Fate of the worty flavours in a cold contact fermentation

3-Methylbutanal, 2-methylbutanal and 3-methylthiopropionaldehyde are descri bed in the literature as preponderantly responsible for the worty taste of alcohol-free beers. Even in a cold contact process, such aldehydes are redu ced 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 degrees C. The role of Sacchar omyces cerevisiae brewer's yeast, in the reduction of wort aldehydes, is co nfirmed here. Only viable yeasts allow a significant decrease in carbonyl l evel. Unfortunately, residual concentrations are higher for Strecker aldehy des among which 3-methylthiopropionaldehyde is characterized by a very low flavour threshold. Effects of yeast strain, pitching rate and inhibitors ha ve been assessed. (C) 1999 Elsevier Science Ltd. All rights reserved.