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Authors
Advisor(s)
Abstract(s)
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.