Aqueous Extraction of Oil and Protein from Soybeans with Subcritical Water

Aqueous extraction using subcritical water is an environmentally friendly alternative to extracting oil and protein from oilseeds with flammable organic solvents. The effects of solids-to-liquid ratio (1:3.3-1:11.7), temperature (66-234 degrees C), and extraction time (13-47 min) were evaluated on the extraction of oil and protein from soybean flakes and from extruded soybeans flakes with subcritical water. A central composite design (2(3)) with three center points and six axial points was used. Subcritical water extractions were carried out in a 1-L high-pressure batch reactor with constant stirring (300 rpm) at 0.03-3.86 MPa. In general, oil extraction was greater for extruded soybean flakes than with soybean flakes. More complete oil extraction for extruded soybean flakes was achieved at around 150 degrees C and extraction was not affected by solids-to-liquid ratios over the range tested, while oil extraction from soybean flakes was more complete at 66 degrees C and low solids-to-liquid ratio (1:11.7). Protein extraction yields from flakes were generally greater than from extruded flakes. Protein extraction yields from extruded flakes increased as temperature increased and solids-to-liquid ratio decreased, while greater protein extraction yields from soybean flakes were achieved when using low temperatures and low solids-to-liquid ratio.