[旧课件] meat# Food - 画饼充饥
b*t
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ppt直接导出来的，格式有点乱，不过有耐心的话看看还挺有意思的。
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Part 3: Arts and Methods of Kitchen Arts
TOPIC: MEAT
Cooking meat
Cooking meat is all about producing the right texture and flavours.
Texture concerns the structure of meat.
Flavours are all about chemistry –the Maillard reaction.
Components of muscle
Water: 75%
Protein: 18%
Fat: ~4-10%, varies among different types of meat
Carbohydrate: just over 1%
Vitamins, minerals, various organic compounds…
Sliding-filament model of muscle contraction
Contraction and relaxation of muscles
Both muscle contraction and relaxation require energy, which they get from
the energy-carrying molecule ATP
The most efficient generation of ATP requires oxygen, which muscles get from
circulating blood.
What will happen when an animal is slaughtered?
ATP regeneration stops, and the actin and myosin remain locked in a
permanent contraction
Resulting in very tough meat!
Effect of heating on muscle fibres
When muscle fibres are heated above about 40 ℃ the proteins start to
denature, and they change their shape irreversibly.
When the protein molecules are denatured
muscles shrink
meat becomes harder
the meat becomes tough.
Muscle structure in fish
Fish muscles vs. poultry muscles
No tough connective tissue between the muscles and the bones in fish
→ no need to cook fish for any length of time to make it tender
Two types of muscle fibres and meat colour
Specialize in exerting force rapidly and briefly
Use oxygen to burn glycogen
When they generate energy faster than they blood can deliver oxygen, a waste
product, lactic acid, accumulates until oxygen arrives
Two types of muscle fibres and meat colour
Used for prolonged efforts
Fueled primarily by fat, whose metabolism requires oxygen
Red colour contributed by a pigment proteins called myoglobin, which adpot a
purple colour when they give up oxygen
Heavily used muscles need lots of myoglobin and hence darker, e.g. legs
Effect of sodium nitrite
Gives meat the red color
By prohibiting oxidation of iron (II) to iron (III) in the myoglobin
Summary on two types of muscle fibres
Muscle fibre and meat colour
Cows and pigs are both sources of dark meat, though pig is often called "the
other white meat." Pigs' muscles do contain myoglobin, but the
concentration is not as heavy as it is in beef.
Chickens have a mixture of both dark and white meat, and fish is mainly
white meat.
Connective tissue
Holds the muscles together and connect them to the bones
Usually is tough and strong
Mainly has 3 kinds of tissue:
Collagen
Reticulin
Elastin
Collagen
A complex molecule made up from 3 strands of amino acids that are twisted
together
Collagen in poultry
Mostly found around bundles of muscle fibres and helps to hold them together
. The muscles are then joined to the bones with yet more sinews, which cooks
recognize as tough “gristly” material.
Collagen in fish
Fish with little collagen (e.g. trout, bass) is relatively drier when cooked
than those with more (e.g. halibut, shark)
Because the motion for steady swimming comes mostly from the back end of the
fish, the tail region contains more connective tissue than the head end,
and seems more succulent.
Comparison of Connective Tissues
Connective tissue of fish is weak because its collagen contains less
structure-reinforcing amino acid
Connective tissues in land animal is progressively reinforced with age
Meat collagen is relatively tough and must be cooked for some time near the
boil to be dissolved into gelatin
Fat
A special form of connective tissue
Can also serve as energy storage
Found in 3 different parts of the body:
Under the skin (provide insulation and energy)
Body cavity (often around kidneys, intestine and heart)
In connective tissue separating muscles and the bundles within muscles
Role of fat in meat cooking
Provide flavour
Act as lubricant which soften the meat when we eat –marbling in meat
Role of fat in meat cooking
Demonstration:
Compare the texture of meat with and without marbling.
Demonstration- Role of fat in meat cooking
Rib Eye Steak
Sirloin Steak
Fat in fish
Fat content of fish muscle runs a tremendous range from 0.5% in cod and
other white fish to 20%
Fat storage cells are found primarily in distinct layers under the skin, and
then in the visible sheet of connective tissue that separate the myotomes
Both gelatin and fat can contribute an impression of moistness to fish
texture
Role of water in meat
Determine texture and taste:
Trapped by some of the proteins in the meat
Locked in a piece of meat - “bound water”
Will escape when the proteins are denatured by heating
If significant amounts of water are lost in this way, the cooked meat will
seem to be rather dry.
