Showing papers on "Guar gum published in 1981"

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

Rheology of galactomannan solutions: comparative study of guar gum and locust bean gum

Abstract: The rheological properties of several samples of guar gum and locust bean gum, characterized by light scattering and intrinsic viscosity measurements, were studied. The flow curves of concentrated solutions were obtained with a cone-plate viscometer and their viscoelastic properties were measured with a concentric hemispheres viscoelastometer. The two flow-units Ree-Eyring model and the Cross equation gave a good fit to the experimental flow curves. The zero shear rate viscosity, and the relaxation time, of the Ree-Eyring model depend mainly on the reduced concentration c[η]. This result, as well as the viscoelastic properties, indicate that entanglements play a dominant role in concentrated solutions. From a practical viewpoint, it is possible to predict the flow curve of a galactomannan solution at any concentration if the intrinsic viscosity of the sample is known. However, there are secondary differences in the flow parameters, mainly in the relaxation time, which are not ascribed to [η]. It is hypothesized that these differences are due to the mean branching degree rather than to the botanical origin. As, in solution, the smoothest galactomannan macromolecules are more probably aggregated than isolated, further work should aim at establishing the relationships between aggregate formation and degree of branching.

Improved diabetic control and hypocholesterolaemic effect induced by long-term dietary supplementation with guar gum in type 2 (insulin-independent) diabetes.

Abstract: The effects of dietary supplementation with granulated guar gum (21 g/day in three divided doses at the main meals), were compared with placebo response during three months in a doubleblind, cross-over trial in 11 Type 2 (insulin-independent) diabetics. The nine patients who completed the study (two dropped out because of side-effects) showed a significant reduction in both basal and postprandial hyperglycaemia as well as of urinary excretion of glucose during guar gum supplementation. No change in mean bodyweight was observed during the study. Mean fasting and post-prandial plasma insulin levels were similar during both study periods, but the two subjects who received no oral hypoglycaemic agents had lower insulin levels during the guar gum period. Mean serum total- and LDL-cholesterol concentrations were significantly lower during the guar gum period, whereas the HDL-cholesterol level remained unchanged. Long-term administration of guar gum induced a sustained improvement in diabetic control in Type 2 diabetes.

The effect of guar gum on the viscosity of the gastrointestinal contents and on glucose uptake from the perfused jejunum in the rat.

Abstract: 1. Male Wistar rats were meal-fed for at least 10 d a control semi-synthetic diet containing no guar gum, or one of three similar test diets containing 3, 10 or 20 g dry guar gum/kg. 2. Rats were killed 6 h after feeding, and contents of stomach, small and large intestine were collected separately. The apparent viscosities of stomach and small intestine contents from animals fed on diets containing 10 and 20 g guar gum/kg were increased relative to control animals, but large intestine contents were unchanged. 3. In the second part of this study, male Wistar rats were anaesthetized and two consecutive lengths of jejunum were perfused, initially with Ringer only (control) or Ringer plus 5 or 6 g guar gum/1 (test). Following this pre-perfusion, both segments were perfused with Ringer containing glucose (10 mM), [3H]glucose and [14C]inulin, and the rate of glucose absorption was determined. 4. The rate of glucose absorption was decreased relative to control values in segments pre-perfused with both 5 and 6 g guar gum/1 solution, but this reduction was significant only in the instance of the 6 g/l solution (P less than 0.001). 5. These results provide evidence to support previous assumptions that ingestion of guar gum will increase the apparent viscosity of the contents of the stomach and small intestine. We propose that a possible mechanism by which guar reduces post-prandial glycaemia is a reduction of glucose absorption from the small intestine, resulting from an increase in viscosity of the contents.

Effect of pH and Heat Treatment on the Binding of Calcium, Magnesium, Zinc, and Iron to Wheat Bran and Fractions of Dietary Fiber

Abstract: The effect of pH and heat treatment on the binding of added food grade sources of calcium, magnesium, zinc, and iron to a standard wheat bran, cellulose, and lignin was investigated. 1% solutions of pectin and guar gum were examined for their ability to bind these metals in aqueous solution. Lignin and pectin was found to have high metal binding capacities. Metal binding to fiber was found to be pH dependent. Toasting had no effect on metal binding by cellulose, but had a significant effect on the binding of metals by lignin and wheat bran. Boiling had a significant effect on the binding of metals by cellulose, lignin, and wheat bran.

