Introduction to Xanthan Gum
Xanthan gum (CAS 11138-66-2) is a high molecular weight, water-soluble exopolysaccharide produced by the bacterium Xanthomonas campestris during aerobic fermentation of carbohydrate. Since its commercial introduction in the 1960s it has become one of the most widely used bio-based hydrocolloids in industry, valued for a combination of properties that few synthetic or natural thickeners can match at the same time: very high low-shear viscosity, strong shear-thinning (pseudoplastic) behaviour, broad pH stability, excellent tolerance to salts, good thermal stability, and ready biodegradability.
In food it carries the additive code E415 and the FCC designation “Xanthan Gum”; in industrial use it is a workhorse of oilfield drilling fluids, textile printing, paper, agriculture and household and industrial cleaning. This article reviews the chemistry and molecular structure of xanthan gum, its physical properties, the industrial fermentation route by which it is made, the grades and specifications that are traded, and the applications and formulation practice that follow from its rheology.
Xanthan gum is supplied by PolyBlueChem in food grade and API grade, at 80 mesh and 200 mesh, with the specification table given later in this article.
Chemical Structure and Composition
Xanthan gum is a polysaccharide built from a repeating pentasaccharide unit. The molecule has a cellulose-like backbone of (1→4)-linked β-D-glucopyranose residues, on every second glucose residue of which a trisaccharide side chain is attached at the O-3 position. The side chain consists of β-D-mannose, β-D-glucuronic acid and a terminal β-D-mannose, and the terminal mannose frequently carries a pyruvic acid ketal group. Roughly half of the internal mannose residues carry an acetyl group at O-6. The pentasaccharide repeat can be summarised as: glucose–glucose(acetate)–mannose–glucuronic acid–mannose, with variable pyruvate on the terminal mannose.
The presence of glucuronic acid and pyruvate makes xanthan gum an anionic (negatively charged) polyelectrolyte. This charge is central to its behaviour: it keeps the rigid, ordered double-helix conformation that the molecule adopts in solution, which in turn is the origin of its unusually high viscosity and its stability against heat, pH and salt.
Key structural features
- Backbone: repeating β-1,4-D-glucose units (the same linkage found in cellulose), giving a stiff, ribbon-like chain.
- Side chains: trisaccharide branches of mannose–glucuronic acid–mannose on alternating glucose residues.
- Anionic groups: glucuronic acid carboxyl groups and, on part of the polymer, pyruvate ketal groups.
- Acetate and pyruvate content: typically around 4–6% acetate and 3–6% pyruvate by weight; these substituents influence viscosity, solubility and interaction with other hydrocolloids.
- Molecular weight: very high, generally reported in the range of about 1 to 20 million Da, depending on the X. campestris strain, fermentation conditions and recovery method.
Because the properties depend on the degree of acetylation and pyruvylation, and on molecular weight, xanthan gum is not a single fixed molecule but a family of related polymers. Producers control these variables to steer the product toward food, pharmaceutical or oilfield performance.
Physical and Chemical Properties
The commercially important properties of xanthan gum all follow from its anionic, high-molecular-weight and rigid-rod conformation. The table below summarises the physical and chemical behaviour that formulators rely on.
| Property | Typical behaviour |
|---|---|
| Appearance | Off-white to light-yellow free-flowing powder |
| Solubility | Readily soluble in hot and cold water; insoluble in most organic solvents; soluble in solvents in the solubility-parameter range of about 7.7–9.4 |
| Viscosity (1% in 1% KCl) | Approximately 1,300–1,700 cP (Brookfield LVDV-II+, No.3 spindle, 60 rpm, 25 ± 1 °C) |
| Flow behaviour | Highly pseudoplastic (shear-thinning) with a measurable yield value |
| pH stability | Stable over a broad range, commonly quoted as about pH 3–12 (some grades function outside this window for short periods) |
| Thermal stability | Retains viscosity on heating, usefully up to about 90–100 °C in many systems |
| Salt (electrolyte) tolerance | High; viscosity is relatively insensitive to monovalent and divalent salts compared with many polyelectrolytes |
| Surface tension | Similar to water; xanthan does not introduce significant surface activity on its own |
| Biodegradability | Biodegradable bio-based polymer |
Two features deserve emphasis. First, xanthan gum dissolves in cold water, unlike many natural gums that require heating; this makes it convenient in cold-process and continuous processes. Second, its viscosity is largely independent of ionic strength, which distinguishes it sharply from polyelectrolytes such as carboxymethyl cellulose (CMC) or sodium polyacrylate, whose thickening power collapses in brine or hard water.
