Criteria for the Extraction of Fish Oil

The effect of pre-treatment of mackery (Scomber scombrus) on oil recovery and quality was investigated. Fish oil was extracted using the screw expeller press after heat pre-treatment of the fish sample. The effect of cooking temperatures and cooking times was evaluated. It was observed that the oil yield has a positive relationship with cooking temperature. The oil yield increased with increasing cooking temperature at all the cooking times investigated and also increased with increasing cooking time from 5-15 minutes and then decreased for 20 minutes cooking time at all the cooking temperatures investigated. The results revealed that a highest yield of 22.8 % was obtained when the fish was treated at 90 0C cooking temperature for 15 minutes. The lowest oil yield of 16.5 % was obtained for the conditions of 60 0C cooking temperature and 5 minutes cooking time. Analysis of oil quality indices (e.g. colour, specific gravity, refractive index, free fatty acid value, saponification value. iodine value, peroxide value, unsaponifiable matter and microbiological analysis) of oil extracted by non pre-treatment and heat pre-treatment indicated that mackery oil from both processes has comparatively similar fatty acids composition. In addition, mackery fish oil was extracted by heat pre-treatment and mechanical press had lower lipid oxidation compared to several standards

Effect of Expeller Press Parameters on Fish Oil Extraction

An investigation was carried out on the effect of expeller press parameters such as choke clearances (1, 2 and 3 mm), screw clearances (1, 2 and 3 mm) and screw (worm) shaft speeds (50, 60 and 70 rpm) on fish oil extraction. The oil extraction rate and extraction efficiency had a negative relationship with choke clearances and screw clearances but had a positive relationship with screw (worm) shaft speeds. The oil extraction rate and extraction efficiency were found to decrease with increase in choke clearances and also decreased with increase in screw clearances. Increase in screw (worm) shaft speeds from 50 to 70 rpm was observed to increase oil extraction rate and extraction efficiency. The extraction loss had a positive relationship with choke clearances and screw clearances but had a negative relationship with screw (worm) shaft speeds. The extraction loss was found to increase with increase in choke clearances and also increased with increase in screw clearances. Increase in screw (worm) shaft speeds from 50 to 70 rpm was observed to decrease extraction loss. The results obtained from the study of the effects of expeller press parameters on fish oil extraction showed that choke clearance, screw clearance and screw speed influenced oil extraction significantly at 95 % confidence level. The best extraction condition was 1 mm choke clearance, 1mm screw clearance and 70 rpm screw speed, which gave oil extraction rate of 18.91 kg/hr, extraction efficiency of 83.96 % and extraction loss of 5.76 %. The results of this study are useful in optimising the design of presses for fish oil extraction