Guar bread: acceptability and efficacy combined. Studies on blood glucose, serum insulin and satiety in normal subjects

Abstract: 1. Bread alone and supplemented with guar gum at three levels (50, 100 and 150 g/kg) was given to eleven non-diabetic subjects, and blood glucose and serum insulin were determined preprandialy, and at 30 min and 60 min after commencement of the meal. The satiating effect, up to 120 min, of the guar bread and its acceptability to the same group of normal volunteers was also studied.2. No significant differences in blood glucose were observed between control and guar breads at 30 min and 60 min, apart from 100 g guar/kg bread at 30 min (P < 0·05). A significant difference in serum insulin was indicated between: control and 50 (P < 0·02) and 150 (P < 0·02) guar/kg breads at 30 min; control and 50 (P < 0·05), 100 (P < 0·001) and 150 (P < 0·05) guar/ke breads at 60 min.3. There were no significant differences in the satiety scores for control and guar breads. Significant increases in satiety attributed to 150 g guar/kg bread were found when compared to: 50 g guar/kg bread immediately after eating (P < 0·05), 100 g guar/kg bread at 60 min (P < 0·02) and 50 and 100 g guar/kg breads at 120min (both P < 0·05).4. There was a positive correlation between hedonic score and relative replacement of guar (r 0·62, P < 0·001, n 44) and from the regression line it was found that 50 and 100 g guar/kg breads produced hedonic scores close to a neutral response of 5, whereas 150 g guar/kg bread at a predictive score of 6·3 appeared to be unacceptable to our subjects.5. Guar bread at the 100 g/kg level (59 g guar/kg bread) reduced the serum insulin by 48% at 60 min and is found to be an acceptable food product at this level of incorporation. However, more information is required to demonstrate the possible satiating potential of guar bread.

Effect of two kinds of pectin and guar gum on 1,2-dimethylhydrazine initiation of colon tumors and on fecal beta-glucuronidase activity in the rat.

Abstract: The effect of 5% low-methoxylated pectin, high-methoxylated pectin, and guar gum on 1,2-dimethylhydrazine initiation of colon cancer was investigated using groups of 30 rats. The growth of the rats in the different groups was very similar to that of control group fed a fiber-free diet. Both kinds of pectin increased the multiplicity of color tumors, whereas guar gum did not significantly influence carcinogenesis. Bacterial beta-glucuronidase activity in feces and colonic content was the same in pectin-fed rats and controls but significantly lower in the guar gum group. Thus, it was not related to the number of tumors in each group.

Dietary fibres. VI: Binding of fatty acids and monolein from mixed micelles containing bile salts and lecithin.

Abstract: Mixed micelles were prepared containing sodium taurocholate, monolein dioleyl lecithin, cholesterol, and an equimolar mixture of palmitic, oleic, and linoleic acids. These were incubated with commercial bile acid-sequestering resins, cholestyramine and DEAE-Sephadex, or various dietary fibers and fiber components including wheat bran, cellulose, alfalfa, lignin, and two viscosity grades of guar gum. Binding of monolein and fatty acids was determined as the difference between the radioactivity of the added micellar component, and that recovered in the centrifugal supernatant after incubation. In general, the extent of monoglyceride or fatty acid sequestration was characteristic and reproducible for each binding agent. Cholestyramine and DEAE-Sephadex essentially quantitatively bound monoglycerides and all three fatty acids from micellar medium. Low- and high-viscosity grades of guar gum sequestered 15-23% of the monolein and 32-33% of the fatty acids, showing a significant preference for linoleic a...

