GUAR GUM
EC / List no.: 232-536-8
HS-Code: 130.232.30
CAS No. :9000-30-0
EEC No. : E412
EINECS No.: 232.536.8
Imco-Code: Harmless
Synonym: Galactomannan Polysaccharide, Edible Gum (Guar Gum), Edible Gum (Gum Acacia), Edible Gum (INS 412), Emulsifier (E412), Emulsifier (INS 412), Emulsifier and Stabilizer (412), Emulsifying Agent (Guar Gum), Guar gum (INS412), Guar Gum E412, Gum, Natural Guar Gum, Stabilizer (E412), Stabilizer (INS 412), Stabilizing Agent (INS 412), Thickener (412), Thickener (INS 412), Thickeners(E412), Thickening Agent (E-412), Thickening Agent (INS 412)
Raw guar gum rapidly forms a thick gel when hydrated, rendering it less than palatable.
To improve the consumer experience, most marketed guar gum products are “partially hydrolyzed guar gum” (PHGG), but hydrolysis degrades viscosity/gel formation.
Hence, the degree to which guar gum is hydrolyzed determines the degree to which viscosity and efficacy are attenuated/abolished.
Seeds of the guar plant are the principal source of this polysaccharide gum.
Guar (Cyamposis tetragonoloba) is a member of the legume plant family, and its functional polysaccharide is found in the endosperm of its seeds.
Guar gum is a polymer composed of two monosaccharides, mannose, and galactose, and is referred to as a galactomannan.
Properties
Chemical composition
Guar gum is a galactomannan polysaccharide whose backbone structure consists of a linear chain of mannose with short lateral branches of galactose.
Chemically, guar gum is an exo-polysaccharide composed of the sugars galactose and mannose.
The backbone is a linear chain of β 1,4-linked mannose residues to which galactose residues are 1,6-linked at every second mannose, forming short side branches.
Guar gum can withstand temperatures of 80 °C (176 °F) for five minutes.
Guar-gum-based products form films when cast from an aqueous solution.
Film properties depend to a great extent on the type of product used.
Unmodified turbid guar gum sols that contain many insoluble particles form hazy and rough films.
Carboxymethylguar gum can be cast into clearer films.
Guar-gum films have high tensile strength, are brittle, and do not elongate under stress.
These properties are due to the gum’s linearity, high molecular weight, and strong hydrogen bonds between polymer chains.
Hydrophobic guar gum derivatives or plasticizers, such as glycerol or polyglycols, can improve film flexibility.
Guar gum is added to various dairy products, such as ice cream (for preventing ice crystal growth and for textural improvement), milkshakes (for preventing serum separation and adding viscosity and shear resistance), yogurt (for improved texture and mouthfeel and for preventing syneresis), aerated desserts (for gelation and foam stabilization), and slimming dietary products (for satiation and as a health-promoting nutritional fiber).
Guar gum is added to ice cream to prevent ice crystal growth and control texture during freezing.
Guar gum is suitable for ice creams using high-temperature short-time processing due to its short hydration time.
However, because guar gum is thermodynamically incompatible with milk proteins, phase separation is an issue.
Therefore, guar gum is generally added along with other hydrocolloids, such as κ-carrageenan, to prevent phase separation in ice cream.
Even with the addition of κ-carrageenan, microscopic phase separation still occurs.
However, if guar gum is added in the range of 0.015%–0.020%, it prevents macroscopic phase separation and thus stabilizes the mix (Robijn, 2006).
Although κ-carrageenan is the most widely used stabilizer with guar gum, current research is focusing on optimizing various hydrocolloid blends that can provide excellent sensory quality and prevent phase separation.
Javidi et al. (2016) have optimized a blend of guar gum and basil seed to prepare low-fat ice cream with excellent sensory qualities.
Similarly, BahramParvar et al. (2013) have optimized a blend of basil seed, guar gum, and κ-carrageenan that meets various sensory and rheological parameters.
Similarly, guar gum has also been added to yogurt for stabilization and to prepare low-fat yogurt and products with high dietary fiber.
Yogurt with improved rheological characteristics was prepared by Lee and Chang (2016) by adding guar gum.
The use of guar gum as a fat replacer to prepare low-fat yogurt has been successfully demonstrated by Brennan and Tudorica (2008).
The addition of guar gum reduced syneresis and improved texture and rheological characteristics, resulting in low-fat products comparable to full-fat products.
Low-fat products containing guar gum as a fat replacer were found to be sensorially acceptable.
Guar gum has also been added to yogurt as a source of dietary fiber.
Mudgil et al. (2016b) prepared high-fiber yogurt with an acceptable sensory quality by adding PHGG.
Rajala et al. (1998) previously demonstrated that regular intake of yogurt containing guar gum over four weeks increased defecating output by 1.6 times.
Guar gum is also added to cheese as a stabilizer.
Guar gum prevents syneresis, or weeping, through water-phase management, and thus also improves the texture and body of the product.
In cheese products, guar gum can consist of up to 3% of the total product weight.
Guar gum is used as a stabilizer, a fat replacer, and in the preparation of low-fat cheese.
Oliveira et al. (2011) demonstrated that guar gum when added in the range of 0.0025% in low-fat milk, resulted in cheese with a thermal, textural, and rheological profile similar to that of the full-fat control.
In addition, Chatziantoniou et al. (2014) have demonstrated guar gum’s usefulness in preparing cheese spreads.
Solubility and viscosity
Guar gum is more soluble than locust bean gum due to its extra galactose branch points.
Unlike locust bean gum, it is not self-gelling.
Either borax or calcium can cross-link guar gum, causing it to gel.
In water, it is nonionic and hydrocolloid.
It is not affected by ionic strength or pH but will degrade at extreme pH and temperature (e.g., pH 3 at 50 °C).
It remains stable in solution over the pH range of 5–7.
Strong acids cause hydrolysis and loss of viscosity, and alkalies in strong concentration also tend to reduce viscosity.
It is insoluble in most hydrocarbon solvents.
The viscosity attained depends on time, temperature, concentration, pH, rate of agitation, and particle size of the powdered gum used.
The lower the temperature, the lower the rate at which viscosity increases, and the lower the final viscosity.
Above 80°, the final viscosity is slightly reduced.
Finer guar powders swell more rapidly than larger particle-size coarsely powdered gum.
Guar gum shows a low shear plateau on the flow curve and is strongly shear-thinning.
The rheology of guar gum is typical for a random coil polymer.
It does not show the very high low shear plateau viscosities seen with more rigid polymer chains such as xanthan gum.
It is very thixotropic, above 1% concentration but below 0.3%, and the thixotropy is slight.
Guar gum shows viscosity synergy with xanthan gum.
If a biphase system forms, guar gum and micellar casein mixtures can be slightly thixotropic.
The rheological characteristics of guar gum solutions are predominantly determined by the following factors: the solvent’s nature, solution temperature, the concentration of guar gum, the pH of the solution, and the presence of foreign substances.
Guar gum is generally insoluble in hydrocarbons, alcohols, esters, and organic solvents.
Conversely, in cold or hot water solutions, guar gum hydrates rapidly and forms high-viscosity colloidal solutions.
In contrast to the other hydrocolloids, guar gum forms highly viscous solutions even in cold water.
Furthermore, the effect of increased temperatures on guar gum structure, and therefore guar gum solutions, is reported insignificant as the treated guar gum solutions retain high-viscosity values when cooled to room temperature.