With the use of Fourier Transform Infrared (FTIR) analysis applied to methylcellulose (MC) films, the hydrogen bonding formation between MC-MC molecules and between MC and a series of different-molecularweight PEGs was studied. The spectra of the films were interpreted in terms of the symmetry distortion of hydroxyl stretch at 3466.5 cm Ϫ1 , which is the measure of hydrogen bonding interactions in the polymer matrix. The symmetry distortion was determined to be affected by the MC concentration, indicating the presence of intra-and intermolecular hydrogen bonding between MC molecules. Neither ethanol nor its concentration influenced the symmetry distortion. A competition for hydrogen bonding via hydroxyl groups between MC-MC and MC-PEG occurred when PEG was incorporated into the polymer matrix.

Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. The desorption data were exploited to estimate equilibrium moisture contents of the peppers at drying temperatures other than 30C by using a semi‐empirical method. Red pepper samples were dried in a tunnel‐type drier with an air velocity of 2 m/s at 50C, 60C, 70C, and 80C. The blanched samples dried faster than the unblanched ones. The drying behavior of unblanched and blanched samples was characterized by falling rate period, and constant and falling rate drying periods, respectively. The interphase mass and heat transfer coefficients of the blanched sample during the constant rate period were not affected by temperature and estimated to be 1.94*10−3 kg mol/s. m2 and 57.3 W/m2. K, respectively. Effective moisture diffusivity was estimated between 6.83*10−10−17.4*10−10 m2/s for the unblanched sample and 11.4*10−10−31.0*10−10 m2/s for the blanched sample within the given temperature range. Effect of temperature on the diffusivity was described by an Arrhenius‐type equation with an activation energy of 28.4 kJ/mol for the unblanched pepper and 33.3 kJ/mol for the blanched pepper.

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Drying behavior of the hydrated corn starch, hydrated starch/sucrose, and hydrated starch/sodium chloride mixture and their gels were investigated. Drying data were obtained on slabs of samples in a laboratory tunnel dryer at 40 to 70 °C. The rate-of-drying curves for hydrated starches with or without sucrose showed that the moisture movement may be the result of capillary action rather than diffusion. In the hydrated starches containing sodium chloride, case-hardening was the controlling mechanism. In gelatinized samples, however, diffusion was the main mechanism. The effective diffusivity was estimated by the methods of slopes. Gelatinization of starch reduced the moisture diffusivity significantly. The presence of sucrose or sodium chloride decreased the coefficient significantly in hydrated starch, but their effect was small in gelatinized samples.Key words: native corn starch, hydrated and gelatinized, sucrose, sodium chloride, effective moisture diffusivity Hylon 7 and Amioca). Also, it has been stated that the gelatinization reduced the moisture diffusivity of starch significantly (Saravacos and others 1990). Previous studies on the moisture diffusivity of different starches, both in hydrated and gelatinized forms, show that the mass transport properties can be related to the changes in physical structure (bulk porosity) during drying. Marousis and Saravacos (1990) estimated the bulk porosity of the Hylon 7 and Amioca as a function of moisture content. In hydrated state, no significant differences were detected between the bulk porosities. The bulk porosities of the gelatinized forms, however, were quite different, those of Hylon 7 being higher than those of Amioca. The authors stated that the gelatinized amylose developed higher porosity than gelatinized amylopectin, and the changes in porosity could affect the effective moisture diffusivity. Besides this, the presence of solutes, nonionic such as sucrose and ionic such as sodium chloride, may change the drying behavior and moisture diffusivity. Previous reports indicated that the addition of sucrose to granular starches decreased the moisture diffusivity substantially, but it had a smaller effect in gelatinized starches (Marousis and others 1989; Saravacos and others 1990). However, there was no research on the effect of sodium chloride on the drying behavior and the water diffusivity in hydrated and gelatinized starches. The purposes of the present research were: (1) to determine the drying behavior and effective moisture diffusivities of hydrated and gelatinized native corn starches (23% amylose) (Hoseney, 1990) and (2) to determine the effects of sucrose and sodium chloride on the drying behavior and diffusivities in both hydrated and gelatinized forms. Theory M OST FOOD DEHYDRATION PROCESSES TAKE PLACE IN THEfalling rate period, during which water is transported from the interior to the surface by various mechanisms and is usually analyzed by diffusion. For one-dimensional diffusion in an infinite slab with homogenous structure, constant dimensions a...

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