The individual and total isoflavone content in commercial soybean protein products has been determined by high-performance liquid chromatography. Dehulled, defatted soybean flours contain the following mean isoflavone content (mg/100 g): daidzin, 61.7; glycitein 7-/S-glucoside, 12.9; genistin, 119.8; daidzein, 32.8; genistein, 26.7. The same isoflavones were found in soybean protein concentrates and soybean protein isolates but in decreased amounts.
Total carbohydrate content and the amounts of each sugar present in commercial samples of soybean protein products were determined by hydrolysis and gas-liquid chromatography of the alditol acetate derivatives of the sugars. Dehulled, defatted soybean flours contained the following mean sugar content: rhamnose, 0.6%; fucose, 0.1%; ribose, 0.1%; arabinose, 2.4%; xylose, 1.0%; pinitol, 0.9%; mannose, 0.9%; galactose, 7.6%; and glucose, 8.1%. The same sugars were found in soybean protein concentrates; however, the amount of each was less. Soybean protein isolates contained mannose, 0.8%; galactose, 0.5%; and glucose, 0.5%, with traces of the other five sugars.Compared to oil and protein, carbohydrates of soybeans have received comparatively slight attention by chemists. This neglect is a result of the greater economic importance of the oil and protein constituents in foods and feeds. It is generally assumed that the carbohydrate content of soybeans and defatted meal is equal to the nitrogen-free
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