## 3 Results
### Physicochemical Properties of Beer Processed Using Pulsed Light with/without UV Filters  
Table 3 summarizes the selected physicochemical properties of BA and CA beer samples. CA beers had an overall higher SRM than BA beers. Control BA had significantly higher SRM than all the treated BA samples (\(p<0.05\)), and there were significant but small differences (\(p<0.05\)) among the color of the treated BA samples. Specifically, BA samples treated with no filter for 5 min had the lowest SRM, indicating that it became lighter in color with PL treatment, while the CA beer treated for 5 min and with no filter had the highest SRM, indicating that it became darker in color with PL treatment. Beers treated with a bronze-tinted filter had the lowest color change, followed by those treated with a clear filter, and maximum color change was observed with those treated without filters. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Filter** & **Beer Style** & **Residence Time** & **Concentration of 3-MBT** \\  & & **(min)** & **(ng/L) *** \\ \hline Control & Blonde ale (BA) & 0.0 & \(<\)LOQ \\  & Centennial red ale (CA) & 0.0 & \(<\)LOQ \\ No filter & BA & 5 & 1832 \(\pm\) 149 \({}^{\mathrm{ax}}\) \\  & & 2.5 & 1629 \(\pm\) 156 \({}^{\mathrm{ax}}\) \\  & & 0.5 & 1521.9 \(\pm\) 320.1 \({}^{\mathrm{ax}}\) \\  & & 0.25 & 759.4 \(\pm\) 251.5 \({}^{\mathrm{bx}}\) \\  & CA & 5 & 682.4 \(\pm\) 81.2 \({}^{\mathrm{ay}}\) \\  & & 2.5 & 548.1 \(\pm\) 114.8 \({}^{\mathrm{ay}}\) \\  & & 0.5 & 469.6 \(\pm\) 94.1\({}^{\mathrm{aby}}\) \\  & & 0.25 & 238.2 \(\pm\) 24.6 \({}^{\mathrm{by}}\) \\ Clear filter & BA & 5 & 121 \(\pm\) 39 \({}^{\mathrm{z}}\) \\  & & 2.5 & \(<\)LOQ \\  & & 0.5 & \(<\)LOQ \\  & & 0.25 & \(<\)LOQ \\  & CA & 5 & \(<\)LOQ \\  & & 2.5 & \(<\)LOQ \\  & & 0.5 & \(<\)LOQ \\ Bronze-tinted & & 0.25 & \(<\)LOQ \\ filter & BA & 5 & \(<\)LOQ \\  & & 2.5 & \(<\)LOQ \\  & & 0.5 & \(<\)LOQ \\  & & 0.25 & \(<\)LOQ \\  & CA & 5 & \(<\)LOQ \\  & & 2.5 & \(<\)LOQ \\  & & 0.5 & \(<\)LOQ \\  & & 0.25 & \(<\)LOQ \\ \hline \hline \end{tabular}  
* Data are shown as mean \(\pm\) standard deviation (\(n=3\)). Two-way analysis of variance (ANOVA) was conducted for values above the LOQ. Letters a and b reported after values indicate significant differences between treatments of each beer style (\(p<0.05\)). Letters x-z reported after values indicate significant differences between beer styles (\(p<0.05\)). LOQ: limit of quantification; 3-MBT: 3-methylbut-2-ene-1-thiol.  
\end{table} 
Table 2: Concentration of 3-MBT (3-methylbut-2-ene-1-thiol) in control and pulsed-light-treated beers. Control BA and CA had IBU values of 23.0 and 41.4, respectively. The IBU of control BA was significantly higher (\(p<0.05\)) than its treated counterparts, while that of CA was significantly lower (\(p<0.05\)) than treated samples. Among treated samples, the mean IBU of BA samples had an overall decreasing trend as fluence increased, while that of CA had an overall increasing trend with the increase in fluence. The pH levels of CA samples were all higher than that of BA samples. The pH of the control BA was significantly higher (\(p<0.05\)) than its treated counterparts. The pH levels of control CA were significantly higher (\(p<0.05\)) than the other treated CAs, except for clear-filter and bronze-tinted-filter-treated CAs for 0.25 min. PL treatment with higher residence times tended to decrease the pH of both beers. The TSS in BA beers were relatively higher compared to that of CA beers. For BA samples, all PL treatments, except clear and bronze-tinted filters at 0.25 min residence times, generally resulted in a significant decrease in TSS (\(p<0.05\)), with no-filter treatment at 5 min producing the lowest TSS. For CA samples, only PL treatments greater than 2.5 min residence time produced significant differences (\(p<0.05\)) in TSS for bronze-tinted-filter and no-filter treatments, whereas no significant differences were produced with clear filters.