## 4 Discussion  
The PL treatment of beers without filters allowed exposure to the broadest spectrum of electromagnetic radiation from 200 to 1100 nm, including UV, visible light, and IR rays, resulting in 4.2 and 2.4 log reductions, respectively, for BA and CA beers for 5 min of treatment. However, this treatment without filters imparted 16.8 J/cm\({}^{2}\), exceeding the fluence regulatory limits for food and beverage. Following this, at 8.4 J/cm\({}^{2}\) for 2.5 min residence time, PL treatment without a filter resulted in a maximum usable 2.7 and 1.6 log reductions for BA and CA beers, respectively. Treatment at this intensity resulted in the generation of 1629 ng/L 3-MBT, as well as significant changes in color, bitterness, pH, and TSS. Generally, higher fluence was needed to achieve higher and more practical microbial reductions. The microbial deactivation of beers treated without filters at 2.5 min and 5 min residence time (8.4 J/cm\({}^{2}\)) was comparable to the study conducted by [PERSON] et al. (2016), where they observed more than three log reductions for _E. coli_ in non-alcoholic beer using 266 nm-wavelength lasers for 10 J/cm\({}^{2}\). However, the differences in reductions could be due to the different wavelengths used, the penetration depth of the beverages treated, the bacteria targeted, and liquid volume per cm\({}^{2}\) of surface exposed to PL. The application of a clear filter, for 5 min residence time (8.9 J/cm\({}^{2}\) fluence, only marginally larger than the 2.5 min residence time treatment without a filter) resulted in 1.2 (BA) and 1.0 (CA) log reduction in _L. brevis_ but led to minimal 3-MBT formation and fewer significant changes in physicochemical parameters as compared to 2.5 min of treatment without a filter. The application of a bronze-tinted filter resulted in fewer than 1.0 log reductions of _L. brevis_ at all treatment fluences tested (0.1-1.3 J/cm\({}^{2}\)), with non-quantifiable 3-MBT formation and fewer significant changes in physicochemical properties as compared to a clear filter. [PERSON] et al. (2017) highlighted the importance of the UV-C (200-280 nm) portion of the spectrum for microbial deactivation. As both the clear and bronze-tinted filters blocked UV radiation, treatments with filters underwent significantly less (\(p<0.05\)) or insignificantly different (\(p>0.05\)) microbial reductions in the same beer style and residence time as compared to treatment without filters. With the bronze-tinted filter, as further areas of visible light and IR rays were removed, resulting in less than 1/6 th of the fluence of a clear filter, the decontamination power was significantly reduced. It must be mentioned that a maximum tested fluence of 1.3 J/cm\({}^{2}\) is considerably low, and achieving higher decontamination with a longer residence time cannot be discarded. Moreover, the temperature rise was recorded to be less than 5 \({}^{\circ}\)C in all cases with or without filters at all residence times, suggesting a limited increase in temperature due to IR's thermal effects, possibly due to the mixing of the liquids. Although treatments with both filters had reduced deactivation effects in our study, both BA and CA beers still had recognizable deactivation power contributed by visible light and IR rays; deactivation was possibly achieved due to the photothermal effect of IR rays and the phototoxic effect of inducing high levels of bacterial-produced ROS from intense visible light ([PERSON] et al., 2012; [PERSON] et al., 2013). Significantly higher (\(p<0.05\)) microbial reduction, the generation of 3-MBT, and changes in physicochemical parameters were observed in BA beers compared to CA beers, which was attributed to the contribution of increased light penetration depth in the lighter-colored BA, as shown with overall lower SRM values. Penetration depth is influenced by light absorbance, the inverse of transmittance ([PERSON] et al., 2013). Fluids of lighter color have lower absorbance and higher transmission in the visible light spectrum ([PERSON] et al., 2013).