Deacidification of soybean oil by membrane technology

After extracting free fatty acids (FFA) from a model crude vegetable oil with methanol, FFA were separated from methanol by nanofiltration. Of the several commercially available membranes that were evaluated, the best resulted in FFA rejection of >90% and flux of >25 Lm⁻²h⁻¹. A combination of high-rejection and low-rejection membranes resulted in a retentate stream of 35% FFA and a permeate stream with less than 0.04% FFA, which can be recycled to the extractor. No alkali is required, no soapstock is formed, and almost all streams within the membrane process are recycled with little discharged as effluent.