Guar gum: processing, properties and food applications—A Review

Bhupendar Singh Khatkar, Phone: +91-1662-263313, Fax: +91-1662-263313, Email: ni.oc.oohay@raktahkradnepuhb .

Abstract

Guar gum is a novel agrochemical processed from endosperm of cluster bean. It is largely used in the form of guar gum powder as an additive in food, pharmaceuticals, paper, textile, explosive, oil well drilling and cosmetics industry. Industrial applications of guar gum are possible because of its ability to form hydrogen bonding with water molecule. Thus, it is chiefly used as thickener and stabilizer. It is also beneficial in the control of many health problems like diabetes, bowel movements, heart disease and colon cancer. This article focuses on production, processing, composition, properties, food applications and health benefits of guar gum.

Introduction

Guar gum is derived from the seeds of the drought tolerant plant Cyamopsis tetragonoloba, a member of Leguminosae family (Whistler and Hymowitz 1979; Kay 1979; Prem et al. 2005). The common names used in the scientific literature for the bean, guar gum flour and the galactomannan fraction are Indian cluster bean, guar and guaran, respectively. There is lack of general consensus with regard to the origins of this plant (Whistler and Hymowitz 1979), although the concept of transdomestication was originally proposed by Hymowitz (1972). This hypothesis explained how the domesticated guar plant, C. tetragonoloba, developed from the drought-tolerant wild Africa species C. senegalensis. The latter species was originally taken from Africa to South Asian subcontinent by Arab traders as fodder for horses probably some time between the 9th and 13th centuries A.D. The domesticated species is normally associated with India and Pakistan, where the plant has been grown for centuries as food for both human and animals (Whistler and Hymowitz 1979). Guar gum industry developed in the 1940s and 1950s in United States (BeMiller 2009). Guar was brought into the United States before World War I primarily as a green manure but was not used in industrial applications until 1943 and probably it was the main reason why it has been studied to a limited scale. At that time, the supply of locust bean gum, which was widely used in the paper and textile industries and imported from Europe and North Africa had declined and was difficult to get. Therefore, the Institute of Paper Chemistry, Appleton, Wisconsin and United States Department of Agriculture made an effort to find a domestic plant that could provide a substitute for locust bean gum. This search led to the reexamination of guar gum and it was found to be the best solution of the problem. The commercial development was made at the University of Arizona during World War II. At the close of the war the gum was examined by Whistler (1948) at Purdue. He worked on the molecular structure and, in examining the properties of the pure polysaccharide, guaran, visualized its wide industrial potential and recommended development of the guar plant as a domestic crop for industry (Whistler 1948; Whistler and Hymowitz 1979). Studies had revealed that the gum is a valuable paper maker's adjunct in obtaining temporary wet strength in sheets, such as paper toweling and this gum facilitates hydration during the beating of various pulps. The services of the Soil Conservation Commission of the U. S. Department of Agriculture were enlisted and as a result, numerous seeds were investigated for their potentialities. The most satisfactory results were found from those of guar or Cyamopsis tetragonolobus, an annual drought-resistant leguminous plant, three to six feet tall, which has been cultivated in certain sections of India for centuries as fodder for cattle and horses.

Guar gum resembles locust bean gum in being composed essentially of the complex carbohydrate polymer of galactose and mannose, but with different proportions of these two sugars. It is reported that guar flour is of value as a beater additive for improving the strength of certain grades of paper. It has also been reported that guar possesses properties which might be useful in warp sizing, printing pastes, and in certain finishing operations. In order to obtain the gum it is necessary to separate the gum-containing endosperm of the seed from the outer and largely fibrous portions.

Consumption of guar gum rapidly increased but it was the development of anionic and cationic guar gum derivatives and their use in oil and gas well stimulation that gave guar gum its present commercial importance. In textile and carpet printing, guar gum thickens the dye solutions which allow more sharply printed patterns to be produced. Guar gum has been used in explosives for over 25 years as an additive to dynamite for water blocking. In recent years, it has become the primary gelling agent in water based slurry explosives. The production of paper is enhanced by an addition of small amounts of guar gum to the pulp. It serves as a fiber deflocculent and dry-strength additive.

Guar seed endosperm is a source of water soluble gum which is used as stabilizer, emulsifier and thickener in various food products and contributes to soluble dietary fiber (SDF) portion of seed total dietary fiber (TDF). TDF and SDF, respectively, made up 52–58% and 26–32% of seed dry weight (Kays et al. 2006). As a food additive, it emulsifies, binds water, prevents ice crystals in frozen products, moisturizes, thickens, stabilizes and suspends many liquid–solid systems. It is used in ice cream, sauces, cake mixes, cheese spreads, fruit drinks and dressings usually in amount of

Production

Guar gum is a gel-forming galactomannan obtained by grinding the endosperm portion of Cyamopsis tetragonolobus, a leguminous plant grown for centuries mainly in India and Pakistan where it is a most important crop that has long been used as food for humans and animals (Chandirami 1957). The guar plant is essentially a sun-loving plant, tolerant of high environmental temperatures but very susceptible to frost (Whistler and Hymowitz 1979; Kay 1979). For maximum growth the plant requires a soil temperature of 25–30 °C and ideally, a dry climate with sparse but regular rainfall. Guar plant requires rain for optimum growth before planting and again to induce maturation of seeds (Anderson, 1949). Excess of moisture during early phase of growth and after maturation of seeds results in lower quality guar beans (Heyne & Whistler 1948; Venkateswarlu et al. 1982). The rain pattern of the monsoons in the northern parts of India and Pakistan generally provides ideal growing conditions for guar. Almost 90% of world’s guar is grown in India and Pakistan. Unique requirement of right amount of rain at a particular time of growth and maturation makes this crop largely dependent on annual rainfall pattern and causes occasional wide swings in guar supply and prices. Guar is also cultivated in the southern hemisphere in semi-arid zones in Brazil, Australia, South Africa and Southern part of the USA like Texas or Arizona. The total production of guar seed in these countries is estimated at 15,000 MT annually. The agro-climatic conditions in Australia are also quite conducive to the cultivation of guar. Efforts have been made to promote cultivation of guar in Australia by the Department of Agriculture and Rural Industrial Development Agency. Similarly, it is reported that countries like China and Thailand are also trying to grow guar. Therefore, in future guar may not remain monopoly of India and Pakistan.

India accounts for 80% of the total guar produced in the world and 70% of it is cultivated in Rajasthan. India is the world leader for production of guar, which is grown in the northwestern parts of country encompassing states of Rajasthan, Gujrat, Haryana and Punjab. During 1970s guar was also grown regularly in the State of Uttar Pradesh (U.P.), Madhya Pradesh (M.P.) and Orissa. As the processing facilities have been closed down in U.P. and M.P., the cultivation in these states is negligible now. In Orissa too guar is not cultivated any more. The annual production of guar during last 3 years ranged from 11, 00,000 to 12, 87,000 MT.

In Pakistan, before 90s, about 80% of the guar was grown under irrigated conditions therefore per hectare yield was higher. During that period guar was grown in Punjab, Multan, Muzaffargarh, Mianwali and Sargoda. The other areas include Bahawalpur, Banawalnagar and Sind Province. The annual production of guar during this period ranged between 180,000 and 250,000 MT annually. List of Indian guar products importing countries is as given in Table 1 .

Table 1

Country wise export data of Indian guar gum from 2008 to 2010 (APEDA 2011)