Although protein isolates have been proven as a potent raw material for protein hydrolyzate preparation, the fishy odor associated with lipid oxidation is still detected. The remaining hemoglobin (Hb) in protein isolates can effectively induce lipid oxidation, leading to the formation of fishy odor in the resulting hydrolyzate. The aim of this study was to elucidate the impact of Hb with different forms, oxyhaemoglobin (oxy-Hb) and methaemoglobin (met-Hb), on lipid oxidation and the development of fishy odor during hydrolysis of protein isolates.
During hydrolysis of protein isolate up to 120 min, non-haem iron content, peroxide value and thiobarbituric acid reactive substances slightly increased (P <0.05). When oxy-Hb or met-Hb was incorporated, the marked increases in all parameters were observed, especially within the first 60 min of hydrolysis. The higher increases were obtained with the latter, suggesting that met-Hb was more pro-oxidative than oxy-Hb. However, no differences in degree of hydrolysis of all samples were observed (P > 0.05). The marked increases in the b*, ΔE*, ΔC* values, fishy odor / flavor and volatile compounds were also found in the resulting hydrolyzate containing either oxy-Hb or met-Hb.
Hb, particularly met-Hb, induced lipid oxidation and the development of a fishy odor / flavor in fish protein hydrolysate. © 2013 Society of Chemical Industry