Optimization of acid ensilaging method for the extraction of oil from Lake Victoria nile perch’ lates niloticus viscera

Abstract

A study was carried out to optimize the wet acidic rendering for extracting oil from Nile perch viscera. Oil was extracted at 93oC by varying the acid concentration from 0 – 10% and heating time from 5 – 25 minutes. The oil yield, lipolytic, oxidative and color qualities were determined to compare the effect of acid and time using a factorial completely randomized design. Statistical analysis of data was carried out at p  0.05 using GenStat 13th edition software. There was significant difference in yield, with interaction between acid concentration and heating time, the yield being highest at 15 minutes and declining thereafter with increasing acid concentration. There was significant difference in free fatty acids (%FFA), with interaction between acid concentration and heating time, values increasing with acid concentration and heating time. Heating times of 5 and 15 minutes produced the lowest %FFA at 0% acid concentration, being significantly higher after 15 minutes. All the %FFA values were within permitted limits for crude fish oil, however. There was difference in peroxide value (PV) with interaction between acid concentration and heating time, decreasing with increasing concentrations. Heating for 15 and 25 minutes produced lower PV for 0% acid concentration, with no difference between them. But the PVs were within permitted limits for crude fish oil. There were differences in color intensity, with acid concentrations, heating time not producing a significant difference, and the interaction between acid concentration and heating time not significant. There was significant difference in color intensity between 0% and subsequent acid concentrations, increasing with acid concentration. Heating for 15 minutes without acid is therefore the most suitable combination for mass production of crude oil from Nile perch viscera.