Analyzing odorants without artifacts

Odorants are volatile compounds that contribute significantly to the sensory perception of food and therefore have a decisive influence on consumers' purchasing decisions. However, analyzing them is a challenging task. In science and research, gas chromatography-olfactometry has established itself as an indispensable method for identifying odor-active compounds and distinguishing them from the majority of odorless volatile substances.

In this method, researchers separate the individual volatile substances, previously isolated from the food as gently as possible, by using a gas chromatograph and sniff the effluent to determine which compounds smell and which do not.

Two sources of artifacts

In general, artifacts can arise during both the isolation and the analysis of volatile compounds. "The formation of artifacts during sample preparation has been well studied and can now be minimized to a large extent. Automated Solvent-Assisted Flavor Evaporation, in whose development our research group played a major role, has proven to be very effective," explains principal investigator Martin Steinhaus: "However, the formation of artifacts during sample injection has been largely underestimated, partly due to the lack of meaningful comparative data."

Julian Reinhardt, first author of the study, therefore examined ten different injection methods using 14 test compounds. As the doctoral student's research shows, high injection temperatures in particular led to odor-active artifacts and thus have the potential to significantly distort odorant analyses.

Gold standard on-column injection

"On-column injection proved to be particularly reliable because the sample is not exposed to high temperatures," reports Martin Steinhaus, who heads the Food Metabolome Chemistry research group at the Leibniz Institute. "In contrast, splitless injection at high temperatures showed significant artifact formation, especially in combination with headspace solid-phase microextraction," the food chemist continues. He recommends using on-column injection in all cases to obtain a reliable and representative odorant spectrum of a food.