Enzyme Engineering
Open Access

Abstract

Extraction of Oil from Mackerel Fish Processing Waste using Alcalase Enzyme

Ramakrishnan VV, Ghaly AE, Brooks MS and Budge SM

After removing the flesh during fish processing operations, all other parts are considered waste which is not properly utilized. Fish and fish waste can be used to produce oil for further production of omega-3 fatty acids, and/or biodiesel. Fish oil is found in the flesh, head, frames, fin, tail, skin and guts of fish in varying quantities. In this study, enzymatic extraction of fish oil was carried out using alcalase enzyme at three enzyme concentrations (0.5, 1 and 2%) and four time intervals (1, 2, 3 and 4 h). The highest oil yield was obtained from the head and the lowest oil yield was obtained from the frame. The oil obtained after enzymatic hydrolysis was dark in color due to the formation of brown pigments from the reaction of carbonyls produced from oxidation of polyunsaturated fatty acids with amino acids and proteins. The addition of buffer during the hydrolysis played an important role, as it increased the formation of emulsion, decreased the production of free oil and increased the recovery of soluble proteins. The initial heating of raw material played an important role as it helped to increase the oil yield, but it would have been more effective if no water or buffer was added to the system. The highest oil yield (76.26% from head and 75.71% from the whole fish) was obtained using 2.0% enzyme concentration after 4 h of hydrolysis. The results showed that increasing the enzyme concentration by from 0.5 to 2% (400%) increased the oil yield by 0.10-63.71%, depending upon the fish part and reaction time used. Increasing the enzyme concentration for a small increase in oil yield may appear unjustified. Therefore, the concentration of 0.5% should be used for the oil extraction, unless the enzyme is recycled or an immobilized reactor is used in order to reduce the cost associated with the enzyme. The results also showed that increasing the reaction time by from 1 to 4 h (400%) increased the oil yield by 26.62-59.29%, depending upon the fish part and enzyme concentration used. Increasing the time for a small increase in oil yield will increase the capital and operating costs of production. A shorter reaction time will allow more throughputs, and/or reduce the volume of the reactor, thereby reducing the cost of oil extraction. Therefore, a 1 h reaction time for oil extraction is recommended.