Guar gum

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

Effect of viscous indigestible polysaccharides on pancreatic-biliary secretion and digestive organs in rats

Abstract: Effects of viscous indigestible polysaccharides on the pancreas exocrine function were investigated in growing rats. Rats were fed a nonfiber diet or a diet containing approximately 5% of one of the following fibers: apple pectin, lambda-carrageenan, locust bean gum, gum xanthan, guar gum or sodium (Na) alginate. Pancreatic-bile secretion was found to be elevated in rats fed for 2 wk the highly viscous polysaccharides, sodium alginate, locust bean gum, gum xanthan and guar gum. The polysaccharides may have interfered with the digestion and absorption of nutrients, resulting in a decreased digestibility and an enlargement of digestive organs. When alginic acid and calcium alginate, insoluble polysaccharides that did not contribute to viscosity, were given to rats, they had no effect on pancreatic and biliary secretion compared with sodium alginate. The results demonstrate that consumption of viscous indigestible polysaccharides leads to changes in the exocrine pancreatic-biliary function and may depress the process of digestion and absorption. Rats may compensate for the inefficiency of digestion and absorption with a hyperplasia/hypertrophy of digestive organs and an increased secretion of digestive juice.

Effect of gel-forming gums on the intestinal unstirred layer and sugar transport in vitro.

Abstract: The effect of two gel-forming polysaccharide gums, guar gum and Na-carboxymethyl-cellulose (CMC), on glucose transport in vitro was investigated using everted sacs of rat jejunum. The gums were added to the mucosal bathing media to give apparent viscosities in the range of 1-110 Pascal seconds X 10(-3), mPa.s(cP). Serosal glucose transport fell steeply by about 60% as the viscosities of the mucosal media rose to 20mPa.s, and levelled off thereafter. A similar effect was observed in sacs preincubated with guar gum (15 minutes) and exposed to glucose in a subsequent guar-free incubation. Glucose transport with and without the addition of guar gum was found to be sensitive to mucosal stirring, so that, when shaken at 130 oscillations per minute, sacs exposed to guar gum (0.25 %, viscosity c.a. 16 mPa.s (cP) transported glucose at a similar rate to sacs incubated without guar at 80 oscillations per minute. By measuring the time course for the establishment of osmotic induced potentials, it was shown that incubation with guar or CMC led to an increase in the apparent thickness of the unstirred fluid layer overlying the mucosa (guar-free thickness = 317 +/- 15 mu, guar treated thickness = 468 +/- 25 mu). It is suggested that the presence of a polysaccharide gum in the fluid film surrounding the villi increases its viscosity, and thus gives rise to a thickening of the rate-limiting unstirred layer. If such an effect occurs in vivo, this could contribute to the diminished post-prandial glycaemia observed in human subjects fed guar gum.

Gelatinization of wheat starch as modified by xanthan gum, guar gum, and cellulose gum.

Abstract: Cereal Chern. 58(6):513-517 Amylograph curves and Corn Industry Viscometer curves show that guar, xanthan, and carboxy methylcellulose gum hasten the onset of initial paste viscosity and substantially increase final peak viscosity of wheat starch. The early onset of initial viscosity is attributed to detection of the first stage of swelling and is dependent on media viscosity only. Further development of paste consistency can be attributed to interactions of solubilzed starch, gums, and swollen starch granules. Media isolated from starch-guar and starch-xanthan dispersions display synergistic viscosity. Hydrocolloids have been used widely in food products to modify texture, improve moisture retention, control water mobility, and maintain overall product quality during storage (Glicksman 1974). Because wheat starch is a basic ingredient of so many foods, changes in its granule structure and pasting properties in the presence of gums were studied to extend knowledge on the function of starch in cooked and baked products and to expand uses of wheat starch and low-gluten flours in protein-fortified foods (Christianson 1976, Christianson et al 1974). Starch granules, including those from wheat, are composed of linear and branched starch molecules associated by hydrogen bonding either directly or through hydrate bridges. The molecules may form radially oriented crystalline areas or be in amorphorus regions. Micellar networks formed by association of segments of individual molecules in various patterns impart durability to the granular structure and control the swelling behavior of starch during heating. Heating in water weakens the more crystalline network within the granules by disrupting hydrogen bonds with a concurrent loss of anisotropy. In the more amorphous areas, where the molecules are not as closely associated, progressive hydration and swelling occur more rapidly. Molecules of linear amylose are eventually released into solution. Hydrogen-bonding forces in wheat starch granules relax at two different stages of swelling (Leach et al 1959). In the first stage, occurring at 55-70° C, granules swell tangentially and simultaneously lose their characteristic polarization crosses. This initial stage is not normally detectable visco metrically. However. Crossland and Favor (1948) noted that the initial gelatinization stages were observable when wheat starch granules were dispersed in carboxymethyl cellulose (CMC) or alginate solutions. They concluded that the changes in the work required to move the swollen granules past each other are magnified in the more viscous media. Sandstedt and Abbott (1964) have shown similar effects with other cereal starches. An appropriate cause for the large increase in viscosity of wheat starch pastes observed during the second stage of swelling and gelatinization is difficult to assign, even in purely aqueous suspensions. Miller et al (1973) concluded that the increase in viscosity (after most of the granule swelling ceases, 94° C) is due to the released exudate (soluble amylose) and its entanglement with itself, which enhances the viscometric effects. Addition of CMC or alginate could also contribute to this network formation and result in even greater final paste viscosity. Other explanations also need consideration. Purely mechanical