Guar Gum known as guar flour is natural water soluble nonionic polysaccharides isolated from the seeds of Cyamopsis tetragonolobus (Linn, Family leguminous). This plant is cultivated from centuries in India and Pakistan. Extraction technology of guar gum was commercialized in USA in 1953. It is also grown in Australia, Brazil and South Africa in the southern hemisphere or in the Southern part of the USA, like Arizona and Texas. In 1949, guar gum is used in the food products in USA for the first time. In the US guar gum was brought before 1st World War principally as a green manure but was not applied industrially until 1943.
Out of total world production India accounts for 80% and takes its 70% production from Rajasthan. Leading country for production of guar in the world is India. Before 90s, in Pakistan 80% of the guar was cultivated in irrigated conditions so there was a higher yield per hectare. At that time guar was produced in Punjab (Muzaffargarh, Multan, Sargodha and Mianwali). It is also cultivated in Bahawalnagar, Bahawalpur and Sind Province. Production of guar gum at that time was between 180 and 250 thousand million ton in Pakistan.
STRUCTURE AND COMPOSITION
The kernel of guar comprises of many layers, i.e. outer covering the husk which is 16-18%, the endosperm 34-40% and 43-46% germ. It is the endosperm that contains guar gum.
Fig 2: Internal Structure of Guar Seed
germ part of guar seed mainly contains protein while the endosperm part is mainly galactomannan (gum). Guar gum consists of the high molecular weight polysaccharides which consist of (1→4)-linked β-D-mannose units linear chain with (1→6)-linked α-D-galactose as side chains. The ratio between galactose and mannose is around 1:2. Its molecular weight ranges between 50,000-8,000,000 depending on chain length.
Fig 3: Repeating units of guar gum
It belongs to the galactomannan family chemically. The composition of guar gum includes soluble fiber 75%, moisture contents 9.55%, insoluble fibers 7.6%, crude protein 2.16%, ash 0.54% and fat 0.78%. In guar gum, total dietary fiber is present in soluble form (80-85%) that may aid to reduce the glucose and cholesterol levels.
In polar solvents, guar gum dissolves and swells on dispersal and form strong hydrogen bonding while in non-polar solvents there is weak hydrogen bonding. With decreasing pH, increasing temperature and minimizing particle size the guar gum dissolution and viscosity development speed is usually enhanced. It is used as emulsifying agent, thickener and stabilizer in a variety of foodstuffs and contributes to total dietary fiber (TDF) of the seed as soluble dietary fiber (SDF). TDF made up 52–58% and SDF made up 26–32% of dry weight of seed. It is used as an additive in frozen food products due to its emulsifying and water binding properties to prevent ice crystals. It is used to moisturize, stabilize, thicken and suspend numerous liquid–solid systems.
Guar gum is diversified for its miraculous curing properties:
- Guar gum lowers cholesterol and glucose levels.
- It helps in prevention of obesity and weight loss.
- Due to of slow gastric emptying by gel forming capability of guar gum an enhanced satiation is attained.
- Guar gum supplemented diets decrease the hunger, appetite, and desire for eating.
- Hypotriacylglycerolemic effects are due to reduction in dietary lipids absorption and fatty acid synthase activity in liver.
- Sufficient guar gum intake as dietary fiber facilitate in
- control of diabetes,
- the maintenance of bowel regularity,
- enhancement of mineral absorption,
- considerable attenuation in total and low density lipoprotein cholesterol
- prevention of constipation like digestive problems.
- Guar gum is also helpful in weight reduction and cancer therapy especially colorectal cancer most common form of cancer due to intestinal disorder.
A. Food Applications:
- Guar gum is used as a food additive in a range of food commodities as stabilizer and as fiber source.
- Due to its numerous intrinsic properties it is used in beverages for viscosity and thickening control.
- Helps to prevent syneresis or weeping problems in cheese product.
- It is added in frozen products as a stabilizer because of its water binding capacity especially in ice-cream
- Used as a hydrocolloid
- In ice cream guar gum improves the texture, body, chewiness and resistance to heat shock
- The machinability of the dough of biscuits and cakes is improved by the addition of guar gum
- Significant increase in loaf volume on baking is achieved by adding guar gum in wheat bread dough
- In salad dressing, pickle and relish sauces it is used as a thickener
- Guar gum increase the stability of tomato ketchup more notably as compared to other hydrocolloids
- Partially hydrolyzed guar gum is added in low fat yoghurt to decreases whey separation and enhance the rheological and textural properties
- Guar gum together with xanthan gum delay staling in chapati and gluten-free cakes by controlling retro-gradation of starch
B. Non-Food Applications
- Other than food uses guar gum is also applied in many other industries for instance pharmaceutical, textile, paper and explosives.
- Guar gum and its derivatives are used as binder and disintegrator in tablets to add cohesiveness to drug powder
- Thickener and stabilizer in pharmaceutical formulation
- Thickens the solutions of dyes in textile and carpet printing, which allow production of more sharply printed patterns
- It is used in oil and gas well stimulation particularly hydraulic breaking in which high pressure is applied to crack rock
- In water based slurry explosives as a gelling agent
- It serves as a dry-strength additive and fiber de-flocculent. The production of paper is improved by adding small quantities of guar gum to the pulps.