting hydrolysates prepared from both fresh and unfresh samples. Therefore, hydrolyzate from Nile tilapia muscle with reduced fishy odor and lighter color could be prepared by using fresh fish and incorporation of mixed antioxidants during hydrolysis.