Microbiological stability of dealcoholised wines: effect of SO2 and sorbic acid

The removal of ethanol and relatively high sugar content in dealcoholised wines create vulnerability to microbiological threats. The actual study is one of the first attempts to understand whether the traditional preservatives like SO2 and sorbic acid alone can provide the required microbiological stability in dealcoholised wines. The experiments were conducted with molecular SO2 concentrations in the range of 0.3–1.8 mg/L in a dealcoholised Riesling wine. When sterile bottled, ~1 mg/L of molecular SO₂ prevented fermentation in the bottles of the studied wine and also maintained microbial stability during simulated wine consumption, especially in combination with sorbic acid (partially emptied bottles stored at room temperature). At the same time, in another experiment, up to 1.8 mg/L of molecular SO2 was insufficient to deactivate intentionally inoculated Saccharomyces cerevisiae yeasts in the dealcoholised Riesling wine at a level of approximately 5000 cells per bottle. Depending on the pH and SO2 levels, yeast overgrowth (membrane filtration) was observed between Day 1 and Day 7 after inoculation. Regarding sorbic acid, it also revealed an additional antimicrobial effect.