GuarThe guar or cluster bean, with the botanical name Cyamopsis tetragonoloba, is an annual legume and the source of guar gum. It is also known as gavar, gawar, or guvar bean.
The origin of Cyamopsis tetragonoloba is unknown since it has never been found in the wild. It is assumed to have developed from the African species Cyamopsis senegalensis. It was further domesticated in South Asia, where it has been cultivated for centuries. Guar grows well in semiarid areas but frequent rainfall is necessary. This plant has been grown in India for centuries and was probably introduced to the United States in the 1890s. It is widely distributed throughout India, Pakistan, and Burma.
The guar bean is a nitrogen-fixing legume that usually lives for 3 years but sometimes up to 6 years. Although it can tolerate poor soils with pH values less than 6.0, its yield is highest when grown on neutral soils with a pH between 7.0 and 8.5. The optimum soil for guar is a deep sandy loam that allows good root penetration and has adequate drainage.
Guar spreads by both creeping stems (stolons) and seeds; it also reproduces by seed. The stolons can develop roots when they touch the soil, allowing guar to survive even prolonged periods of drought. There are both diploid and tetraploid forms of guar with 2n=20 or 42 chromosomes, respectively. Female flowers are borne on short lateral branches while male flowers are clustered terminally on long erect spikes. The pods are small, usually less than 3 inches long, and contain two or three seeds each. When fresh, the seeds are dark green but dry to a light gray color. Seed viability is high; under proper conditions, guar seed can remain viable for up to 5 years.
The flowering season varies according to latitude, with flowers appearing during April and May in India but not until September in the United States. The pods ripen 6 to 10 weeks after flowering, depending on environmental conditions. Harvest is usually carried out by hand or by gathering with small sickles both when the plants are partly dry (bleeding stage) and while still green (milky stage).
The guar plant can also be propagated from nodal cuttings or from pieces of the stem. There are three stages for processing guar gum: first, separation of the endosperm from the seed coat; second, grinding the endosperm to a fine powder; and third, mixing it with other ingredients. The last two steps may be accomplished at the same time by a simple mechanical process.
Guar gum can be used as a stabilizer in food processing and as a thickener in both the food and pharmaceutical industries. It has been widely used as a texturizing agent, particularly to improve frozen dairy products such as ice cream, frozen desserts, milk shakes, and yogurt.