Human nose can smell about 10 basic types of odour, scientists, including one of Indian-origin, have found.
Researchers have used a mathematical method to identify 10 basic aromas that the nose can smell: fragrant, woody/resinous, fruity (non-citrus), chemical, minty/peppermint, sweet, popcorn, lemon and two kinds of sickening odours: pungent and decayed.
While taste can be classified into five flavours that we sense, it was unclear how many odours humans can smell.
There are likely about 10 basic categories of odour, according to research by Jason Castro from Bates College, Chakra Chennubhotla from the University of Pittsburgh, and Arvind Ramanathan from Oak Ridge National Laboratory.
The researchers used advanced statistical techniques to develop an approach for systematically describing smells.
Working with a standard set of data, Andrew Dravniek's 1985 Atlas of Odor Character Profiles, the researchers applied a mathematical method to simplify the olfactory information into coherent categories, similar to the way compressing a digital audio or image file reduces the file's size without, ideally, compromising its usefulness.
"It's an open question how many fundamental types of odour qualities there are," said Castro.
"This is in striking contrast to olfaction's 'sister sense', taste, where we know that five basic qualities seem to organise sensations," he said.
In ongoing work, the researchers are now approaching the problem from the other direction, applying the current research to a bank of chemical structures in an attempt to predict how a given chemical is going to smell.
"That's something that nobody's really done with any kind of compelling accuracy. And obviously perfume companies, flavour and fragrance companies, are really interested in doing that well," Castro said.
"This study supports the idea that the world of smells is tightly structured, and organised by a handful of basic categories," he said.
The study was published in the journal PLOS ONE.