Protein, Fiber, and Lipid Content of Vegetable Soybean

Abstract

There has been an increased interest in soybean nutrition. Soybean is harvested for oil and soyfood production, but may also be for use as a vegetable. Matured soybean and field-type soybean, from which soyfood and oil are manufactured, are high in protein and linoleic acid, respectively. Little is known about these nutrient contents in vegetable soybean. We analyzed the vegetable soybean's protein, fiber, and fatty acid composition. Thirty-one vegetable soybean genotypes from Maturity Groups III-VI harvested between Growth Stages 6 and 7 were shelled and freeze dried. Kjeldahl and Weende methods were used to analyze nitrogen and crude fiber, respectively. After extraction by Maxwell's method, gas chromatography was used to analyze total lipid and fatty acids. Protein was calculated by multiplying nitrogen by 6.25. Mean grams % of dry vegetable soybean were: 7.5 crude fiber; 36.9 protein; and 18.3 total lipid. Mean fatty acids % of total lipid were: 19.08 palmitoleic acid; 15.80 oleic acid; 44.77 linoleic acid; and 12.94 linolenic acid. There were significant correlations (p>0.01) among these nutrients. All nutrients showed significant differences among the genotypes, indicating high variabilities. When selecting genotypes for production, attention should be given to the nutrient content of the genotypes to breed a vegetable soybean having enhanced oleic acid and fiber content.