Nutritional evaluation of processing discards from tiger tooth croaker, Otolithes ruber

Processing discards from tiger tooth croaker, such as head, viscera, and swim bladder, were analyzed for proximate, biochemical, fatty acid, and mineral composition. The proximate analysis showed high protein content (21.04%) in the swim bladder and high fat content (4.10%) and ash content (2.26%) in the head. The biochemical quality indices such as non-protein nitrogen, total volatile base, trimethylamine, free fatty acids, peroxide value, and thiobarbituric acid reactive substances in the viscera were higher than those in the head and swim bladder. Gas chromatographymass spectrometry analysis of fatty acids composition showed high polyunsaturated fatty acids in the head (58.82%), followed by the viscera (45.80%) and the swim bladder (35.57%). The major available saturated fatty acid, i.e., palmitic acid, was higher in the swim bladder (30.49%). Mineral and heavy metals analyzed via inductively coupled plasma-optical emission spectrometer showed high calcium, sodium, and magnesium contents in the head region (346.80, 62.55, and 14.89 mg/kg respectively). Heavy metal levels were within the permissible limit.