The Senses – Smell
Our sense of smell – and how we eat with our nose, too
The smell of freshly baked bread at the bakers next door, or a pizza in the oven – these can really stimulate our taste buds. Alongside taste, hearing, touch and sight, smell is one of the five senses with which we experience food.
We perceive smells through our nose, via the fragrances that enter together with the air we breathe in. This is known as orthonasal olfaction. When we breathe in, a series of rapid chemical processes takes place in our nasal mucosa to enable us to perceive a given smell. This takes place through receptors, i.e. cells that are located in the nasal mucosa and bind fragrances. They pass on an impulse to various centres in the brain. In addition to this orthonasal olfaction, we also perceive fragrances retronasally, in this case via the oral cavity. When we chew, fragrances pass to the corresponding receptors by means of a direct connection between the pharynx and the inner nasal cavity, and these receptors then in turn serve to aid perception as in the case of orthonasal olfaction. Therefore, we perceive the smell of food both directly through our nose and indirectly through our mouth.
Even when we think we are tasting something, 80% of the time we are actually perceiving it through our nose - i.e. we are actually smelling it. Our noses can distinguish between countless smells and fragrances, far more than the number of flavours we can tell apart using our sense of taste. There are almost 20,000 different smells, each with at least 10 levels of intensity. We do not perceive every individual fragrance emitted by a food or a dish - the aroma of coffee, for example, is composed of some 800 different aromatic substances.
Our sense of smell is thus particularly important when it comes to enjoying food or a meal, as smell and taste are closely related and bear joint responsibility for our experience of taste. Perhaps you can remember the last time you had a cold, when your nose was blocked and you lost your sense of smell? In cases like these, food suddenly becomes bland, with the taste leaving something to be desired. This side-effect is a good illustration of the importance of smell in our experience of taste.
Impressions of taste that arise through our sensory perception remain stored in our memories, and can often remind us of past taste experiences for a long time to come. Over the course of our lives, we will smell many dishes that take us back to our childhood. Negative memories can also be aroused, such as a sense of revulsion caused by spoiled fish, rancid oil or rotten fruit. As such, our sense of smell also serves as an inbuilt protection mechanism.
Büttner, A.: Spaß an Essen und Trinken –Retronasale Geruchswahrnehmung. Nachrichten aus der Chemie 52 (2004) 540 - 543
European Food Information Council (EUFIC; Hrsg.): Eine Frage des Geschmacks. Food Today 11/2000. www.eufic.org
Frasnelli, J.; Hummei, T.: Neue Techniken zur Darbietung ortho- und retronasaler Duftreize. Die Ernährung – Nutrition. 12, 2007
Thews, G. et al.: Anatomie, Physiologie, Pathophysiologie des Menschen. Wissenschaftliche Verlagsgesellschaft, 2007