Fate of the worty flavours in a cold contact fermentation

3-Methylbutanal, 2-methylbutanal and 3-methylthiopropionaldehyde are described in the literature as preponderantly responsible for the worty taste of alcohol-free beers. Even in a cold contact process, such aldehydes are reduced through fermentation. The chemical removal of aldehydes by amino acids or proteins does not exceed 20% of the initial concentration, although such mechanisms appear much more effective at 28°C. The role of Saccharomyces cerevisiae brewerʹs yeast, in the reduction of wort aldehydes, is confirmed here. Only viable yeasts allow a significant decrease in carbonyl level. Unfortunately, residual concentrations are higher for Strecker aldehydes among which 3-methylthiopropionaldehyde is characterized by a very low flavour threshold. Effects of yeast strain, pitching rate and inhibitors have been assessed.