Potato starch compressibility

Native starches are used as disintegrants, diluents, and wet binders. However, their poor flow and high lubricant sensitivity make them less favorable in direct compression. Different chemical, mechanical, and physical modifications of native starches have been used to improve both their direct compression and controlled-release properties (Sanghvi, 1993 van Aerde and Remon, 1988). Schinzinger and Schmidt (2005) used potato starch as an excipient and compared its granulating behavior with a-lactose-monohydrate and di-calcium phosphate anhydrous in a laboratory fluidized bed granulator using statistical methods. 

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. 

It has been shown by Boruch et al.66 61 that solid starch changes its electrical conductivity on compression. At constant temperature and humidity there is a positive correlation between the tamping of starch layers in cylinders, containers, and silos and their electrical conductivity.67 Figure 10 shows how the electrical conductivity varies for potato starch as a function of the humidity and pressure applied. 

Sawayanagi et al. [301] reported the fluidity and compressibility of combined powders, viz., lactose/chitin, lactose/chitosan, potato starch/chitin, potato starch/chitosan as well as the disintegration properties of tablets made from these powders in comparison with those of combined powders of lactose/MCC and potato starch/MCC. This was done in order to develop direct compression dilutents as a part of their studies on pharmaceutical applications of chitin and chitosan. 

The addition of various salts to potato starch on its compression up to 1.2 X 109 Pa had only a small effect on the thermal properties of starch, as measured by thermogravimetry/differential thermogravimetry/differential thermal analysis (TG/DTG/DTA). Only FeCl3, CoCl2, and I2 caused significant effects.62... 

In the above studies compression and injection moulding were carried out with native potato starch dried at room temperature and then mixed with 7% water. After processing, the samples were subjected to ambient atmosphere and investigated after a storage time of at least 4 weeks. 

Both compression mechanisms in fine and agglomerated powders are influenced by particle size and size distribution, particle shape, and surface properties. Potato starch and powdered milk have demonstrated that powders will crackle during compression, that is, change in volume... 

Mechanical testing on the foam is performed to measure the compressive stress and the resiliency. The results from diese tests are shown in table 2, in which the properties of extruded polystyrene foam (XPS) and commercial starch-based loose-frll foams (Eco-foam and Mater-Bi) together with EPS loose-fill foam (Pelaspan Pac) are added for conq>arison. The values of XPS are obtained from tests on typical XPS retail packaging trays. The table shows that the compressive stress reached with potato starch foam is comparable with that of XPS. Through the cell structure of the potato starch foam (high cell density, very small cells) a good resiliency can be obtained, although pure starch plastics exhibit brittle fracture behavior. This brittle fracture still is present on the microscopic scale of the individual cells but due to the cell density, the foam exhibits resiliency on macroscopic scale. 

HuUeman. S.H.D., Kalisvaart M.G., Janssen F.H.P., FeU H., Vhegenthart J.F.G., Origins of B-type crystallinity in glycerol-plasticized, compression moulded potato starches, Carbohydr. Polym., 39, 1999,351-360. 

Tablets of 8 furosemid content were compressed with or without disintegrant using microcrystalline cellulose as binder. 2,5 CDP or 12,5 potato starch played the role of disintegrant. The properties of tablets are listed in Table IV.

Thunwall M., Boldizar A., Rigdahl M. Compression molding and tensile properties of thermoplastic potato starch materials. Biomacromolecules 1 (2006) 981. 

The applicability of a 25 L high-shear mixer for moisture-activated dry granulation of phenobarbital was investigated by Christensen et al. (6). MCC, potato starch, or a mixture of 50% of each was used as moisture absorbing material. The results of the study showed that the physical properties of the tablets were primarily affected by the water content, the moisture absorbing material, and the compression force. 

Volume increases in wheat starch and potato starch granules during the compression and release phases were measured microscopically (Douzals et al, 1996a). Gelatinization of wheat starch began at pressures above 300 MPa and the largest increase in granule... 

Figure 4.16 Influence of glycerol content on maximum stress of granulates from potato starch at compression depending on blend moisture.

Figure 4.18 Influence of extrusion repetition on stress maximum at compression of granulates from potato starch.

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.

A number of starch modifications are used in pharmaceutical applications. Pregelatinized or compressible starch has been chemically or mechanically processed to rupture all or part of the granules in water. It is then dried to yield an excipient material suitable for direct-compression formulations. Sterilizable maize starch contains magnesium oxide (not greater than 2.2%) and has been chemically or physically treated to prevent gelatinization on exposure to moisture or steam sterilization. Soluble starch results when potato or maize starch has been chemically treated to destroy the gelatinizing ability of starch. 

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