Dietary Fiber Contents of Soybean and Soybean Foods

Abstract

Dietary fiber (DF) contents of soybean and soybean foods, kinako, natto, akadashi-miso, hacchomiso and okara, were determined by the detergent fiber method of Van Soest. Pectin, main undigestible polysaccharide of soluble DF, and crude fiber were also determined. Okara had the largest total DF value. Fermented foods, miso and natto, were low in hemicellulose and pectin contents. Kinako had remarkable high value in neutral detergent fiber (NDF). The NDF fraction from soybean contained nitrogen compounds which increased with heating. By means of differential thermal analysis using DSC, it was found that insoluble compounds was derived from protein, pectic substance and others during the heating procedure and were taken into NDF fraction at the time of DF determination. Since insolubilized protein in the NDF fraction was digested by the treatment of proteases such as pepsin and trypsin, it was proposed to treat NDF with proteases for the determination of DF in the heated soybean products such as kinako.