Maize ( Zea mays) grains were obtained from the Agricultural Research Council (ARC Grain Crops), Potchefstroom, South Africa (26°43′31.0″S 27°04′53.8″E). The grains were milled (Perten Laboratory Mill 3310, Perten Instruments AB, Helsinki, Finland) and the resulting maize flour was mixed with sterile distilled water (1:1, v/w) and spontaneously fermented at 35 ^oC (Incotherm, Labotec, Johannesburg, South Africa) for 24, 48 and 72 h. Each fermentation process was done in triplicate.

The volatilome analysis was carried out at the University of Johannesburg (Doornfontein Campus), Johannesburg, South Africa (26 ^o11′32.6″S 28 ^o03′28.9″E). Five grams (5 g) of the respective sample was loaded into amber headspace vials (Restek, Bellefonte, USA). The vial was heated and incubated at 40 ^oC for 20 min with intermittent agitation on and off for 10 and 1 seconds (s), respectively, at 250 rpm. Subsequently, sampling was done by exposing the 50/30 μm SPME fiber coated with divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) (Supelco, Inc., Bellefonte, USA) at 54 mm injection penetration vial depth for 20 min. The extracted volatiles were analyzed on a GC-HRTOF-MS system (Agilent 7890A gas chromatograph, Agilent Technologies, Inc., Wilmington, DE, USA and LECO Corporation, St. Josheph, MI, USA), equipped with a Gerstel MPS multipurpose sampler (Gerstel Inc. Mülheim an der Ruhr, Germany) and Rxi ^®-5 ms column (30 m × 0.25 mm ID × 0.25 μm) (Restek, Bellefonte, USA). The extracts were injected in a spitless mode and desorped for 60 s, with helium as the carrier gas. Inlet and transfer line temperatures were set at 250 and 225 ^oC, respectively, and the ion source temperature was 250 ^oC. The oven temperature cycle used was: initial temperature of 30 ^oC for 0.5 min; then an increase of 10 ^oC/min to 220 ^oC held for 0.5 min; then ramped to 270 ^oC for the fiber at 43 mm penetration to ‘bake-out’ for 5 min pre-and post-bake out times. Experiments for blanks were also conducted to observe possible impurities and contamination. To identify the metabolites, spectra were matched with the National Institute of Standards and Technology (NIST), Mainlib and Feihn reference library databases, and their identities were determined. To process raw data, parameters such as signal-to-noise ratio of 100, similarity match above 70% and the occurrence of metabolites at least two times out of the triplicate data were strictly adopted ( Achi & Asamudo, 2019). The raw and processed data ( Adebo et al., 2022a, 2022b) provides information on the volatilome of maize and derived fermented products at different fermentation periods (24, 48 and 72 h). The retention time, observed mass, average peak area and volatilome class of each compound are presented in Table 1. The compounds were also classified and the percentage distribution is shown in Figure 1.

Mendeley Data: Raw SPME-GC-HRTOF-MS data and spectra of maize and sourdough volatilome. https://data.mendeley.com/datasets/kytshjccrc/2 ( Adebo et al., 2022a).

This project contains the following underlying data: -

Maize and Fermented Maize Volatilome SPME-GC-HRTOF-MS Spectra Data.pdf (Mass spectra of compounds from maize and fermented maize volatilome, obtained using solid phase microextraction coupled with a gas chromatography-high resolution time of flight-mass spectrometry (SPME-GC-HRTOF-MS))

University of Johannesburg’s Open Access Data Repository: UJ Research Data. https://doi.org/10.25415/ujhb.20223447.v1 ( Adebo et al., 2022b).

This project contains the following underlying data: -

(SPME-GC-HRTOF-MS dataset of fermented maize flour volatilome) (The raw dataset (.MZML) of compounds from maize and fermented maize volatilome, obtained using SPME-GC-HRTOF-MS). WM0H (unfermented maize); WM24H – sourdough fermented for 24 h; WM48H – sourdough fermented for 48 h and WM72H – sourdough fermented for 72 h

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).