Influence of Selected Technological Conditions on the Flavour Stability of Unpasteurised Top-Fermented Craft Beer

Craft beers are usually unpasteurised and unfiltered, causing a different ageing behaviour compared to pasteurised and filtered beers. In this work, the influence of microfiltration, storage temperature, and fresh yeast addition for refermentation on the flavour stability of a top-fermented beer was studied. The determination of the main quality parameters (e.g. extract, haze, foam, pH) and volatile compounds was performed. Also, a trained panel evaluated the sensory profile of the beers. A statistical data (analysis of variance and PCA) processing approach was used to better understand how different treatments interact with the stability of an unpasteurised beer. The main quality parameters were not influenced by the different storage conditions. Microfiltration at 0.45 µm led to decreased head retention and flavour stability in all beers. In fact, oxidation and stale notes were detected only in the microfiltered beers. About volatile compounds, the aldehydes content decreased during storage for all the samples. Furthermore, there were significant differences between cold-stored and room-stored beer after 6 months in terms of aroma and flavour, especially for the hop character. This study highlighted the interesting flavour stability of unpasteurised beer, where yeast acts as a natural stabiliser during refermentation and storage. The results confirmed that cold storage (4 ± 1 °C) is the best option for beer flavour stability.