## 2 Materials and Methods
### Analysis of Basic Fruit Wine Parameters
#### 2.4.3 Sample Preparation and GC-MS Analysis  
Headspace solid phase microextraction (HS-SPME) followed by gas chromatography mass spectrometry (GC-MS) was used for the investigation of the juices and apple wines after optimising the analytical procedure (details on method development not shown). For the analysis of volatiles from the apple juice, 10 mL of juice were mixed with 4 g of NaCl. An aliquot of 200 \(\upmu\)L was transferred into a 20 mL headspace glass vial. For the apple wines, 50 \(\upmu\)L of apple wine was transferred into a 20 mL headspace vial with the addition of 50 mg NaCl. In all cases, 2-octanol was added as an internal standard (10 ng absolute; Sigma-Aldrich, Vienna, Austria; purity \(\geq\) 98%). The extraction/enrichment of the volatiles was performed by headspace solid-phase micro extraction (HS-SPME) using a CTC Combi PAL sampler (CTC Analytics, Zwingen, Switzerland). A 50/30 \(\upmu\)m DVB/Car/PDMS 2 cm stable flex SPME fibre (Supelco, Bellefonte, PA, USA) was used for the enrichment of the volatiles. Prior to the extraction of the volatiles, the samples were equilibrated in the oven of the autosampler at 40 \({}^{\circ}\)C for 5 min, followed by a 20-min exposure of the SPME fibre to the headspace of the samples. Samples were stirred thoroughly during the equilibration and enrichment process. Immediately after the exposure, the fibre was transferred into the injector of the gas chromatographic system for thermo-desorption. The SPME fibre was left in the injection port for re-conditioning (20 min) before it was exposed to the headspace of the next sample. The GC-MS analysis was conducted on two GC columns of different polarities of the stationary phases. For both column types, GC-MS chromatograms were recorded on Shimadzu GC-2010 Plus, MS QP 2020 (Shimadzu Europa GmbH, Duisburg, Germany). For the semi-polar column (Rxi(r)-5 ms, 30 m \(\times\) 0.25 mm \(\times\) 1 \(\upmu\)m, Restek Corporation, Bellefonte, PA, USA) the following conditions were used: temperature program starting at \(-\)10 \({}^{\circ}\)C for 1 min with a temperature ramp of 8 \({}^{\circ}\)C min\({}^{-1}\) up to 280 \({}^{\circ}\)C (holding time 12 min). The injector temperature was 270 \({}^{\circ}\)C, splitless injection was applied. Special SPME liners (constant inner diameter of 0.75 mm) were used in the GC injection systems. Cryo-focussing by blowing liquid nitrogen into the GC-oven was applied to reach the start temperature of \(-\)10 \({}^{\circ}\)C with the aim of obtaining higher resolution and better peak shape for compounds with very high volatility. Helium was used with a linear velocity of 31 cm s\({}^{-1}\) (constant flow). The mass selective detection was performed in the scan mode (35-350 amu, EI (70 eV), interface temperature 270 \({}^{\circ}\)C, ion source temperature 230 \({}^{\circ}\)C). For the polar column (ZB-Wax Plus, 20 m \(\times\) 0.18 mm \(\times\) 0.18 \(\upmu\)m; Restek Corporation, Bellefonte, PA, USA) the following conditions were used: temperature program starting at 40 \({}^{\circ}\)C for 1 min with a temperature ramp of 8 \({}^{\circ}\)C min\({}^{-1}\) up to 240 \({}^{\circ}\)C (holding time 3 min). The injector temperature was 250 \({}^{\circ}\)C, splitless injection was applied. Helium was used with a linear velocity of 35 cm s\({}^{-1}\) (constant flow). The mass selective detection was performed in the scan mode (46-250 amu, EI (70 eV), interface temperature 200 \({}^{\circ}\)C, ion source temperature 220 \({}^{\circ}\)C). All samples were analysed threefold or fourfold in randomized order. Data deconvolution and integration of the deconvoluted peaks was performed with PARADISe software, based on the PARAFAC2 model [26; 27]. After the deconvolution procedure, the identification of the volatiles was based on probability-based matching of their mass spectra with those from MS libraries (NIST14, Adams Essential Oils library, FFNSC 3), authentic reference compounds and linear temperature-programmed retention indices.