Extraction of Proteins and Pasting and Antioxidant Properties of Soybean Hulls

Soybean hulls are a by-product from soybean processing for oil and meal production which comprise approximately 8% of the whole seed. This study investigated water holding capacities and pasting properties, and first reported the phenolic contents and antioxidant activities from soybean hulls which are important to our long-term health. In addition, the conditions for extracting proteins from soybean hulls including optimum pH, as well as homogenizing and separation methods for extraction, were also studied. Higher protein content in extracts and recoveries was obtained with extraction at pH 9. Using sieve separation may be an effective way to extract proteins from hulls for industrial applications. The precipitated protein content increased from 51.52% to 59.29% after purification by washing with water once; however, after two washes, no further improvement was shown. The extracted proteins can be used for food applications. The ground hull powders (10% protein), dried supernatant (14% protein) and sediments (7-8% proteins) along with valuable fibers should be good food ingredients for several food categories. This research explored the great potential of converting the low value by-products into value-added functional food uses along with the benefit of reducing food and agricultural wastes.