Recall that we were talking about different kind of sensation and
texture and we mentioned that in fact we can also feel pain.
Pain is felt by this kind of receptor called a nociceptor.
Now somehow in fact when we feel pain,
a lot of time is because of it is associated with
something like injury or something is too hot or too cold,
that it needs our attention.
Now there's some interesting thing about it.
These are all through these nerve ending that perceive the so-called pain.
And we respond to this because we will have
withdrawal and then we try to pay attention and try to stay away from it.
So in a way it's helping us to survive.
Now and it is telling us that we get injured and some how there may be information also.
Now so this is for that purpose.
But remember, when we are sensing
temperature when it's too high it is hot, it can be damaging.
When it's too low the temperature is very cold,
it's freezing it can also be damaging.
So therefore in fact somehow this perception of pain and a perception of temperature,
when it reaches a certain point they overlap.
So what happens is that when the temperature is below five degree or
over 50 degree in fact this pain receptor would be activated.
In fact they share something in common in the processing of the neuro input.
Now also when you think about well,
we need to understand actually how our body is
positioned and how we sense something inside our body.
So this proprioception is also very important.
In fact it can tell us what our stationary position is and whether we have any movement.
Now may I ask you to try this out and simply close your eye and see whether you can
raise your left hand or raise your right hand and you
can even turn around for 360 degree.
I believe that you can close your eye and you can do all this.
Why? Because in our body we have all this receptor around our body on our skin,
in our muscle, in our bone,
that allows us to sense to
corresponding position of our body parts,one versus the other so that we can tell.
Now that become important.
May I suggest you to do an exercise again.
Try to close your mouth and try to use a tongue.
Your tongue can do the same thing.
Try to use a tongue and count how many teeth you have on your upper jaw.
Now you can go one by one.
And in fact you don't see them but just
based on your tongue you will be able to tell them apart,
one tooth after another and you can count the total number of it.
Now that essentially is a way that what this proprioception is an ability that we have.
We can control our tongue to move around our oral cavity,
and we can perform the function to differentiate one tooth versus the other.
Now that is a very important function that we have with our tongue.
Now in fact when I talk about tongues and counting of teeth,
don't think that our teeth are just used for biting.
In fact you look at our teeth of this for example as a representation of the tooth.
What you have is that in fact the tooth is embedded into our bone of the jaw.
And what happens is that between the jawbone and the tooth there is
a something we call periodontal ligament
which helped to attach them together on this particular place.
In fact it is heavily populated by nerves.
And what are these nerve sensing?
They're trying to sense how the tooth is being pressed on the bone.
And so in a way it's telling us if we bite on to something,
how hard is it.
Is it a bone or is it jelly?
Or is it just meat,
so that when you bite on it the pressure exerted on this ligament is going
to tell us what's the hardness of the food that we are eating.
Now having all this, essentially,
I would like you to review it again and say,
"Well what are the factors that influence our perception of texture?"
Of course these whatever that we put into
our mouth they are made to have certain texture.
That's of course it's made in the product already.
Something outside our oral part is that well when we are handling it for example,
when we look at it we see the visual cues about what the texture is like.
We can smell them and see where they are that they are like a bad smell,
it looks like it's rotting,
so if it is rotting then it must be very soft.
And when we are handling them our hand is telling us some information about it.
But when it goes into our mouth,
in fact we are masticating it.
We are biting on it,
telling how hard they are through our teeth.
We are sensing the temperature of it.
We are sensing whether,
how it makes our saliva,
and then through the sensitivity of our mouth,
we'll be able to tell what kind of texture will quality test.
And of course all this as I always say in the past,
combined with our experience in the past,
and how they integrate together whether they are making any consistent sense,
that tells us the information about texture now.
So all this combined together we call that the mouthfeel.
And in fact when any food that come into our mouth,
the first part that we would perceive the quality of
it is through our palate. When we bite on it.
So it tells us how hard it is and then you start to masticate it.
You start chomping it into small pieces.
How fast you can chomp it into smaller pieces and how
grainy you feel them and all this would combine together.
And so therefore, a lot of times in the process we are mixing it with saliva.
So if it comes in as like a biscuits or bread usually they are a little bit dry.
Over time they become softer but sometimes for example if you are
biting on a watermelon when it comes into your mouth it's already very watery.
So that tells you what the quality is.
So all this together defines mouthfeel.
Having all this how are we begin to
elevate the level of satisfaction based on the texture.
I'm going to tell you next.
King L. ChowProfessor
Lam Lung YeungAssociate Professor
