Raffinose

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Raffinose is a sugar made from three smaller sugars: galactose, glucose, and fructose. It belongs to the raffinose family of oligosaccharides (RFOs), a group of α-galactosyl derivatives of sucrose. The most common member is raffinose, followed by stachyose and verbascose.

Raffinose occurs in many plants, including beans, cabbage, broccoli, Brussels sprouts, asparagus, and other vegetables and whole grains. It is especially common in seeds and is one of the most abundant soluble carbohydrates in plants after sucrose. It typically forms white crystals called a pentahydrate, has no odor, and tastes about 10% as sweet as sucrose.

Humans and other monogastric animals can’t digest raffinose because they lack the enzyme α-galactosidase. The sugar passes through the stomach and small intestine to the large intestine, where certain bacteria that can break it down ferment raffinose. This fermentation produces short-chain fatty acids (like acetic, propionic, and butyric acids) and gas, which can lead to flatulence. Digestive aids containing α-galactosidase (such as Beano) can help some people digest raffinose-containing foods.

In plants, raffinose and other RFOs help plants cope with stress, including extreme temperatures, drought, and salinity. They are also involved in seed vigor, resistance to pathogens, and protection against drying out. The enzyme galactinol synthase (GolS) helps make RFOs, and changing GolS activity can influence defense signaling and resistance to disease.

RFOs serve as an energy and carbon source during germination and help protect seeds during maturation and drying. They may stabilize cellular structures by maintaining hydration or by forming a glass-like state that preserves cellular integrity under stress. In some plants, raffinose can act as an alternative sugar for storage and transport instead of sucrose.

The amount and composition of raffinose can vary among plants and can be influenced by environmental conditions. Raffinose and related oligosaccharides are widely studied for their roles in plant biology, nutrition, and industrial applications, including their use in cryopreservation and other research or agricultural settings.