## 4 Materials and Methods
### Determination of Chromatic Characteristics According to CIELab  
The colour of the wine was evaluated using tristimulus colorimetry, based on transmittance spectra using equations proposed by the International Commission of Illumination (CIE). The wine was clarified by centrifugation (15 min, 5000 rpm, MPW 350R centrifuge) and the absorption spectrum was measured (380-770 nm, CM-5 spectrophotometer, Konica Minolta, Tokyo, Japan). The CIELab parameters were calculated. Coordinate L* represents a perceptual brightness, ranging from 0 (black) to 100 (white), while a* and b* are chromatic coordinates. The a* value is relative to the green/red colour component, with negative values toward green (\(-\)100) and positive values toward red (+100), while the b* value represents the blue/yellow colour component, with negative numbers toward blue (\(-\)100) and positive toward yellow (+100) [73]. Analysis of the Volatile Compounds Profile of Apple Wines-SPME-GC-MS (Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry)  
About 2 mL of a saturated saline solution mixed with an internal standard solution (4-methyl-2-pentanol at 5 mg/L and ethyl nonanoate at 0.05 mg/L, sourced from Sigma-Aldrich, Saint Louis, MO, USA) and 0.05 mL of the wine sample were combined in a 10 mL vial. Initially, the SPME device from Supelco Inc. (Bellefonte, PA, USA), coated with a PDMS (100 \(\upmu\)m) fibre, was preconditioned by heating it in the GC injector port at 250 \({}^{\circ}\)C for one hour. The fibre was then exposed to the sample's headspace, with stirring at 300 rpm for 30 min at 40 \({}^{\circ}\)C. Subsequently, the SPME device was inserted into the injector port of an Agilent Technologies 7890B chromatograph system, equipped with a LECO Pegasus HT High-Throughput TOFMS and held in the inlet for 3 min. The GERSTEL MultiPurpose Sampler (MPS, GERSTEL Inc., Linthicum, WA, USA) facilitated the SPME procedure. Volatile compounds were separated using an Rtx-1 ms cross-bond 100% dimethyl polysiloxane capillary column (30 m \(\times\) 0.53 mm \(\times\) 0.5 \(\upmu\)m), with the detector temperature set at 250 \({}^{\circ}\)C. The temperature of the column was initially set at 40 \({}^{\circ}\)C for a period of 3 min, after which it was increased at a rate of 8 \({}^{\circ}\)C per minute until it reached 230 \({}^{\circ}\)C, where it was maintained for a further 9 min. The flow of helium was maintained at 1.0 mL/min. The electron impact mass spectra (EIMS) energy was established at 70 eV, with the ion source and connection parts heated to 250 \({}^{\circ}\)C. The analytes were transferred in splitless mode, and the mass storage device (MSD) operated in SIM mode for m/z = 30 to m/z = 300. Volatile compounds were identified through mass spectral libraries and linear retention indices (LRIs), computed from a series of n-alkanes (C6 to C30). A semi-quantitative analysis was executed by measuring the relative peak area of each identified volatile compound using the NIST database, with the internal standard serving as a reference. The table also includes the thresholds for each compound as specified in the literature [29]. The odour activity value (OAV) is commonly used to determine the \"weight\" of an odorant's perception. This value is calculated by dividing the abundance of the odorant molecule by its odour detection threshold. Values greater than 1 mean that the volatile compound can be perceived and are highlighted in green in the table. The Examination of Volatile Substances by GC-FID-O (Gas Chromatography-Flame Ionisation Detector with Olfactory)  
The identification and analysis of aroma-active volatile compounds in wines were performed using olfactory techniques with a Hewlett Packard 5890 Series II chromatography system. All samples of wines matured in the presence of woodchips and in barrels were analysed in a minimum of three physical replicates. A mixture containing 2 mL of the wine sample and 1 g of NaCl was placed into a 10 mL vial.