Rachel B. Allison* and Gavin L. Sacks
*Cornell University, Department of Food Science, Stocking Hall, Ithaca, NY 14853 (rba55@cornell.edu)

The appearance of hydrogen sulfide (H2S) and related sulfur-like off-aroma (SLO) compounds in reductive storage environments presents a significant challenge to winemakers. Recent work has established that there are multiple pools of SLO precursors in wine, including soluble copper-sulfhydryl complexes. Due to their low concentrations and instability, these complexes are challenging to measure directly in wine. However, copper-sulfhydryl complexes are disrupted in the presence of strong brine, and complexes can be quantified indirectly by measuring H2S or other sulfhydryls following dilution of a sample in a concentrated NaCl solution. The concentration of copper-sulfhydryl complexes also correlates with sulfhydryl release during storage, particularly for H2S. However, this correlation is imperfect, possibly because different components of the brine-releasable H2S pool differ in their stability during reductive storage. In initial work to evaluate this hypothesis, we investigated the mechanism by which brine dilution promotes H2S release from copper-sulfide complexes. Real and model wines were prepared with different copper and sulfide concentrations and brine-dilution assay parameters varied. Quantitation of free or released H2S was performed using commercial gas detection tubes. Preliminary results suggest a pH dependence of copper sulfide stability in model solutions treated with brine, and that the efficacy of brine dilution in disrupting copper sulfhydryl complexes is inhibited at higher relative copper and sulfide concentrations.

Funding Support: Natural Sciences and Engineering Research Council of Canada, Saltonstall Wine Endowment