## 2 Materials and Methods
### Analysis of the Volatile Profile  
The experimental wines (variants 0-3, plus samples from the large-scale trial, plus samples from the prototype trial) were analysed by means of gas chromatography-mass spectroscopy for the off-flavours geosmin (trial wine A), 2,4,6 trichloroanisole (trial wine B), and 4-ethylpaional, 4-ethylgaiaicol, and 4-ethylcatechol (trial wine C, D). Additionally, the concentrations of positive volatile compounds, including 34 ester compounds (test wine A-C), 15 free monoterenes (test wine A, B), and 24 subtle wood aromas (test wine C) (carbonyl compounds, lactones, phenols) were determined. A gas chromatograph from Agilent Technologies (Santa Clara, CA, USA) and a total of five methods were used for the analysis of the different volatile substances. The system, consisting of a 7890A GC system with a 5975C Inert MSD with Triple Axis Detector and a CTC Analytics Autosampler (Zwingen, Switzerland), was equipped with a ZB-5 MS column (length: 60 m, I.D. :0.25 mm, df = 0.25 \(\upmu\)m) from Phenomenex (Torrance, CA, USA). The quantification of geosmin and TCA was carried out according to the method developed by [5] and modified by [7], using headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS SPME GC-MS) technique by multiple standard additions. The quantification of ester compounds was performed by the partial stable isotope (SIDA)-SPME-GC-SIM-MS method according to [35]. The determination of 15 free monoterene compounds wasperformed by the HS-SPME-GC-SIM-MS method and was based on the method published by [36]. Information on the calibration and validation of these methods can be found in the Supplementary Material (Table S2). The determination of 4-ethylphenol, 4-ethylguaiacol, and 4-ethylcatechol was carried out by means of a liquid-liquid extraction. First, 1.4 g potassium hydrogen phosphate (\(\geq\)98%; Merck KGaA, Darmstadt, Germany) was weighted into centrifuge tubes. Exactly 10.0 mL of wine was mixed in a volumetric flask with 100 \(\upmu\)L of internal standard 2,4-dimethylphenol (target concentration 1 mg/L, Sigma Aldrich Company (St. Louis, MO, USA)), and 3 mL of this mixture was transferred into the centrifuge tube and vortexed until the salt was completely dissolved. These tubes were placed in the refrigerator for approximately 10 min; 200 \(\upmu\)L of propionic anhydride was added and mixed intensively for 1 min, then extracted with 0.5 mL hexane, vortexed for 15 s, and centrifuged at 6000 rpm for 7 min. Then, 0.4 mL of the supernatant was removed, and 1 \(\upmu\)L of it was injected into the GC system. The injector temperature was 250 \({}^{\circ}\)C, and the procedure was operated in splitless mode. The starting temperature in the oven was 50 \({}^{\circ}\)C with a hold time of 3 min. The temperature was increased at a rate of 20 \({}^{\circ}\)C/min to 135 \({}^{\circ}\)C, then at a rate of 1.5 \({}^{\circ}\)C/min to 166 \({}^{\circ}\)C, then at 5 \({}^{\circ}\)C/min to 205 \({}^{\circ}\)C, and subsequently at a rate of 40 \({}^{\circ}\)C/min to 270 \({}^{\circ}\)C, where the temperature remained constant for 12.6 min. The total run time was 49.942 min. The mass spectrometer was operated in selected ion monitoring (4-ethylphenol: quantifier: 107; qualifier: 122/178; retention time 19.058 min; 4-ethylguaiacol: quantifier: 152, qualifier: 137/208, retention time 27.191 min; 4-ethylcatechol: quantifier: 138, qualifier 123/1974, retention time: 35.825). The calibration was performed in a calibration wine (red wine vintage 2018; sensory inconspicuous, 150 mg/L free SO2) in the steps 12.5 \(\upmu\)g/L, 25 \(\upmu\)g/L, 250 \(\upmu\)g/L, and 500 \(\upmu\)g/L per compound. Table 1 shows the calibration and validation data. The limit of detection (LOD) and the limit of quantification (LOQ) were estimated from the peak area to noise ratio. Reproducibility was determined by repeating a red and a white wine four times, and the average relative standard deviation was calculated.