The phenolic composition of red wine impacts upon the colour and mouthfeel and thus quality of the wine. Both of these characteristics differ depending on the age of a wine, with the purple of young wines changing to brick red and the puckering or aggressive astringency softening in older wines.
This study investigated the colour parameters, tannin concn. and tannin composition of a 50 yr series of Cabernet Sauvignon wines from a commercial label as well as 30 yr series of Cabernet Sauvignon and Shiraz wines from a separate commercial label to assess the impact of wine age on phenolic composition and concn.
The wine colour density in wines of 40 to 50 yr old was around 5 AU compared with 16 AU of wine <12 months old, which correlated well with the concn. of non-bleachable pigments and pigmented polymers.
Conversely, the anthocyanin concn. in 10 yr old wines were substantially lower than that of recently bottled wines (around 100 mg/l compared with 627 mg/l, respectively), adding further evidence that non-bleachable pigments including pigmented polymers play a much larger role in long-term wine colour than anthocyanins.
No age-related trend was observed for tannin concn., indicating that the widely noted softer astringency of older red wines cannot necessarily be directly related to lower concn. of soluble wine tannin and is potentially a consequence of changes in tannin structure.
Wine tannins from older wines were generally larger than tannins from younger wines and showed structural changes consistent with oxidation.
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