Determination of the optimal phenolic extraction yield in red wines using the glories method

Abstract

This work addresses the phenolic composition and colour parameters in red wines throughout the vinification. The main purposes were to test the effectiveness of the Glories method in the evaluation of the maceration process and to observe the evolution of phenolic compounds during different stages of the winemaking process. The experiments were carried out with two red dry table wines and one Port wine. The Glories method was modified to test the ripeness of the grapes and the pomace during maceration. Furthermore other spectrophotometric methods were used to assess the content of anthocyanins and total polyphenols. The same parameters and other phenolics were also quantified using the Skogerson-Boulton model. Classical colour parameters and CIELab values were determined by the methods recommended by OIV. It was recognized that the application of the Glories method to the grape pomace during the winemaking process could potentially be used for the evaluation of the maceration. Regarding the polyphenol compounds, their extraction mostly occurs during the initial maceration stages. Moreover, alcoholic fermentation and malolactic fermentation do not seem to extensively affect the colour parameters of the wine, as well as the content of different phenolics including anthocyanins. Colour parameters remained relatively stable during the initial winemaking stages following maceration, although the increase of all parameters except hue after malolactic fermentation suggests changes in the content and structure of pigments. Furthermore it was found that the Skogerson-Boulton model can be used as tool to rapidly quantify different classes of phenolic compounds.