## Materials and Methods
### GC\(\times\)GC-ToFMS Analysis  
The GC\(\times\)GC-ToFMS experimental parameters were adapted from [PERSON] et al. (2020) [65]. The equipment used was a LECO Pegasus 4D GC\(\times\)GC-ToFMS system (LECO, St. Joseph, MI, USA) consisting of an Agilent GC 7890A gas chromatograph (Agilent Technologies, Inc., Wilmington, DE, USA) with a dual-stage jet cryogenic modulator (licensed from Zoex) and a secondary oven, and a mass spectrometer equipped with a time-of-flight (ToF) analyzer. The SPME fiber was manually introduced into the port at 250 \({}^{\circ}\)C for analyte desorption. The injection port was lined with a 0.75 mm I.D. glass liner. Splitless conditions (30 s) were used. An Equity-5 30 m \(\times\) 0.32 mm I.D., 0.25 \(\upmu\)m film thickness (Supelco, Bellefonte, PA, USA) was used as a first-dimension column (\({}^{1}\)D), and a DB-FFAP 0.79 m \(\times\) 0.25 mm I.D., 0.25 \(\upmu\)m film thickness (J&W Scientific Inc., Folsom, CA, USA) was used as a second-dimension column (\({}^{2}\)D). The carrier gas was helium at a constant flow rate of 2.50 mL min\({}^{-1}\). The primary oven temperature was programmed from 35 \({}^{\circ}\)C (5 min) to 230 \({}^{\circ}\)C (2 min) at 10 \({}^{\circ}\)C min\({}^{-1}\), and the secondary oven program was 30 \({}^{\circ}\)C offset above the primary one. The MS transfer line and MS source temperatures were set at 250 \({}^{\circ}\)C. The modulation period was 5 s, keeping the modulator at 20 \({}^{\circ}\)C offset above the primary oven, with hot and cold pulses by 0.80 and 1.70 s, respectively. The mass spectrometer ran in the EI mode at 70 eV and detector voltage of -1530 V, using an _m/z_ range of 35-350. In an initial approach, the total ion chromatograms were processed using the automated data processing software ChromaTOF (LECO) at the S/N threshold of 100. The obtained GC\(\times\)GC total ion chromatogram contour plots exhibited more than 1200 peaks. As the present study focused on the compounds mainly produced during baking, in a second approach, all the compounds belonging to the characteristic chemical families associated with the Maillard and caramelization reactions were selected. In addition, the volatile compounds described in the literature as key aromas of bread or maize-based foods and which were not detected using the automated data processing (S/N \(<\) 100) were searched on the chromatograms based on extracted ion chromatogram contour plots of the characteristic ions, and the corresponding peak areas were also included. For identification purposes, the mass spectrum and retention times (\({}^{1}\)D and \({}^{2}\)D) of the analytes were compared with the mass spectral libraries, namely an in-house library of standards and two commercial databases (Wiley 275 and US National Institute of Science and Technology (NIST) V. 2.0-Mainlib and Replib). Additionally, the linear retention index (LRI) was experimentally determined according to the van den Dool and Kratz LRI equation [84]. A C\({}_{8}\)-C\({}_{20}\)_n_-alkane series was used for LRI determination (the solvent _n_-hexane was used as the C\({}_{6}\) standard). These values were compared with those reported in the literature for chromatographic columns similar to the \({}^{1}\)D column mentioned above. A positive identification was considered when the experimental spectra shared at least an 80% similarity with spectra from the software libraries and the LRI deviation was less than 5%. This difference in LRI takes into account that (i) the literature data are obtained from a large range of GC stationary phases (several commercial GC columns are composed of 5% phenylpolysilphenylene-siloxane or equivalent stationary phases), and (ii) the modulation causes some inaccuracy in the first dimension retention time, and the majority of the values reported in the literature were determined in a 1D-GC separation system [64]. The Log \(p\) values were calculated using ALOGPS 2.1 to confirm the identification of some compounds which did not match all the criteria described above [85].