An older name for stachyose, a tetrasaccharide composed of two galactose units, one glucose, and one fructose. Stachyose occurs naturally in legumes such as soybeans, lentils, and chickpeas, as well as in certain vegetables. Humans lack the enzyme alpha-galactosidase needed to digest it, so it passes intact to the large intestine, where gut bacteria ferment it, producing the gas associated with eating beans. This same fermentation feeds beneficial bifidobacteria, giving stachyose prebiotic properties. Food scientists study it in the context of flatulence reduction, through soaking, sprouting, or enzyme treatment, and as a functional fibre ingredient.