Rheology: Shear-Thinning and Yield Stress
The single most important property of xanthan gum is its rheology. A xanthan solution is pseudoplastic: at rest its molecules form a weakly structured, entangled network that produces very high viscosity and a small but real yield stress; when the solution is sheared, the network aligns with the flow and the viscosity falls. When the shear is removed the structure recovers almost instantly. This behaviour is sometimes described as “shear-thinning with rapid recovery”.
The practical consequences are:
- High viscosity at low shear. Xanthan is an efficient suspension and stabilising agent: it holds pigments, particles, proppants, cuttings or dispersed solids in place while the fluid is not moving, and prevents sedimentation over long storage periods.
- Lower viscosity at high shear. When pumped, sprayed, mixed or poured, the same fluid becomes thinner, so it is easy to move and does not build excessive pressure in pipes or on mixing equipment.
- Enhanced pick-up and cling. At the moderate shear of brushing or spreading, viscosity rises again, so the fluid clings to surfaces and carries solids with it — important in drilling fluids, textile printing pastes and agrochemical tank mixes.
The temperature and concentration dependence follows expected patterns: apparent viscosity rises steeply with concentration and falls slowly with temperature. Because xanthan behaves as a yield-stress fluid, even quite low use levels can keep a formulation stable.
Production Process of Xanthan Gum
Xanthan gum is produced industrially by aerobic submerged fermentation. The main steps — fermentation, cell removal, recovery (precipitation), purification, drying, milling and standardisation — are common to most producers, with differences in the carbon source, the solvent used for precipitation and the finishing treatment.
| Stage | Purpose | Typical conditions / notes |
|---|---|---|
| 1. Inoculum and medium preparation | Grow a clean, active culture of Xanthomonas campestris | Carbon source (glucose, sucrose, starch hydrolysate or molasses), nitrogen source, minerals; medium sterilised before inoculation |
| 2. Fermentation | Synthesise and excrete the exopolysaccharide | Aerobic, stirred and aerated bioreactor; temperature around 28–30 °C; pH controlled near neutrality; several days’ duration |
| 3. Cell removal | Separate biomass from the broth | Filtration or centrifugation; also heat treatment or enzyme treatment in some processes |
| 4. Recovery / precipitation | Isolate the polymer from water | Precipitation with an alcohol such as isopropyl alcohol or ethanol |
| 5. Purification and washing | Remove residual salts, colour and low-molecular-weight impurities | Washing with alcohol/water mixtures, filtration |
| 6. Drying | Convert the wet polymer to a stable powder | Spray drying (preferred, gives controlled particle size) or drum drying |
| 7. Milling and standardisation | Obtain the required mesh size and blend to specification | Milled to 80 or 200 mesh; grades standardised for viscosity and clarity |
| 8. Quality control | Confirm the product meets the target specification | Viscosity, pyruvic acid, ash, moisture, micro counts, heavy metals |
Fermentation conditions strongly influence the final product. Higher shear and adequate aeration during fermentation favour high molecular weight, while nitrogen limitation and other stresses can raise pyruvate content and change the viscous behaviour. Two finishing choices are worth noting: clarification, which produces low-residue grades for transparent applications such as clear beverages and personal care; and standardisation, in which the powder is blended to guarantee a viscosity range rather than only a chemical purity.
Quality control. Throughout production the batch is monitored against a fixed set of parameters — viscosity, pyruvic acid, moisture (loss on drying), ash, pH of a 1% solution, residual alcohol and heavy metals, together with microbiological counts. The specification quoted in the next section is representative of a food/API grade.
Grades, Types and Specifications
Xanthan gum is traded in several grades that differ mainly in regulatory category, purity and clarity rather than in the polymer itself.
- Food grade (E415 / FCC): the largest volume; must meet the purity and microbiological limits of the food-additive monograph.
- Pharmaceutical grade (USP/EP/NF): produced under stricter control for use as a suspending and thickening excipient.
- Oilfield / technical grade: optimised for viscosity and brine tolerance rather than food purity; often supplied as a dispersible (coated) grade that hydrates without lumps.
- Clarified / transparent grade: low residue for clear beverages and transparent cosmetic gels.
