The aim of the diploma thesis is to find out the difference in the polyphenolic composition and colour in wines of different vintages and varieties. The analysis was performed on four red wines from the Vipava Valley winegrowing district. For the samples, we used two wines Cabernet Sauvignon of vintages 2015 and 2017, and two wines Merlot, vintages 2016 and 2017. It was found out that the samples had different polyphenolic composition. The content of the phenolic compounds decreases with age. The highest absorbance of the red wines is at the wavelength of 520 nm as the red coloured pigments are the most common. The content of total and monomeric anthocyanins is higher in younger wines, and when compared to the same vintage of different varieties, Cabernet Sauvignon has higher content than Merlot wines. The polyphenolic composition of the wine samples was determined by carrying out a qualitative and quantitative LC-MS analysis. In the older vintage, Merlot significantly reduced the content of caftaric acid and increased the content of catechin. To a lesser extent, there was a decrease in the content of vanillic acid, piceid and quercetin. When comparing different samples of Cabernet Sauvignon, in the older vintage the content of caftaric acid, piceid and catechin decreased, while vanillic acid content increased. Concentration of ferulic acid did not change with vintage in both varieties. Differences in the polyphenolic composition are due to the grape variety, vinification and vintage.
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