Abstract
The soybean contains about 10% oligosaccharides consisting of 5% sucrose, 1% raffinose, and 4% stachyose and they are distributed among edible leguminous seeds. Among them sucrose is freely utilized by men and animals after enzymatic digestion into glucose and fructose, while raffinose or stachyose with one or two α-galactosyl linkages cannot be decomposed to simple sugars to be absorbed. However, the acidity of gastric juice may contribute in their hydrolysis. The pH of human gastric juice varies widely; normal values are 1.1-2.6. The gastric parietal cells secrete a fluid of constant composition, which is practically a pure solution of 0.17 N HCl (pH 0.87). Thus the hydrolysis of sucrose, raffinose, or stachyose was examined at various degrees of acidity of HCl (in the range of normal gastric acidity), and the hydrolyzates were identified as fructose and fructosyl-free reducing oligosaccharides by paper chromatography. By using the experimental values of reducing power of hydrolyzates and mixed standard sugars, 0.7-12.6% of raffinose and 0.57-9.36% of stachyose were found to be decomposed (as fructose) at pH 2.1-0.86 at 37°C after 3 hours.
