4.7: Smelling good makes it tastes better!

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En provenance du cours de The Hong Kong University of Science and Technology

The Science of Gastronomy

202 notes

The Hong Kong University of Science and Technology

The Science of Gastronomy

202 notes

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

À partir de la leçon

Module 3 and Module 4

This week, we will talk about how flavor and aroma of food affects our perception of taste of food.

4.0: The Sense of Smell - Topic Outline0:27

4.1: What are we smelling?9:57

4.2: Demonstration – Factors affecting diffusion rate4:37

4.3: How do I smell coffee?10:52

4.4: Why do orange and lemon smell different?9:41

4.5: Why can’t I taste the “strawberry”?11:08

4.6: Demonstration – How does aroma affect our taste?4:35

Assignment 5 – Instruction Video2:24

Assignment 5 – Result Sharing1:39

4.7: Smelling good makes it tastes better!14:03

4.8: Demonstration – It is all about congruency!3:25

4.9: The Sense of Smell - Topic Summary1:01

Rencontrer les enseignants

King L. Chow
Professor
Division of Life Science
Lam Lung Yeung
Associate Professor
Department of Chemistry

Knowing that taste and smell they interact with each other.

So we wonder whether smelling good would make a dish taste better.

Here it goes, we try to understand how

the aroma and the taste that would have interaction.

And there's a few thing that we need to learn about.

The first one we call the halo effect. What is halo effect?

What we are saying is that, sometimes the positive character, characteristics of

a product in fact it can induce a positive response.

People talk about that in marketing a lot.

But in fact it also happens when you prepare food.

Because you have one positive perception, it

generate a positive feeling about another property.

So what is this?

In a situation such as in bakery they are

having a very good aroma being released from the shop.

So what you have is this pervasive aroma.

In fact, it'll give you a very refreshed a feeling.

And so therefore, whenever you buy from the shop, they all taste very good.

It's because of this aroma, halo effect.

There's another effect which is called dumping effect.

What it mean is that we have some

perceived quality of sense and that is going

to affect another quality.

Which is not really perceived by the same sensory organ, such as our tongue.

In this case, we say that these olfactory

input allows us to perceive the taste better.

Even though actually it does nothing in the taste, all right?

So it is like some sort of like a so called

the learned association when the dog, you ring the bell, they,

they kind of think that there's food.

In fact there's no food but you ring

the bell they still thought that there's a food.

Now what kind of things is it?

It's such in a situation that you put in vanilla.

vanilla, when we smell it, sometimes

we always associate vanilla with something sweet.

So even though actually there's no sweet substance around, and the same

thing when we have some fruity thing, like strawberry, where this ethyl butyrate.

Whenever you smell it, I can smell that it's very sweet.

But in fact, did I taste anything which is sweet?

No, nothing.

So, very often in practice this halo effect

and this dumping in fact they come together.

We call it halo dumping effect.

And because of that it changes the way you perceive the quality of a particular food.

Let me give you some application of it.

Sometimes we say that if you want to have something which is sweet, as

I said strawberry fruity, pineapple fruity, that

gives you a sense of something sweet.

Now, you may now have some food which is not very sweet but once

you put strawberry or some fruity smell here, you find that it's much sweeter.

On the other hand, like for example we will have the whipped cream, the whipped

cream actually by itself is not very

sweet, But whenever you have strawberry odor

together with it, people always tell you

the strawberry whip cream actually is very sweet.

Now think about that.

When you add peanut butter there, do you feel the same thing?

No, because peanut butter really doesn't match with the whip cream.

Now why, why is that?

Because we need to come to the point talking about something called congruency.

What is congruency,

is that one or two thing that go along with each other well.

Now let me look at this example first.

In fact an odor would be able to

decrease the taste intensity because they're not congruent.

So what exactly am, am I referring to?

In this case, we say that let me give you some caramel odor.

Caramel odor a lot of time is going along with

sweet taste.

But then it doesn't really go along with sour taste.

So what we find then, if you put caramel odor together with some vinegar

or so, in fact, you find that well, they don't go along with each other.

And therefore, you find that the sour taste seems to be weakened now.

But if they're congruent, then just opposite.

They will enhance each other.

Such is the case is that when you have a cocoa drink, the cocoa

drink in general, the taste actually is very bitter, but if you got a cocoa flavor

then you find they're actually very congruent, and

then you find that's really a cocoa drink.

And you find that it give you a very strong

feeling of how a cocoa drink is supposed to be.

The same thing is that when you add the

vanilla in it, in fact, it can increase sweetness.

Vanilla smell is always congruent with sweetness.

And when they come together, they enhance it.

Now, so this is really what congruent is about.

Congruency refers to a situation that you have a mixture of multiple component.

And which constitutes a something which is in a harmonious combination very

consistent with our everyday experience. We always see them coming hand and hand.

And, when we see

that, or when we sense that, we find that they are more pleasant.

The, and more than just each of them alone.

And the same time is when they are not congruent with each other.

You just find them, actually they're not matching.

So, therefore, the perception of pleasantness

for this combination actually would be worse.

Now, using that, in fact we can do something which combines

something we learned in the past about taste together with this kind of odor and

taste interaction. For example, we know that

when you have a vanilla odor, that can generates a very sweet taste.

This is the dumping effect that we are referring to.

And, as a result, when we know that,

when you put something sweet together with something

bitter, something sweet is going to suppress the bitterness.

Okay, that's the taste interaction that we learned.

