Gellan Gum Glossary: The Terms That Actually Come Up

The vocabulary around gellan gum is small and used inconsistently, which causes a lot of avoidable confusion — particularly between buyers and suppliers, and between food and non-food applications.

These are the terms that actually come up in practice.

The polymer

• Gellan gum — A high molecular weight anionic polysaccharide produced by fermentation using the bacterium Sphingomonas elodea, and used as a gelling agent, stabiliser, suspending agent and texturiser. Food additive E 418.
• E 418 (E418) — The European Union designation for gellan gum as a food additive. Used on labels in the EU and in many other markets.
• Sphingomonas elodea — The bacterium that produces gellan gum. Formerly classified as Pseudomonas elodea, and reclassified following taxonomic revision.
• ATCC 31461 — The culture collection reference number for the industrial strain used to produce commercial gellan gum.
• Repeating unit — The four-sugar building block of the polymer: two D-glucose units, one D-glucuronic acid unit and one L-rhamnose unit.
• Acyl group — A chemical group attached to the polymer backbone. Gellan gum carries two: a glyceryl group and an acetyl group.
• High acyl (HA) — Native gellan gum retaining both acyl groups. Produces soft, elastic, thermally reversible gels.
• Low acyl (LA) — Gellan gum from which the acyl groups have been chemically removed by alkali treatment. Produces firm, brittle, heat-stable gels and requires cations to set.
• Degree of acylation — How much acyl substitution is present. Gellan gum grades form a spectrum rather than two discrete categories.
• Deacylation — The alkaline process that removes acyl groups. It also reduces molecular weight.
• Molecular weight / Mw — The average chain length of the polymer. Drives viscosity, gel strength and suspension efficiency.
• Polydispersity (PDI) — The breadth of the molecular weight distribution. Same Mw with different PDI means different behaviour.
• PHB (polyhydroxybutyrate) — A natural polyester the bacterium accumulates. A non-gelling fraction of the finished powder that affects clarity and cost efficiency.

Behaviour

• Hydration — The process by which the polymer absorbs water and becomes functional. Requires heat, typically above 80–90 °C.
• Dispersion — Separating powder particles in water so water can reach them. Distinct from hydration, and the more common failure point.
• Cation — A positively charged ion. Calcium, magnesium, potassium and sodium are the ones that matter for gellan gum.
• Sequestrant / chelating agent — A substance such as sodium citrate that binds cations and holds them unavailable, delaying gelation.
• Setting temperature — The temperature at which a gel forms as the product cools.
• Melting temperature — The temperature at which a gel liquefies on reheating.
• Thermal hysteresis — The gap between setting and melting temperatures. Large in LA gels, small in HA gels.
• Heat-reversible — A gel that melts on heating and re-forms on cooling. Characteristic of HA gellan.
• Heat-stable — A gel whose network survives thermal processing such as retort. Characteristic of LA gellan.
• Gel strength — A measure of the force needed to deform or break a gel. Only meaningful with a stated test method.
• Brittle gel — A gel that fractures rather than deforms. The characteristic texture of LA gellan.
• Elastic gel — A gel that deforms and recovers. Characteristic of HA gellan.
• Syneresis — The release of water from a gel over time. A common quality defect.
• Yield stress — The stress a liquid must exceed before it flows. The mechanism by which gellan gum suspends particles without thickening.
• Shear-thinning — The property of becoming less viscous when agitated. Relevant to pumping and filling.
• Fluid gel — A structured liquid that holds particles at rest but flows when poured or pumped.
• Gelation — The formation of a three-dimensional polymer network.

Product and specification

• Mesh — A particle size grade based on sieve openings. Higher mesh means finer powder.
• Particle size distribution (D10 / D50 / D90) — The full size profile of a powder. More informative than a single mesh number.
• Agglomerated / instant grade — A powder built into porous clusters so it disperses without high shear.
• LOQ (limit of quantification) — The smallest amount a test method can reliably measure. Reporting "not detected" is meaningless without it.
• COA (certificate of analysis) — The batch-level document reporting measured values for a specific production lot.
• Specification — The document defining the limits a product is released against.
• Loss on drying (LOD) — Moisture content, determined by drying under defined conditions.
• Nitrogen content — A measure of residual proteinaceous material; a purification indicator.
• Residual enzymatic activity — Surviving enzymes from the producing organism that can degrade the polymer slowly during storage.

Regulatory and commercial

• JECFA — The Joint FAO/WHO Expert Committee on Food Additives. Evaluated gellan gum in 1991 and allocated an ADI "not specified".
• ADI (acceptable daily intake) — The amount that can be consumed daily over a lifetime without appreciable risk. "Not specified" means no numerical limit is considered necessary.
• EFSA — The European Food Safety Authority, which re-evaluated E 418 in 2018.
• GRAS (Generally Recognized As Safe) — A US regulatory concept. In the US, gellan gum is authorised as a food additive under 21 CFR 172.665.
• GB 25535 — The Chinese national food safety standard covering gellan gum as a food additive.
• USP-NF — The United States Pharmacopeia–National Formulary, which includes excipient monographs used for pharmaceutical applications.
• ICH Q3D — The guideline setting permitted daily exposures for elemental impurities in drug products.
• ETO (ethylene oxide) — A sterilant gas whose residues are strictly limited in food additives in the EU.
• Hydrocolloid — A substance that forms a gel or increases viscosity in water. The category gellan gum belongs to.
• Cost in use — The cost contribution per unit of finished product, as opposed to price per kilogram of ingredient.
• MOQ (minimum order quantity) — The smallest order a supplier will accept.
• Incoterms — Standard international trade terms defining who arranges and pays for each stage of a shipment.
• HS code — The customs tariff classification for a traded product.
• INCI name — The international naming convention for cosmetic ingredients. For gellan gum: "Gellan Gum".
• Retort — In-pack sterilisation using pressurised steam, typically at 115–125 °C.
• UHT — Ultra-high-temperature processing, typically 135–150 °C for a few seconds.
• IDDSI — The International Dysphagia Diet Standardisation Initiative framework for classifying food and drink consistency.
• Gelrite / Phytagel — Trade names for gellan gum used in microbiological culture media and plant tissue culture.
• KELCOGEL — A trade name for food-grade gellan gum.

For specification data and technical definitions applied to a specific product, contact Cinogel.