Abstract
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 Pallagrello, 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.
Highlights
Older vintages of some red wines are often more expensive than younger ones (Carew and Florkowski, 2010)
The main form of SO2 at wine pH, the bisulfite ion (HSO3−; which is in equilibrium with molecular SO2), is consumed by reactions with hydrogen peroxide and several electrophilic wine components, such as those derived from the oxidation cascade, including quinones and acetaldehyde (Waterhouse et al, 2016)
After 5 years of aging, the effect of closure was still significant for a few parameters; some differences were very small, and the influence of closure on phenolic composition can be considered as negligible, especially when compared to that observed after shorter aging
Summary
Older vintages of some red wines are often more expensive than younger ones (Carew and Florkowski, 2010). As the concentration of bound sulfur dioxide in wine depends on i) the concentration of the HSO3- ion, ii) the amount of compounds susceptible to electrophilic attack in wine (Jackowetz and de Orduña, 2012; Ferreira et al, 2015), and iii) the reversibility of the equilibrium between covalent adducts and their original active components (Boulton et al, 1996), it is of interest to evaluate how the various forms of sulfur dioxide (free and bound) change over time Within this context, regulating the reactions resulting from the complex mixture of phenolic compounds in red wine during bottle aging is quite difficult and requires controlled storage conditions and knowledge of the factors involved in oxidative processes. The effect of the oxygen transfer rate (OTR) of closures on the polyphenolic composition of three Southern Italy red wines with high total tannin content (Aglianico, Casavecchia and Pallagrello) was determined after 15 months of bottle aging, and SO2 protection was found to have a strong influence (Gambuti et al, 2017)
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