The nose knows: as few as three compounds encode food smells

While foods contain more than 10,000 different volatile substances, only between three and 40 of these key odours are responsible for encoding the typical smell of an individual foodstuff, research from Germany has revealed.

Scientists from Technische Universität München (TUM) and the German Research Center for Food Chemistry (DFA) carried out a meta-analysis of the odorant patterns of 227 food samples. The compounds that encode the typical smell of a strawberry, for instance, are decoded by around 400 olfactory receptors in the nose.

The researchers were surprised to find that the almost unlimited variety of food smells is based on just 230 key odorants. In addition, each foodstuff has its own odour code which comprises a core group of between three and 40 of the 230 key odorants, in specific concentrations.

“So, for example, the smell of cultured butter is encoded by a combination of just three key molecules, but fresh strawberries have 12,” explained Professor Peter Schieberle, the TUM Chair of Food Chemistry.

Cognac reportedly has the most complex odour profile of all the foods tested: its smell is attributable to 36 key molecules.

When people perceive external chemical odour patterns and process them in the brain, the individual odour components do not just add up. Rather, the individual olfactory notes are translated into a new odour identity.

“In view of the chemical odour code combinations possibilities and the 400 or so different olfactory receptors, it appears that there is a more or less unlimited number of discernible odour qualities,” said Professor Schieberle.

So far, scientists have identified 42 receptors that respond to food odours - with the majority binding multiple odour molecules.

“By mapping the odorous substances of the 230 currently known key odours, scientists can test which receptor combinations are ‘reserved’ for food odours,” said Professor Dr Thomas Hofmann, the TUM Chair of Food Chemistry and Molecular Sensory Science.

“This will help us explain the biological relevance of odours in even greater detail.”

These findings lay the scientific groundwork for the next generation of aroma products, which use the potential of optimised biosynthetic pathways in plants for industrial-scale production of high-quality food odorants, the researchers say.

The odorant mapping process will also enable more precise natural simulation of odours. According to the researchers, this brings us closer to new applications in mobile communication systems such as sending olfactory messages by smartphone or even bioelectronics noses.

The researchers’ findings are presented in chemistry journal Angewandte Chemie.