Drying and rehydrating kinetics of green and red peppers

WOS: 000173893100030The effects of air temperature, air velocity; and pretreatments (blanching, sulphiting, and sodium chloride dipping) on drying kinetics of green- and red-pepper slices were investigated. Drying experiments were performed in a fluidized bed dryer. In the falling rate period, moisture transfer from peppers was described by applying the unsteady state Fickian diffusion model, and the apparent moisture diffusion coefficients (D-a) were calculated. The effect of temperature on D-a could be interpreted according to Arrhenius law. Drying rate and therefore D-a values were found to be affected by pretreatments. Rehydration rates of dried peppers at 25 and 45degreesC were also determined and found to be independent of drying conditions and rehydration temperature. Predrying treatments were found to Improve partly the rehydration characteristics of peppers

Moisture sorption isotherm characteristics of peppers

WOS: 000165576600008Moisture sorption isotherms of green and red peppers were determined at three different temperatures (30 degreesC, 45 degreesC and 60 degreesC) and relative humidities (10-90%), using the standard static, gravimetric method. The GAB, Halsey, Oswin and BET sorption models were tested to fit the experimental data. A nonlinear regression analysis method was used to evaluate the constants of four sorption equations. The Halsey equation gave the best fit to the experimental sorption data for a wide range of water activity while BET gave the best fit for a water activity range of 0.1-0.5. The agreement between experimental and calculated values was found to be satisfactory. The isosteric heats of desorption and adsorption of water were determined from the equilibrium data at different temperatures using the Clasius-Clapeyron equation. (C) 2000 Elsevier Science Ltd. All rights reserved