Gellan gum is a water-soluble anionic

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...

produced by the bacterium '' Sphingomonas elodea'' (formerly ''Pseudomonas elodea'' based on the taxonomic classification at the time of its discovery). The gellan-producing bacterium was discovered and isolated by the former Kelco Division of Merck & Company, Inc. in 1978 from the lily plant tissue from a natural pond in Pennsylvania. It was initially identified as a substitute gelling agent at significantly lower use level to replace

agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...

in solid culture media for the growth of various microorganisms. Its initial commercial product with the trademark as Gelrite gellan gum, was subsequently identified as a suitable agar substitute as gelling agent in various clinical bacteriological media.

Chemical structure

The repeating unit of the polymer is a tetrasaccharide, which consists of two residues of D- glucose and one of each residues of L-

rhamnose Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose predominantly occurs in nature in its L-form as L-rhamnose (6-deoxy-L-mannose). This is unusual, since most o ...

and D-

glucuronic acid Glucuronic acid (from Greek γλεῦκος "''wine, must''" and οὖρον "''urine''") is a uronic acid that was first isolated from urine (hence the name). It is found in many gums such as gum arabic (c. 18%), xanthan, and kombucha tea and ...

. The tetrasaccharide repeat has the following structure:
small>D-Glc(β1→4)D-GlcA(β1→4)D-Glc(β1→4)L-Rha(α1→3)sub>n Gellan gum products are generally put into two categories, low acyl and high acyl depending on number of

acetate An acetate is a salt (chemistry), salt formed by the combination of acetic acid with a base (e.g. Alkali metal, alkaline, Alkaline earth metal, earthy, Transition metal, metallic, nonmetallic or radical Radical (chemistry), base). "Acetate" als ...

groups attached to the polymer. The low acyl gellan gum products form firm, non-elastic, brittle gels, whereas the high acyl gellan gum forms soft and elastic gels.

Microbiological gelling agent

Gellan gum is initially used as a gelling agent, alternative to

, in microbiological culture. It is able to withstand 120 °C heat. It was identified as an especially useful gelling agent in culturing thermophilic microorganisms. One needs only approximately half the amount of gellan gum as agar to reach an equivalent gel strength, though the exact texture and quality depends on the concentration of the divalent cations present. Gellan gum is also used as gelling agent in plant

cell culture Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This te ...

Petri dish A Petri dish (alternatively known as a Petri plate or cell-culture dish) is a shallow transparent lidded dish that biologists use to hold growth medium in which cells can be cultured,R. C. Dubey (2014): ''A Textbook Of Biotechnology For Class- ...

es, as it provides a very clear gel, facilitating light microscopical analyses of the

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

and tissues. Although advertised as being

inert Inert may refer to: * Chemically inert, not chemically reactive ** Inert gas ** Noble gas, historically called inert gas * Inert knowledge, information which one can express but not use * Inert waste, waste which is neither chemically nor biol ...

, experiments with the

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

'' Physcomitrella patens'' have shown that choice of the gelling agent—

or Gelrite—does influence phytohormone sensitivity of the plant cell culture.

Food science

As a

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salt ...

, gellan gum was first approved for food use in Japan (1988). Gellan gum has subsequently been approved for food, non-food, cosmetic and pharmaceutical uses by many other countries such as US, Canada, China, Korea and the European Union etc. It is widely used as a thickener,

emulsifier An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...

, and stabilizer. It has

E number E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...

E418. It was an integral part of the now defunct Orbitz soft drink. It is used as the gelling agent, as an alternative to

gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...

, in the manufacture of vegan varieties of "gum" candies. It is used in plant-based milks to keep plant protein suspended in the milk. Gellan has also become popular in haute cuisine, and in particular in molecular gastronomy and other scientifically-informed schools of cooking, to make flavorful gels; British chef Heston Blumenthal and American chef Wylie Dufresne are generally considered to be the earliest chefs to incorporate gellan into high-end restaurant cooking, but other chefs have since adopted the innovation. Gellan gum, when properly hydrated, can be used in ice cream and sorbet recipes that behave as a fluid gel after churning. The benefit of using gellan gum is that the ice cream or sorbet can be set in a dish of flaming alcohol without actually melting.The Fat Duck Cookbook, Heston Blumenthal, ISBN 978-0-7475-9737-7, p238-241, "Flaming sorbet"

Production

Gellan was discovered and developed as a commercial biogum hydrocolloid product by Kelco, then a division of Merck & Co. In the United States, Kelco was responsible for obtaining food approval for gellan gum worldwide. In other markets that are fond of innovative food ingredients such as Japan, the process for obtaining food approval has been undertaken by local food and beverage manufacturers. Kelco, now the CP Kelco family of companies owned by J.M. Huber Corporation historically, produced the majority of food grade gellan gum. However, since the entry into the segment of Royal DSM, the Dutch science and food nutrition conglomerate, users of food grade gellan gum now procure from 2 high quality suppliers. Chinese suppliers have also been increasingly aggressive in gellan gum production. However, the lack of consistent quality production, adherence to stringent food grade requirements and lack of a strong technical and application support means that such gellan gum is primarily destined for use in personal care or household care applications. Pure gellan gum is one of the most expensive hydrocolloids. Its cost in use, however, is competitive with the other much lower priced hydrocolloids.

References

External links