This course introduces a number of basic scientific principles underpinning the methodology of cooking, food preparation and the enjoyment of food. All topics covered have a strong basis in biology, chemistry, and physics application. Among others, they include the consumption of cooked food, the physiological and evolutionary implication of the senses, geographic and cultural influences on food, and the rationale behind food preparation. We will also discuss issues such as coupling of senses to improve sense stimulation; altering flavor by chemical means; and modification of the coloration to improve the appearance of dishes. Following the video demonstrations of the scientific principles of cooking, you will learn to recognize the key ingredients and their combinations for preparing good healthy food. At the end of this course, you will be able to: - appreciate the scientific basis of various recipes; - develop your own recipes by integrating some of the scientific principles into new dishes; - recognize the influence of the material world on human perception from the different senses; - appreciate the art of integrating science into cooking and dining. Important Note: This course is not designed for people with special dietary needs such as vegetarian, diabetic, and gluten-free diets. If you feel uncomfortable with any part of the assignments or activities of this course, you can substitute some of the ingredients or ask friends and family members to help with the tasting of your assignments. Alternatively, you may skip that specific assignment provided that you have fulfilled all other qualifying requirement to pass the course. Course Overview video: https://youtu.be/H5vlaR0_X2I
6.1: How do we feel the texture in our mouth?
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En provenance du cours de The Hong Kong University of Science and Technology
The Science of Gastronomy
202 notes
À partir de la leçon
Module 5 and Module 6
This week, we will talk about how color and texture of food affects our perception of taste of food.
Rencontrer les enseignants
King L. ChowProfessor
Division of Life Science
Lam Lung YeungAssociate Professor
Department of Chemistry
Today we're going to continue to, to talk about how to improve the fruit quality.
You remember last time that we were talking about the orange.
What we have is that we can look at a particular fruit of a certain color.
In fact, what we're looking at is not just the color.
We are focusing also on the texture. When I show you this particular fruit,
you can all tell that it's a lemon. Now, why?
It's not because it's yellow color, it's also because of its texture.
So, texture actually tells us what's the quality of a food.
Now, today we are going to talk about how texture is being sensed.
So the texture actually is sensed by our Somatosensory system which tells us about
the touch. The temperature, whether it is going to
be very tough or not. Now, with that, in fact, sometimes we
refer to it as something that we call mouthfeel.
This particular aspect/g, we want to introduce an idea about so-called texture
contrast theory and how we can improve the quality of food.
Now in this, to change the texture. In fact one very important component that
we constantly focus on is about osmosis. How to change the texture of food.
Now let's look at what texture is. We have already covered taste, through
our tongue. Aroma, through our nose.
Color for our eyes. So when we talk about texture that is
something that we need to use our mouth. all the buckle cavity and all the lining
of it to tell us about the shape, the texture as well as temperature.
Now texture, what exactly it is? Texture is the attribute of a particular
substance therefore all the features it has.
Which is a combination of all it's physical properties including those which
we can sense by touch, we can sense because of pressure, because of how it
look as well. And sometimes bear in mind, how it sounds
when we eat them. And all this combined together,
collectively, it tells us what exactly what the texture it is.
And all these would have something more. Which is about the size of the food.
the shape of it. And actually, how detailed they are.
And these are all properties of texture. Now, sometimes we say that when we have
food in our mouth. We, we sense, actually, how good they
are. We used the kind of word that's, well,
it's hot, it's salt, it's crispy, it's crunchy.
We have all this kind of word, words to, to describe them.
But basically these are also called a combined quality.
The combined quality sometimes tells us something about the informations of a
particular food. For example.
When we say that we see fresh meat, we want to collectively combine all this
information and say, well, fresh meat usually is red.
They're a bit tender, they're more elastic and usually, they have a lot of
water content in them. So, therefore, we say, moist.
So, when these all come together, we call that fresh.
But sometimes when we have the meat, the are left there for a while but being dry
still this stale meat. They usually the color turns to be a
little bit dull and they are a little bit brownish and they are a little bit stiff
because they are drying up. So, all this collectively combine
together define well, what kind of qualities stale meat.
Something which has been left there to be dry for awhile.
But, how about meat which are decomposing?
So, we say that usually when they're decomposing the meat would start to
collapse and disintegrate. so, they would have a little bit more
watery feeling and sometimes they even have a bad smell.
And combined together we say well, this kind of meat we don't want them.
So, remember. It is a combined quality of all these
things that tells us whether it's a good food or bad food.
So, therefore having texture being felt by us through our mouth in fact it help
to add additional pleasure for our eating.
Now then the focus on this somatosensary system again and say actually what kind
of things are we sensing. Now in fact we are sensing touch which is
the mechanical reception. we touch something, we press on it, so
therefore we can few there's something which is having resistance.
Temperature. We talk about what kind of temperature,
high or low. And sometimes high and low, they're, it's
going to affect the quality of food. These are called thermoception.
How about pain? Well, sometimes pain is related to some
of the body damage. we have the wound, we get hurt, we feel
pain. But sometimes, pain can be something
acquired. when we eat something that is so
irritating that it's reaching a point that in fact it caused pain.
And sometimes this acquired quality is also preferred when we are eating
something. And also when we talk about somatosensory
systems, we can't go without talking about self-awareness.
about the proprioception. That is talking about well, we are aware
of what kind of things that we perceive in our body.
these include a so called interoception which is about how a body
part is like. Have you ever felt that, you have a
stomach ache. Do you see it?
