Microwaves, an auxiliary tool to improve red wine quality in warm climates

Abstract

AIM Current winery efforts in Spanish warm climate regions, as Andalusia, are aimed at red wine production in spite of sub-optimal climatological conditions. This climate, characterized by high temperatures and sunlight, result in fast and heterogeneous ripening and, as a consequence, a lower polyphenolic concentration is detected in some grape varieties, thus leading to poor colour stability and intensity [1] compared to those achieved in colder regions. Polyphenolic compounds in red winemaking, strongly related to wine color and mouth feelings, are normally extracted in the maceration step during the fermentation process, thus phenolic content in red wines highly depends on the applied winemaking process. For this reason, several winemaking techniques have been assayed to improve color extraction allowing to obtain products with market demanding characteristics [2]. On the other hand, microwave-assisted extraction (MAE) is a technique that enhances the extraction yield of organic compounds submitted to microwaves (attributed to the dipolar rotation of molecules and heating generated in the solvent caused by this electromagnetic radiation) with low instrumental requirements [3]. The aim of this study was to assess the effect of microwaves on color characteristics of wines of Garnacha variety (Vitis vinifera L.) cultivated in a warm climate zone.

METHODS Microwave-assisted extraction was applied at the beginning of alcoholic fermentation of red wines from Garnacha grapes (grown in a warm climate zone) to enhance wine color versus conventional winemaking. Enological and color parameters were analyzed and compared along winemaking processes during vinification and bottled aging.

RESULTS Significant enhancement was found for microwave submitted wines in color intensity, CIELAB coordinates, and hue at each step of the process when compared to the control wine, including the content of different phenolic compounds. 

CONCLUSIONS: This practice seems a feasible alternative to improve quality characteristics of young red wines from grapes grown in warm climates with color difficulties.