Quality and fatty acid profile of the oil extracted from fish waste (head, intestine and liver) (Euthynnus affinis)

Marine lipid contains long-chain n-3 (omega-3) polyunsaturated (PUFA), particularly eicosapentaenoic acid (EPA) (C20:5 n-3) and docosahexaenoic acid (DHA) (C22:6 n-3). Consumptions of these PUFAs have been perceived to be important in human nutrition, health and disease prevention. Tuna, the important industrial fish, discharged substantial amount of wastes. These wastes include the head, liver and intestine. Considerable amount of lipid can be extracted from these wastes. The yield and chemical quality of the oils were determined. All the extracted oils were less than 8%, of which the highest was in head (7.01%). Among different lipid sources (head, intestine and liver), the free fatty acid and peroxide value significantly increased (P < 0.05) from head to liver. The highest iodine value was found in head lipid. The predominant fatty acids in tuna wastes were palmitic (C16:0; 27.63 - 32.74%), stearic (C18:0; 8.82- 13.62%), oleic (C18:1c; 9.16- 11.95%) and docosahexaenoic acid (DHA; C22:6; 14.18- 15.70%). Differential scanning calorimetery results for tuna waste lipid samples indicated that higher unsaturation in lipid sample showed lower cooling and melting temperature. The n-3 / n-6 ratio of the respective head, liver and intestine lipid samples showed value higher than 1. Due to n-3 fatty acid compound and n-3 / n-6 ratio, lipid from tuna head may be a valuable source for human consumption.