Vacuum-assisted HS-SPME/GC×GC-MS to enhance the volatile chromatographic fingerprint of commercial dark chocolate

Background: This study explored the potential of vacuum-assisted headspace solid-phase microextraction (Vac–HS–SPME) coupled with two-dimensional gas chromatography mass spectrometry for the evaluation of the volatile profiles of dark chocolate samples. Comparative analyses between Vac- and classic HS-SPME sampling were performed at different sampling times. To simulate the release of volatile compounds during human con sumption and the possible synergistic effect with Vac, experiments were carried out at the physiological tem perature (37 ◦ C) on powdered chocolate alone and with the addition of salty water as surrogate saliva. Results: Overall, Vac–HS–SPME showed higher extraction efficiencies of the overall profile, and based on the area of nine key odorant volatiles compared to classic HS-SPME. The addition of salty water showed an increased extraction yield comparable to the effect of vacuum. When the addition of salty water was then under Vac–HS–SPME conditions, the increase in extraction yield was proportionally higher. The different combined conditions, i.e., salty water or not, and HS-SPME and Vac–HS–SPME were compared in a complete untargeted way, exploiting the structured information provided by the two-dimensional plot generated using comprehensive two-dimensional gas chromatography (GC × GC) coupled to a quadrupole mass spectrometer. Additionally, the volatile profiles of the dark chocolates tested were compared selecting nine key aroma compounds. Novelty: This work explored for the first time the combined effect of vacuum and the addition of salty water simulating saliva on the overall volatile profile. The two-dimensional plots generated by GC × GC were treated as chromatographic fingerprints, building for the first time what we called an “improvement plot” showing the zone of increment corresponding to specific chemical classes.