RT Journal Article
SR Electronic
T1 Conventional Measurements of Sulfur Dioxide (SO<sub>2</sub>) in Red Wine Overestimate SO<sub>2</sub> Antimicrobial Activity
JF American Journal of Enology and Viticulture
JO Am J Enol Vitic.
FD American Society for Enology and Viticulture
SP ajev.2018.17037
DO 10.5344/ajev.2018.17037
A1 Patricia A. Howe
A1 Randy Worobo
A1 Gavin L. Sacks
YR 2018
UL http://www.ajevonline.org/content/early/2018/02/23/ajev.2018.17037.abstract
AB Conventional approaches to measurement of sulfur dioxide (SO2) in wine, such as aeration-oxidation (A-O), iodometric titration, and flow injection analysis (FIA), are known to overestimate molecular SO2, particularly in red wine due to 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 (HS-GDT) measurements. However, it is unclear whether SO2 values achieved through conventional methods (“Molecular SO2”) or non-perturbing 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, where 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 S. cerevisiae strain EC1118 (Lallemand), and viability and culturability evaluated at regular intervals. Both culturable and viable cell counts decreased significantly for treatments with 0.5-2.0 mg/L molecular SO2 in the white and red wines, and for 0.5-2.0 mg/L “Molecular SO2” in the white wine, but concentrations &gt;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.