Recent work suggests that copper complexes may serve as a latent source of free H2S and other malodorous volatile thiols during wine storage. However, measurement of these complexes require analytical tools that are unavailable to most wineries. To facilitate further studies, an inexpensive and convenient method for detection of copper-complexed H2S in wine was developed using commercially available colorimetric gas detection tubes (GDT). Using brine dilution as a pre-treatment, this approach showed acceptable detection limits (0.34 μg/L) and excellent recovery in both model and real wines. Alternate approaches to H2S release from copper sulfide complexes were also investigated (EDTA, neocuproine, ascorbic acid, TCEP) alone and in combination. EDTA resulted in a loss of free H2S. Partial recovery (35–70%) of H2S from model wines was achieved with the other reagents, with the release induced by ascorbic acid of particular interest to winemakers. In a survey of seven commercial wines, the fraction of complexed H2S released by brine was 80–95% of the total H2S pool, with lesser release observed for neocuproine and ascorbic acid. However, in several wines, higher concentrations of H2S could be released by treatment with TCEP from unknown precursors.
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