Origin 2021b

The ATR-FTIR spectra were collected on an IRTracer-100 spectrophotometer. All spectra were measured between 4000 and 400 cm⁻¹ in the absorbance mode. The following spectrometer parameters were used: resolution: 4 cm⁻¹, the number of scans: 400, and apodization: Happ–Genzel. The sample was placed directly on the ATR crystal. Solid samples were pressed against the ATR crystal and the ATR-FTIR spectrum was scanned. LabSolutions IR software (version 1.86 SP2, Shimadzu, Kyoto, Japan) was used to calculate the second derivative of all spectra. The software performed calculations according to the Savitzky–Golay numerical algorithm. The smoothing parameter was 25 points. A derivative spectrum allowed us to identify the peak positions of the original spectrum and to separate multiple peaks, which were adjoining or on the shoulder. The minima of the second derivative corresponded to the extremes of the original ATR-FTIR spectrum. Origin 2021b (OriginLab Corporation, Northampton, MA, USA) was used to analyse the acquired data.

All data from independent triplicate fermentations (n = 3) were recorded as the average value ± standard deviation (SD). One-way ANOVA with Tukey’s post hoc test was conducted by SPSS^® 20.0 (Windows version, Chicago, IL, USA) to check the significant differences (p < 0.05) among samples. Heatmap was plotted by Heatmapper [19 (link)]. Principal component analysis (PCA) of selected aromatic compounds was performed by Origin 2021b (OriginLab Corporation, Northampton, MA, USA).

All measurements were repeated at least three times. Data were recorded as mean ± standard deviation and statistically analyzed for a significant difference (p < 0.05) by IBM SPSS statistics 26 (IBM, NY, USA). All curve fittings were applied by the program Origin 2021b (OriginLab Corporation, MA, USA).