Doymaz I., Kipcak A.S., Piskin S. (2015): Microwave drying of green bean slices: drying kinetics and physical quality. Czech J. Food Sci., 33: 367-376.Several microwave power settings were applied to green beans in order to determine the effect on the drying kinetics along with the rehydration ratio and colour values. In the experiments, several microwave power settings were studied as 180, 360, 600, and 800 W. From the results, it is seen that the level of microwave power affected the drying kinetics, rehydration ratio, and colour of the beans slightly. The nine best known thin-layer drying models that were used in literature were applied to the experimental data and the results showed that Midilli et al. model best fits the experimental data for the drying kinetics of green bean slices. Effective moisture diffusivity was found to be between 1.387 × 10 -8 and 3.724 × 10 -8 m 2 /s. Using modified Arrhenius type equation the activation energy was found as 19.185 kW/kg. The rehydration ratio of samples dried at 800 W was higher than those of samples at other power settings. It was observed that an increase in the microwave power increased the brightness and yellowness, on the contrary, it decreased the greenness of the dried samples. L -half-thickness of slices (m); MR -moisture ratio (dimensionless); M e -equilibrium moisture content (kg water/kg dry matter -DM); M 0 -initial moisture content (kg water/kg DM); M t -moisture content at any time (kg water/kg DM); M t+Δt -moisture content at t+ Δt (kg water/kg DM); N -number of observations; n -positive integer, empirical constant; P -microwave power (W); P -probability; R -universal gas constant (kJ/(mol.K)); R 2 -coefficient of determination;RR -rehydration ratio; RMSE -root mean square error; T -temperature (°C); t -drying time (min, s); W 1 -weight of dried matter (g); W 2 -weight of moisture in the material (g); z -number of constants; c 2 -reduced chi-square

Doymaz I., Kipcak A.S., Piskin S. (2015): Characteristics of thin-layer infrared drying of green bean. Czech J. Food Sci., 33: 83-90.The effect of infrared (IR) power on drying kinetics, rehydration, and colour of green beans was investigated. The drying experiments were carried out at 83, 104, 125, 146, 167, and 188 W. It is observed that drying characteristics, rehydration, and colour of bean slices were greatly influenced by infrared power. The drying data were fitted with five thin-layer drying models available in the literature. Results showed that Midilli et al. and Aghbashlo et al. models are superior to the other models for explaining the drying kinetics of green bean slices. Effective moisture diffusivity was calculated in the range of 6.57 × 10 -10 to 4.49 × 10 -9 m 2 /s. Activation energy was estimated by a modified Arrhenius type equation and found to be 11.379 kW/kg.

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The acrylamide-sodium acrylate hydrogel was synthesized by free radical polymerization of the method of solution polymerization. Dynamic swelling tests were conducted at 25, 40, and 60°C temperatures, in order to investigate the swelling properties of the synthesized hydrogel. The results have shown that swelling content and swelling rate of the hydrogel increase with increasing the swelling water temperature. The diffusivity values changed from1.81×10-7to2.97×10-7 m2 s−1over the temperature range. The activation energies were found as 3.56, 3.71, and 3.86 kJ mol−1at 25, 40, and 60°C, respectively. The experimental drying curves obtained were fitted to a three different models, namely, Peleg’s, first-order absorption kinetic, and exponential association equation models. All the models applied provided a good agreement with the experimental data with high values of the coefficient of determination (R2), the least values of the reduced chi-square (χ2), and root mean square error (RMSE). Comparing the determination of coefficient, reduced chi-square, and root mean square error values of three models, it was concluded that the exponential association equation model represents swelling characteristics better than the others.

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