The Nature Group journal Scientific Reports published the results of a study conducted by a research team from the Fondazione Edmund Mach and the University of Trento. The scientists have discovered that sulfur dioxide (SO2) influences wine quality in more ways than is currently known.
Today oenologists and winemakers recognise SO2 as an indispensable additive in winemaking, able to protect wine from various unwanted reactions. The use of this additive is controlled by legal limitations, but the recommended doses are imprecise and it is still not known why very similar wines consume the added SO2 differently.
With the scope of generating knowledge for better targeted use of SO2, and based on their earlier findings regarding new SO2-binders in wine, the research team developed an analytical method and measured 195 commercial wines from the 1986-2016 vintages.
The study published in Scientific Reports demonstrates that the quality of aged premium wines, as we know them today, is strongly characterised by the addition of SO2. A very slow reaction between SO2 and wine tannins, thus the major responsible metabolites of wine body, leads to products that highly characterise the chemical fingerprint of red wines aged at length. This reaction could also be partly responsible for alleviating the aggressiveness of young red wines, although this remains to be proved in the future.
On the other hand, white and sparkling wines were found to be characterised by a relatively fast reaction between SO2 and catabolites of the amino acid tryptophan pathway (a.k.a. indoles). These metabolites, with high concentrations in wines, could be responsible for the phenomenon (well known among winemakers) of unexpectedly large doses required by some wines. The same sulfonated metabolites could also influence the aromatic characteristics of wines.
The scientists believe that these new findings will enable better understanding of the chemical changes occurring in wine during ageing and offer new prospects for more precise use of SO2 in winemaking.
“The impact of SO2 on wine flavanols and indoles in relation to wine style and age” Panagiotis Arapitsas, Graziano Guella & Fulvio Mattivi www.nature.com/articles/s41598-018-19185-5