## 3 Results and Discussion
### Filtration Impact on NABs Breved and Analyzed
#### 3.3.1 NAB Filtration Performance and Impact on Fresh Products
In contrast, beer fermented with the highly flocculent yeast W-34/70 showed the lowest turbidity (1.28 EBC) after filtration with AF 11, falling below the human eye's turbidity perception threshold of \(>\)2 EBC [18; 45], and thus would have been classified as non-hazy. When considering only the turbidity results, the filtration efficiency of AF 31, AF 71, and AF 101 was notably superior, yielding outlet turbidity values well below 2 EBC, categorizing these beers as clear or nearly brilliant [18; 45]. This finding is particularly relevant, as it indicates that all filter sheets effectively clarified beers fermented with medium- or non-flocculent yeasts (LA-01 and LoNa), while the presence of highly flocculent and potentially clumped yeasts (W-34/70) did not significantly impair filtration efficiency. Although filtration time and flow rate were not quantitatively recorded, qualitative assessment suggested that AF 11 exhibited the highest flow rate, followed by AF 101, while AF 31 performed more slowly and AF 71 had the lowest filtration efficiency in terms of flow rate. To optimize filtration performance, particularly for beers fermented with non-flocculent, maltose-negative yeasts such as LA-01 or LoNa, additional pretreatment steps (e.g., centrifugation) may be necessary and should be explored in future trials. In addition to turbidity-based filtration performance, the effects on color and bitterness were also evaluated (Table 2). For most of the NAB filtration trials, a statistically significant reduction in color was observed in the filter outlet samples. However, the color reduction was independent of the filter sheet used, indicating that all filtration setups performed similarly in this regard. This outcome aligns with expectations, although the existing literature does not provide a definitive conclusion regarding color changes due  
Figure 2: Turbidity results of NABs produced with the three different yeast strains and filtered using various filter sheet setups. Error bars represent the standard error. to filtration [46; 47]. Notably, the most pronounced color reduction was detected in the low-alcohol beer fermented with W-34/70. Given that the word composition was identical across all fermentation trials, this suggests a potential reduction in color during fermentation. This hypothesis is further supported by the observation that the filtered low-alcohol beer exhibited a lower color intensity compared to the NABs. The reduction in bitterness observed after the filtration of the W-34/70 NAB (Table 2) is in line with the previous literature [48; 49] and may be attributed to strain-specific interactions between the yeast and hop-derived bitter compounds, particularly iso-\(\alpha\)-acids. W-34/70, a strongly flocculating _Saccharomyces pastorianus_ strain [29], exhibited the highest yeast concentration (6.2 \(\times\) 10\({}^{6}\) cells/mL) at the filter inlet. At the same time, its pronounced tendency to aggregate during cold conditioning and clarification likely promoted the removal of suspended solids, including yeast-bound hop constituents. One plausible explanation is the adsorption of iso-\(\alpha\)-acids onto the yeast cell wall [50]. Strains with elevated flocculation capacity and more hydrophobic cell surfaces, such as W-34/70, may display a greater ability to bind and sequester these bittering compounds, thus reducing their concentration in the final beer. Moreover, the elevated cell count (6.2 \(\times\) 10\({}^{6}\) cells/mL) at the point of filtration could further intensify the adsorption and physical retention of iso-\(\alpha\)-acids within the filter cake. Collectively, these effects, strain-specific adsorption, flocculation-driven sedimentation, and filtration-related retention, likely contributed to the observed decline in bitterness in the W-34/70 sample. Overall, the different filter sheets (except for AF 11) resulted in clear beers. Highly flocculent yeast strains, such as W-34/70, might lead to a minor reduction in color and bitterness post filtration.