Applications of Xanthan gum

Abstract: Xanthan gum, the extracellular polysaccharide from Xanthomonas comperstris, provides aqueous solutions with properties that are extremely useful in a large number of industrial applications, both food and non-food. These properties, a consequence of xanthan gum's particular molecular shape, are: high at-rest or low-shear viscosity even at low gum concentrations, yield value, high pseudoplasticity, increased viscosity in the presence of added salt depending on gum concentration, stable viscosity over a wide range of temperature and pH in the presence of added salt, synergistic increase in viscosity in the presence of guar gum and locust bean gum, thermoreversible gelation with locust bean gum at appropriate gum concentratins, and gelation with di-and trivalent metal ions and borates under specific conditions. Xanthan gum is thus an excellent stabiliser for a wide variety of suspensions, emulsions, and foams and is highly effective over a range of temperature, pH and ionic strength. In addition, its pseudoplasticity allows the formulation of products which require not only high at-rest viscosity but also low viscosity under highshear application conditions.

Flushable premoistened wiper

Abstract: Pre-moistened wiper comprising a nonwoven web impregnated with a modified guar gum and wet with an aqueous lotion containing borate ions.

Viscosity differences between various guar gums

Abstract: Guar gum from four industrial sources was investigated. The viscosity of two preparations of hydrated guar gum in the form of powdered flour and one granulate flour was measured at 22° and 32 °C and pH 1.0 and pH 4.0. Viscosity measurements on wax-coated guar granules proved impossible but visual assessment indicated an extremely low viscosity in all conditions. These findings were compared with the ability of the equivalent of 5 g guar gum of the various preparations to modify the absorption of a 50 g liquid glucose load. The mean post-prandial blood glucose curve was not significantly different from the control situation after the incorporation of each preparation. Despite the granulate flour attaining a considerably lower viscosity than the powdered flour they were equally effective in significantly reducing the mean post-prandial insulin curve (area under the curve (0–180 min) reduced by 46 and 50% respectively). The wax-coated granules which achieved minimal viscosity caused significantly less reduction of post-prandial insulin levels (area under the curve reduced by 37%). The viscosity of guar gum upon hydration is of importance in assessing the efficacy of a preparation in clinical use.

Evaluation of Some Binding Agents for Crustacean Diets

Abstract: Eleven binding agents were added at 3.0% dry weight or less to a trout feed intended for use as a crustacean diet. Moist and dry food pellets were prepared, oscillated in beakers of 30°C water for 24 h, and inspected periodically for integrity. Two to six pellets prepared with each binding agent were tested. Dry pellets were generally less stable than moist ones. Only agar and the sodium alginates Keltone and Kelvis gave 24-h stability for both types of pellets. The alginates, when used with sodium hexametaphosphate as a sequestrant, produced much firmer pellets than agar, and Keltone produced slightly firmer pellets than Kelvis. Less successful binders, in approximate order of decreasing stability, were GFS (a mixture of three natural gums), Viscarin (a sodium carrageenin), a low viscosity chitosan, collagen, guar gum, Vitosan HMW (a chitosan), carboxymethyl cellulose, and cornstarch.

Degradation of guar gum by enzymes produced by a bacterium from the human colon

Abstract: A strain of Bacteroides ovatus from the human colon was grown on guar gum, a highly-branched galactomannan which is widely used as a food additive. Growth on guar gum induced production o f extracellular enzymes which partially degraded and/or deaggregated guar gum. The enzymes rapidly reduced the viscosity of guar gum solutions, while breaking only a limited number of glycosidic bonds. The molecular weight (versus dextran standards) of the guar gum decreased sharply as the viscosity decreased. No mono-, di- or trisaccharides were produced during enzyme action, although small quantities of higher oligomers were present after longer (5–8 h) incubations. The enzyme had a sharp temperature optimum at 37°C for an incubation time of 60 min, but was stable for only a few hours at this temperature. These results demonstrate how enzymes produced and elaborated by human colon bacteria can markedly alter the physical properties of a dietary component which reaches the colon. Further studies of both substrate and enzymes will be required to establish the mechanism of this alteration and to establish how B. ovatus is able to utilize guar gum for growth.

