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
8.4: What else does a piece of meat contain?
Loading...
En provenance du cours de The Hong Kong University of Science and Technology
The Science of Gastronomy
257 notes
À partir de la leçon
Module 7 and Module 8
This week, we will look at how fruits and vegetables can enhance the quality in cooking and to learn about the properties of meat.
Rencontrer les enseignants
King L. ChowProfessor
Division of Life Science
Lam Lung YeungAssociate Professor
Department of Chemistry
After knowing different type of muscle fiber, you may ask the question, what
else does those meats contain? The first one I would like to tell you is
so called connective tissue. For the connective tissue, it's function
is responsible to hold all the muscles together.
Actually, it can able to organize and coordinate the actions.
For those muscle, which require more force, or more energy.
Normally, it contain more connective tissues, so that it can able to hold more
muscle, so that it able to do much harder work.
So, that's why the connective tissue, normally, it is tough, and very strong.
For connective tissue in most so-called land animal is actually
relatively stronger. As you recall for the fish muscle,
basically, it's only contain less amount of connective tissues because it's mostly
don't required to work quite often. But, however, for those animal who live
on the land, basically, they require the muscle function quite often.
And then, eventually, the connective tissue in those lands animal
is relatively stronger and tough. But however, as those animal getting old,
the connective tissue is relatively tougher.
So you may wonder what's inside the connective tissue.
In fact it contains three type of tissues.
The first one is so-called Collagens, second one is the Reticulin, and the
third one is so-called Elastin. I will focus more in the Collagen,
because Collagen constitutes The higher percentage in the connective tissues and
especially for collagen. You may have experience that is when we
try to heat it for certain temperature, the collagen is become softer.
The main reason is for the structure of collagen.
In fact, it contains three strands of amino acids.
When it is being heated to a certain temperature, these three strands of amino
acids start to unwind. Eventually, it becomes so-called gelatin,
which has much softer textures as compared to collagen.
To give you some idea is collagen, in most of the animals before it was born,
once it's born basically the amount of collagen is more or less constant.
It won't actually change too much. So that will explain why when those
animals, when they are young. Once you hit it, basically, although it
contains certain amounts of collagen, you still can able to change to gelatin.
We still can give you some soft textures. But, however, as I mentioned, if that
particular animal or the muscle is coming from the animal which is really old,
those collagen, as times goes by, it becomes coalescing to each other.
Even though, you try to heat it for high temperature, it won't break down any
more, because it contains more elastin. So that explain why, for some old
animals' muscle, even though sometime you heat it for a long period of time, it
won't give you a tender structure. So, that's why collagen, in fact, it play
a really important role in the meat textures.
And for collagen to gelatin, as I explained to you a bit earlier, when you
heat it to about 60 degrees the three strands of amino acids start to unwind.
And then it converts to become gelatin. So this explain why, when or though your
muscle contains lot of, so called conductive tissue, even though once you
hit it at 60 degree for a longer period of time, it becomes so in structure.
How about collagen in fish. As you all in know, in fish, it connect,
it contain much less connective tissue. But for fish, if we look at the top part
and also the tail, so you might know that most of the propelling force is actually,
come from the tail of the fish. So you can actually immediately tell the
tail of the fish, those muscle actually contain more connective tissue because it
actually have to use quite often. But however, for those muscle in front of
the fish, they hardly move, so that they contain much less collagen.
So that's why, if, if the tail of the fish contain more so-called collagen or
the connective tissue, basically, when you try to heat it to a certain
temperature, eventually, the tail is give you more succulent texture compared to
those muscle in the middle of the fish. So, gelatin and the fat in fat is just
contribute the impression of the juiciness, moistureness of the fish's
texture. So if, to a certain extent, if your
muscle doesn't contains too much connective tissue, it actually give you a
feeling of dried meat, normally, more or less in the middle of the fish muscle.
But, however, for the tail, it actually contain more connective tissues.
At a high temperature, it can able to connect to gelatin.
It gives you a much more juicy texture afterwards.
The next I'm going to tell you is the fat.
Fat in fact we call a special form of connective tissue.
And why do muscles normally contain fat? As you all know that this kind of fill
actually was used by the so-called slow stitch muscle.
And very importantly, fat is a source of energy.
You can able to store normally under the skin.
Not only under skin, sometime. To serve as a cushion, but it also
being stored in the layer of the connective tissues.
That is when the connective tissue try to hold the muscle fiber together there is
always some fat, actually serves as a buffer as a cushion.
So as I mentioned here, it can store under the skin, under the body cavity as
a cushion. And it also lies in between the
connective tissues, and separate all the muscle bundles together.
And the role of fat especially in cooking.
People think that fat actually is the component actually providing the flavor.
