MICROWAVE-ASSISTED EXTRACTION AS AN OENOLOGICAL ALTERNATIVE FOR RED WINES

SARI, SANTIAGO; FANZONE, MARTÍN; CORONADO, IGNACIO; MORATA DE AMBROSINI V.I.; MERCADO, LAURA; ALESSO, R.; JOFRÉ, BIBIANA; PEÑA NEIRA, ALVARO

Bordeaux

Simposio; OENOIVAS 2019 - 11th International Symposium of Oenology, Bordeaux- 11th edition In Vino Analytica ScientiaOENO IVAS 2019; 2019

OIV

Microwave-assisted extraction (MW) is an unconventional method for winemaking, able to reduce the duration ofmaceration and to enhance the color intensity and the amount of phenolic compounds in wines, with the advantage ofbeing a ?green? technology of low cost compared to other oenological techniques used to similar purposes. Additionally,MW could be an effective technique for pasteurization or sterilization of the must, with capacity of enzymatic inactivation,essential in the wine industry, especially in diseased vintages with high levels of polyphenol oxidases. Therefore, the aimof this study was to evaluate the effect of MW application at different temperatures in Malbec grapes crushed, prior tofermentation, on grape-associated microflora, enzymatic activity and chemical composition of wines. During the 2018season, 300 kg of grapes were harvested (25°Brix) from a commercial vineyard (Mendoza, Argentina), and made intowine in 30 L food plastic fermenters following a standard protocol. The experimental design consisted of four treatmentswith three replicates [control (C), and three microwaved-assisted extraction (2450 MHz, 7600 W) conditions (MW40, 40°C,7 min; MW50, 50°C, 14 min; MW60, 60°C, 21 min)]. Must from each treatment was sampled to evaluate grape associatedpopulations (filamentous fungi and yeast) and pectinase activity, after MW application. Wines were analyzed for basicchemistry, as well as for phenolic composition (global and anthocyanin profile) and color parameters (CIELAB). Resultsshowed a significant decrease of must yeasts with MW application at 50°C and 60°C, and of filamentous fungi only at60°C, while the pectinase activity was not affected. The wine pH increased with the process temperature (MW50, 0.1,MW60, 0.2) compared to the control. Concerning to phenolic composition, the MW60 treatment improved tannin andanthocyanin extraction from skins, obtaining wines with enhanced color (greater saturation) and higher polymericpigments (SPP and LPP). Likewise, the major differences between MW60 and control were occurred in acylatedderivatives (>40%) and pyranoanthocyanins (>20%) levels, indicating possibly more color stability over time. Thesepreliminary results will be supplemented by the determination of grape polysaccharide fractions, volatile aromas and sensory evaluation