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Both physiological and psychological factors come into play and in many cases, they cannot be separated. Take-for example- a fine wine drunk from a polystyrene cup; the shape of the cup will affect the perceived smell and flavour of the wine (physiological) and the material will affect the feel of the cup in the hand and on the lips (psychological).
Taste is one of the six senses (some say we have more), the others being touch, sound, sight, smell and proprioception, (the sense of "ourselves") our bodies own on-board computer.
The sense of taste can then be broken down into five basic categories. All of which happen in the mouth and nowhere else. These categories are salt, sweet, sour, bitter and Umami (the most recently identified taste named by Ikeda in Japan in 1908). There is a current theory that fat is actually a taste but this has yet to be proved.
We have up to 10,000 taste buds on the tongue and in the mouth. These regenerate so that the receptors that we use today will not be the same as were used a couple of days ago. Although different parts of the tongue can register different tastes, the classic drawing of the tongue showing it divided into different sections for the four different tastes (there were only four known at the time of this 19th century illustration) is totally wrong.
The aroma-or what we sometimes call flavour-is registered in the olfactory epithelium situated between the eyes at the front of the brain. It contains hundreds of receptors that register aroma molecules contained in everything that we eat and smell.
There is a simple but effective and enjoyable way of demonstrating what most of us don't realise; Smell and taste-are registered in different parts of the head. Have ready some table salt and biscuits, fruit or in fact, anything easy to eat. Squeeze your nostrils tightly enough to prevent breathing through them but obviously not too tight to hurt. Take a good bite of biscuit or fruit and start chomping, making sure that the nostrils remain clenched.
You will notice that it is impossible to perceive the flavour or aroma of the food being eaten.
Now, with nostrils still squeezed and food still in the mouth, lick some salt. Although it was impossible to detect the flavour of the food that was being eaten with clenched nostrils, the taste of the salt is unhindered.
Finally, let go of your nostrils and notice the flavour of the food come rushing into your headspace.
When we eat, taste buds on our tongue and in our mouths pick up only taste but no flavour. The molecules in food that provide flavour (known as odour or aroma molecules) pass up into the olfactory bulb where the flavour of the food is registered.
When the nostrils are squeezed however, the air supply passing through the olfactory bulb is cut off, preventing us from registering flavour.
As if this wasn’t enough, the brain has to process information
given to it by the other senses and sometimes, things can be not quite
what they seem.
Here are just a few examples of the senses influence on determining what
we taste and our emotional response to it.
1/ A few years ago at a Sommelier school in France, trainee wine waiters were put through a routine wine tasting until-unknown to them- a white wine that they had just tasted had been dyed red with a non flavoured food dye and brought back out to taste and evaluate. Something very interesting happened. They all made notes on the assumption that the wine was what it looked like; red. In this case, the eyes totally influenced flavour perception.
2/ True or false; chewing gum loses its flavour after a certain period of time? True, but not as quickly as we might think. Basically, what happens is that when we chew, the sweetening agent in the gum gradually dissolves in the mouth and is then swallowed, reducing its sweetness. We grow up with the association of menthol and mint with sweet taste every day when we brush our teeth.
The brain tracks the sweetness and as this reduces so too does the perception of the mint and menthol flavours. In reality however, it has been proven that these aromas are still in our headspace for several hours.
Basically, we register the rate of change of flavour and it is this that can enable a more exciting eating experience.
One way to avoid this satiated effect is to create bursts of flavour. At the restaurant, we do this by using small cubes of jelly that literally burst in the mouth. It is actually quite easy to do this at home. Certain spices-coriander seed for example-can give a wonderful burst of flavour, much more exciting than incorporating the same amount of coriander powder.
Another example of this is to make a cup of coffee with one ground bean; it will be most insipid. Now take the coffee bean whole and pop it into your mouth. Crunch it several times and then knock back the cup of water. The same amount of coffee and water when served like this will provide a far greater burst of coffee that will last in the mouth.
In fact, it is this principle that was the catalyst for the much publicised
bacon and egg ice cream. The idea with this dessert was not to create
a dessert that was based on breakfast but to play with the whole concept
of encapsulation.
Eggs thicken ice cream custard because the proteins in the egg coil up
and thicken the mix when subjected to heat. Like the coffee bean, the
coiled up proteins are now in an encapsulated form and can have a tendency
to make the resulting ice cream taste of egg by supplying bursts of egg
flavour.
In order to avoid this potential egg flavour, I reduced the cooking temperature of the custards accordingly, resulting in incredibly clean ices. I then started to wonder what would happen if I made custard loaded with egg yolk and overcooked it, to the point of scrambling.