Effect of Heat Treatment on the Flow Properties of Aqueous Guar Gum and Sodium Carboxymethylcellulose (CMC) Solutions

Abstract: Prolonged heat treatment of 1% (w/v) guar gum and sodium carboxymethylcellulose (CMC) solutions resulted in a permanent loss of their apparent viscosity. The consistency index (K) of the power law model: τ= K γn, indicated well the loss of viscosity. The reduction in K due to heat treatment could be characterized by D and z parameters. The D250 and z values for guar gum were 32 min and 62°F, respectively; the magnitudes for CMC were 7.9 min and 48°F, respectively. These values were obtained from experiments in which the solutions were placed in sealed cans (201 × 304) and subjected to temperatures between 210–260°F. Because the solutions were viscous, corrections were made for heating and cooling lags during heat treatment. Dilutee solution viscosity data showed that heat treatment resulted in lower magnitudes of intrinsic viscosities and interaction coefficients. The activation energy of flow of the heat-treated solutions was not affected significantly due to heat treatment.

Determination of the yield stress of hydrocolloid dispersions [Guar gum, cornstarch].

Abstract: The yield stresses of dispersions of guar gum (0.5–2.0% by weight) and gelatinized cornstarch (2.5–5.0% by weight) were measured using several different established experimental methods. The yield stresses in these polysaccharide dispersions result from intermolecular hydrogen bonding and molecular entanglements, thus the higher yield stress and hysteresis effect in guar gum dispersion was interpreted in terms of the greater hydrogen-bonding density and molecular entanglements caused by the more extended chain conformation. The results confirm that there is no one absolute value for the yield stress of the hydrocolloid dispersions and that the viscoelastic characteristics of the test materials influence the shear rate and time dependence of yield stress. Therefore, experimental determination of yield stress must be made relevant to the practical application.

Effects of Locust Bean Gum on Glucose Tolerance, Sugar Digestion, and Gastric Motility in Rats

Abstract: Effects of selected undigestible gel-forming complex carbohydrates, including locust bean gum, guar gum, and pectin, on glucose tolerance and food motility were studied in rats. Addition of 2.5% of guar gum or locust bean gum to an oral glucose tolerance test solution significantly altered the postprandial serum glucose response. Although all three complex carbohydrates tested did not reduce the initial rise in serum glucose, locust bean gum and guar gum significantly reduced its subsequent rebound hypoglycemia. Further tests with locust bean gum showed that these effects were dependent on the concentration of the gum added to the test solution or diet. Addition of locust bean gum to test diets reduced the rate of gastric emptying and thus slowed down the passage of food from the stomach into the upper small intestine. The study suggests that addition of locust bean gum to the diet can flatten the postprandial serum glucose curve by slowing the rate of food passage from the stomach into the small intestine. It is probable that locust bean gum and other similar materials may be useful as an adjunct dietary treatment of diabetes mellitus in humans.

Determination of the yield stress of hydrocolloid dispersions

Abstract: The yield stresses of dispersions of guar gum (0.5–2.0% by weight) and gelatinized cornstarch (2.5–5.0% by weight) were measured using several different established experimental methods. The yield stresses in these polysaccharide dispersions result from intermolecular hydrogen bonding and molecular entanglements, thus the higher yield stress and hysteresis effect in guar gum dispersion was interpreted in terms of the greater hydrogen-bonding density and molecular entanglements caused by the more extended chain conformation. The results confirm that there is no one absolute value for the yield stress of the hydrocolloid dispersions and that the viscoelastic characteristics of the test materials influence the shear rate and time dependence of yield stress. Therefore, experimental determination of yield stress must be made relevant to the practical application.

Effects of guar on plasma viscosity and related parameters in diabetic children

Abstract: Ten diabetic children supplemented their normal diets with 0.45 g/kg/day guar gum for 4 weeks. They experienced a decrease in (1) plasma fibrinogen, (2) insulin requirement, (3) serum osmolality and (4) plasma viscosity; and an increase in serum albumin and total serum protein concentrations. The decrease in plasma viscosity, which was statistically significant, depended on the increase of albumin and the decrease of fibrinogen and may have some significance to the development of diabetic microangiopathy. The sequence of events eventually leading to a decrease of plasma viscosity is possibly mediated by gip and glucagon, consecutively.

Purification and properties of alpha-galactosidase from immature stalks of Saccharum officinarum (sugar cane).

