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The guar bean or cluster bean (Cyamopsis tetragonolobus) is an annual legume and the source of guar gum. It grows best under conditions with frequent rainfall, but tolerates arid conditions well. 80% of world production occurs in India, but, due to strong demand, the plant is being introduced into new areas.
Guar can be eaten as a green bean, but is more important as the source of guar gum. Guar beans have a large endosperm that contains galactomannan gum, a substance which forms a gel in water. This is commonly known as guar gum and is used in dairy products like ice cream and as a stabilizer in cheese and cold-meat processing.
Another use is as a fiber supplement. After being partially hydrolyzed, guar gum is completely soluble in water and soft food. Being approximately 75% dietary fiber, it allows fiber to be added to a food with a minimal effect on taste and texture.
Partially hydrolyzed guar gum (PHGG) is produced by the partial enzymatic hydrolysis of guaran, the galactomannan of the endosperm of guar seeds (guar gum). It is a neutral polysaccharide consisting of a mannose backbone chain with single galactose side units occurring on almost two out of every three mannose units. The average molecular weight is about 25,000 Daltons. This gives a PHGG that still assays and functions as a soluble dietary fiber. PHGG as sold commercially is completely soluble, acid and heat stable, unaffected by ions, and will not gel at high concentrations.
PHGG is fully fermentable in the large bowel with a high rate of volatile fatty acid formation. The pH of the feces is lowered along with an increase in fecal bulk that mainly consists of bacteria cell mass and water. Clinical studies have demonstrated a prebiotic affect of PHGG. Studies have also shown that PHGG can be used to maintain regularity. PHGG is used in foods for particulate suspension, emulsification, anti-staling, ice crystal control, and reduced fat baked goods.
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