The nose can decipher between a straight-out-of-the-oven baked cake and freshly brewed coffee with one sniff, but how? German researchers, who published their findings in the journal of Technische Universitaet Muenchen, narrowed up to 40 key odors that are responsible for decoding smells of individual foods.

Food contains more than 10,000 different smells, but only about 227 of them contribute to the actual odor that comes from the foods we eat. It is already well-known that how we taste something is accompanied by the smell. Scientists from Technische Universität München (TUM) and the German Research Center for Food Chemistry (DFA) evaluated 227 food samples and how it interacts with the five basic tastes of the tongue’s palate: sweet, bitter, salty, sour, and umami.

"So for example, the smell of cultured butter is encoded by a combination of just 3 key molecules, but fresh strawberries have 12," said Peter Schieberle, a professor and chair of food chemistry at TUM.

They discovered there was a seemingly limitless variety of food smells they could construct by using just the 227 key odors. There are 42 taste receptors that respond to food odors and a majority of them actually bind the odor molecules. Cognac, a popular brandy among more drinkers with a more sophisticated palate, has the most complex smell of them attributable to 36 key molecules.

"A combination of between just few key odorants creates an authentic perception of odors. This is all the more surprising given that the olfactory quality of the combinations is not determined by the individual components," said co-author Thomas Hofmann a professor at TUM Chair of Food Chemistry and Molecular Sensory Science.

Each time a smell crosses our path, the olfactory receptor of neurons in the brain processes the odor, which creates a pattern. The researchers watched the patterns each smell formed and found certain ones wouldn’t add up inside the receptors. When a new odor is identified, it’s logged into the brain as a new combination of olfactory notes.

"By mapping the odorous substances of the 230 currently known key odors, scientists can test which receptor combinations are 'reserved' for food odors," Hofmann said. "This will help us explain the biological relevance of odors in even greater detail."

Source: Dunkel A, Steinhaus M, Hofmann T, et al. Nature’s Chemical Signatures in Human Olfaction: A Foodborne Perspective for Future Biotechnology. Angewandte Chemie International Edition. 2014.