LILLE 2024

To strive for the highest quality global and local beer brands, controlling flavor and taste is absolutely essential. The flavor and taste of beer are a result of the ingredients, yeast, and fermentation process used. For lager and many specialty beers, yeast and the fermentation process are the main contributors to the overall flavor profile. To reach the desired beer flavor profiles from fermentation, a careful optimization is required, especially when considering different operational scales and fermentation assets and designs worldwide. AB InBev’s experience will be illustrated from case studies on optimizing and controlling flavor through fermentation at operational scale. The most critical parameters requiring fine-tuning adapted to the choice of the yeast strain will be discussed with a perspective on fermentation process for flavor and product quality consistency.

During fermentation, technologically used yeasts come into contact with Maillard reaction products (MRPs) originating from the malt or wort cooking. We could demonstrate in model studies as well as in brewing experiments that the carbonyl compounds 5-HMF and 3-deoxyglucosone are metabolized by commercial beer yeast strains to 2,5-bishydroxymethylfuran (BHMF) and 5-formyl-2-furancarboxylic acid or 3-deoxyfructose (3-DF), respectively. Brewer’s yeast strains showed a significantly higher 3-DG stress resistance than yeast strains isolated from natural habitats. Using synthetic dipeptides of the MRPs pyrraline and formyline we found a preferred uptake of peptide-bound glycation compounds, followed by a yeast-specific metabolization via the Ehrlich pathway. Again, a faster uptake and higher metabolization rate was observed for brewer’s yeasts compared to wild strains. These results indicate a domestication-dependent adaption of brewer´s yeasts to Maillard reaction products in beer wort. Metabolites produced by yeasts from MRPs such as 3-DF or the Ehrlich alcohol of pyrraline were found in commercial beers, indicating a practical relevance of the observed metabolic pathways.

Malt-induced premature yeast flocculation (PYF) is a sporadic problem within the brewing industry. The use of PYF malts is concomitant with a number of negative impacts on beer quality, including incomplete fermentation and/or flavor defects. Although malt-induced PYF is widely acknowledged, actions taken so far have proved insufficient to solve the PYF-related issues. To limit the detrimental effects of PYF malts on beer production, an adaptive laboratory evolution (ALE) process was applied in this study to an industrial lager brewing yeast strain, in an attempt to generate variant strains with improved fermentation performance in PYF wort. Through a batch fermentation-based adaptation process, evolved variants were isolated and screened for their phenotypic and metabolic traits. The investigation focused mainly on the tendency to remain in suspension, fermentation capacity and final acetaldehyde concentration. We successfully obtained a variant with improved fermentation properties. The improvement was seen in worts prepared from different types of PYF malt as well as normal malt. Furthermore, ALE of lager brewing yeast in PYF wort yielded a wide array of mutations.

Polyfunctional thiols such as 3-sulfanylhexan-1-ol (3SH) and 4-methyl-4-sulfanylpentan-2-one (4MSP) are known to impart tropical flavors, and we hypothesized that fermentation temperature impacts thiol release in beer. We brewed 18 different beers at 1.4hL pilot scale varying fermentation temperature (15°C, 22°C, 30°C) and LalBrew® commercial yeasts (BRY-97™, Nottingham™, Verdant IPA™, London™, Diamond™) in an all-pilsner malt recipe hopped with Cascade (1.2g/L kettle and 3.0g/L whirlpool). Beers were analyzed for 31 aroma-related compounds, including thiols and thiol precursors, and sensory descriptive analysis. Thiol release correlated with fermentation temperature. For instance, 3SH increased 45-72% from 15 to 30°C, ranging from 55-162µg/L across yeast strains. Sensory results indicated that free thiols alone do not provide the most citrus-tropical beers: Diamond™ had 2x higher levels of 3SH and 4MSP than the other beers but the lowest citrus-tropical character. Nottingham™, Verdant IPA™, and London™ strains produced elevated thiols levels plus β-ionone, β-damascenone, 2-phenylethanol, and α-terpineol to name a few, yielding the most citrus-tropical aroma.