Pulsed electric field processing of white grapes (cv. Garganega): Effects on wine composition and volatile compounds

Pulsed electric field (PEF) processing of white grapes (cv. Garganega) after crushing was studied on pilot-plant scale, to investigate the effects of the treatment on must and wine composition, wine color and predisposition to browning, wine aroma compounds and extraction of aroma precursors from grapes. PEF pre-treatment of grapes did not change the must or wine basic composition, nor was it able to modify the evolution of alcoholic fermentation. By contrast, PEF produced an increase in total dry extract, wine color and total phenolics. Treatment corresponding to a total specific energy of 22\u202fkJ\u202fkg 121 allowed more intense extraction of varietal aroma precursors without provoking excessive color evolution and extraction of phenolic compounds, apparently increasing the stability of wine towards oxidation. Due to the few papers available on this subject, PEF applications on white grapes should be optimized in further experiments

Application of Pulsed Electric Fields on crushed grapes

Pulsed electric fields (PEF) is a promising technology for promoting the extraction of compounds from grape berries, during skin maceration. PEF promotes the electrically-induced formation of pores in the cell membranes, facilitating the migration of anthocyanins, proanthocyanidins and total phenolics in the juice, in an even more efficient way respect to pectolytic enzymes. The intensity of the treatment affects the final results. PEF processing of crushed grapes showed no effects on the behavior of alcoholic fermentation, as well as on juice and wine basic quality control parameters, with the exception of a slight increase of juice pH, which basically disappeared in the final wines. Wines processed by PEF were generally perceived as more colored and full-bodied. The latter characteristic might be connected with a higher HCl and ethanol index, reflecting a more favorable composition of tannins in PEF treated samples. When PEF treatment is carried out after crushingdestemming, the maximum color extraction observed during maceration was achieved immediately after the treatment; this makes PEF technology particularly useful for reducing the processing time, allowing its application in several situations, such as the vinification of low-ripe grapes, grapes affected by molds, or the production of concentrated musts from red grape varieties

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 \u2013 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