Starch humidity effects

Tablets prepared with dicalcium phosphate dihydrate increased in crushing strength due to increasing temperatures (A,sir(s) ). The relative humidity had a negative effect on the SIR of crushing strength of the tablets prepared with dicalcium phosphate dihydrate, except for the tablets prepared with potato starch. Also a significant interaction between the temperature and relative humidity effect was seen (A3,sir(S) 0), indicating that the effect of the relative humidity on the SIR of crushing strength of dicalcium phosphate dihydrate tablets depended on the level of temperature and vice versa.

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 ... 

Of the tablets prepared with sodium starch glycolate, only the 6-lactose/sodium starch glycolate combination was influenced by all three adjustable factors (Table 8.8). Moreover, the effect of the relative humidity depended on the level of the temperature as well as the level of the disintegrant concentration and vice versa. 

Each combination behaves differently after storage. In all cases there was an effect of the starch concentration (y i sir(d) is significant). In most cases the relative humidity as well as the interaction between the relative humidity and the disintegrant concentration plays a role in the disintegration time of tablets prepared with either lactose. The dicalcium phosphate dihydrate/rice starch combination is influenced very strongly by the three factors studied. This combination is not suitable for use in tropical countries. Neither is the combination of B-lactose and crospovidone. 

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. 

Fig. 10.—Effect of pressure on the conductivity of starch of various humidity contents (from Ref. 66).

Fig. 12.—Effect of pressure, P, on dielectric constant, e, of starch of 20.05% humidity (from Ref. 67).

Esters are formed similarly. Formic acid contributes to the total acidity of irradiated starch, as displayed in Fig. 22. This Figure also presents the effect of the dose of radiation, temperature, and humidity.169 Other radiation-specific products are also formed177 (see Table XVI). 

Sorptive capacity is one of the most important properties, and it has been investigated by many authors for several varieties of starch.331-333,335,419 Sair and Fetzer,420 and also Rakowski,331-333 compared the water-retention capacities of wheat, arrowroot, and potato starch, and the results were similar. Among the following starch varieties, the sorptive capacity decreases in the order given potato > arrowroot > wheat. The order potato > corn > wheat was reported by El-Khawas et al.42] Nara el a/.407 reported the order potato > tapioca > waxy rice > sweet potato > rice Smolina422 reported the orders potato > maize > rice > wheat at low humidity and potato > rice > maize > wheat at high humidity. These orders do not agree with the order reported in Table XVII on the effect of desiccation on the water retention of starch. Based on these data, the... 

Fic. 35.—Apparatus for measuring the effect of humidity on the damping of electromagnetic waves. 1, screw press 2, measurement cell 3, electrode 4, bow dynanometer 5, starch sample. (Reprinted with permission from M. Boruch, S. Brzezinski, and A. Palka, Acta Aliment. Pol., 11 (1985) 115-124.)... 

Solid-state cellulose can also be noncrystalline, sometimes called amorphous. Intermediate situations are also likely to be important but not well characterized. One example, nematic ordered cellulose has been described [230]. In most treatments that produce amorphous cellulose, the whole fiber is severely degraded. For example, decrystallization can be effected by ball milling, which leaves the cellulose as a fine dust. In this case, some crystalline structure can be recreated by placing the sample in a humid environment. Another approach uses phosphoric acid, which can dissolve the cellulose. Precipitation by dilution with water results in a material with very little crystallinity. There is some chance that the chain may adopt a different shape (a collapsed, sixfold helix) after phosphoric acid treatment. This was concluded because the cellulose stains blue with iodine (see Figure 5.12), similar to the sixfold amylose helix in the starch-iodine complex. 

An off-white free flowing powder which dissolves in water to give low viscosity size solutions particularly effective for synthetic staple yarns and blends. It can be used alone or in conjunction with starch or C.M.C. One particular advantage over other acrylic sizes is that it can be used as the single ingredient of a size mix where Relative Humidities are high. 

We have already noted that the moisture content of some substances is substantially changed by variations in humidity and temperature. Colloidal materials containing large amounts of sorbed moisture are particularly susceptible to the effects of these variables. For example, the moisture content of a potato starch has been found to vary from 10% to 21% as a consequence of an increase in relative humidity from 20% to 70%. With substances of this sort, comparable analytical data from one laboratory to another or even within the same laboratory can be achieved only by carefully specifying a procedure for taking the moisture content into consideration. For example, samples are frequently dried to constant mass at 105°C or at some other specified temperature. Analyses are then performed and results reported on this dry basis. While such a procedure may not render the solid completely free of water, it usually lowers the moisture content to a reproducible level. 

In this study, we investigated effects of binary mixtures (1 1) of glycerol, xylitol, and sorbitol on physical and mechanical properties of potato starch-based edible films stored at various relative humidities. 

Mathew, A.P. and Dufresne, A. Plasticized waxy maize starch effect of polyols and relative humidity on material properties. Biomacromolecules, 3, 1101, 2002. 

As shown by the present authors, atmospheric oxygen does not affect DTA, DTG, and TG curves to such an extent that oxidation can be accepted as an important process in the range up to 300°. The dextrinization of starch does not change the points of thermal effects, that is, an endothermic effect, with its maximum at —80° (loss of humidity), a very small endothermic effect between 200 and 222°, which ceases at the stage of fully soluble... 

Figure 1. The effect of relative humidity (RH) on mechanical properties [stress-strain curves] of at thermoplastic starch polymer.

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