Now, when we combine that, so you

put vanilla odor together with cocoa drink which

is bitter by itself, the vanilla flavor is going to make the cocoa drink less bitter.

And it's kind of like a taste a little bit sweet.

So combined together in fact vanilla

combined with the coco drink, it makes a good mix and we will enjoy such a drink.

And that's what you have in most of the bakery store or coffee shop.

Now on the other hand, what I want to focus on is congruency

It is a necessary condition to have this odor induced taste enhancement.

But then the degree of enhancement

varies from one taste, one odor, to the other,

and there's no general rule that you can apply.

And the most important part of it, this congruency, in fact it's

not more than, not working just on the taste or the odor.

In fact, intensity of the level of the

senses that it can detect is also very important.

We find that if you have a very strong smell but then with a very weak

taste, they are not congruent.

And you'll find that that the food is not as pleasant as you would want.

On the other hand, you can have a very weak smell and yet a very strong taste.

Again, that doesn't really match very well.

So congruence is really talking about a harmonious a association with each other.

Now sometimes we also say that when we put food

together they're congruent.

And they are very commonly put together and give you a very pleasant taste.

Why?

And why those flavors, they go hand in hand?

For example in this case we have fish.

You always mix it with chips.

Now sometimes when you have strawberry, you mix it with cream.

Why?

There's a general hypothesis which I think is supported by some examples, is that a

lot of these components or these food, they share some common molecules.

For example, here we have say that jasmine.

Jasmine, a lot of time people use it to cook the pork liver.

Why?

Because both of them carry indole.

And indole is the common component that link these two food together.

So when we mix them together, we don't find it odd.

We seem to find that they enhance each other's perception.

Now, having talked about all this aroma and taste let me repeat again

and say well, for the olfactory input, a lot of time we need to have smell.

And this smell, as I've pointed out, it come from the nostril and go into

the nasal cavity and you will be

able to perceive it using our olfactory epithelium.

The important part of this is that this aroma in fact,

it can also go from the back, from the rear because when you're chewing something

in your oral cavity you would be able

to generate all this release of aroma molecule.

And when you swallow, this vacuum pressure here allows

some of this aroma molecule to go from the back.

That's something we call the retronasal olfaction.

And both are equally important. So combining

all these I want to talk about how these kinds of perception, in

fact, allow us to perceive what is really a particular flavor.

This is the hypothesis they provide, it's called shape theory, or

sometimes they use the term called odotope theory, or weak shape theory.

What it's referring to is that, well, you

know that actually we have olfactory epithelial cell.

epithelium, there's a lot of cells, sensory cells that are distributed there.

Each of them, they carry a single receptor.

But when you throw into your nasal cavity a molecule,

this molecule is going to bind on to different receptors

and so some of them would get activated more than

the other depending on how well they bind to each other.

So what happens is that if you have a large area of major olfactory

epithelial, such as something like this.

You may have some cell here being activated,

some cell here being activated, with different extent.

Collectively, they would send out signals which would be integrated in your brain.

And that gives you a perception of what this molecule is really about.

It's quite different form what we learned in the past about well one

single neuron when it's activated it tells you that this is a particular smell.

It's not really

like that.

So, so the question is that knowing that's

the case, would you be able to generate ideas?

Or create a, a, a novel, recipe?

Which allows you to activate this group of neuron, activate

this group of neuron, and activate this group of neuron.

And this kind of like a map, that you

will be able to activate for the multiple, sense results.

That will allow you to generate a new kind of odor, or flavor.

Now, having said that, I have not finished.

In fact the trigeminal nerve stimulation is equally important.

In fact when we talk about flavor, we say

that the taste, the gustatory input, the smell, the

olfactory epithelial from your nose, we also have a

few nerve which is called the trigeminal nerve that we

have covered a little bit earlier.

This trigeminal nerve innervates your mandible, the lower jaw,

your facial, including the sinuses, as well as your eye.

So what it has is that mostly, we think that

is used for us to sense something which is harmful or

pungent but sometimes we like it, and some of the food

would be able to induce, or activate this kind of nerve.

What are they?

So these are very pungent substances, such as garlic.

Oh, we have some garlic here.

So garlic. We can have onion.

Onion here.

So these fruits in fact they do have enzymes and when they are

broken they will be able to generate some of these very pungent molecules.

Such as the allicin or this one is the sulfenic acid.

More than that

sometimes we can have some of the rotting fish.

These would produce the trimethylamine and we would have

the mustard, which is going to generate all this isothiocyanate.

These are very irritating kind of molecules.

All this would be able to ge, generate a stimulation of our trigeminal nerves.

Combining all these, let's look at it again.

We can have the olfactory input from the olfactory epithelium.

We have the gustatory input from our tongue, we can taste.

We have the trigeminal input which tells us all this pungent

or a very irritating like stimulation Remember when this all go into

our cortex they will pass on signal to your amygdala, give

you a sense of how rewarding it is, how good it is.

It would also send signal to the hippocampus and

what it is in fact visual cortex sometimes can also be stimulated.

And what happens is that all this input, they will all come together and at, on a

place which is right in the front of your brain, in an area around here.

That is called orbitofrontal cortex.

Through the integration of all these signal from the smell, from

the taste, from all the trigeminal stimulation You would now be

able to integrate them together to give us a notion of what excited this flavor.

So from this point onward I hope that you'll be able to recognize that.

If you want to prepare a good dish, think about a smell, think about a taste.

It can be a little irritating, and the visual part of

it, as well as whether it recalls some of the good memory.

And that's allows you to make a good dish.

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