This study aimed to develop a fish oil-extracting machine. An electric-motor powered screw press machine was used for extracting oil from fishes. The machine is made up of a feed hopper, upper casing, screw drum, perforated screen, shaft, oil trough, cake tray, and frame. The total weight of the machine is 82 kg with height of 132 cm. The components of the machine were fabricated using locally available materials which include mild and galvanised steel, that were sourced from the local market. The extractor was tested with fish at cooking times of 10, 15 and 20 minutes and cylinder speed of 80, 100 and 120 rpm. Minced Atlantic mackeryspecie of fish was used for the evaluation of the machine performance. Fish oil yield and physio-chemical/biological (micro) analysis were performed. It was observed that the oil yield increased with increasing cylinder speeds at all the heating times investigated. The best oil yield (20.9 %) was obtained for 120 rpm speed and 15 minutes cooking time and the lowest oil yield was obtained at 80 rpm and 20 minutes cooking time. Analysis of variance showed that cylinder speed, cooking time and their interaction made significant effects (p≤0.05) on the parameters evaluated and the separation of means using F-LSD also showed significant difference at . Analysis of Variance (ANOVA) at showed significant difference in the extraction loss at all the speeds investigated for the 10 and 15 minutes cooking times but there was no significant difference at the speeds of 80 rpm and 100 rpm for the 20 minutes cooking time. The extraction reduces with increasing cylinder speed at each of the cooking time. The value of free fatty acids (FFA) in the extracted fish oil was found to be 2.3%, which is within the standard value of 2% to 5% for fish oil. The iodine value was 168 I2/100g which is which is within the standard value of between 160 to 190 I2/100g. The peroxide value (PV) was 11.4 meq/kg, which is well below acceptable limit of 20 meq/kg oil. This indicated that the fish oil extracted had low lipid oxidation rate. The saponification value was187 mgKOH/g which is within the range of 165-195 mgKOH/g for fish oil. The microbiological analysis of the extracted oil showed that the total coliforms count was 6.0×103CFU/ml of oiland the faecal coliforms count was 0.25 CFU/ml of oil which are safe for human consumption. The combination of cooking time of 15 minutes and cylinder speed of 120 rpm provided the best combination for the developed fish oil extraction machine using oil yield as the main criterion.
