Vacuum Drying of Carrot: Evaluation of Different Pre-Treatments and Post-Drying Quality Parameters

Abstract

This study aimed to evaluate the influence of steam blanching and the combination of citric acid dipping with blanching as pre-treatments on the vacuum drying of carrots. Carrot slices of two thicknesses, 2 mm and 5 mm, were subjected to varying periods of pre-treatments and citric acid concentrations of 0.5% (w/w) and 1.0% (w/w). The drying behavior, moisture loss, energy consumption, and other post-drying quality parameters, such as colour, water activity, rehydration ratio, tensile strength, and microstructure, were assessed. Pre-treatments enhanced moisture removal through osmotic dehydration and structural modification, resulting in improved drying efficiency by reduction of drying time, with maximum reductions of up to 34.78%, along with notable energy savings. Pre-treatments did not result in statistically significant differences (p < 0.05) in colour or tensile strength of the dried carrot samples. In addition to this, the rehydration ratio was found to be higher than that of the untreated samples. Further, all the dried samples were found to have lower water activity readings (<0.61). Scanning electron microscopy confirmed increased pore formation in pre-treated samples. The above results indicate that combined citric acid dipping followed by blanching enhances drying efficiency while preserving the quality of vacuum-dried carrots.