Effect of Extraction Methods on the Quality Characteristics of Catfish ( Clarias gariepinus ) Oil

Abstract

The effect of kiln smoking and manual extraction of oil from catfish was investigated. Oil from African Catfish, Clarias gariepinuswas extracted by smoking with a WAAPP-NIOMR 50kg capacity Kiln and by manual extraction from the fish abdominal walls and around the organs was rinsed under running water and boiled over medium heat with a Salad master titanium T316pot. Smoking was done for the purpose of preserving, imparting colour and increasing the palatability of fish. The oils obtained through these methods were evaluated physically and chemically. Physical examination showed two clear oils (supernatants) and two sludge obtained through the above methods, respectively. The smoked extracted oil and sludge were associated with darker colour than those obtained by manual method. Manually extracted oil and sludge showed a significant difference (p≤0.05) and an increase in peroxide value (PV) of 6.90±0.34 and 6.54±0.36meq/kg and a decrease with significant difference (p≤ 0.05) in per-cent free fatty acid (%FFA) of 0.54%±0.03 and 0.39%±0.08 respectively when compared with the oil and sludge of kiln smoking with peroxide values of 4.56±0.12 and 3.11±0.14meq/kg and per-cent free fatty acid of 7.27%±0.06 and 6.30%±0.02, respectively. The kiln smoked oil and sludge showed an average per-cent Moisture, Impurity and Volatiles (%MIV) of 1.085±0.13 and 0.743±0.06%, respectively which was insignificant (p≥0.05) with the manually obtained oil and sludge 0.084±0.01 and 0.1385±0.02%, respectively. Fatty acid profile of the oils showed the existence of twelve fatty acids in the kiln smoked oil and sludge with lignoceric acid (15.08% and 16.70%,respectively) as the predominant saturated fatty acid and linolenic acid (33.26% and 37.05%,respectively) as the major polyunsaturated fatty acid, while the manually extracted oil and sludge were found with fifteen fatty acids with myristic acid (18.89% and 8.61%) as the predominant saturated fatty acid and linolenic acid (43.03% and 48.14%,respectively) as the total unsaturated omega-3 fatty acid.