Effects of solvent, temperature, time, solvent-to-sample ratio, sample size, and defatting on the extraction of soluble sugars in soybean

Extraction solvent, temperature, time, and solvent-to-sample ratio were studied to identify the optimal conditions for extracting sugars from nondefatted soybean. Water and 10%, 50%, and 80% (v/v) ethanol were used as the solvents. Extraction temperatures of 25 degrees C, 50 degrees C, and 80 degrees C, for 15, 30, and 60 min and solvent-to-sample ratios of 5:1, 10:1, and 15:1 (v/w) were combined with different solvents. The sugar composition in the soybean extracts was analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection. The sugar appropriate to be used as the standard in the phenol-sulfuric acid method in sugar quantification, and effects of sample size and defatting on sugar extraction were also evaluated. The optimum extraction protocol concluded from this study includes the use of water as the solvent at a solvent-to-sample ratio of 5:1 at 25 degrees C or 50 degrees C for 15 min. Sucrose was shown to be the best sugar as the standard to quantify the total soluble sugars in soybean. Extractions from sample size of 1 g and 0.1 g yielded similar soluble sugars. A greater amount of sugars was extracted with the defatted soybean meal than with the nondefatted sample.