Gellan gum is a high-molecular weight extracellular heteropolysaccharide produced by fermentation of a carbohydrate with a pure culture of the bacterium Sphingomonas elodea . Gellan is a high molecular weight linear tetrasaccharide of one rhamnose, one glucuronic acid, and two glucose units ( Fig. 3.8 ). Once the fermentation is complete, gellan gum is isolated and dried. The unique characteristics of gellan gum are its ability to gel in the presence of ions and the diverse properties of the gels produced by its interaction with different ions.

As a functional additive, Gellan gum has been broadly applied in the fields of food (e.g. gel products, fruit-based products, starch-based products, beverage), medicine (e.g. soft or hard capsule), cosmetic (e.g. personal tending products), chemical industry (e.g. air-freshening gels), textile, petroleum, etc. Gellan gum is used mainly in the food industry as an anti-settling agent, thickeners, stabilizer or to structure prepared foods. Used in very small doses, it acts as an anti-settling agent in liquids, while adding only a very light viscosity. It may well allow, for example, the uniform distribution of cocoa in chocolate milks or strengthening agents like calcium or fiber in all kinds of beverages. At present Gellan gum has gradually replace agar agar and carrageenan use. It can be used into the pet food, candy, dairy products, jam, flour product.

Shand, Sofos, and Schmidt (1993) showed that gellan gum helped increase the cook yield of alginate-structured meat, but had no effect on a salt/phosphate system. In addition, as the amount of water increased, the firmness decreased, which the author attributed to a decrease in ionic strength. Tang, Tung, and Yanyin (1995) found that gellan gels were strongest in the presence of calcium, which could create some competition in alginate-structured steaks.

Fig. 3.9 Basic structure of curdlan (from Chaplin, 2007a . Reprinted with permission).

Regulatory Status

Gellan gum has been shown to be completely safe for use in food. In the European Union it is a generally permitted additive (E 418). It has GRAS status in the United States, and is not limited when used following GMP.