Ethanol pretreatment before air drying of beetroot: drying kinetics

This work investigates the effects of ethanol pretreatment on the kinetics of air drying of beetroot at 70 °C, a temperature commonly used in the dehydration process to preserve color and phytochemical integrity. Three parameters of pretreatment - ethanol concentration, temperature, and duration - were assessed at five different levels to evaluate their impact on both drying time and rate. The analytical solution obtained from the diffusion model was utilized. However, this study also considers moisture diffusivity as a criterion for assessing the effects of pretreatment, factoring in elements such as shrinkage and moisture variability. The results indicated that pretreatment significantly enhanced drying rates and positively influenced diffusivity, while the reduction in volume was comparatively minor when juxtaposed with untreated samples. The optimal conditions for pretreatment were achieved at 55 °C, utilizing pure ethanol for 30 min, which led to a 30% reduction in drying time and a 36.6% increase in diffusivity.