Abstract: The immature sugar cane stalks studied contained less than 7% sucrose, and showed the activities of enzymes such as invertase, alpha-galactosidase, alpha-mannosidase, beta-N-acetylglucosaminidase, beta-glucosidase, beta-xylosidase, and beta-galactosidase. The alpha-galactosidase was highly purified by ammonium sulfate fractionation, gel filtration on a Sephadex G-100 column, ionexchange chromatography on DEAE-cellulose, and CM-cellulose columns, and heat treatment (60 degrees C, 15 min) in the presence of 0.2 m D-galactose. In polyacrylamide gel electrophoresis, the purified enzyme was homogeneous, having a molecular weight of approximately 46,000. In gelfiltration, it was approximately 47,000. The activity was optimum at pH 4.5 and at 60 degrees C. The purified enzyme hydrolyzed p-nitrophenyl-alpha-D-galactopyranoside (Km, 0.83 mM; Vmax, 25.0 mumol/mg/min), raffinose (Km, 25.9 mM; Vmax, 15.4 mumol/mg/min), and stachyose (Km, 13.0 mM; Vmax 2.7 mumol/mg/min), in addition to melibiose, guar gum, and locust bean gum. The hydrolysis of p-nitrophenyl-alpha-D-galactopyranoside was markedly inhibited by HgCl2, AgNO3, p-chloromercuribenzoate (PCMB), L-ascorbic acid, melibiose, stachyose, and D-galactose. Also the purified enzyme showed a lectin activity with trypsinized erythrocytes.

Fabric softening composition and a process for preparing it from cationic surfactant and thickener

Abstract: A rinse conditioner containing cationic surfactant and optionally other surfactants or fatty materials is prepared to relatively high viscosity at which it is stable. The process step necessary to achieve this is first to prepare a relatively mobile dispersion of the active materials and to thicken this mobile dispersion with a nonionic or weakly anionic thickener. Examples of such thickeners are guar gum, polyvinylacetate and polyacrylamide.

Guar gum is not a panacea in diabetes management.

Abstract: Guar gum was incorporated into the diets of six insulin dependent diabetics drawn from one general practice. Amounts between 6 and 59.6 g daily were used for four to six weeks and compared with a previous two week control period. Unlike some other studies, little improvement was obtained in diabetic control and a small reduction in cholesterol levels occurred. The guar was well tolerated in amounts below 30 g a day.

Glycosylated haemoglobin, blood glucose and serum cholesterol levels in diabetics treated with guar gum.

Abstract: The diet of 10 insulin-dependent diabetics was modified for 3 months by the addition of guar gum to buttermilk rusks. Control of glycaemia was assessed by serial determination of total glycosylated haemoglobin A1. The effect of guar on serum cholesterol levels was noted. Guar gum supplementation failed to improve the long-term diabetic control, but significantly reduced serum cholesterol levels (P less than 0,01). The effect of guar on lipoprotein levels should be investigated more fully.

Aqueous skin cleaner containing hydroxypropylated guar gum and paraffin sulfonate/alkyl sulfate detergent mixture

Abstract: An aqueous liquid skin cleaning composition containing hydroxypropylated guar gum, paraffin sulfonate, and C8-16 alkyl sulfate, and a method of washing the skin therewith.

.BETA.-Mannanase of bacteria isolated from natural habitats.

Abstract: The culture fluids of 117 bacterial strains isolated from natural habitats were assayed for β-mannanase activity by using codium mannan as a substrate. The highest β-mannanase productivity was detected in the strain F-25 of Aeromonas sp. isolated from the intestinal contents of freshwater fish, Salmo gairdnerii. β-Mannanase form the strain was induced enzyme. Konjac glucomannan and commercially available konjac powder were superior inducers. The β-mannanase productivity of the strain was susceptible to the influence of culture temperature; the strain showed the highest β-mannanase activity when incubated at 25°C for 3 days, but hardly showed the activity at 37°C. The culture fluid of Aeromonas sp. F-25 was separated into two fractions with β-mannanase activity by DEAE-Sephadex A-50 column chromatography. One fraction eluted by a salt gradient contained an endo-β-mannanase, which hydrolyzed codium mannan, coffee mannan, konjac glucomanna and guar gum galactomannan to give several mannooligosaccharides. The other fraction eluted through the column without adsorption contained an exo-β-mannanase of novel type, which attacked codium mannan and coffee mannan to form only mannobiose but not konjac glucomannan and guar gum galactomannan.