Title : Influence of process conditions on the flavour stability of unpasteurized craft beer
Abstract:
Craft beer is an emerging brewing field which is more and more important in terms of production and value. Unfortunately, 2020 was an awful year for small craft breweries which seen their beers unsold for long time. Thus, to produce a stable beer is important for craft beer too. Craft beers are usually unpasteurized and unfiltered, causing a different aging behaviour compared to a pasteurized and filtered one. In this work the influence of some process conditions (e.g. microfiltration, storage temperature, refermentation with fresh yeast) on the flavour stability of a beer during 6 months of storage was studied. A golden unpasteurized top-fermented beer was used as sample. Analyses of quality parameters, volatile compounds and sugars profile were performed. Further, beers were judged by a trained panel. The samples were analysed in duplicate for a total of 36 samples. Results confirmed that cold stored (4±1 °C) refermented with fresh yeast resulted to have higher flavour stability. Beer had stable quality parameters both for cold and room stored samples. Apparent attenuation, alcohol, colour, pH, haze did not significantly change. Dissolved oxygen was reduced by the presence of yeast. Microfiltration at 0,45 μm caused a reduced foam persistence and a reduction of flavour stability. Judges found oxidation and stale descriptor only into the microfiltered beers. Cold storage contributed to preserve the hop flavour, which resulted significant different after 6 months between cold and room stored beer. The sum of aldehydes unexpectedly decreased during storage for all samples. This work highlighted an interesting flavour stability of the unpasteurized beer where the yeast can act as antioxidant during refermentation and storage.
