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The effect of different air drying temperatures on mango slices in convective trays was investigated and based on findings a computer programme has been prepared. The mango fruits of cv. Rampuri Gola were procured from farmer's field, washed, sliced and blanched. The slices were spread in single layer in tray dryer. The drying was carried out in a tray dryer with heated air at temperatures of 50, 60 and 70°C and their combinations. The time elapsed to attain constant weight was observed to be 480-330 minutes in selected drying conditions (50-70°C). The logarithmic drying model indicated the best fit to the data obtained (coefficient of determination R2 0.994-0.999). The maximum moisture diffusivity was found (1.91 x 10-10) at 70°C. Various quality parameters of dehydrated product such as maximum ascorbic acid (56.6% at 60°C) and polyphenols content (1700 mg/100g GAE at 70°C) were recorded. Rehydration ratio was observed as 8.73 at 70°C, because of short drying time and lesser damage to cells. Samples dried at lower temperature had better colour retention as compared to those dried at higher temperature. On the basis of RSM, optimum operating conditions for drying were observed to be 67.54 C drying air temperature, and 0.48 g/cm3 loading density. A computer programme to present the moisture loss with exposure time has been developed in 'visual basic' language based upon outcome of drying experiments. The programme can be used for calculation of drying characteristics during dryer operation. [ABSTRACT FROM AUTHOR]

Desorption isotherms for sliced gingers have been measured. A non-linear regression programme was used to fit four moisture sorption isotherm models to the experimental data. The Modified Halsey and Modified Oswin models gave the best fit for Xe= f(RHe, 7) and RHe f(Xe, T), respectively. Tray and heat pump dehumidified drying incorporated by single and two stage drying were conducted. It was found that the modified Page model was the most effective. The drying constant was fitted to drying air temperature using the Arrhenius model. Effective moisture diffusivities were determined using the drying data. The heat pump dehumidified drying incorporated by the two stage drying could reduce the drying time at 40°C by 59.32% and increase 6-gingerol content by 6%. Quality evaluation by 6-gingerol content, rehydration ratio and ΔE° showed the best quality for dried sliced gingers in the heat pump dehumidified drying incorporated by the two stage drying at 40 °C. [ABSTRACT FROM AUTHOR]

Desorption isotherms of mature kaffir lime leaves are determined and a nonlinear regression program was applied to the experimental data to fit with any of the four moisture sorption isotherm models. It was found that the modified Halsey model could fit the best. Tray and heat pump-dehumidified drying of kaffir lime leaves were conducted and it was found that the modified Page model was the most effective one. The drying constant was fitted to drying air temperature using the Arrhenius model. Effective moisture diffusivities were determined using the drying data. Heat pump-dehumidified drying reduced drying time and provided dried kaffir lime leaves with higher amount of citronellal than tray drying. [ABSTRACT FROM AUTHOR]

Effect of varying drying air temperature, air velocity, initial total solids, and starch addition on the drying rate of tomato paste were studied using a tray dryer. The increase in the inlet air temperature in the range 60–100°C markedly increased tomato paste drying rate. Also, increasing air velocity (0.8–1.2 m/s) increased the drying rate of tomato paste. Increasing tomato paste initial total solids had a significant effect on the time required to reach the equilibrium moisture content. Starch was added at different amounts (0.0–1.0 kg dry starch/ kg dried tomato paste); it has a significant effect on tomato paste drying rate. [ABSTRACT FROM AUTHOR]