Pulsed Electric Fields – assisted vinification

Pulsed Electric Fields (PEF) treatments can be profitably applied as pretreatment to the extraction process from vegetable tissues, in order to increase the release of valuable compounds. In the present work we propose to apply PEF treatments during the vinification process for the permeabilization of the grape skins, in order to increase the polyphenolic content after maceration of red wines made from four Italian grape varieties, Aglianico, Piedirosso, Nebbiolo and Casavecchia. Prior to the fermentation/maceration step, the grape skins were treated at different PEF intensities (field strengths of 1.5 and 3.0 kV/cm and energy inputs of 10 and 20 kJ/kg), with their permeabilization being characterized by electrical impedance measurements. The fresh wine, obtained after pressing, was characterized for alcohol content, total acidity, pH, color intensity, total polyphenols, anthocyanins content and antioxidant activity.PEF treatment on Aglianico grapes induced a significantly higher release of polyphenols (+100%) and anthocyanins (+30%), thus improving the color intensity (+20%) and the antioxidant activity of the wine (+40%), while preserving the other organoleptic characteristics. Similar results were obtained over two different harvest years (2008 and 2009), confirming the repeatability of the process. In contrast, there was only a minor impact on the polyphenolic release kinetics of Piedirosso, Nebbiolo and Casavecchia grapes, despite the significant degree of cell membrane permeabilization, with it probably being due to the predominance of mass transfer limitations through the vacuole membrane. (c) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of 11th International Congress Engineering and Food (ICEF 11) Executive Committee.