Gellan gum is a water-soluble

anionic An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

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 w ...

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 Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

. 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 i ...

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 Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...

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 ...

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 ...

. 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 formed by the combination of acetic acid with a base (e.g. alkaline, earthy, metallic, nonmetallic or radical base). "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called ...

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 Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...

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 tec ...

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-X ...

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, 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 ...

Physcomitrella patens ''Physcomitrium patens'', (synonym: ''Physcomitrella patens'' ) the spreading earthmoss, is a moss (bryophyte) used as a model organism for studies on plant evolution, development, and physiology. Distribution and ecology ''Physcomitrella p ...

'' 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 Taste, 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), sal ...

, 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 A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties. Edible thickeners are commonly used to thicken sauces, soups, and puddings without altering their t ...

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. Althoug ...

, 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 ''Haute cuisine'' (; ) or ''grande cuisine'' is the cuisine of "high-level" establishments, gourmet restaurants, and luxury hotels. ''Haute cuisine'' is characterized by the meticulous preparation and careful presentation of food at a high pric ...

, and in particular in

molecular gastronomy Molecular gastronomy is the scientific approach of nutrition from primarily the perspective of chemistry. The composition ( molecular structure), properties (mass, viscosity, etc) and transformations (chemical reactions, reactant products) o ...

and other scientifically-informed schools of cooking, to make flavorful gels; British chef

Heston Blumenthal Heston Marc Blumenthal (; born 27 May 1966) is a British celebrity chef, TV personality and food writer. Blumenthal is regarded as a pioneer of multi-sensory cooking, food pairing and flavour encapsulation. He came to public attention with u ...

and American chef

Wylie Dufresne Wylie Dufresne (born 1970) is the chef and owner of Du's Donuts and the former chef and owner of the wd~50 and Alder restaurants in Manhattan. Dufresne is a leading American proponent of molecular gastronomy, the movement to incorporate science ...

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