* For correspondence: T. Bako (Email: engbako@gmail.com ) ISSN: 2348-4330 Journal of Postharvest Technology 2018, 06(4): 116-125 http://www.jpht.info R E S E A R C H A R T I C L E Effects of heat treatment on fish oil extraction process using a single screw expeller Tanko Bako * , Victor Imolemhe Umogbai, John Okanagba Awulu Department of Agricultural and Environmental Engineering, University of Agriculture, Makurdi, Nigeria Received: 23.07.2018 Accepted: 16.09.2018 A B S T R A C T Effects of heating temperature and duration on yield and quality (free fatty acids value, saponification value, para-anisidine value and peroxide value) of oil extracted from fish using a single screw expeller was studied. Heating temperature and duration were 60, 70, 80 and 90 °C and 5, 10, 15 and 20 minutes respectively. All data collected were subjected to analysis of variance (ANOVA) to test for significant effects at 95 % confidence limit. When significant difference was observed, treatment means were separated using the F- LSD. The oil yield ranged between 17.2 % and 21.6 %, free fatty acid values (2.2–4.5 %), saponification values (134-189 mgKOH/g), para-anisidine values (7.3-12.2 mEq/kg) and peroxide values (8.1–11.7 mEqO2/kg). The treatments have significant effects on oil yield, free fatty acid value, saponification value, para-anisidine value and peroxide value or at p<0.05. The mean separation also shows significant effects on oil yield, free fatty acid value, saponification value, para-anisidine value and peroxide value at p<0.05. Optimum temperature and duration of heating were 90 °C and 15 minutes respectively. This combination gave 21.6% oil yield, 2.5 % free fatty acid value, 136 mgKOH/g saponification value, 10.8 mEq/kg para-anisidine value and 8.3 mEqO2/kg peroxide values. Keywords: Oil extraction; fish oil; screw expeller; process parameters Citation: Bako T., Umogbai, V.I., Awulu, J.O.2019. Effects of heat treatment on fish oil extraction process using a single screw expeller. Journal of Postharvest Technology, 6(4): 116-125. INTRODUCTION Fish is one of the most popular food items for human consumption throughout the world. Fish oils have gained much more importance because of the presence of health beneficial omega-3 fatty acids in them. These polyunsaturated fatty acids (PUFA) especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) play a crucial role in the prevention of atherosclesis, heart attack, depression, stroke, diabetes, obesity, premature ageing, hypertension, cancer and improve the vision power and memory (Adeniyi, 2006; Hee-Guk et al., 2008). Fish oil is the lipid fraction extracted from fish and fish by products. Generally, fish oils are more complex than land- animal oils or vegetable oils due to long – chain unsaturated fatty acids. Fish oils are unique in the variety of fatty acids of which they composed and their degree of un-saturation (Fournier et al., 2007; Zhong et al., 2007; Valeria et al., 2010). Refined fish oils are rich in polyunsaturated fatty acids of the linolenic acid family. Current medical research suggests that these fatty acids might have a unique role to play in prevention of coronary artery disease and the growth of different types of cancers. The oil is industrially used in leather tanning, production of soap and glycerol, and other