Galactomannans

Galactomannans are plant-derived polysaccharides composed of a linear chain of β-1,4-D-mannose units with randomly distributed α-1,6-D-galactose side chains. The degree of galactose substitution and the molecular weight influence their solubility, viscosity, and gelling behavior. They are non-ionic hydrocolloids used as thickeners, stabilizers, and, in some cases, gelling agents.

Commercial galactomannans are mainly extracted from legume seeds. Locust bean gum (carob bean gum) comes from Ceratonia siliqua; guar gum is from Cyamopsis tetragonoloba. Other galactomannans used commercially include tara gum from Caesalpinia spinosa and tamarind seed gum.

In food and industrial applications, galactomannans impart viscosity at low concentrations, stabilize emulsions and suspensions, and improve texture. They are widely used in gluten-free baked goods, dairy products, sauces, dressings, and ice creams, and they often act in synergy with other hydrocolloids such as xanthan. They are also used in cosmetics and pharmaceuticals as thickening agents and excipients.

Properties and regulation: viscosities are affected by concentration, temperature, pH, and ionic strength; different sources and grades yield different performance. Most galactomannans are approved for use in foods under regulatory frameworks (for example, GRAS in the US and equivalent approvals elsewhere).

Health considerations: they are not digested in the small intestine but are fermentable by colonic bacteria, contributing to dietary fiber and short-chain fatty acids. High intake can cause gas or laxation in some individuals.