## 2 Materials and Methods
### Aroma Compound Analysis  
Stock solutions of 15 aroma compounds and internal standard with a concentration of 200 mg/L were prepared in HPLC-grade ethanol. Working solutions were prepared by dilution with MilliQ water. Harvested fruit samples were immediately frozen in liquid nitrogen and stored at \(-80\)\({}^{\circ}\)C. Prior to analysis, the fruit was powdered in liquid nitrogen with a blender (IKA), with each sample representing the homogenised powder of 10 fruits. Samples were incubated at 30 \({}^{\circ}\)C for 5 min, and then the extracts were prepared. 3 g of NaCl was placed in a 20 mL Solid Phase Microextraction (SPME) vial, followed by 0.1 g of homogenised sample (to determine 2-heptanone, cis-2-hexen-1-ol, geraniol, hexanal, octyl acetate, trans-2-hexen-1-al and trans-2-Hexen-1-ol) or 0.5 g of homogenised sample (for the rest of the aroma compounds). Then 6.5 mL (when 0.5 g of sample was used) or 6.9 mL (when 0.1 g of sample was used) of deionised MiliQ water and 100 \(\mu\)L of deuterated analytical standard d3-\(\alpha\)-terpineol (internal standard) with a concentration of 400 \(\mu\)g/L was added. The vial was closed and shaken to dissolve the NaCl. Three technical replicas were performed for each sample. The samples were analysed using a gas chromatograph (GC, Agilent Technologies 7890A, Shanghai, China) equipped with a Gerstel MPS2 multipurpose sampler (Gerstel, Mulheim an der Ruhr, Germany) and column, a DB-WAX (Agilent Technologies, 30 m, 0.25 mm i.d., 0.25 \(\mu\)m film thickness) with a constant flow of helium at 1.5 mL/min. The vial was incubated for 10 min at 30 \({}^{\circ}\)C. SPME on PDMS/DVB fibre (Supelco, Bellefonte, PA, USA) was performed for 40 min at 30 \({}^{\circ}\)C with constant stirring at 350/min. The GC injector was held at 220 \({}^{\circ}\)C for 3 min for the analytes to desorb from the fibre. The GC oven was programmed as follows: 40 \({}^{\circ}\)C for 10 min, from 40 to 220 \({}^{\circ}\)C at 4 \({}^{\circ}\)C/min, held at 220 \({}^{\circ}\)C for 15 min. To determine analytes, a mass spectrometer (MS, Agilent Technologies 5975C, upgraded with a triple-axis detector, Palo Alto, CA, USA) was used. The temperature of the ion source was 200 \({}^{\circ}\)C, the auxiliary temperature was 220 \({}^{\circ}\)C, and the quadrupole temperature was 150 \({}^{\circ}\)C. For qualitative determination, retention time and mass spectrum in selective ion monitoring mode (SIM) were used. The ions, scanned in SIM, are presented in Table 1. For the internal standard, the ions scanned in SIM were 62 (target ion), 124 (qualifier ion 1), 139 (qualifier ion 2) \(m/z\). For quantitative determination, the peak area of the target ion was used. Linearity was verified by using standards in water solution, which were also used for calibration. Linearity was checked using 5-10 concentration levels and five repetitions at each level. Linearity and range were determined by multiple linear regressions, using the F test. According to the guidelines for single-laboratory validation [28] R2 should be \(\geq\)0.96. The limit of detection (LOD) and the limit of quantification (LOQ) were determined at an S/N ratio of at least 3 and 10, respectively. In cases where the concentrations in samples were high, they were set much higher. To determine precision [29], namely repeatability and reproducibility, two spiked samples of strawberries and two unspiked samples of strawberries were analyzed within a period of 10 days. The standard deviation of repeatability (r) of the level and the standard deviation of reproducibility (R) of the level were both calculated. The uncertainty of repeatability and uncertainty of reproducibility were calculated by multiplying the standard deviation of repeatability and standard deviation of reproducibility by Student's t factor with 9 degrees of freedom and a 95% confidence level (95;9 = 2.262). Accuracy was verified by checking the recoveries. Ten spiked samples of strawberries and ten unspiked samples of strawberries were analyzed within a period of one day.