Evaluation of temperature and pulsed electric field conditions on sugar extraction from carrots

Cell membranes are the main preventive of intracellular solute extraction. Mechanical destruction and thermal treatment are pre-treatment methods commonly used to destroy cell membranes and facilitate the release of solute into the solvent during the extraction. However, the overall rupture of membranes requires excessive heating that leads to altering plant tissue, passing solid materials through membranes (such as pectin in sugar production) to the adjacent solvent, and altering the chemical structure cell walls by hydrolytic reactions which itself requires further purification cost. Applying a pulsed electric field (PEF) with low heat treatment of products significantly enhances mass transfer into the biological tissues of food crops, which leads to saving  much time and energy. In this study, extraction of sugar from carrots under both different pulsed electric field conditions (including  field strengths of  250, 750, and 1250 V/cm and number of 10, 45, and 80 pulses) and thermal treatments (20, 45, and 70ºC) was investigated based on full factorial design experiments. Carrot slices treated with PEF were suspended in water at the desired temperature and liquid to solid (L/S) weight ratio of  2. Immediately after the PEF treatment, a significant increase in the solute extraction was observed because of the cell membrane permeability, which led to the enhancement of solute convection on the surface of the tissue.