Impact of 5-year bottle aging under controlled oxygen exposure on sulfur dioxide and phenolic composition of tannin-rich red wines

Aim: This study aims at understanding the impact of the initial phenolic composition on the evolution of red wines after long bottle aging. Materials and results: three different red wines rich in tannins, Aglianico, Casavecchia and Pallagtello, bottled with the same amount of total sulfur dioxide and different amounts of free sulfur dioxide, were analysed after 5 years of bottle aging under controlled exposure to oxygen passing through the closure. Acetaldehyde and monomeric anthocyanins were determined by HPLC, the chromatic characteristics and the main phenolic classes by spectrophotometry, the saliva precipitation index (SPI) by CHIP electrophoresis, and the astringency subqualities by sensory analysis. The results confirmed that during aging there is an increase in polymerisation reactions. A higher amount of acetaldehyde was detected in wines which were bottled with a lower content of free SO2 and were less rich in anthocyanins and tannins; a significant closure effect was observed for these wines. Regarding the influence of closure on tannins, significant slight differences in vanilline reactive flavans and SPI content were observed for Pallagrello wines only, which were characterised by higher values for tannins at bottling. Astringency subqualities differed with closures for each wine. Conclusion: this study indicates that the amount of initial free and combined sulfur dioxide, as well as that of anthocyanins and tannins, are key factors in driving polymerisation reactions and the aging of red wines. After five years of bottle aging the influence of closure could still be observed. Significance of the study: this study provides new insights into the parameters that need to be evaluated before bottling in order to avoid the wrong evolution of red wines after long bottle aging.