A three-sugar oligosaccharide, galactose joined to the glucose-fructose pair of sucrose, common in beans, lentils, brassicas, and whole grains. The human small intestine lacks alpha-galactosidase, the enzyme that would split it, so it travels intact to the colon where resident bacteria ferment it enthusiastically, releasing the gas behind bean-induced flatulence. Food scientists therefore class it among legumes’ antinutritional factors. Soaking, sprouting, fermentation, and the enzyme supplement sold for this purpose all reduce its load. Commercial enzyme supplements containing alpha-galactosidase help sensitive consumers enjoy legumes.