|
Abstract
|
The purpose of the presented study was to describe the effects of various drying conditions on the drying behavior of zucchini slices as well as specifications of diffusivity, activation energy, shrinkage, and color. Zucchini samples, as the richest fount of macronutrient and micronutrient, were subjected to periodic microwave vacuum drying (at 450 W) at three levels of temperature (40, 50 and 60 °C), absolute pressure (20, 40 and 60 kPa) and exposure time (20–3, 30–4.5 and 40–6 s-min). An increase in the drying temperature and exposure time along with a decrease in absolute pressure caused a reduction in total drying time, however, greater heat damages and adversely texture and color effects were observed in this case. The effective moisture diffusivity of zucchini varied between 5.41×10−10 and 1.75×10−9, indicating that under circumstances of high temperature, long exposure time and low absolute pressure water was able to rapidly diffuse out of the tissue in the experimental domain. Lowering the absolute pressure of vacuum flask and increasing the exposure time led to the reduction in the activation energy of samples. The shrinkage coefficient was within the range of 79.91 to 84.92%. As such, the greatest total color difference was calculated between the color of raw and dried samples for those experiments with the largest increase in temperature, exposure time and a decrease in absolute pressure.
|