The flavor profile of beer is subject to changes during storage. Since, possibly, yeast has an influence
on flavor stability, the aim of this study was to examine if there is a direct impact of brewing
yeast on aged aroma. This was achieved by refermentation of aged beers. It was shown that
several aged aroma notes, such as cardboard, ribes, Maillard and Madeira, were removed almost
entirely by brewing yeast, independently of the yeast or the beer type. This was explained by the
reduction of aldehydes, mainly (E)-2-nonenal, Strecker aldehydes, 5-hydroxymethylfurfural and
diacetyl, to their corresponding alcohols. Furthermore, it became evident that the reducing capacity
of brewing yeast is high, but that yeast strain and compound specific residual concentrations
remained in the refermented beer independently of the initial concentration. Finally, it appeared that
aldehydes were not only reduced but also formed during refermentation.