Tracing oxidation reaction pathways in wine using 13C isotopolog patterns and a putative compound database

Quinones are key reactive electrophilic intermediates that are formed in abundance during wine oxidation and have a significant impact on wine character, altering color and flavor. They readily react with nucleophiles, such as SO2 and glutathione. Some nucleophiles have been reported to react with quinones in model wines, but many of the corresponding products have not been confirmed in real wines. Here, a stable isotope labeling approach employing C-13(6) labeled ortho-quinone was evaluated in combination with an exact-mass list of putative products. The measurements were taken using high performance liquid chromatography coupled to time-of-flight mass spectrometry. Fourteen compounds were detected based on a match in the table plus an M+6 mass isotope pattern derived from the labeled quinone mixture. The presence of the mass label also establishes reaction pathways for the formation of these compounds, and suggests how wine catechols could react during wine oxidation, demonstrating the insight provided by this analytical technique. (C) 2018 Published by Elsevier B.V.