Master of Science in Viticulture & Enology
Joint diploma “EuroMaster Vinifera” awarded by:
Institut National d'etudes superieures
agronomiques de Montpellier
and Turin University
Master thesis
Role of gallic and ellagic tannins on composition and
consumption kinetics of wine
Jasmina UROSEVIC
2015-2017
Supervisor 1: Antonio Giovanni, TIRELLI, Università degli Studi di Milano
Supervisor 2: Daniela, FRACASSETTI, Università degli Studi di Milano
Asti, September 18th, 2017
Abstract
The quality of wine is influenced by different factors, such as grape variety, winemaking techniques and oxygen presence. Grape composition has a huge impact on the future wine, where phenols are one of the most important components involved in wine oxidation.
In red wine production, condensed tannins are extracted from skins and seeds during fermentation while hydrolysable tannins are liberated through the barrel aging. The new winemaking approach is the addition of commercial tannins (condensed tannins, hydrolysable tannins or their mixture) in purpose to enhance the wine composition and quality. The main hydrolysable tannins are gallotannins and ellagitannins, categorized by the type of acid that is formed. Those tannins have protective function on wine phenols, producing peroxide and acetaldehyde from oxidation, and promoting flavonoid polymerization. The aging in wood, promote gentle oxidation helping the polymerization of tannins and ANCs that make a huge difference between tank and barrel aging.
Our study was done in three phases: a) simil wine test with tannin powders (galla, oak and chestnut), with and without; b) preliminary test with white wine and added powders; c) final test with powders addition in Merlot and Pinot noir wine.
Analysis of variance (ANOVA) was performed to determine significant differences among two red wines by studying two components: a) time (zero and final); b) treatment (tannins powder). Observed parameters were: color intensity, hue, TPI, flavanols, ACNs, mDP and conversion yield. Significant parameters in term of time for Merlot wine, were conversion yield and mPD while in Pinot Noir, color intensity, hue and flavanol concentration. Among the treatments, the major role had galla and oak tannins thus chestnut had an influence on the hue. Oxygen kinetic was different among two red wines, with clear fast consumption by powders, providing the protection of wine phenols.
Finally, the addition of commercial tannins have an influence on phenolic profile during accelerated aging, as well as on oxygen kinetic. Different results obtained among two red wines can support the fact that different wine composition have a huge influence during barrel aging.
Key words: Gallic tannins, ellagic tannins, proanthocyanidins, oxygen consumption, aging