Aqueous extraction of solutes from fennel (Foeniculum vulgare) assisted by pulsed electric field

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.