WINETECH Technical Yearbook 2019

THE ROLE OF ELLAGITANNINS IN THE OXIDATIVE STABILITY OF WINE PHOTOS. Ellagitannins can be extracted from barrels and alternative wood products.

Ellagitannins are hydrolysable tannins, which do not occur naturally in grapes. They are however the tannins mostly allowed as legal additives during winemaking. The ellagitannins that occur in wine are extracted from wooden barrels or added as legal enological tannins to wine. Ellagitannins play an important role in the maturation of white and red wine in barrels, due to their oxidation ability and flavour characteristics. During the maturation of wine in barrels, a constant oxygen migration occurs through the barrel pores and the ellagitannins present in the wood dissolve

gradually into the wine. This creates an effective buffer against the potential oxidation of the wine during barrel maturation. The ellagitannins, whether they originate from the barrels, alternative wood products or added enological tannins, are readily oxidised. It is a catalytic chemical reaction, known as peroxidation. Any oxygen exposed to the wine will react with ellagitannins and temper the direct oxidation of other wine constituents. Ellagitannins will consequently promote the crimson colour of red wine and limit the formation of a brown brick colour. Ellagitannins also decrease the astringency and colour deposits of red wine (Vivas et al. , 1996).

CHARL THERON: Private consultant KEYWORDS: Ellagitannins, oxidative stability. JULY 2019