Aqueous Extraction of Wheat Germ Oil

Abstract

In this study, the aqueous extraction of wheat germ oil was examined. The effects of three different buffers and pH on oil extraction yields were evaluated. Preliminary tests carried out at a liquid:solid ratio of 12:1 (v/w) and extraction time of 4 h showed that relatively high oil yields could be obtained at alkaline pH (pH = 8.0). Tris-HCl buffer at pH 8.0 produced the highest oil yield, about 49%. Response surface methodology was used to optimize the processing parameters (liquid:solid ratio and extraction time) to maximize oil yield. Quadratic models with R2 values higher than 0.94 were developed for the three buffer systems: Tris-HCl at pH 8.0, sodium borate (boric acid-NaOH) at pH 8.0, and citrate-phosphate buffer at pH 5.0. In general, oil extraction yield improved with increasing liquid:solid ratio and decreased with prolonged extraction time at pH 8.0. The highest predicted oil extraction yields were similar for Tris-HCl and sodium borate buffers at pH 8.0, about 70%. The verification experiments carried out at the optimum conditions predicted by the models, liquid:solid ratio of 20 (v/w) and extraction time of 0.5 h, resulted in oil yields of 65% and 55% for Tris-HCl and sodium borate buffers, respectively. This study demonstrated the potential of aqueous extraction as a viable technique for recovery of oil from wheat germ. Even though the oil recovery rates achieved in this study were not very high, aqueous extraction of wheat germ oil could be economically feasible because of the higher nutritional and commercial value of wheat germ oil as compared to commodity oils such as soybean oil.