A representative food/API grade specification is given below. It is the specification supplied with the PolyBlueChem material and conforms to the standard of E415 and the FCC.
| Parameter | Specification |
|---|---|
| Appearance | Off-white or light-yellow free-flowing powder |
| Mesh size | 80 mesh / 200 mesh |
| Viscosity, 1% XG in 1% KCl | 1,300–1,700 cP (Brookfield LVDV-II+, No.3 spindle, 60 rpm, 25 ± 1 °C) |
| Assay (of carbon dioxide) | 91–108 (4.2%–5%) |
| Shearing ratio | ≥ 6.5 |
| pH (1% solution) | 6.0–8.0 |
| Loss on drying | ≤ 13.0% |
| Ash | ≤ 13.0% |
| Pyruvic acid | ≥ 1.5% |
| Total nitrogen | ≤ 1.5% |
| Ethanol and isopropyl alcohol | ≤ 500 ppm |
| Total heavy metals (as Pb) | ≤ 20 ppm |
| Pb / As / Hg / Cd | ≤ 2 / ≤ 2 / ≤ 1 / ≤ 1 ppm |
| Total plate count | ≤ 2,000 cfu/g |
| Yeasts and moulds | ≤ 100 cfu/g |
| Coliforms | ≤ 3 MPN/g |
| Escherichia coli | Absent in 5 g |
| Salmonella | Absent in 25 g |
| Xanthomonas campestris | Absent in 1 g |
Buyers should read a xanthan specification in terms of function, not only purity. The viscosity value, the shearing ratio (the ratio of low-shear to high-shear viscosity, an indicator of how strongly pseudoplastic the sample is) and the pyruvic acid content together determine how a given grade will perform in a target formulation.
Applications Overview
Xanthan gum is used across food, pharmaceutical, personal care, oilfield and general industrial markets. The table below maps the main sectors to the function xanthan performs and the property that makes it suitable.
| Industry | Primary function | Why xanthan |
|---|---|---|
| Food and beverage | Thickener, stabiliser, suspending agent, bodying agent | Shear-thinning, cold-water solubility, pH and salt tolerance, clean label (E415) |
| Pharmaceuticals | Suspending agent, thickener, tablet and gel excipient | High low-shear viscosity, stability, compatibility |
| Personal care | Thickener, emulsion stabiliser, gelling aid | Salt tolerance, smooth skin feel, synergy with other gums |
| Oil and gas | Drilling-fluid viscosifier, suspension, EOR mobility control | Brine tolerance, shear-thinning with recovery, thermal stability |
| Textile | Printing-paste thickener | Sharp print definition, easy wash-out, stable pastes |
| Paper | Wet-end additive, coating rheology modifier | Water retention, formation and strength improvement |
| Agriculture | Drift control, tank-mix thickener, seed coating | Shear-thinning, cling and suspension of actives |
| Cleaning products | Thickener and suspending agent | Salt tolerance, stability at alkaline pH |
| Construction / ceramics | Rheology modifier, water retention | Yield stress, suspension of solids |
Food and Beverage Applications
In food, xanthan gum thickens, stabilises emulsions and suspensions, controls ice-crystal growth and improves the texture of reduced-fat and gluten-free products. It is effective at low use levels, typically from 0.05% to about 0.5% of the finished product, and it works across the acid, salt and temperature ranges encountered in food processing.
Representative food uses and typical addition levels
| Application | Function | Typical use level |
|---|---|---|
| Salad dressings and sauces | Thickening, emulsion stabilisation, cling | 0.1–0.5% |
| Soups, gravies and ready meals | Body, suspension, freeze–thaw stability | 0.05–0.3% |
| Gluten-free baked goods | Gluten replacement, crumb structure, moisture retention | 0.5–2.0% (flour basis) |
| Beverages and syrups | Suspension of pulp or minerals, mouthfeel | 0.02–0.2% |
| Ice cream and frozen desserts | Ice-crystal control, overrun, meltdown | 0.05–0.3% |
| Dairy products (yoghurt, dressings) | Syneresis control, body | 0.05–0.3% |
Two food applications are particularly valuable. The first is gluten-free baking: because gluten normally provides the viscoelastic network that traps gas and gives crumb structure, gluten-free formulas rely on hydrocolloids such as xanthan (often combined with a galactomannan) to mimic that network and to hold moisture. The second is suspension in beverages: xanthan’s yield stress keeps insoluble ingredients evenly dispersed over long shelf life without making the drink unpleasantly thick.
Pharmaceutical and Personal Care Applications
Pharmaceutical and cosmetic grades of xanthan gum act as suspending agents, thickeners, emulsion stabilisers and gelling aids. In pharmaceutical suspensions and syrups, the yield stress of xanthan keeps insoluble drug particles uniformly dispersed, so the patient receives a consistent dose with each shake. Because xanthan is compatible with a wide range of excipients and stable over the usual pH range, it is a common choice for oral suspensions, topical gels, ophthalmic preparations and tablet coatings.
