Stachyose

Stachyose is a non-reducing tetrasaccharide of legumes and other plants; hydrolysis yields two galactose molecules plus one each of glucose and fructose. Humans lack the alpha-galactosidase enzyme needed to digest it fully in the small intestine, so it passes to the colon where gut bacteria ferment it, producing the gas behind beans’ famous flatulence effect. Food technologists study it in connection with legume processing, since soaking, germination, and fermentation all reduce stachyose levels and improve digestibility. Breeding low-stachyose bean varieties is another route to gentler legumes.