Chemical and physical characterization of galactomannan extracted from guar cultivars (Cyamopsis tetragonolobus L.)

Guar gum, known as galactomannan, is a heteropolysaccharide of galactose and mannose. Because of its unique rheological properties, guar gum has a diverse range of applications in various industries (hydraulic fracturing, paper, textiles, pharmaceuticals, and food). Chemical and physical characterization of guar gum using different analytical techniques is very important to understand the gum chemistry, optimize its applications, and investigate the impact of the purification. Therefore, galactomannan extracted from two guar cultivars planted in West Texas was characterized using different analytical tools to elucidate the variation in the physical and chemical properties with various levels of impurities. The gum was extracted with minimal contamination with continuous sample assessment using Fourier transform infrared spectroscopy (FTIR) and was purified using ethanol precipitation. The purified and unpurified gum samples were characterized using high-performance liquid chromatography, thermogravimetric analysis, X-ray diffractometry, and FTIR spectroscopy to determine the mannose to galactose ratio, thermal stability, level of crystallinity and chemical composition, respectively. Pure guar galactomannan and food-grade guar gum were used as reference materials. The effect of sodium chloride and potassium chloride on guar gum was also investigated. Scanning Electron Microscopy was employed to visualize the morphology of guar seeds. (C) 2015 Elsevier B.V. All rights reserved.