And more importantly as a lubricant. It make the meat don't have a really dry
and tough texture. And it always soften the meat when we eat
it. So you're looking at these two pictures,
what we can see on my right-hand side. Is a kind of rather lean structure
whereas in this side what you can see is, you can see the fat is more or less
evenly distributed among the meat, the, the muscle.
Basically, it correspond to a more even kind of distribution.
We use a term to describe it so-called marbling in the meat.
So marbling means the pattern of the white spottage that goes, or actually
distributed around the meat. If we have a really even structure, this
is so-called the best, better quality. Whereas, if we don't find any so-called
fat. This build in the meat, this will cause
one to a relatively low-grade kind of steak.
So, as I mention, the role of fat in the meat cooking is actually, it make the.
the whole steak become more have more flavor and more tender and more
suluent. And the fat is fish, it actually wear
this. Some fish actually contain much less fat
just like cod fish. Whereas other fish, it actually, like
salmon, is contain a much higher content of fat.
And primarily the fat actually store under the skin, or, in terms of between
all the connective tissue, that it actually separate the so called myotomes.
And if this actually contributes so-called both gelatin and fat.
Both actually contribute to the juiciness of the meat when we prepared it or when
we cooked it. The final component I would like to tell
you is the role of the water. So, you may wonder, what is the role of
water in the meat. Also, similar to the fat and also the
connective tissue like gelatin it actually determines the texture and also
to certain extent it correspond to taste. Most of water as you still remember,
water is the major component inside the meat.
Some meat actually contain over 70% water.
So where is those water? Most of the time it's being trapped
inside the protein of the meat. And it like, more less, it is locked
inside the meat fiber. But, however, imagine when the protein,
so called denatured. Denatured, I'm going to mention this term
later in this course. The meaning of denature, what I would
like to tell you here is just like it change to another form.
So, if the protein, that the nature. The, the, the property of these proteins,
once changed, it made it to the escape of the water coming out from the protein.
Now, one questions, I guess some of you may experience is, why frozen meat always
seems to be drier than the fresh one. The main reason is, the frozen meat, once
it's been frozen, those trapped water may start to flow out from the thaw.
And then, eventually, this phenomenon is so-called the free the bond water when
they are defrost. That's why in those frozen meats, when
they undergo thawing, those meats, once you cooked it, it appears to be much
dryer compared to a fresh meat. Some people, once they defrozen some
meat, they try to refreeze it afterwards, but in here I would say I try not to
recommend you to do it. You know why?
It's because when you try to frozen the meat the water inside the meat muscle,
they start to crystalize. They become ice crystal.
And the ice crystal is really sharp because they're solid they start to
rupture the cell wall. Aand then, eventually, when you try to do
the defrosting those trapped water will start to run out from the meat muscle.
And then, it result to a kind of letting juice to escape out for meat's muscle
become to a dry meat. And you may wonder why the water can able
to rupture the protein molecule. So here is the water molecule H, which
contain two hydrogen and one oxygen. In fact this molecule is extremely
beautiful. It can actually organize itself to a
really really regular structure. But before it goes to solid, it actually
random, just like this structure. Water for it crystallize, become a ice
basically, it just randomly arrange by themselves.
But, however, when we try to lower the temperature.
The water molecules start to crystallize, but how it can able to become a solid is
because those water molecule, they become arranged really organized by themselves.
This kind of rearrangement of the water molecule.
Make the volume of the water molecule become larger.
This explains why sometimes you might have an experience, that is you have a
can of Coca Cola for example. If you put it in the freezer, if you
don't, just you forgot you put a can of soft drink in the freezer, after two
hours, what will happen? The whole can of the soft drink will
burst itself. Why?
It's because, as I just mentioned, the water molecule inside of soft drink is
start to reorganize the volume. In fact, it's much bigger.
Than the irregular form. It actually expand.
The, the, the expose of this kind of, the expansion of this kind of water molecule
actually, not only can able to burst, or soft can.
But what you can imagine, you can burst. Protein molecules as well.
So that's why when the meat actually, when we try to frozen it in fact the
water molecule inside the meat muscle becomes crystallized it actually expands.
In fact, to a certain extent this type of frozen meat, in fact, some of cell wall
has been ruptured. And then, if you cooked it, you need to
defrost it. And once you defrost it and the water,
being at, or, or beginning, is being found in the protein.
Start to running out and then eventually it reduced the water-holding capacity of
the meat, and then it will result to a dry meat of those frozen meat compared to
a fresh meat.
Explorer notre catalogue
Rejoignez-nous gratuitement et obtenez des recommendations, des mises à jour et des offres personnalisées.
Coursera propose un accès universel à la meilleure formation au monde,
en partenariat avec des universités et des organisations du plus haut niveau, pour proposer des cours en ligne.
© 2019 Coursera Inc. Tous droits réservés.
