Effect of steam explosion pretreatment on the aqueous extraction efficiency of soybean oil

Abstract

Soybeans belong to low oil content oilseeds, it is very difficult to obtain free oil through aqueous phase extraction, and the residual oil rate of soybean meal is relatively high. After steam explosion pretreatment of soybeans, oil was extracted with aqueous ethanol. The effects of steam explosion and extraction conditions on the yield and quality of free oil were investigated, in order to establish a green processing technology for soybean oil. After steam explosion pretreatment at a pressure of 1.0 MPa for 15 s, soybean oil was extracted by shaking at 140 r/min and 70 °C for 2 h using a 45 % (v/v) ethanol aqueous solution with a liquid to material ratio of 3:1 mL/g. The free oil yield of soybean increased from (61.91 ± 0.77)% of the control to (96.69 ± 0.50)%, and the residual oil rate of the meal decreased from (13.38 ± 0.61)% to (1.32 ± 0.28)%. The free oil obtained from soybeans subjected to steam explosion pretreatment met the national standards of first-class soybean oil in terms of color, acid value and peroxide value. Steam explosion pretreatment led to the rupture of soybean cells, an increase in protein hydrophilicity, and the aggregation and fusion of oil bodies into larger oil droplets outside the cells, thereby promoting the release of free oil. However, the structural and property changes of soybean meal protein were relatively small. This provides a new method for efficient, safe and environmentally friendly production of soybean oil, with broad application prospects, laying the foundation for innovation in soybean oil processing.