After ultrasonication, the mixture was left to settle for 2 h and the liquid phase (methanol with crude FAME) was separated and centrifuged at 1000 rpm for 10 min. The spent soybean flakes were washed by using methanol at 2:1 v/w ratio. The mixture of methanol and soybean flakes was left to settle for 2 h. The liquid phase was separated from the solids and centrifuged at 1000 rpm for 10 min to remove the solids. Hexane was used to separate the fatty acid methyl ester from the excess methanol which was used for washing.