In personal care, xanthan gum thickens and stabilises lotions, creams, cleansers, shampoos, toothpaste and gels. Its tolerance to salts (present in many cosmetic actives and buffers) helps formulators achieve a stable, uniform texture, and its gentle, non-tacky rheology contributes a favourable skin feel. Combined with galactomannans such as locust bean gum, it forms a soft elastic gel useful for clear aqueous gels and masks.
Oil and Gas Applications
Xanthan gum is one of the standard viscosifiers for water-based and brine-based drilling fluids. In a drilling fluid it performs three jobs at once: it thickens the fluid so that it can carry drill cuttings to the surface, it provides the yield stress that suspends cuttings and weighting material when circulation stops, and it gives the shear-thinning profile that keeps pumping pressures manageable. Its distinguishing strength versus many alternatives is that all of this is retained in high-salinity and hard-water fluids.
Beyond drilling, xanthan is used in workover and completion fluids, in drill-in fluids for reservoir sections where low formation damage matters, and as a mobility-control polymer in chemical enhanced oil recovery (EOR). In EOR the polymer thickens the injected water so that it sweeps the reservoir more uniformly, improving the ratio of oil recovered to water produced.
When selecting a viscosifier for a given well, the choice usually comes down to a small set of candidates. The comparison below summarises the qualitative trade-offs.
| Viscosifier | Brine / salt tolerance | Thermal stability | Shear-thinning | Biodegradability |
|---|---|---|---|---|
| Xanthan gum | Very good | Good up to moderate temperatures | Strong, rapid recovery | Good (bio-based) |
| Guar gum and derivatives | Good | Moderate | Moderate | Good (bio-based) |
| Polyacrylamide (PAM) | Fair (viscosity sensitive to brine) | Limited at very high temperature | Moderate | Poor to moderate |
| CMC / cellulose ethers | Fair | Moderate | Moderate | Moderate |
Handling notes for oilfield use. Xanthan gum must be hydrated before it meets high-salinity brine, otherwise the polymer can clump or fail to fully develop viscosity. The standard practice is to prepare a mother solution in fresh water (for example a 1% pre-mix) and then dilute it into the brine under agitation. For high-temperature wells, a proportion of the polymer may be cross-linked, or a temperature-resistant grade selected, to extend performance. Where a fluid must meet strict environmental standards, xanthan’s bio-based and biodegradable profile is a meaningful advantage over synthetic polymers.
Other Industrial Applications
- Textile printing and dyeing: xanthan gum is used as a thickener in print pastes. It gives sharp pattern definition, stable paste rheology and easy wash-out, and it improves dye penetration into the fabric. It can also act as a finishing aid.
- Paper: as a wet-end additive, xanthan improves formation, strength and water retention and helps retain fillers and fibres; in coating colours it modifies rheology and water retention.
- Agriculture: xanthan thickens spray tank mixes, reduces drift and improves the adhesion and rainfastness of actives on leaf surfaces; it is also used in seed coatings and in some fertiliser formulations.
- Cleaning products: in household and industrial cleaners, xanthan provides thickening and suspension that survive alkaline pH and dissolved salts, and it keeps abrasive or insoluble particles in suspension.
- Construction and ceramics: xanthan modifies rheology and water retention in mortars, grouts, ceramic bodies and glazes, improving green strength and application behaviour.
- Pet food and animal feed: as a binder and suspension aid in gravies and wet feeds.
Formulation and Handling Guide
Xanthan gum is easy to use once a few practical rules are followed. The most common problems in production are lumping during hydration and an uneven viscosity from poor dispersion.
- Hydration and dispersion. To avoid lumps, disperse the dry powder in the dry phase or in a non-solvent such as oil or a polyol before adding water, use high-shear agitation, or use a dispersible (coated) grade. Adding powder slowly to a vortex is more effective than dumping it into still water.
- Order of addition. Hydrate xanthan before adding high concentrations of salt or acid. Premature electrolyte or acid addition can prevent full viscosity development.
- pH. Xanthan is tolerant across a broad pH range. For acid systems, hydrate first and lower the pH afterwards, since very low pH can reduce solubility.
- Preservation. Xanthan solutions are nutrients for micro-organisms. In aqueous products that are not otherwise protected, include an appropriate preservative or biocide to prevent viscosity loss during storage.
- Synergy with galactomannans. A small addition of guar gum or locust bean gum to a xanthan solution produces a synergistic viscosity increase or a soft gel, allowing the formulator to reach a target texture with less total hydrocolloid.
- Storage. Store the dry powder in a cool, dry place in sealed packaging; it is hygroscopic and readily takes up moisture from the air.
