Seeing the smell of garlic: Detection of gas phase volatiles from crushed garlic (Allium sativum), onion (Allium cepa), ramsons (Allium ursinum) and human garlic breath using SESI-Orbitrap MS.

Allicin is the main flavour component of crushed raw garlic. This plant defence molecule has strong antibiotic properties. While measurements in the liquid phase using LC-MS are established, accessing reactive organosulfur compounds in the gas phase is still a challenge due to heat-degradation in the gas chromatograph. Using a gentle secondary electrospray ionisation coupled Orbitrap mass spectrometry procedure (SESI-Orbitrap MS), we measured gas phase concentrations of allicin evaporating from a pure solution. Despite the mild conditions, two quantitatively major allicin-derived breakdown products were found. The SESI-Orbitrap MS technique was used to follow the known chemistry of alliin, isoallin and methiin conversion in garlic, onion and ramsons. Allicin and its metabolites were also measured over two hours in human breath after garlic consumption. These results demonstrate the utility of SESI-Orbitrap MS for analysis of sulfur-containing volatiles from plants in the genus Allium and potentially for capturing volatilomes of foodstuffs in general.