| Abstract: | Diketone and α-acetohydroxyacid levels have been monitored during ale fermentations both in stirred fermentors and in a pilot brewery. It was found necessary to bring samples to neutral pH and protect them from air until assayed. Little diketone was formed during normal fermentations. Addition of sodium metabisulphite trapped α-acetohydroxyacids and high concentrations persisted in the beer. Lowering the wort pH decreased the peak concentrations of α-acetohydroxyacids without a corresponding increase in diketone concentrations. Alterations in the oxygen supply during preculture of the yeast or at pitching had little effect on diketone formation. α-Acetohydroxyacids have been detected in beer in keg from a continuous fermentation. |
