9.6: What makes an ideal sauce?

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Del curso dictado por The Hong Kong University of Science and Technology

The Science of Gastronomy

202 calificaciones

The Hong Kong University of Science and Technology

The Science of Gastronomy

202 calificaciones

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

De la lección

Module 8 (continued) and Module 9

This week, we will continue our focus on the preparation and cooking of meat and learn about the elements that affect the preparation of sauces.

9.0: Sauces - Topic Outline0:56

9.1: The Importance of sauce in a dish3:23

9.2: Sauce and viscosity8:37

9.3: Things to know when changing the viscosity of a sauce10:40

9.4: Changing the viscosity of a sauce I: Larger or smaller molecules?13:04

9.5: Changing the viscosity of a sauce II: Particles and bubbles16:17

9.6: What makes an ideal sauce?5:59

Conoce a los instructores

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

Making an ideal sauce.

There's number of factor we need to consider.

The first one is it has to be easy to be poured out from the container.

Secondly, once it's been poured out, especially pour onto our food,

those food, that means the sauce can still able to cover the whole food.

And finally,

once it can be covered the food, and

all the sauce will actually run over the plate.

So these are the m, three major factor we

have to consider when we try to prepare our sauce.

So you wonder any liquid can have these properties.

So in fact of the physical property of an ideal sauce, that is, if we can

actually do these three things. Firstly, it has be a low viscosity

when we try to pour out from a container; so that it's be easy to pour out.

But however once is being poured out on the food basically.

In order to stop it for one all over the plate the

viscosity has to he increased after is being poured out from the container.

Now, if we look at that by the, the physics, really classical physics,

many kind of fluid, in fact, they are served as a Newtonian fluid.

You wonder what's the meaning of Newtonian fluid.

Newtonian fluid means the viscosity, it doesn't

change, even though there is any pressure change.

Like for example, we have a bottle water. So if

we tried to apply certain pressure onto the water, it flow at a certain rate.

But however, when we increase the pressure, what

you can see, the flow rate will also increase.

So that actually refer to when we

have pressure change, the flow rate also change.

But in fact, the viscosity, it is more or less stayed constant.

So, this is so-called the classical, so-called a Newtonian fluid.

But however, there's always exception in science.

We have not only Newtonian fluid, we have Non-Newtonian fluid.

So what is so-called a Non-Newtonian fluid?

Instead of a constant viscosity with change in the pressure,

we have two type of Non Newtonian fluid.

One is so called a shear thinning. That is, if the

viscosity just try to decrease when we exert pressure.

Or in other words, if the food, if we don't exert any

pressure on it, the viscosity more or less, remain at a high value.

But, if we

try to increase the pressure, the viscosity sudden drops, right.

So, in our daily life,

which type of food, referring to so-called shear thinning

so, Zoe. I've one very good example.

One of the example is so-called ketchup, here. So,

when Zoe is try to open up bottle ketchup

and we try to tip it up, it won't, it, the ketchup won't,

won't flow out from a container. But however, when a

slight pressure add on to it, it suddenly flow.

So this actually demonstrate so-called, a shear thinning example.

So that means before, it actually tip up

the bottle because the pressure is not large enough.

To change the viscosity so that those

ketchup will still remain in the container.

But when Zoe just tried to apply

more pressure onto it, the viscosity of the ketchup suddenly decreased.

So you can see all the ketchup immediately suddenly run out from the container.

Apart from the shear thinning I just demonstrate, the

opposite of shear thinning is so-called the shear thickening.

Now I'm going to also demonstrate

what is so-called shear thickening.

So here we have cornstarch and we have water.

So when we just try to add the two things together, It form a something

like a suspension. And this special

suspension has an interesting property of so called shear thickening.

As I just mentioned, shear thickening in fact is opposite of shear thinning.

So that means it act oppositely.

Basically, when we try to apply pressure on to it, the viscosity suddenly increase.

It just try the opposite, the extra pressure we have.

On the contrary, when we try to do it at

a slow, so-called pressure, the viscosity in fact is really small.

So, Zoe had

and so, we prepared a small bowl of this corn starch suspension.

Right now we have a larger bottle of suspend, of corn starch suspension.

What we want to demonstrate is try to apply large pressure.

So you see she can get her hands get into the suspension.

But, however, when she was trying to do it in the slow way,

she can able to immerse all his finger into a suspension.

So you can see.

So this is exactly how sheer thickening behave.

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