Enhanced Extraction of Phenolic Compounds from Merlot Grapes by Pulsed Electric Field Treatment

The objective of this investigation was to study the influence of pulsed electric field application on fermentation process and wine characteristics. Investigations were related, in particular, to the effects of pulsed electric field pretreatment (500-700 V/cm) of grapes with a short treatment duration (40-100 ms) on the evolution of color intensity, anthocyanins, and phenolic content during the alcoholic fermentation of Merlot grapes and seven months after bottling. The kinetics of the extraction of valuable compounds during the vinification stage was established. Sensory analyses of untreated wines were compared to those of pulsed electric field-treated wines. These results showed that the permeabilization of Merlot skin by a pulsed electric field treatment resulted in increased extraction of polyphenols and anthocyan ins. Pulsed electric field of moderate intensity and short duration accelerated the flow kinetics of phenolic compounds through the cell membranes. Compared to the classical process, pulsed electric field treatment has the advantage of nonthermal selective extraction (<5 degrees C) involving no loss of product quality. Phenolic compounds have an important role in enology owing to their contribution to the sensory properties of wine and to their participation in various phenomena during the vinification and aging processes. Sensory analysis indicated that pulsed electric field treatment contributes to the enhancement of the sensory attributes of wine. This technique seems to be an interesting alternative to current prefermentative techniques.