Gellan gum has a number of functional properties that can be readily modified. These include:
• Versatile texture, which is one of its most important features. This is usually defined in terms of hardness (measure of rupture strength), modulus (measure of gel firmness) , brittleness (strain required to break the gel), and elasticity (measure of rubberiness).
• Stability of the gum after heating or to pH variations.
• Setting temperature and melting point flexibility. Gellan gels can be formulated to set with or without heating. The melting point can be either below or above 100°C, allowing the design and production of both heat resistant gels and gels that should liquify during processing.
• Dispersibility. Gellan is easily and fully dissolved in water without any preparatory steps.
• Compatibility. Gellan can be easily combined with other gums/polymers, offering an even broader "repertoire" of functional properties and applications. For example, gelatine gels, which have pleasant organoleptic qualities but low melting point, can be stabilized satisfactorily when gellan is added to the mixture. An increase of the melting point occurs, while the desirable properties of gelatine are retained. Also, a combination of gellan, xanthan and locust bean gum can result in versatile textures, while the addition of gellan to starch enhances overall starch performance in foods by improving gas and moisture retention.Therefore, the levels of starch (in backing) can be reduced, while flavor release can be improved when gellan is added to starch. Compatibility with other gums has also been one of the most attractive features of the market leader, xanthan gum. The latter interacts well with guar gum, locust bean gum, gelatine, carageenans, and alginates (i.e., it can be cross-linked with regions of these gums and produce thickeners and stabilizers with modified properties)
• Low concentration requirements. Usually, gellan gels are prepared with only 0.04 to 0.05% (w/v) gellan gum. When divalent cations are added, this amount can be reduced further. By comparison, rheological studies on xanthan, a weaker gelling agent than gellan, showed that addition of only 1% of the polysaccharide into water increases viscosity by a factor of 100,000 at low shear rates (although a small 10% increase is observed at high shear due to the highly pseudoplastic character of xanthan, which produces gels of decreasing viscosity at increasing shear rates).
• Flavor release. This is made possible due the water binding properties of gellan molecules. For example, when used in fruit fillings gellan permits a quick release of flavor and, similarly, when added to cheese it contributes to desirable flavor (in contrast to other hydrocolloid additives,like carrageenan) . Xanthan has also been reported to enhance flavor release in reduced fat sausages and other food products, possibly because xanthan forms weak gels rather than true solutions, so the flavor release characteristics are not impaired.
The rapid flavor release of microbial polysaccharides such as gellan and xanthan, especially when compared with foods formulated with starch or modified starch, has been a key factor in their adoption by the food industry. Apart from native gellan, which has properties similar to xanthan-locust gum mixtures and, thus, rather limited uses, there are three types of (modified) gellan gum: (Sanderson and Clark, 1983)
• High acetyl gellan (partially deacetylated), which provides a thermoreversible gel, fairly soft, elastic, and nonbrittle
• Low acetyl gellan (highly deacetylated),which is preferred for most food applications, as it forms firm and brittle gels
• High clarity gellan (highly deacetylated and clarified), which is suitable for some confectionary products where clarity is a crucial quality issue. In addition, it can be used as a gelling agent for microbial growth media.
references:http://www.cinogel.com