Quality, Regulatory and Safety
Food-grade xanthan gum is regulated as a food additive under the code E415 in the European Union and is listed in the FCC monograph; in the United States it is a permitted direct food additive (GRAS) under 21 CFR 172.695. It is also used widely in pharmaceutical formulations and has a long history of safe use as an excipient. Xanthan gum is generally recognised as a non-toxic, non-sensitising material, and because it is a high-molecular-weight, largely non-absorbed polymer it passes through the digestive tract without being metabolised.
As with any powder, good industrial hygiene applies: fine dust can be generated during handling, so local exhaust ventilation and appropriate dust protection are recommended. Material should be stored away from strong oxidisers. Documentation available on request typically includes the certificate of analysis (COA), material safety data sheet (SDS), and, where applicable, food-grade and GMP statements. Buyers requiring REACH registration, halal or kosher certification, or non-GMO and allergen statements should confirm availability at the time of order, as these can vary by production site.
Procurement and Sourcing Guide
When purchasing xanthan gum, the specification and grade matter more than the headline name. A practical checklist:
- Grade and regulatory status. Confirm whether you need food (E415/FCC), pharmaceutical (USP/EP) or oilfield/technical grade, and request the corresponding COA.
- Viscosity and shearing ratio. Check that the viscosity and shearing ratio match your target, since these drive performance far more than purity alone.
- Mesh size. Finer mesh (200) disperses and hydrates faster and is preferred for cold and continuous processes; coarser mesh (80) is common in drilling-fluid and general industrial use.
- Clarity. For clear beverages and transparent gels, specify a clarified grade.
- Packaging. Xanthan gum is typically supplied in 25 kg multiwall paper or fibre drums with inner liners; confirm the packaging that suits your handling.
- Consistency. Because batch-to-batch viscosity can shift with fermentation and standardisation, ask the supplier for a recent batch history if viscosity is critical to your process.
PolyBlueChem can supply xanthan gum (CAS 11138-66-2) in food grade and API grade at 80 or 200 mesh. To request current specifications, a COA or a quotation, contact the PolyBlueChem team.
Frequently Asked Questions
What is xanthan gum and what is its CAS number?
Xanthan gum is a high-molecular-weight polysaccharide produced by fermentation with Xanthomonas campestris. Its CAS number is 11138-66-2 and its food-additive code is E415. For the full product specification, see the xanthan gum product page.
Is xanthan gum soluble in cold water?
Yes. Xanthan gum hydrates in both hot and cold water, which makes it convenient for cold-process and continuous manufacturing. It is insoluble in most organic solvents.
Why does a xanthan solution become thinner when stirred?
Xanthan is pseudoplastic (shear-thinning): its entangled network aligns with the flow under shear, lowering the viscosity, and recovers almost immediately when the shear is removed. This is why it suspends solids at rest but pumps and pours easily when moving.
How is xanthan gum different from guar gum or CMC?
Xanthan gum has a stronger yield stress and better salt and pH tolerance than guar gum, and it stays functional in brine where CMC and many polyelectrolytes lose viscosity. Guar gum is cheaper and gives higher low-shear viscosity but is less stable; CMC is a good cold-water thickener but is more sensitive to salts. Xanthan and guar are often combined for a synergistic viscosity boost. See the dedicated comparison in the related reading below.
What use level is typical in food?
Most food applications use roughly 0.05% to 0.5% xanthan gum; gluten-free baked goods may use about 0.5% to 2% on a flour basis. Always confirm the level by bench trial.
Is xanthan gum safe and approved for food use?
Yes. Xanthan gum is approved as food additive E415 in the EU and is a permitted direct food additive (GRAS) in the US under 21 CFR 172.695. It has a long history of safe use.
Can xanthan gum be used in high-salinity drilling fluids?
Yes. Salt tolerance is one of xanthan’s strengths. The polymer should be pre-hydrated in fresh water and then diluted into the brine to avoid clumping.
How should xanthan gum be stored?
Keep the powder cool, dry and in sealed packaging. Xanthan gum is hygroscopic and readily picks up moisture, which can cause lumping and reduce shelf life.
References and Disclaimer
References. Food Chemicals Codex monograph for Xanthan Gum; European food-additive specifications for E415; US 21 CFR 172.695; manufacturer technical data for food and oilfield grades. Specifications quoted in this article reflect a representative food/API grade and should be confirmed against the current certificate of analysis for each shipment.
Disclaimer. This article is provided for general technical information only. Statements about properties and applications are indicative and do not constitute a specification or a warranty of fitness for any particular use. Users are responsible for confirming regulatory status, safe handling and suitability for their own application.