Gellan gum
Gellan gum is a water-soluble polysaccharide which is produced through the fermentation of sugar by the bacterium Sphingomonas elodea. It is unique among hydrocolloids in that it has the ability to form gels at very low concentrations (e.g. 0.02-0.03%). It is available in two distinct types, each type producing a different kind of structure or texture.
The High Acyl Form (HA) produces soft elastic, flexible gels, opaque to translucent. It produces creamy textures. It is thermally reversible, meaning that it can allow for foods to be suitably remelted, and it sets at higher temperatures. It requires heating to 85-95C to fully hydrate and sets and melts at 70-80C. It is highly resistant to wide pH ranges and less sensitive to calcium ions than the low acyl type.
The Low Acyl Form (LA) produces firm brittle gels with a crystal-clear appearance. It provides crisp mouthfeel in application. It is heat stable, and it does not remelt easily, thus is non-reversible. It hydrates fully at higher temperatures (90-95C) and quickly snap-sets upon cooling (around 60C). The resulting gels are heat stable and can withstand high processing or baking temperatures. It requires a pH above 4.0 to properly gel.
Gellan Gum is listed as GRAS and is approved for use in foods; 21CFR Part 172.665.