Galactoglucomannans

Galactoglucomannans (GGM) are plant polysaccharides belonging to the hemicellulose group, found in the secondary cell walls of many softwood species.

They are heteropolysaccharides with a backbone consisting of β-D-mannose and β-D-glucose units linked by β-(1→4) glycosidic bonds, with side chains of α-D-galactose attached to some backbone residues via α-(1→6) linkages. The galactose content and the mannose-to-glucose ratio vary with species, giving different degrees of branching and solubility.

GGM occur predominantly in softwoods such as spruce and pine and can also be found in some hardwoods and cereals to a lesser extent. In wood processing, they are extracted during pulping and can be recovered as water-soluble fractions or as part of the residue.

As isolated polymers, GGMs have high molecular weight and form viscous solutions. Solubility and rheology depend on galactose substitutions and molecular weight; they are generally more soluble with higher galactose branching. Their behavior in solution makes them useful as hydrocolloids in various applications.

Industrially, GGMs are used as hydrocolloids in paper production and as binding components. In food and nutrition, they function as dietary fiber and thickening/stabilizing agents in some products and may be included to increase fiber content; they are also studied as prebiotic substrates.

Human enzymes do not digest GGM; fermentation by gut microbiota yields short-chain fatty acids. Tolerance is generally good, but high intake can cause gas and bloating in some individuals.

See also: hemicellulose, glucomannan, galactomannan.