## 1 Introduction  
With the continuous improvement of consumers' health consciousness, functional food is now the first choice for an increasing number of consumers [1, 2]. Beer is a popular beverage due to its unique flavor, pleasing organoleptic properties, and lower cost. Consumers pay simultaneous attention to the stability of beer flavor, quality, and functionality [3]. Beer is the most widely consumed alcoholic beverage in the world [4]; its alcohol content is low, and it contains essential compounds produced by malt and hops and through microbial fermentation [5]. Malt and auxiliary materials in the raw materials are the main sources of carbohydrates, vitamins (vitamin B complex), and dietary fiber, and hops contain many nutrients such as polyphenols and flavonoids. When beer is consumed in moderate amounts, these active ingredients may regulate human functions by activating specific enzymes [6]. As an important neurotransmitter, GABA is naturally produced during barley germination, and research results have confirmed its physiological functions, such as regulating blood pressure, relieving anxiety, and improving water and salt metabolism [7]. GSH, as a key antioxidant (1-20 mg/L), is not only effective in scavenging free radicals but also plays an important role in maintaining the stability of beer flavor [8]. B vitamins in beer exist in various forms, among which nicotinic acid (NA), nicotinamide (Nam), and nicotinamide ribose (NR) can be converted to the coenzyme NAD+, and this conversion pathway has been demonstrated during yeast fermentation [9]. \(\beta\)-Glucan, as a barley cell wall degradation product (0-1152 mg/L), is classified as an important functional ingredient due to its efficacy in immune regulation, intestinal flora balance, and metabolic regulation [10]. In addition, polyphenols in beer excel in free radical scavenging by virtue of their high bioavailability and strong antioxidant activity [11]. However, due to the diversity of raw material selection and differences in brewing techniques, the chemical composition of different beers will show evident differences [12]. A variety of analytical techniques are employed for the detection of functional compounds in liquor. High-performance liquid chromatography (HPLC) is suitable for the separation and determination of amino acids, flavonoids, phenolic acids, and so forth. The \(\gamma\)-aminobutyric acid (GABA) and glutamic acid content in fermented foods can be determined through pre-column derivatization with o-phthalaldehyde (OPA) in combination with HPLC [13; 14], and glutathione and \(\gamma\)-glutamylcysteine in wine can be determined simultaneously through the use of high-performance liquid chromatography with a fluorescence detector (FLD) [15]. The phenolics found in beer can be extracted using ethyl acetate, and the main hydroxycinnamic acids (HCAs) and their derivatives, monophochols and flavonoids, and phenolic acids can be identified using high-performance liquid chromatography (HPLC) with a diode array detector [16; 17]. The binding of Congo red to \(\beta\)-glucan is highly specific, and the determination of \(\beta\)-glucan in beer can be achieved readily and rapidly through Congo red spectrophotometry [18]. Mass spectrometry (MS) is often coupled with chromatography to achieve high sensitivity, and liquid chromatography-mass spectrometry (HPLC-MS) is suitable for the qualitative and quantitative analysis of non-volatile substances, with the quantitative and simultaneous determination of seven B vitamins in nutritional products using LC-MS/MS after enzymatic digestion [19; 20].