Viscosity of Cellulose Gum

Viscosity of a 2 %, Weight in Weight, Solution Determine as directed under Viscosity of Cellulose Gum, Appendix IIB. 

Viscosity Transfer a 4-g sample, finely powdered, into the container of a stirring apparatus equipped with blades capable of being adjusted to about 1000 rpm. Add 10 mL of alcohol to the sample, swirl to wet it uniformly, and then add 390 mL of water, avoiding the formation of lumps. Stir the mixture for 7 min, pour the resulting dispersion into a 500-mL bottle, insert a stopper, and allow to stand for about 12 h in a water bath at 25°. Determine the apparent viscosity at this temperature with a model LVF Brookfield, or equivalent, viscometer (see Viscosity of Cellulose Gum, Appendix IIB) using a suitable spindle, speed, and factor. 

Procedure Determine the absorbance of each solution with a suitable spectrophotometer and in 1-cm cells at the maximum at about 375 nm, using sodium carbonate TS as the blank. The absorbance of the Sample Preparation is equal to or greater than that of the Standard Preparation. Viscosity Prepare two identical solutions, each containing 1% of sample and 1% of potassium chloride in water, and stir for 2 h. Determine the viscosity (Vj) of one solution at 23.9° as directed in the Procedure under Viscosity of Cellulose Gum, Appendix IIB, using a No. 3 spindle rotating at 60 rpm (Brookfield, or equivalent). The viscosity thus determined is not less than 600 cp. Determine the viscosity (V2) of the other solution in the same manner, but maintain the temperature at 65.6°. The ratio of the viscosities, V1/V2, is between 1.02 and 1.45. 

Viscosity of Cellulose Gum. .. 850 Method II Ion-Selective Electrode Method ... 

The viscosity of natural gums, such as cellulose gums, mannogalactans, seaweed, pectin, locust bean gum, guar gum, and tragacanth has important industrial applications in the food, pharmaceutical, cosmetic, textile, adhesives, and paint fields. The characteristics of viscosity are related to specific uses and to the economics of the process. 

Apparatus Use a Brookfield Model LV series viscometer, analog or digital, or equivalent type viscometer for the determination of viscosity of aqueous solutions of cellulose gum within the range of 25 to 10,000 centipoises at 25°. Rotational viscometers of this type have spindles for use in determining the viscosity of different viscosity types of cellulose gum. The spindles and speeds for determining viscosity within different ranges are tabulated below. 

Thickeners can be added to increase the viscosity of the NR adhesives. Natural materials can be used such as casein or karaya gum, but currently synthetic polymers are used (methyl cellulose and derivatives, polyacrylates). 

Flavor emulsions are similarly stabilized by the viscosity produced upon addition of a vegetable gum, such as tragacanth, Irish moss extract, arabic, a cellulose gum, or one of the alginates, to the aqueous phase. Here the oil phase, in the form of the flavor, is in small proportion to the water. In the absence of the acetic acid, contained in the vinegar of the French dressing. 

For suspensions primarily stabilized by a polymeric material, it is important to carefully consider the optimal pH value of the product since certain polymer properties, especially the rheological behavior, can strongly depend on the pH of the system. For example, the viscosity of hydrophilic colloids, such as xanthan gums and colloidal microcrystalline cellulose, is known to be somewhat pH- dependent. Most disperse systems are stable over a pH range of 4-10 but may flocculate under extreme pH conditions. Therefore, each dispersion should be examined for pH stability over an adequate storage period. Any... 

Commercial bakeries and doughnut shops normally use a system that extrudes a batter from a reservoir directly into the deep fat fryer (Figure 5). In such a system the rheology of the batter is vitally important. The batter must flow and spread as needed. The major influence on the batter viscosity is the water content, which is around 70% of the flour or around 40% of the dry mix. Various gums are sometimes added to the dry mix to bind water, reduce fat absorption, and control the viscosity. Examples of these gums are guar gum, locust bean gum and carboxymethyl cellulose. 

Other thickeners used include derivatives of cellulose such as methylcellulose, hydroxypropylmethylcellulose, and cellulose gum natural gums such as tragacanth and xanthan (see Cellulose ethers Gums) the carboxyvinyl polymers and the poly(vinyl alcohol)s. The magnesium aluminum silicates, glycol stearates, and fatty alcohols in shampoos also can affect viscosity. 

Young, S.L. and Shoemaker, C.F. 1991. Measurement of shear-dependent intrinsic viscosities of carboxymethyl cellulose and xanthan gum suspensions. J. Appl. Polymer Sci. 42 2405-2408. 

Additivity obtains when a measured property, e.g., viscosity, is the sum of the contributions made by each cosolute. Additivity for any pair of compatible polysaccharides fits the following equation developed for cellulose gums... 

Blends of starch and konjac gum (Tye, 1991) and of some modified celluloses (Hercules, Inc., 1980) are synergistic. A ternary dispersion of 1% methylcellulose and 2.9% starch had almost 2.5 times the viscosity of a blend of 0.5% methylcellulose and 2.9% starch, and approximately 20 times the viscosity of 3.9% starch (Hegenbart, 1989). Methylcellulose-starch viscosity synergism was suggested as a formula to decrease caloric content (Henderson, 1989). Guar gum can increase starch paste viscosity tenfold (Christianson et al., 1981). 

The formation of cellulose ethers aims, in general, at permanent and irrevocable disruption of crystallinity, and at controlling viscosity properties of aqueous solutions (i. e., rheology modification). Since stiffening water and gel formation are primary targets for many natural polysaccharides (in gums as well as body fluids), cellulose ethers aim to achieve solutions with... 

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