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Extraction of sugar from sugar beet slices was studied following various pulsed electric field (PEF) treatments (intensities from 300 to 800 V cm −1 and number of pulses varying between 50 and 1000). Slices treated by PEF were immersed in water at ambient temperature at a liquid/solid ratio of 3. A significant increase in extraction yield was observed. This enhancement was due to permeabilisation of the cellular membrane and to the additional quantity of juice appearing on the surface of slices after PEF treatment being extracted rapidly by convection. The optimal conditions of PEF treatment were an intensity of 670 V cm −1 and 250 pulses. The extraction kinetics was studied on the basis of two approaches: Fick's diffusion equation and a two-exponential kinetic model. The coefficient of diffusion was only slightly influenced by the conditions of PEF treatment. The two-exponential model successfully described both the rapid and prolonged stages of extraction. By heating the solution at mild temperatures of 30-50 • C, the coefficient of diffusion was increased and the kinetics of extraction was enhanced. The quality of cellular juice obtained after PEF treatment was higher than that of juice obtained after thermal pretreatment at 75 • C.

Aqueous nonthermal extraction was performed from thin and coarse fennel gratings of seven different sizes in order to obtain extracts, which could be used as natural food preservatives (antioxidants). A moderate pulsed electric field (PEF) with different intensities, E = 0–600 V/cm, and number of pulses, n = 0–850, was used to electropermeabilize the cell membranes and to accelerate the following extraction. The optimal parameters of PEF were found for each size of grating to maximize the yield of solutes. Extract turbidity and color were evaluated. Additionally, the thermal extraction from coarse gratings was studied at different temperatures (60–90C). The concentration of vitamins C and E in extracts, obtained with thermal and PEF treatments, was estimated. The PEF treatment was more effective for coarse gratings (the juice yield increased from 60 to 98%, and the obtained extracts were less turbid and less colored) than for thin gratings. Furthermore, extracts obtained from coarse gratings treated by PEF contained more vitamins C and E than extracts obtained by thermal extraction. PRACTICAL APPLICATION Researches presented in this article should find their entire practical application in the field of food industries. They will permit preparation of fennel extracts, used as food preservatives (antioxidants), by PEF‐assisted aqueous extraction, which preserves better antioxidant substances. Extracts should be of good quality and the energy consumption should be reasonable.

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