People will often say they can’t taste anything, but understanding how the senses work together can help you on the road to improving your enjoyment of food.
Smell + Taste = Flavour
Taste We use 'taste' in two ways; one to refer to gustastion or 'true taste' which registers the sweet, salty, bitter, sour, and umami elements of foods. The true taste receptors are distributed on the tongue and the mouth has other receptors also on the inside surfaces of the mouth that perceive other sensations like creaminess. This remains as long as there is no impairment to the gustatory nerve. When smell is gone, often people begin to crave the true tastes of salt and sweet.
The other kind of taste, which we mean when we say "this tastes soooo good" is something else. The combination of the true taste signals and the smell of food, perceived orthonasally, together make a different perception: flavour. But because this all comes together in the mouth, we say "taste"--something English shares with other languages also.
Smell is the process by which we experience and interpret odour molecules. This happens in the brain from signals transmitted by the olfactory epithelium. Odour molecules reach the olfactory epithelium by two pathways: through the nose, and also through the back of the throat when we eat.
So smell and taste combined is what we perceive to be flavour.
There are two ways to smell. One is through the nostrils-easy. The second way to smell is retronasally: through chewing and swallowing. When you chew, you release volatile molecules in the food, which bounce around inside your mouth. When you swallow, the action of the soft palate and throat forces the food down into your gullet, but some of that air, now full of volatile molecules, travels up to the nose via the retronasal pathway. Look into a mirror and locate your uvula (that thing dangling in the back). The passage way is behind this.
Your brain puts the received information from the tongue (true taste) and retronasal olfaction together and then recognises the flavour of the food.
Chrissi, our founder, adds: "I would try to use different words than 'smell' and 'taste' because both of these words have many uses and this confuses the issue. If I ask you if you can smell something, do I mean "are you able to pick up any sort of smell signal when you put this to your nose?" or I could also mean "when you smell this, do you know what this is"?
"Those are two entirely different questions. One depends on a functional sense of smell (even with hyposmia or parosmia), for the other, you need a good sense of smell to recognise the perception. So when I explain I try to keep things clear by steering as far away from conventional use of smell and taste as possible."
And there’s more
Our sense of touch also comes into play as we enjoy food. We think of touch as through the finger-tips, but the sensation of touch in our mouth is an important part of the eating experience. Crunchy, chewy, soft and melty - the perception of texture is integral to enjoyment. Soft potato crisps, anyone?
And finally, the trigeminal nerve completes the picture. This is the largest of the cranial nerves and links eyes, nose and mouth to transmit sensory information to the brain, but also signals that activate muscles and glands. The trigeminal nerve detects the temperature of food, reacts to stimulants like eye-watering, nose-clearing wasabi or notes the cool tingle of peppermint.
Focus on what’s there
Tests to measure what senses are functional and what may be reduced or missing are only really available in research settings at the moment. You have to be your own Sensory Detective and investigate what's happening in your mouth. Next time you eat, think about which senses are doing their job and focus on what you can experience rather than what you can’t.
Thanks to Barry Smith and Alexander Fjaeldstad who are leading research in the perception of our senses. Watch our webinar on Smell, Taste and Flavour for a full insight.