Raffinose is a complex carbohydrate, a trisaccharide composed of galactose, fructose, and glucose. It can be found in beans, cabbage, brussels sprouts, broccoli, asparagus, other vegetables, and whole grains. Raffinose is hydrolysed to D-galactose and sucrose by

Raffinose is also known as melitose and may be thought of as galactose + sucrose connected via an alpha(1-6) glycosidic linkage and so raffinose can be broken apart into galactose and sucrose via the enzyme alpha-galactosidase. Human intestines do not contain this enzyme.

The Raffinose Family of Oligosaccharides (RFO) are alpha-galactosyl derivatives of sucrose, and the most common are the trisaccharide raffinose, the tetrasaccharide stachyose, and the pentasaccharide verbascose. The RFO's are almost ubiquitous in the plant kingdom, being found in a large variety of seeds from many different families, and they rank second only to sucrose in abundance as soluble carbohydrates.

Humans and other monogastric animals (pigs and poultry) do not possess the alpha-galactosidase enzyme to break down these RFO and the oligosaccharides pass undigested through the stomach and upper intestine. In the lower intestine they are fermented by gas-producing bacteria which make carbon dioxide, methane, and/or hydrogen -- leading to the flatulence commonly associated with eating beans. Raffinose is broken down by the intestinal bacteria with the help of the enzyme alpha-galactosidase. Alpha-galactosidase is the enzyme you take when you ingest the product Beano.