## 1 Introduction  
Beer is the third most popular beverage consumed globally after water and tea [1]. There is an upward trend in global beer production where an estimated 1.91 billion hectolters were produced in 2019 [2]. Although current breweries have adopted better food safety and stricter sanitation programs, beer spoilage due to external sources of contamination remains a common problem for the beer industry. For example, the bacterial and fungal contamination of beer can lead to spoilage indexed by the occurrence of turbidity, acidification, and the production of undesirable aromatic compounds, such as diacetyl and hydrogen sulfide. Beer naturally has several intrinsic properties that can collectively provide an unfavorable environment for microorganism viability, including high CO\({}_{2}\) content (\(\text{-5}\,\text{g}/\text{L}\)), an ethanol content of 4.5-5.5% alcohol by volume (ABV), a low pH (3.8-4.7), and a low O\({}_{2}\) content (<0.1 ppm) [3]. Additionally, the presence of iso-\(\alpha\)-acids in beer (derivedfrom the thermal degradation of hops' compounds) at approximately 17-55 ppm has antimicrobial activity against Gram-positive bacteria, specifically lactic acid bacteria (LAB) such as _Lactobacillus brevis_, _Pediococcus damnosus_, _Lactobacillus casei_, _Lactobacillus curatatus_, and _Lactobacillus pantarum_, which are known as major beer spoilage microorganisms [4]. Craft beers made in microbreweries are particularly prone to beer spoilage bacteria as they tend to minimize pasteurization and microfiltration processes in order to showcase the pure flavor of beer [5]. With the popularity of craft beers on the rise in the past decade, an efficient decontamination process that prevents deterioration of beer organoleptic qualities is required [6]. Pulsed light (PL) is a novel and non-thermal food processing technology that is considered a potential alternative to pasteurization or microfiltration. PL kills microorganisms using short bursts of intense light applied on foods through photo-chemical, photo-thermal, and photo-physical effects [7]. PL achieves a high peak power by storing electricity in a capacitor for a relatively long time and releasing it in a shorter period with a wide spectrum consisting of UV rays (\(\lambda\) = 200-400 nm), visible light (\(\lambda\) = 400-700 nm), and IR rays (\(\lambda\) = 700-1100 nm). PL as a technology is well established in the literature for surface decontamination; for example, it can provide up to five log reductions of _L. monocytogenes_[8; 9]. PL has successfully been applied to beverages, such as fruit juices, milk, tea, or wine [10; 11; 12; 13]. However, notable challenges still exist for processing beverages with PL, since the application is limited by its penetration depth. Recent efforts in the PL processing of beverages have focused on optimizing the fluence (energy received by the product per unit area per unit time) to control some of the deteriorative light-induced reactions in beverages. Most efforts concentrate on finding optimal fluence levels that can perform microbial reduction while also producing minimal changes in product quality. [PERSON] et al. [12] reported 3.8 J/cm\({}^{2}\) as the optimal fluence for processing black tea to minimize color change, phenolic degradation, and anti-oxidant activity loss. [PERSON] et al. [14] found a fluence of 2-4 J/cm\({}^{2}\) optimal for the retention of \(>\)80% anthocyanins during the PL treatment of model wine solutions. [PERSON] et al. [15] also reported 3.8 J/cm\({}^{2}\) as the optimal fluence for processing model phenolic solutions. [PERSON] et al. [16] observed more than three log reductions in _Escherichia coli_ K12 when non-alcoholic beer was subjected to 10 J/cm\({}^{2}\) pulsed laser light using 266 nm. However, no published research has investigated the application of PL on beer for routine decontamination purposes. For beverages, the application of PL on beer in a continuous production system poses an attractive solution to limit beer spoilage.