Analysis of total oil in soybeans: A new equilibrium extraction method and the effect of particle size

A new method of total oil analysis is proposed in which the solvent was equilibrated with dissolved oil inside and outside of soybean particles rather than exhaustively removing all oil. By filtering, evaporating, weighing and multiplying by a factor (based on total miscella volume/sample volume) a satisfactory analysis could be done. Particle size was found to have a profound effect on amounts of oil in soybeans extracted by a conventional procedure. Sieving ground, dehulled soybeans into three particle sizes gave 15.3, 21.9 and 24.8% oil for >40 mesh, 40–100 mesh and <100 mesh, respectively, and 23.1% oil for the unsieved sample. Evidence is presented to support the idea that the amount of oil found in the smallest particle size was the true oil content of the soybeans analyzed. Using the equilibrium method to analyze the <100 mesh particles led to a rapid and economical analysis procedure. A comparison of the equilibrium and exhaustive extraction methods showed the exhaustive extraction gave a consistently larger oil content but less than 1% larger. The difference could be attributed to phospholipid.