PEF-dependency on polyphenol extraction during maceration/fermentation of Grenache grapes

Application to different electric field strengths (E) and specific energies (W) with the pulsed electric fields (PEF) technology on the rate of extraction of phenolic compounds during maceration/fermentation of Grenache grapes was studied. A response surface model between the total polyphenol index extraction rate (TPI) and the E and W of the PEF treatments was established, which permitted the determination of PEF processing conditions to achieve a certain TPI. To achieve a TPI of 50, treatments ranged from high intensity and short time (8 kV.cm(-1) and 45 mu s) to low intensity and long time (1 kV.cm(-1) and 2800 mu s) applying an optimum W of 4 kJ.kg(-1) in all cases. The application of these PEF treatments reduced maceration time by a rate of 25 to 37% with respect to the untreated grape. Quality characteristics (color intensity, tannins, and total anthocyanins) were neither affected after fermentation nor after 12 months aging in bottles.