Alternative Techniques for Defatting Soy: A Practical Review

Hexane extraction is the most common technique used to remove oil from full fat soy materials in the production of both soy oil and defatted soy. The popularity of hexane is based on its high oil extraction efficiency and its availability. The solvent, however, has some considerable economic, environmental, and safety drawbacks. A review of alternative soybean defatting techniques is carried out through the description of four main technological approaches including: (1) alternative organic (carbon-based) solvent extraction, (2) aqueous extraction, (3) supercritical carbon dioxide (SC-CO2) extraction, and (4) enzymatically aided extraction. Through detailed discussions of experimental results, the advantages and disadvantages of each approach are presented. The optimum oil yield for the various extraction techniques discussed ranges from as high as 26.0% for mixed organic solvent extraction of full fat soy flour to as low as similar to 7% for some enzymatic treatments of full fat soy brokens extracted by mechanical pressing. An environmentally friendly, safe, and cost-efficient alternative technique has yet to be developed to replace hexane extraction. Current aqueous and SC-CO2 techniques show promise but require further research and development to ensure their practicality in terms of industrial processing.