OLFACTORY CELLS

Your nose is home to around 30 million olfactory cells. It is therefore able to distinguish a very large quantity of odours and aromas – many more than the tastes perceived by your tongue. Our olfactory cells are renewed every four weeks throughout our lives. They allow us to perceive thousands of odorous molecules, generally in very small amounts.

There is a threshold for detecting odorous molecules, but it varies greatly from person to person and molecule to molecule. We each perceive a different amount of odours depending on our innate capacities and our training. A trained and skilled nose can identify thousands of odours, such as jasmine, or animal secretions like musk or amber, traditionally used when making perfume.

keywords > Jasmine, musk, amber, vanilla, cinnamon, aniseed, etc.

Unlike colours, we find it hard to name what we smell. It is quite normal for an odour to remind you of something but to be unable to name or describe it.

ODOROUS MOLECULES

Nearly all of the odours in our environment are a complex mixture of hundreds of different molecules. For example, coffee is composed of around 800 olfactory substances.

keywords > Coffee aroma = 800 olfactory substances

However, often only a few substances are enough to characterise a precise odour. Isoamyl acetate smells like bananas and ethylvanillin smells like vanilla, for example.

The brain does not identify all of the molecules that enter the nose. Two good examples are oxygen and carbon dioxide, two odourless chemical compounds in the air we breathe. Unlike primates and higher mammals, over the course of evolution, we have deactivated two thirds of all the genes in our olfactory receptors. As a result, we only have 350 genes to produce functional receiver proteins. That said, in spite of their low number, they are still the most important family of genes, which proves the importance of our sense of smell and demonstrates just how wrong anyone is who thinks that smell is a secondary sense.

THE IMPORTANCE OF OUR SENSE OF SMELL

Smell is essential if you want to fully enjoy a meal or food. To realise how important your nose is, you simply have to wait for it to be blocked! If you close your eyes, a cold can prevent you from being able to tell even simple fruit and vegetables apart – even to differentiate between a potato and a carrot, for example.

Your tongue can always recognise the 5 basic tastes, but without the sensory abilities of your nose, eating is no longer a pleasure.

EMOTIONS AND MEMORIES

The olfactory brain is connected to the parts of the brain which analyse emotions and memories. This link is the reason why odours can bring back even distant memories. For example, can you remember the smell of some of the food you ate when you were a child? In his famous novel In Search of Lost Time Marcel Proust talks about how the madeleine he had with his tea reminded him of his past.

"When from a long-distant past nothing subsists, after the people are dead, after the things are broken and scattered, still, alone, more fragile, but with more vitality, more unsubstantial, more persistent, more faithful, the smell and taste of things remain poised a long time, like souls, ready to remind us, waiting and hoping for their moment, amid the ruins of all the rest; and bear unfaltering, in the tiny and almost impalpable drop of their essence, the vast structure of recollection."

This connection between odours and our memories can also explain why odours are appreciated in different ways by different people. You cannot say there are 'good' and 'bad' smells or odours. Each individual associates odours with their experiences and their emotions. We each have our favourites. These preferences are very varied and can change. You can also get used to and learn to love an odour.

In conclusion, we can also say that we start to learn odours from a very early age. It has been scientifically proven that some odours can be perceived by an embryo inside its mother’s womb. This may be at the root of some eating preferences.