Pulsed electric fields processing of crushed grapes and effects on wine composition

Pulsed electric fields (PEF) is a non-thermal method for food processing and preservation, based on the application of short pulses of high-voltage current to food products positioned between two electrodes. PEF technology derives from food industry, where it has been proposed for inactivating pathogenic microorganisms, in alternative to the traditional thermal processing methods (e.g. pasteurization), with the major advantage of better preserving food sensory characters and nutritional value. PEF processing promotes the electrically-induced formation of pores in the cell membranes, which may be reversible or irreversible, depending on the intensity of the electric field applied; this leads to the occurrence of specific phenomena, known as cell electroporation, or dielecric breakdown. Basing on such considerations, PEF was also proposed for the extraction of bioactive compounds from vegetal matrices, including fruits, apples and grapes. In the present study, Pulsed Electric Fields processing of grapes after crushing – destemming was evaluated concerning the extraction of phenolic substances and aroma compounds. The overall effects of the treatment on wine composition and sensory characters were also considered. In the conditions tested, PEF did not affect neither the behavior of alcoholic fermentation, nor juice and wine basic quality control parameters (e.g. residual sugars, total acidity, alcoholic strength, yeast assimilable nitrogen). Contrary, it promoted a fast and intense extraction of color and phenolic compounds (e.g. proanthocyanidins and anthocyanins), even in higher amounts with respect to what obtained by pectolytic enzymes. PEF also determined a higher concentration of certain varietal aroma compounds in the grapes after processing, with a potential positive effect on wine aroma composition. From the sensory point of view, wines processed by PEF were averagely perceived as more colored and full-bodied, with respect those obtained from unprocessed grapes. On the basis of these results, the application of PEF in enology might be an interesting perspective, particularly in certain winemaking situations, such as the processing of low-ripe grapes or grapes affected by Botrytis; moreover, this technology might be also useful for the production of concentrated musts obtained from red grape varieties.