xanthan

Xanthan is a high molecular weight polysaccharide produced by the fermentation of glucose or sucrose by the bacterium Xanthomonas campestris. The product, commonly sold as xanthan gum, is used as a thickening and stabilizing agent in food, cosmetics, and industrial applications.

Chemically, xanthan is a heteropolysaccharide with a cellulose-like backbone of beta-D-glucose units. At alternate units, a trisaccharide side chain containing mannose and glucuronic acid residues is attached, and the side chains may be acetylated or pyruvylated. These substitutions give xanthan its rigid conformation and high water-holding capacity.

Production involves aerobic fermentation of carbon sources by X. campestris followed by precipitation and purification to yield a free-flowing powder. The raw gum is typically dried and may be milled or ground; food-grade products undergo additional purification to remove contaminants.

Physically, xanthan dissolves in water to form highly viscous, thixotropic solutions. Viscosity is concentration dependent and exhibits strong shear thinning; the solution is stable across a wide pH range and can withstand heat and freezing, though ionic strength and certain cations can alter its rheology.

In foods xanthan acts as a thickener, stabilizer in emulsions, and texture modifier, often used with other gums. It is also used in personal care products, paints, and oilfield drilling fluids.

Regulatory status: xanthan gum is generally recognized as safe for use in foods by many authorities, including the U.S. FDA and EFSA, when used as directed. It is considered non-toxic and hypoallergenic in typical exposures.