## Materials and Methods
### Chemical Analysis
#### 2.6.2 Liquid Chromatography-Electrospray Ionization Tandem Mass Spectrometry (LC-ESI-MS/MS)  
The phenolic compounds and caffeine content of cold and hot brew coffee were determined using LC-ESI-MS/MS according to the method by [PERSON] et al. (2022) [18]. The MS parameters were: mass range, 50-1000 \(m/z\); positive ion, 3500 V; negative ion, 3500 V; sheath gas (N2), 30 Arb; auxiliary gas (N2), 15 Arb; ion transfer tube temperature, 325 \({}^{\circ}\)C; vaporizer temperature, 350 \({}^{\circ}\)C. The characterization of phenolics was conducted using data obtained with the selective reaction monitoring (SRM) mode. The LC-ESI-MS/MS with a Chromoleleon 7 chromatography data system (version 7.2.9.11323 from Thermo Fisher Scientific, Bremen, Germany) was used for molecular mass analysis of authentic standards of phenolics. The mixed solution of all authentic phenolics was prepared in methanol at different concentrations for calibration curves. The chromatographic separation of the standards was conducted on an Accucore RP-MS column (2.1 mm, 100 mm, 2.6 \(\upmu\)m, Thermo Fisher Scientific, Bremen, Germany) by eluting with a mobile phase containing acetonitrile (eluent A) and 0.1% (\(v/v\)) formic acid (eluent B). The gradient elution at 10% A and 90% B was carried out at a flow rate of 0.5 mL/min for 10 min. The injection volume was 10 \(\upmu\)L. The column temperature was maintained at 35 \({}^{\circ}\)C.  
The validation of phenolics was described by [PERSON] et al. (2022) [18]. The validations of caffeine are shown in Supplementary Tables S1 and S2. Three SRM transitions of caffeine at specific collision energies (V) and radio frequencies (RF-lens; V) were used to analyze the selectivity and specificity of caffeine detection in coffee samples. The caffeine standard calibration curve was prepared using standard stock solutions in methanol. The caffeine calibration curve range was carried out in triplicate. The limit of detection (LOD) and limit of quantification (LOQ) were evaluated from the standard curve according to Equations (4) and (5):  
\[\text{LOD}=(3.3\sigma)/\text{S} \tag{4}\]  
\[\text{LOQ}=(10\sigma)/\text{S} \tag{5}\]  
where \(\sigma\) is the standard deviation of the Y-intercept, and S is the average slope of the linear calibration curve. Precision was determined using values obtained from seven replicate injections within the same day. The variations in retention time were presented as a percentage of the relative standard deviation (%RSD). Accuracy was established using a known amount of the caffeine standard. The solutions of the spiked samples were injected into the LC-ESI-MS/MS system with the SRM system in triplicates. The accuracy of this method was expressed as percentage recovery (% recovery) using Equation (6):  
\[\text{\% recovery}=[(\text{observed amount}-\text{initial amount})\times 100]/ \text{spiked amount} \tag{6}\]  
Prior to analyzing the phenolic and caffeine content, a brewed coffee sample (1.5 L) was freeze-dried. The powder samples (0.5 g dry weight) were dissolved in a mixture of formic acid (40 mL) and 62.5% (\(v/v\)) methanol containing 0.5 g tert-butylhydroquinone (TBHQ) (10 mL) before shaking in a water bath shaker at 80 \({}^{\circ}\)C for 2 h (TW20 series from Julabo GmbH, Seelbach, Germany). The mixture was placed on ice for 5 min, added with 1% (\(v/v\)) ascorbic acid (100 uL), and sonicated for 5 min in an ultrasonic bath (Branson Ultrasonics(tm) M series, Branson Ultrasonics Corp., Danbury, CT, USA). The mixture was adjusted to 50 mL with 62.5% (\(v/v\)) methanol containing 0.5 g TBHQ and filtered through a PTFE membrane (0.22 uM). Phenolic acid standards: chlorogenic acid, caffe acid, syringic acid, p-cumaric acid, ferulic acid, sinapic acid, cinnamic acid, 4-hydroxybenzoic acid, and 3,4-dihydroxybenzoic acid were from Sigma-Aldrich. Gallic acid, vanillic acid, and rosmarinic acid were from the Tokyo Chemical Industry (Tokyo, Japan).