Abstract
The goal of this work was to investigate the presence of novel cyclic proanthocyanidins (c-PD) in wine from South Tyrol and international grape varieties, and if the relative concentrations of these compounds were anyhow affected by the grape variety used or by the winemaking technology, e.g. the ageing procedure (barrel or steel tanks), cold stabilization or other vinification variables. As a result, two c-PD (one tetramer and one pentamer, both with one (epi)gallocatechin in the structure) were identified in the wines.
For the data processing, the relative abundances were normalized to yield the overall proportions of cyclic compounds per composition and number of monomers (%c-4-OH for the tetramer and %c-5-OH for the pentamer).The two normalized variables correlated significantly with the grape variety employed, whereas they did not with the other variables. %c-4-OH was below 20% in most wines except in Chardonnay where it was over 80%. %c-5-OH was between 60 and 100% in the Sauvignon blanc and Chardonnay wines, whereas it was absent in Gewürztraminer.
In the red wines the cyclic proportions were higher in Lagrein and lower in Merlot. Overall, by correlating with just one variable (the grape variety), these proportions can be useful in the development of new protocols for authenticity assessment.