Guar gum

About: Guar gum is a research topic. Over the lifetime, 5611 publications have been published within this topic receiving 105940 citations.

Dynamic Rheology of Rice Starch-Galactomannan Mixtures in the Aging Process

Abstract: The effect of galactomananns (guar gum and locust bean gum) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) on the dynamic rheological properties of aqueous rice starch dispersions (5%, w/w) was investigated by small-deformation oscillatory measurements during aging. Magnitudes of storage (G′) and loss (G′′) moduli measured at 4°C before aging increased with the increase in gum concentration in the range of 0.2–0.8%. G′ and G′′ values of rice starch-locust bean gum (LBG) mixtures, in general, were higher than those of rice starch-guar gum mixtures. G′ values of rice starch-guar gum mixtures as a function of aging time (10 h) at 4°C increased rapidly at initial stage and then reached a plateau region at long aging times. However, G′ values of rice starch-LBG mixtures increased steadily without showing a plateau region. Increasing the guar gum concentration resulted in an increase in plateau values. The rate constant (K) for structure development during aging was described by first-order kinetics. K values in rice starch-guar gum mixtures increased with the increase in guar gum concentration. G′ values of rice starch-galactomannan mixtures after aging were greater than those before aging.

Purification and characterization of two alpha-galactosidases associated with catabolism of guar gum and other alpha-galactosides by Bacteroides ovatus.

Abstract: When Bacteroides ovatus is grown on guar gum, a galactomannan, it produces alpha-galactosidase I which is different from alpha-galactosidase II which it produces when grown on galactose, melibiose, raffinose, or stachyose. We have purified both of these enzymes to apparent homogeneity. Both enzymes appear to be trimers and have similar pH optima (5.9 to 6.4 for alpha-galactosidase I, 6.3 to 6.5 for alpha-galactosidase II). However, alpha-galactosidase I has a pI of 5.6 and a monomeric molecular weight of 85,000, whereas alpha-galactosidase II has a pI of 6.9 and a monomeric molecular weight of 80,500. alpha-Galactosidase I has a lower affinity for melibiose, raffinose, and stachyose (Km values of 20.8, 98.1, and 8.5 mM, respectively) than does alpha-galactosidase II (Km values of 2.3, 5.9, and 0.3 mM, respectively). Neither enzyme was able to remove galactose residues from intact guar gum, but both were capable of removing galactose residues from guar gum which had been degraded into large fragments by mannanase. The increase in specific activity of alpha-galactosidase which was associated with growth on guar gum was due to an increase in the specific activity of enzyme I. Low, constitutive levels of enzyme II also were produced. By contrast, enzyme II was the only alpha-galactosidase that was detectable in bacteria which had been grown on galactose, melibiose, raffinose, or stachyose.

Effect of hydrocolloid (guar gum) incorporation on the quality characteristics of bread.

Abstract: Effect of guar gum on the rheological properties of dough, physico-chemical properties of bread, sensory characteristics of finished product and white bread quality was studied. At all levels of incorporation, there were increases water absorption from 61.2 to 64.5%, lowered the dough development time from 6.20 to 5.60 min, increased gluten development, increased dough stability, increased break down time from 37.3 to 40.5 min, higher the mixing tolerance index from 52.2 to 54.6 BTU and increased the elasticity i.e. 72.3 to 74.6 BU of the dough. The external characteristics like color of crust, symmetry, evenness, character of crust and aroma was improved linearly with increased the concentration of guar gum and also internal characteristics like color of crumb, taste and texture was improved.