Characteristics of Oil and Skim in Enzyme-Assisted Aqueous Extraction of Soybeans

The economic viability of enzyme-assisted aqueous extraction processing (EAEP) of soybeans depends on properties and potential applications of all fractions (skim and insolubles as well as oil). EAEP oil contained lower free fatty acid, phosphorus, and tocopherol contents, similar unsaponifiable matter levels, and higher degrees of oxidation (peroxide and p-anisidine values) than hexane-extracted oil. The phospholipid profile of EAEP fractions was mainly composed of phosphatidic acid, followed by phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Most of phospholipids were present in the skim, except for phosphatidic acid, which was the major phospholipid in the cream fraction. Skim and cream contained 55 and 3 % of the soluble carbohydrates in the original extruded flakes, respectively. Soluble carbohydrates of the skim were mainly composed of stachyose (5.8 +/- A 0.8 mg/mL) and sucrose (9.9 +/- A 0.8 mg/mL), which were hydrolyzed into glucose, galactose, and fructose after addition of alpha-galactosidase. Skim and cream peptides contained < 20 kDa MW molecules. About 71 % of the skim peptides were < 20 kDa MW, with 49 % being < 1.35 kDa MW, 22 % being 17-1.35 kDa MW, and 29 % being 44-670 kDa MW. Skim protein and carbohydrate contents make this fraction suitable for replacing water in ethanol fermentations, thereby improving the fermentation rate/production and the nutritional quality of distiller's dried grains with solubles.