## 2 Materials and Methods
### Measuring AOA  
The AOA of aqueous coffee extracts was measured by using two electron transfer-based assays [18; 37]: spectrophotometry with the use of FCR and potentiometry with the use of potassium hexacyanoferrates. The FCR is non-specific for phenolic compounds; therefore, the spectrophotometric assay with the FCR is currently recommended for the AOA measurement [18; 38; 39]. The spectrophotometric determination of AOA was performed as described by [PERSON] et al. [40]. An amount of 2.5 mL of the FCR (0.2 N) was mixed with 0.5 mL of GA solution of the known concentration or pre-diluted coffee extract (1:100). After 4-6 min, 2 mL of Na\({}_{2}\)CO\({}_{3}\) solution (7.5%) was added. The resulting mixture was remixed and incubated for 2 h in the dark at room temperature to develop a blue color. Absorbance was measured in cuvettes with a path length of 10 mm at 760 nm relative to a blank sample (water) by using an Ecoviev UV-1200 spectrophotometer (Shanghai Mapada Instruments Co., Ltd., Shanghai, China). A linear calibration curve Abs = 0.0133-C\({}_{\rm GA}\) + 0.026 with an approximation factor R\({}^{2}\) = 0.9997 was obtained for solutions with a concentration of GA 0, 10, 20, 30, 40 and 50 mg/L. AOA in mg equivalent of GA in 1 L of extract (mg GAE/L) was calculated on the basis of a previously obtained calibration curve. The potentiometric determination of AOA was performed as described in [PERSON] et al. [41]. An amount of 1 mL of the analyzed coffee extract was added to 10 mL of phosphate-buffered saline (pH 7.4) containing 10\({}^{-2}\) mol/L K\({}_{3}\)[Fe(CN)\({}_{6}\)] and 10\({}^{-4}\) mol/L K\({}_{4}\)[Fe(CN)\({}_{6}\)]. The potential change was recorded for 20 min in a two-electrode cell using a pH/ions meter TA-Ion completed with a DPTA.25.0220.000 SB thermal sensor (RPE Tomanalyt LLC, Tomsk, Russia). The platinum screen-printed electrode (RPIE Iva LLC, Yekaterinburg, Russia) was pre-purified by annealing at 750 \({}^{\circ}\)C for 1 h [42] and was used as an indicator (working) electrode. The silver chloride electrode EVL-1M3.1 (JSC Gomel Plant of Measuring Devices, Gomel, Belarus) was prepared as described in the user manual and was used as a reference electrode. AOA in umol equivalent of iron (II) in 1 L of extract (umol Fe\({}^{2+}\)-E/L) was calculated according to Equation (1):  
\[\mathrm{AOA}=\frac{C_{ox}-\alpha\cdot C_{rad}}{1+a}\cdot q,\ \ \alpha=\frac{C_{ox}}{C_{red}}\cdot 10^{ \frac{AE}{2\hbar\omega}}, \tag{1}\]  
where \(C_{ox}=10^{-2}\) mol/L is the concentration of K\({}_{3}\)[Fe(CN)\({}_{6}\)] in a cell; \(C_{rad}=10^{-4}\) mol/L is the concentration of K\({}_{4}\)[Fe(CN)\({}_{6}\)] in a cell; \(q=11\) is a degree of sample dilution in a cell, non-dimensional value; \(\Delta E=(E_{1}-E_{2})\) is the difference between initial and final potentials,V; \(F\) = 96,485.332 C/mol is the Faraday constant; \(R\) = 8.314 J/(mol\(\cdot\)K) is the molar gas constant; \(T\) = (\(T_{\circ}\)C + 273.15) is the absolute temperature, K.  
The obtained AOA values were recalculated per one gram of dry weight (DW) of coffee beans using Equation (2):  
\[\text{AOA}\left(\frac{\text{unit}}{\text{g}}\text{DW}\right) =\text{AOA}\left(\frac{\text{unit}}{\text{L}}\right)\cdot\frac{\text{V}}{ \text{m}}\cdot\frac{100}{100-\text{W}}, \tag{2}\]  
where V = 0.1 L is the water volume for extraction; m = 5.5 g is the coffee mass for extraction; W is the MC in the analyzed coffee sample, %.  
AOA was assessed under repeatability conditions; the average value of three parallel measurements was taken as the result.