An incredible ability
The nose contains, on average, 30 million olfactory cells, which are able to distinguish an incredible amount of odours and aromas. We all perceive a different number of odours based on our innate abilities and on what we learn.
Almost all odours are complex combinations of hundreds of different molecules. Coffee, for example, comprises around 800 olfactory substances.
The brain does not identify all the molecules that travel through the nose; often only a few substances enable us to distinguish a specific odour. Isoamyl acetate, for example, smells like bananas, and ethylvanillin smells like vanilla.
Compared to primates and higher order mammals, over the course of evolution, we have deactivated two thirds of the genes in our olfactory receptors. We only have 350 genes left to produce the functional receiver proteins that enable us to smell. This is still more than enough.
Is a sense of smell important?
Our sense of smell is essential to really enjoy our food! For example, when you eat, if you close your eyes and pinch your nose while eating, it is really difficult to tell the difference between a potato and a carrot.
Have you ever noticed that, if you have a cold and your nose is blocked, food all seems to have much the same taste?
Why do odours trigger emotions and memories?
Odours can spark distant memories, reminding you, for example, of a meal you ate. This phenomenon may be because the olfactory brain is connected to other parts of the brain that analyse emotions and memories.
Odours are associated with our experiences and emotions. We all have different favourites. These preferences may change with time and experience.