You don't see it. But yes, you can feel that there's a
stomach ache. Why?
Because these are visceral senses. We are are self-aware of what's going on.
So, there are sensory receptors in our body that tells us what our body parts is
like. Whether you feel pain here or there, and
you know that something is going on inside your body.
Now, all these are somatosensory perception.
And all these, in fact, they are using receptor just like we're talking about:
taste, smell, or eyesight. These are receptors that tell us what
kind of information it would be available.
And when we talk about all this mechanical sensory function.
if you talk about our buccal cavity, how we feel the food what the texture is
like. In fact most of the time, a field of
nerves that innovate our innovate our buccal cavity, our toungue, and, and our
face. And all this, they're mostly coming from
the trigeminal nerve. And, when they have this information
collected, they would go to the thalamus. And then, eventually, we integrate it
into the somatosensory cortex in our brain.
Together with our cerebellum, that have to coordinate how different parts of our
body, and different parts of your buccal cavity sense same thing.
They integrate all together. This neural pathway help us to perceive
what exactly the texture is like. Now, so with all these different
components one, two and the somatosensory and the cerebellum.
They complete the so called the pathway that allows us to sense texture.
Now thing about that In fact this somatosensory system and sometimes we
call this receptor, somethetic receptors. What they have is that they're in all
region of our oral cavity. They help to sense the food and, and what
kind of quality it is. And in fact if you try it out our oral
cavity. In fact they have the highest density of
these somethetic receptors. What it means is that we can feel a lot
more details about anything that's touching our oral cavity.
And also that's important part is that the threshold of stimulus for this kind
of receptor is relatively low, so that means in minor difference of it, they can
feel it. Now, think about that, if you try to
touch your skin or you touch the skin on your leg or on your hand or on your
finger. Certainly you can know that, you would
know that your finger in fact can feel much more details than your elbow.
The same thing in fact even our oral cavity all these receptor they can even
sense the better than our finger tips. So therefore I would say they are very
sensitive. And these kind of sensation allows us to
detect something even it's a very light touch, and small vibration, we'll be able
to tell them apart. Now, go back to this receptor, what
exactly are they? we have a whole bunch of receptor.
I'm not going to ask you to remember what they are, but these receptors
that are distributed in our skin. no matter if it's the hairy part of the
skin or the breast skin, or the oral cavity, they are all there.
And, what they have is, in fact, they are sensing some kind of change of pressure
or mechanical property. For example this merkel's disk, it senses
pressure. Well is a press on it at a very low
frequency. Some of them goes to a little bit
stretch, talking about how your skin has been stretched.
Some of them are talking about whether there's some frequency of tapping and
some of them are monitoring vibration of different frequency.
Now, all this combined together help us to resolve the mechanical touch that was
going on on our skin. Now combined together, I want to remind
you, our oral cavity is densely populated with all these receptors.
And one part of it which is the densest is in fact is our lips.
And our lips can tell these apart very in detail.
So these kind of tactile stimuli in fact, in fact provides us the detailed
information of what texture is really about.
An interesting thing is that this kind of receptor they can also differentiate the
two type. One is the so called slowly adapting one.
And these are the one which is around our face and oral cavity these are so called
slow adapting. Slow adapting means that you can give
them a stimulus they would not go away. And if you continue to give the stimulus,
they would not get adapted and they still keep on firing.
So therefore, you can continuously to sense as to what kind of, environment,
what kind of these things can touch. On the other hand, we also say that some
of the tissue, such as tongue. well they are rapidly adapting.
So what it means for you ,they are rapidly adaptive that means if they can
touch something. Well, if you continue to touch same thing
with same pressure well don't fell you that much to like to move away or touch
something else of different quality. So in a way what the tongue allows us to
do is the things to detect big changes. Constant variation of all the stimulates.
So with all this together, then we have this organ that allows us to sense the
quality, texture of the food. At the same time, there's another type of
receptor we call the thermal receptors. That allows us to sense the temperature
which is high or low. And you may recall that in the past, we
do talk about receptor, about temperature.
One is called the Menthol receptor, which is for detecting low temperature, such as
cold water. Or the other one is called the Capsaicin
receptors, which is for the detection of high temperature.
When heat is coming, then, we can sense that the high temperature is there.
Now, these are all slow adapting. So, that means they're very sensitive to
those kind of changes. And these receptors, in fact, they have
an overlapping range of working environment.
For example the cold receptor detects something that's between 20 degree to 40
degree. And the warm or the heat receptor is
detecting somewhere between the 30 and the 48 degree.
So what you see is that they do have the overlap.
And what's our body temperature? 37 degree, so that means, If we are
functioning as a human being basically we can detect both cold and warm substance
at same time very effectively. Now with all of this we'll find that,
that allows us to sense more than just the texture but also the temperature of
the food. Now having all this, I need to remind you
again, for the sensation of this temperature, in fact what we have its in
a face as well as in a buccal cavity. These, they're heavily or densely
populated by this receptor. So it makes the oral cavity as the one
which is the most sensitive to all kind of touch within it.
What quality, there's toughness, whether it is soft or hot.
and what kind of vibration when we taste something and all can be sensed in our
mouth. Now having that in mind, let's go to the
next thing and understand how they are being perceived.
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