galaktomannan

Galactomannan is a class of polysaccharides composed of a linear chain of mannose units with galactose side chains. They occur as major components of plant seed gums and are also found in some fungal cell walls. In plant sources, galactomannans consist of a mannose backbone with galactose residues attached as side chains. The degree of branching, expressed as the galactose-to-mannose ratio, varies by source and influences viscosity and other functional properties. Common sources include guar gum (from Cyamopsis tetragonoloba), locust bean gum or carob gum (from Ceratonia siliqua), and fenugreek.

Structure and properties: The backbone is formed by α-D-mannopyranose units linked mainly by 1→4 bonds, while galactose side chains (α-D-galactopyranose) are attached to the backbone at O-6 via α-1,6 linkages. A higher galactose content reduces intermolecular association and gelling tendency, whereas a lower content yields higher viscosity. Galactomannans are generally soluble in hot water to form viscous, pseudoplastic solutions; they do not gel alone but can interact with other hydrocolloids such as xanthan gum to form gels and enhance stability.

Applications: In the food industry, galactomannans are widely used as thickeners, stabilizers, and binders in dairy products, baked goods, sauces, soups, and ice cream, often at low concentrations. They are also employed in pharmaceuticals and cosmetics as excipients and texture enhancers, benefiting from their high water-binding capacity and texture-modifying properties.

Medical relevance: Galactomannan is a cell-wall–associated polysaccharide used as a clinical biomarker for invasive aspergillosis. Tests detect galactomannan in serum or bronchoalveolar lavage using antibodies or monoclonal reagents; results can be affected by certain antibiotics, dietary factors, or cross-reactivity with other fungi.