Organization of these odors on a logical scale was a challenge presented 100 years ago by Alexander Graham Bell as
‘The science of odor is unveiled using a “smell map” that measures smell, based on its perception by the brain.’
A new study led by Prof. Noam Sobel and his team, at Weizmann Institute of Science, succeeded in measuring the perception of a smell. This helps the scientists to predict the smell of a particular odorant just by their molecular structure.
The research may unveil the new era of technology, for example, adding the aromas of flowers or sea to the vacation pictures on social media. The smells can be designed digitally to reproduce whenever needed, similar to color metamers – a vision of Prof. David Harel, co-author of the study and Vice President of the Israel Academy of Sciences and Humanities.
For instance, color metamers are a set of different colors designed specifically to match the shade of the actual color perceived.
The team conducted a series of experiments where 202participants were asked to perceive nearly 95 pairs of aromatic blends, each comprising of 10 molecular components. The rating scale of the smells ranged from how similar the two molecules were to one another, to the extreme difference among them. At the end of the study, 49,788 perceptual odors were obtained.
The idea of the study was verified from data collected by Bushdid and colleagues from the lab of Prof. Leslie Vosshall at the Rockefeller Institute in New York.
Decoding the digital aromas
A physicochemical measure was used to convert these perceived odors into a mathematical/logical scale. Each odorant was represented by a single vector – that measures the physical and chemical properties of the molecule. The angle between the two vectors (or two odorants) presented the similarity between the two odors. The smaller the angle between the vectors, the more similar are their odors.
This led to the deduction of a reference value – 0.05 radians in the “smell map”. For example, if a new odorant compound is 0.05 radians or less than a rose, it will smell identical to a rose. Odorants beyond 0.05 radians to rose would differ in smell as the distance keep increasing.
“100 years ago, Alexander Graham Bell posed a challenge. We have now answered it: The distance between rose and violet is 0.202 radians (they are remotely similar), the distance between violet and asafoetida is 0.5 radians (they are very different), and the difference between rose and asafoetida is 0.565 radians (they are even more different). We have converted odor percept into numbers, and this should indeed advance the science of odor”, says Prof. Noam Sobel, The Head of the Azrieli National Institute for Human Brain Imaging and Research.
The study would open up digital platforms where computers can design and reproduce smells to interpret it in a way similar to humans. This aids in paving the ways to understand the molecular mechanism of smell perception and bring a revolutionary change in the environmental monitoring and biomedical & food industries.