If then, the mix was pureed and passed through a fine mesh sieve before churning, what would the ice cream taste like?
Well, the first mouthful transported me back to my youth and the fond memory of Saturday mornings when my mother used to make fried egg on toast. Although a study in the science of ice cream making and flavour encapsulation, this ice cream had created the emotion of an English breakfast!
3/ only two types of odour are intrinsically repellent and although I
don't think that it is appropriate to talk about these in a food guide,
many smells that we think would be repulsive can actually be perceived
as being pleasurable if their context is changed. For example, the smell
of old socks has been shown to be pleasurable when introduced as Parmesan
cheese!
Context is so important. What about a wonderful bottle of chilled Muscadet, sipped by the banks of the Loire on holiday in sunny France, tucking into a platter of plump fresh oysters? The same wine brought back to England just doesn’t taste the same.
Context can be created by the most simple of things. The description
of a dish on its own can create all sorts of problems and indeed, it was
this area that was my first foray in to the world of flavour perception,
some seven years ago.
The dish was a crab risotto served with crab ice cream.
Described as crab ice cream, this dish presented a barrier to the diner. Let’s face it; ice cream has to be sweet doesn’t it? Well, no, it doesn’t and indeed didn’t used to be. Savoury ices were popular in Victorian times but have long since fallen out of fashion. The same ice cream however, described as frozen crab bisque, presented no barrier, as the term ice cream had been removed.
4/ Sound can also play an important role in the perception of texture-a valuable part of the whole taste process. The perception of the crispness of a food can be modified by playing with volume and pitch.
In a test carried out by an experimental psychologist at Oxford University. Crisps from the same packet, eaten with the sound of the testers own crunch being fed back to them in real time changed when the volume or pitch were altered.
We have had a sound processor made that can do just this. The results are fascinating and above all, great fun.
Whilst it is not possible to create a crunchy banana, a less than crunchy apple can be made to be crunchier and even perceptively fresher by modifying the sound of the crunch, listened to in real time and popping candy? When listening to the amplified, pitch modified sound of popping candy running riot in the mouth, one cannot help grinning like a Cheshire cat!
5/ Our likes and dislikes are forged by memories. I use this word loosely as we could say that we also have a genetic memory.
For example, we are designed to like fat. It is the learned association of fat with poor health and obesity that prevents us, or rather some of us from liking fatty foods.
The senses act as warning systems, taste being the last of the sensory barriers and bitterness, the last of the taste barriers. It can prevent us from eating foods that could be harmful and although we might be genetically pre-disposed to liking or needing certain tastes, it appears that we have the ability to be able to modify these wants or needs. For example, we grow to like bitter foods; tea, coffee and beer are generally not acceptable until we reach a certain age.
I began thinking about this whole subject a couple of years ago when I noticed that more and more customers were commenting on the fact that the red cabbage with grain mustard ice cream served as an appetiser just got better each time they ate it. Interestingly enough, this was the only dish on the menu whose recipe had not changed over the past year.
It seemed that the barrier being presented (unintentionally) with this dish was the vivid purple colour of the cabbage gaspacho; a colour not normally associated with food. To some diners, the difficulty of accepting this colour interfered with the appreciation of the dish.
Smell is the most powerful memory trigger of all of the senses but we differ so greatly in what smells hit the right or wrong notes. As well as our own emotions differing greatly from person to person, we all live in our own sensory world. I know that this might seem a little spiritual but we do see, hear and smell things differently.
It was-up until quite recently-considered that we had around three hundred receptors that between them were responsible for registering all aroma molecules on earth. It is now thought that we have some four hundred but only use about three hundred of them. We do not all use the same receptors and therefore register flavour molecules differently. Two people tasting the same banana will not necessarily register the same flavour. The same goes for sight and sound.
As if this whole process was not complicated enough, the olfactory system is ipsilateral; that is to say the left side sends signals to the left side of the brain and right to the right. So what relevance does this have to the way that we perceive flavour? Well, the answer is quite a bit actually. The left side of the brain controls speech and the right side controls emotion. It was and in some cases still is thought that flavours presented to the left nostril would be easier to identify and describe whilst flavours presented to the right could elicit a more emotional response.
Whilst this argument does seem to have some evidence to support it, it is by no means conclusive.
What seems to be far more relevant however is the fact that air does not flow through each nostril at the same volume. This asymmetrical difference changes every few hours. Have you ever noticed that when our nose is blocked, it seems to be more blocked in one nostril that the other?
The whole process of flavour perception is multi-sensory. We all have our own perception of life. Not only do we see, hear and taste differently but we have our own, individual personal experiences, emotion and memory. As long as this continues, the world of eating will be a very exciting place.