Winemakers routinely add sulfur dioxide (SO2) to wines to prevent microbial and oxidative spoilage. In red wines, a large portion of SO2 is bound to anthocyanins (red pigments).
Standard approaches to measuring SO2 in wines involve an initial acidification step that releases this anthocyanin-bound SO2, but it was unknown if this affected the accuracy of SO2 measurements for the purposes of predicting microbial stability.
Some authors have proposed that anthocyanin-bound SO2 is also antimicrobial, but this work refutes that claim, and shows that standard approaches do not accurately predict microbial spoilage.
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