Optimising the identification of key odourants in food

The isolation of the volatile fraction from food and beverages is a big challenge, particularly for flavour chemists. In the past 20 years, solvent extraction followed by solvent-assisted flavour evaporation (SAFE) has become the standard approach, particularly prior to GC–olfactometry. However, the manual valve of the SAFE equipment can lead to suboptimal yields and the risk of a contamination of the volatile isolate with non-volatiles.

A research team from the Leibniz Institute for Food Systems Biology at the Technical University of Munich (LSB) has now automated this established method for the gentle, artifact-avoiding isolation of volatile food ingredients by replacing the manual valve with an electronically controlled pneumatic valve. The team’s study has shown automated solvent-assisted flavour evaporation (aSAFE) can offer advantages over the manual process by achieving higher yields on average and reducing the risk of contamination by nonvolatile substances.

The optimised method is particularly important for odourant analysis.

Odourants contribute significantly to the sensory profile of food and have a major influence on eating pleasure. Knowing the key odourants that shape the aroma of a food is therefore of interest both for analytical quality control and for targeted product development in the food industry.

The manual SAFE technique developed in 1999 made it possible for the first time to easily isolate even thermally labile odourants from food without artifact formation. “This is an important prerequisite for using further analytical methods to identify the key odourants,” said Philipp Schlumpberger, who contributed equally to the study with Christine Stübner.

The manual SAFE is established as a standard procedure in aroma research. Nevertheless, the research team saw a need for its optimisation.

“As we discovered, the problems are mainly associated with the manual operation of the valve on the dropping funnel. Therefore, we replaced it with an electronically controlled pneumatic valve. To fully automate the SAFE apparatus, we optionally extended it with an automatic liquid nitrogen refill system as well as an endpoint detection and shutdown system,” explained Martin Steinhaus, principal investigator, and section and working group leader at LSB.

The installation of the automatic valve increased yields, particularly for lipid-rich food extracts and for odourants with comparatively high boiling points. In addition, operator errors, which can lead to contamination of isolates with nonvolatile substances in the manual version, can be eliminated with the aSAFE.

“In the meantime, automated SAFE has replaced the manual variant in our laboratories. Other academic and industrial research groups are already following our example,” Steinhaus said.

_{Philipp Schlumpberger, Christine A. Stübner, Martin Steinhaus. Development and evaluation of an automated solvent-assisted flavour evaporation (aSAFE). European Food Research and Technology, 2022; DOI: 10.1007/s00217-022-04072-1}

Image credit: ©stock.adobe.com/au/Gorodenkoff