Conventional Measurements of Sulfur Dioxide (SO2) in Red Wine Overestimate SO2 Antimicrobial Activity

• Patricia A. Howe ^[2] ; Randy Worobo ^[1] ; Gavin L. Sacks ^[1]
  1. [1] Cornell University

     Cornell University

     City of Ithaca, Estados Unidos

     
  2. [2] Constellation Brands
• Localización: American Journal of Enology and Viticulture, ISSN 0002-9254, Vol. 69, Nº 3, 2018, págs. 210-220
• Idioma: inglés
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• Resumen

  • Conventional approaches to measuring sulfur dioxide (SO2) in wine, such as aeration-oxidation, iodometric titration, and flow-injection analysis, are known to overestimate molecular SO2, particularly in red wine because of the dissolution of weak anthocyanin-bisulfite complexes during analysis. Methods for determining molecular SO2 without perturbing anthocyanin-bisulfite complexes and other weak adducts exist, e.g., headspace gas-detection tube measurements. However, it is unclear whether SO2 values achieved through conventional methods (“Molecular SO2”) or nonperturbing methods (molecular SO2) provide a better measure of antimicrobial activity. In our work, white and pseudo-red wines were prepared with varying additions of SO2; the red wine was produced by spiking the white wine with an anthocyanin extract. “Molecular SO2” and molecular SO2 concentration in white wines were well correlated, but “Molecular SO2” was significantly higher in red wines. Wines were inoculated with Saccharomyces cerevisiae strain EC1118 (Lallemand), and viability and culturability were evaluated at regular intervals. Both culturable and viable cell counts decreased significantly for treatments with 0.5 to 2.0 mg/L molecular SO2 in the white and red wines, and for 0.5 to 2.0 mg/L “Molecular SO2” in the white wine, but concentrations >2.0 mg/L “Molecular SO2” were necessary to decrease cell counts in the red wine. These results indicate that anthocyanin-bisulfite complexes have negligible antimicrobial activity, and that conventional approaches to measuring “Molecular SO2” are poorly suited to predicting the microbial stability of red wines.