Starch compression effect

Star-branched butyl rubber, 4 437-438 copolymers, 4 445-446 Starch(es), 4 703-704, 20 452-453 as blood substitute, 4 111-112 cationic, 18 114-115 in cereal grains, 26 271-274 in cocoa shell from roasted beans, 6 357t compression effects in centrifuges, 5 513 depolymerization, 4 712 in ethanol fermentation, 10 534—535 etherified, 20 563 as a flocculant, 11 627 high-amylose, 26 288 Mark-Houwink parameters for, 20 558t modified and unmodified, 12 52-53 in paper manufacture, 18 122-123 performance criteria in cosmetic use, 7 860t... 

Increasing the DS of the starch results in greater segment-segment repulsion and so resisting the compressing effect of the salt. This may be seen in Fig. 9.11. 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Fig. 17 Effect of starch content of granules on dissolution rate of salicylic acid contained in compressed tablets. Q, 5% . 10% x, 20% starch in granules. (From Ref. 22.).

Fig. 17 Effect of powder bed height, piston height, and compression force on plug ejection force in an instrumented Zanasi LZ-64 automatic capsule-filling machine (pregelatinized starch lubricated with 0.005% magnesium stearate). Note that the first point of each curve is precompression. Piston height (mm) , 15 -jlf, 14 , 13 , 12. Powder bed height (mm) heavy line, 30 light line, 50. (From Ref. 51.)...

Since the levels of the compression load and the starch concentration are not of the same order of magnitude, the effect of adjusting the concentration apparently is larger than the effect of adjusting the compression load. 

In order to allow for the comparison of the effect of adjusting the different variables, the values of the variables were standardized (Table 8.1). When the initial crushing strength (Sq) is expressed as a function of the standardized starch concentration (c) and the standardized compression load (f), the effect of the compression load and the starch concentration are in the same order ... 

By combination of the data, two large models can be calculated which describe the effects of the four adjustable, standardized variables (temperature, relative humidity, starch concentration and compression load) on the crushing strength (Sg) and the SIR of crushing strength after storage (S1R(S)), respectively ... 

Just as may be expected, the initial disintegration time of a-lactose monohydrate/starch tablets is influenced by the starch concentration. The compression load level has a small effect on the initial disintegration time. The effect of the concentration is influenced by the level of the compression load. 

Tablets were prepared either with an insoluble (dicalcium phosphate dihydrate), a soluble (6-lactose) or a moderately soluble filler-binder (a-lactose monohydrate). As a disintegrant four different starches (com, rice, potato and tapioca) were used. As a comparison the effect of two super-disintegrants (crospovidone and sodium starch glycolate) was studied. The disintegrants were added at two concentration levels. The compression load was adjusted in order to obtain tablets with comparable initial cmshing strengths.

Coprocessing of a-lactose monohydrate with cornstarch helped in improving its compressibility, and provided dual benefits of enhanced binding capacity and better disintegration potential, the attributes associated to starch (48). This effect was a result of binding of small starch particles together with a-lactose monohydrate crystals into compound particles. 

E.B. Bagley, D.D. Christianson and W.J. Wolf, Frictional Effects in Compressional Deformation of Gelatin and Starch Gels and Comparison of Material Response in Simple Shear, Torsion and Lubricated Uniaxial Compression, J. Rheol., 29 103-108 (1985). 

Levy, G., Antkowiak, J. M., Procknal, J. A., and White, D. C. (1963) Effect of certain tabletformulation factors on dissolution rate of the active ingredient. II. Granule size, starch concentration, and compression pressure. Pharm. Sci., 52 1047-1051. 

Subsequently a small, but defined effect of compression up to 8 X 107 Pa on the viscosity of starch pastes was reported.38 Paronen and Justin39 investigated this... 

Tomasik and Kudla40 have investigated the effect of humidity, and of pressure and its duration, on potato starch (up to 1.2 X 109 Pa for 360 s). The results are presented in Fig. 4. It may be seen that water favors a decrease of the volume of compressed sample. This effect is observed only up to a certain amount of water. Addition of water in an amount that exceeds the natural capacity of the starch matrix makes the volume of the pellet larger. This observation indicates that water cooperates with high pressure in causing deterioration of the starch matrix. Simultaneously, the ascending portions of the compressibility curves show that the resistance of the starch matrix toward compression decreases as the volume of added water increases. 

Cunningham et al.199-203 investigated the use of starches and dextrins as extenders for polyurethane foams. Starch generally had little effect on the foam density, while compressive strength moderately decreased with increasing starch content. Hydrophilic foams prepared using starch were suggested to have useful horticultural... 

---