Evaluation of phenolic extraction during fermentation of red grapes treated by a continuous pulsed electric fields process at pilot-plant scale

The feasibility of processing red grapes by pulsed electric fields (PEF) at pilot-plant scale to improve the extraction of anthocyanins and phenols during the maceration-fermentation step of the winemaking process has been investigated. With this general purpose a colinear continuous treatment chamber was developed. The influence of field strength (2, 5 and 7 kV/cm) and grape variety (Cabernet Sauvignon, Syrah and Merlot) in the extraction kinetics was studied. Extraction curves were described by an exponential equation that permits to estimate the extraction rate (k) and the maximum extraction yield (Ymax). An increment of the electric field from 2 to 7 kV/cm increased the extraction rate of anthocyanins and total phenols for the three varieties investigated. The increment of Ymax due to the application of PEF was more remarkable in Cabernet Sauvignon than in Merlot and Syrah. The continuous PEF system presented in this work constitutes an important step for the application of PEF technology at commercial scale.