Source & Processing
Xanthan Gum is produced by fermentation, using a pure culture strain of Xanthomonas Campestris with glucose and related chemicals as substrates, followed by purification and recovery with an alcohol solvent. Xanthan Gum consists of repeated pentassaccharide units to form cellulosic backbone through the 1, 4B–D glucosidic linkage and a side chain.
The strain of Xanthomonas Campestris is normally stored as freeze-dried ampoules. To activite a biological effect it is inoculated with a nutrient source under essential conditions; prepared inoculums are ready for large-scale fermentation.
Fermentation is preformed using a batch system during which the pH, foam and aeration are closely monitored. After fermentation is completed, the “broth” or “soup” is sterilized to prevent any contamination to both the “broth” and the environment. Sterilization of the equipment is imperative before, after and in between the next batches to ensure integrity.
The next stage is referred to as the “coagulation phase”. The gum is recovered from the broth by the use of precipitation by alcohol, mainly isopropyl or ethanol. The recovered coagulum is washed, dried and milled to a specific particle size. The powdered Xanthan Gum goes through further processing of interblending and sifting to achieve a more uniform end product.
Uses
The applications for Xanthan Gum seem to be endless. Please note a few widely used below:
Sauces and Dressings
- Adds “cling”
- pH-stable
- Resistant to enzymatic degradation
- Good mouth feel
- Good flavor release with low masking
- Clean fluid break
- Rapid hydration
- Na-stable without adverse viscosity changes
- Excellent thermal stability
Dairy
- Excellent mixing, pumping and filling due to its pseudo-plastic behavior
- Compatible with Guar, Locust Bean Gum and Carrageenan
- Tolerance to electrolytes
- Controls ice crystal size
- Provides heat shock protection
- Controls syneresis
- Improves shelf life of product
- Adds texture and mouth feel
- Shear stability
Bakery
- Gluten substitute @ 1 – 2%
- Controls water migration
- Acid stable in low pH pie fillings
- Suspends solids
- Heat stability
- Controls ice crystal size
- Improves shelf life
- Freeze/thaw stability
- Replaces starch
- Natural label
Beverages
- Improves mouth feel
- Rapid hydration
- Good flavor release
- Pseudo-plastic characteristics improve flow and suspends solids
- Tolerance to salt
- Tolerance to low pH and enzymes
- Shear resistance
- High viscosity at low concentration
- Natural label
Properties
Physical
Guar gum is practically odorless and has a bland taste. Its color is off white to very light yellow tan. Mesh sizes are readily available from 100 to 250.
Solubility
Guar gum will disperse and swell almost completely in cold or hot water. It is insoluble in organic solvents.
Viscosity
The most important characteristic of Guar is its ability to be dispersed in water and hydrate or swell rapidly and almost completely in cold water to form viscous colloidal dispersions or sols. The viscosity attained is dependent on time, temperature, concentration, pH, rate of agitation, and particle size of the powdered gum used. The lower the temperate, the lower the rate at which viscosity increases, and the lower the final viscosity. Above 80° Celsius the final viscosity is slightly reduced. The finer Guar powders swell more rapidly than coarse powdered gum.
Chemical Characteristics
Guar gum, like Locust Bean gum, is a polysaccharide consisting of a straight chain of D-mannopyranose units joined by b – (1à4) linkages with a a side-branching unite of a single D-galactopyranose unit joined to every other mannose unity by a– (1à6) linkages. Locust Bean gum has a single galactose side-branch every fourth mannose unit. The molecular weight o Guar is 220,000_+_10%. Ths greater side-branching of Guar accounts for its cold water hydration as well as its greater hydrogen-bonding activity. An average quality Guar gum contains about 80% galactomannan, 12% water, 5% protein, 2% acid insoluble residue or crude fiber, 0.7% fat, a trace of heavy metals, zero arsenic, and zero lead.
pH
A 1% Guar sol has a pH between 5 and 7. The optimum hydration rate occurs between pH 7.5 and 9. It has a very slight buffering action and is very stable from pH 4 to 10.5. The preferred method to prepare a sol having a very low or very high pH is to prepare a sol at the gum’s normal pH and then adjust to as low as pH 1 or slightly above pH 10.5 to give stable sols.
Compatibility
Guar gum, being a nonionic polymer, is compatible with most other hydrocolloids. It is a compatible with most chemically modified starches, modified celluloses, synthetic polymers, and water-soluble proteins. Guar is compatible with many salts over a wide range of electrolyte concentration. Some multivalent salts affect hydration and viscosity, and even produce gels. Borate ion present in alkaline water inhibits the hydration. If Guar gum is hydrated, a cohesive structural gel may be formed by the borate ion at pH 7.5 to 10.5. This gel is reversible by reducing pH below 7 or by heating the gel. Polysaccharides, having numerous cis hydroxyl groups, can form these three dimensional gels with pentavalent boron. The guar borate gel may also be liquefied by addition of glycerol or mannitol, both low-molecular weight polyols.
Preservatives
Bacterial attack, common to all plant hydrocolloids, may be controlled by a mixture of 0.15% methyl and 0.02% propyl parahydroxy benzoate.