Effectiveness of dimethyldicarbonate to stop alcoholic fermentation in wine

The alcoholic fermentation of Botrytis-affected wines is stopped by the addition of high concentrations of sulfur dioxide (SO₂). The natural microbial unstability of these wines and the binding phenomena forces winemakers to periodically add sulfur dioxide during maturation, leading to a high concentration of a maximum of 400 mg/l in the bottled wine. Dimethyldicarbonate (DMDC) is now considered as a reliable fungicide which could be partially used instead of SO₂, especially just before bottling. This study investigated the use of DMDC to stop alcoholic fermentation. The experiment was carried out on pure cultures of three yeast species present in this type of wine (Saccharomyces cerevisiae, Candida stellata and Zygosaccharomyces bailii). The results were very promising and suggested that DMDC was more effective than SO₂. The yeast cells died after the addition of DMDC whereas they partially entered into a viable but non-culturable (VBNC) state with SO₂. However, the same experiment carried out on botrytized must, whose fermentation was carried out using indigenous microflora, was less conclusive. It pointed out that DMDC, used in a concentration of 200 mg/l, was more effective than SO₂ but leading to the same results: the entering of a part of the cells into a VBNC state. DMDC could be used to stop alcoholic fermentation, but could not replace SO₂. Nevertheless, the concentrations of SO₂ added in this type of wine could be reduced in this way.