P-44 - Filtering the Facts. How Yeast Choice Shapes Non-alcoholic Beer Filtration & Stability

This study evaluates the impact of yeast strain selection on fermentation performance, filtration efficiency, and the stability of non-alcoholic beer (NAB). Three yeast strains (SafBrew™ LA-01, LalBrew® LoNa™, and W-34/70) were assessed based on their fermentation characteristics and subsequent effects on NAB quality. Original extract and bitterness remained statistically unchanged across fermentations, ensuring consistent starting conditions. As expected, maltose-negative strains SafBrew™ LA-01 and LalBrew® LoNa™ produced significantly lower alcohol by volume (ABV 0.53% and 0.56%, respectively) compared to W-34/70 (2.33%). The apparent degree of fermentation (ADF) was similarly reduced for SafBrew™ LA-01 (15.51%) and LalBrew® LoNa™ (16.26%), while W-34/70 reached 68.91%, impacting pH reduction due to organic acid production.

Filtration behavior varied among yeast strains and the filter media tested. The study utilized four different commercially available depth filter sheets, each designed for distinct filtration tasks: FIBRAFIX® AF 11 (coarse), AF 31 (clarifying), AF 71 (fine), and AF 101 (germ-reducing). Filtration trials were conducted at a consistent filtration volume of 50 L/m². Among the tested media, AF 11 provided insufficient clarification, resulting in high turbidity (39.3 EBC for SafBrew™ LA-01 and 71.5 EBC for LalBrew® LoNa™), whereas AF 31, AF 71, and AF 101 achieved turbidity below 2 EBC, ensuring clear beer. Filtration did not significantly affect bitterness, confirming its stability across all trials. A slight but consistent reduction in beer color was observed across all filter types, which was expected given the adjusted filtration volume in the trial setup.

Filtration also influenced volatile compound retention. A statistically significant decrease in aldehydes, particularly 2-methylpropanal and hexanal, was observed post-filtration, suggesting yeast binding as a primary mechanism. However, furfural and nonanal concentrations remained stable, indicating resistance to yeast adsorption. Hop aroma compounds showed minimal changes, preserving key sensory characteristics. Fermentation-derived esters, including ethyl hexanoate and ethyl octanoate, exhibited concentration reductions post-filtration, particularly in SafBrew™ LA-01 and LalBrew® LoNa™, likely due to yeast retention differences across filter sheets.

Short-term haze stability assessments revealed increasing turbidity over two weeks of storage at 4 °C, especially in NABs fermented with SafBrew™ LA-01 and LalBrew® LoNa™. In contrast, W-34/70 filtered with AF 11 initially exhibited low turbidity (1.28 EBC) but also showed increased haze over time. AF 31, AF 71, and AF 101 effectively maintained clarity below 2 EBC during storage, while AF 11 failed to provide sufficient filtration for SafBrew™ LA-01 and LalBrew® LoNa™ beers. These findings highlight the importance of optimized filtration strategies and the potential need for additional pretreatment steps, such as centrifugation, to enhance filtration efficiency in NAB production.
Overall, yeast selection significantly influenced fermentation activity, filtration performance, and haze stability. The study underscores the necessity of selecting appropriate filtration techniques based on yeast flocculation properties to achieve optimal NAB clarity and stability.