Why frozen meats often seem to be drier than fresh ones?
Role of water in meat
Demonstration:
Compare the texture and taste of fresh meat and frozen meat.
This is not recommended !!
Each time meat is frozen there is some deterioration of quality
Ice crystals tend to rupture the muscle fibre, breaking down texture and
letting juices escape
Water-holding capacity of meat
Water-holding capacity is responsible for the sensation of juiciness of meat.
Treatment that may reduce the water-holding capacity of the meat:
Grinding
Proteolysis
Freezing
Salting,
Heating and
pH alternation
Two phases of juiciness perception
The initial release of juices from the meat with early chews;
Further release of serum and increased flow of saliva resulting from the
stimulation by fat in the meat.
The composition of different meat
Eating quality of meat
It is determined by muscle tissue texture and flavours.
For texture and flavours of meats, they are controlled by the following
factors:
Water
Protein,
Fat,
Carbohydrate
Texture of meat (Toughness)
It is determined by the following factors:
Parts of the animal’s body
Animal’s age and activity
Marbling fats
Cut of Beef
1. Parts of the animal’s body
The neck, shoulders, and legs are used continually in walking and standing,
and include a number of different muscles and their connective-tissue
sheaths. They are therefore relatively tough.
The tenderloin is appropriately named because it is a single muscle with
little internal connective tissue that runs along the back and gets little
actions; it is tender.
Poultry legs are tougher than breasts: the protein in chicken legs is 5-8%
collagen compared to 2% in the breast.
2. Animal’s age and activity
Younger animals – veal, limb, pork and chicken all come from younger
animals than beef does – have tenderer muscle fibres because they are
smaller and less exercised.
Collagen in their connective tissue is more rapidly and completely converted
to gelatin than older, more cross-linked collaged.
3. Marbling fats
Tenderize the
sheet of connective tissue
and the mass of muscle fibres by creating liquid;
Melts when heated rather than drying out and stiffening as the fibres do;
Lubricates the tissue, helping to separate fibre from fibre.
Learning Outcomes
Factors that affect the meat flavour
Ways to improve meat texture
Ways to improve meat flavour
Flavour of meat
Major consideration in meeting cooking
Arise from the proteins in energy-generating machinery of the muscle fibres.
Red muscle fibres and its flavour
A high proportion of red fibres are more flavourful because it contains more:
fat droplets and fat-like components of the membrane that house the fat
oxidizers.
substances that help break flavour precursors down into flavourful pieces,
including iron atoms in myoglobin
Fat and flavour
It is considered as one of the important sources of flavour, contributing
the unique flavour of different types of meat.
Fat cells are essentially storage tissue, and any sort of fat-soluble
material, especially aroma molecules, are trapped in them (like dissolve
like!)
The flavor carried in fat gets stronger as animals get older, as more of the
flavor compounds are put into storage.
Fishy Smell
The unique smell of “fishiness” in fish is largely due to the saltwater-
balancing compound TAMO (trimethylamine oxide), which bacteria on the fish
surfaces slowly break down to smelly TMA.
Ways to remove fishy smell
TMA on the surface can be rinsed off with tap water
React with acidic substances such as lemon juice, vinegar, tomatoes :
Contribute a hydrogen ion, which thereby take on a positive electrical
charge, and becomes non-volatile to go into our nose.
Methods to modify the texture of meat
Physical methods
Chemical methods
Physiology
Physical method
Demonstration:
Compare the texture of meat being treated with and without pounding.
Physical Method
Sliced with the grain (i.e., parallel to these fibres) will result in a long
, tough, uninterrupted fibre that may be unchewable
Sliced thinly across the grain will result in tiny length of fibre and is
easy to chew
Slicing and craving
Slicing across the grain is also important when the meat is raw:
When a piece of raw chicken breast or flank steak is sliced lengthwise with
the grain, when it cooks it will shrink into a tough wad.
In chicken or turkey breasts, the grain runs along the length of the breast.
Slicing and craving
Demonstration:
Compare the texture of meats being sliced across the grain and those being
sliced along the grain.
Slicing and flavour
Shaved ham seems more flavorful than the same ham cut thicker:
it is because there is much more surface exposed to oxygen and more surfaces
in the mouth to influence taste.
Chemical methods
Increase the water content and prevent the meat to dry out during cooking,
resulting in meat tendering.
Increase disruption of the structure of muscle fibre so as to open up “
tunnels” in meat structure to hold more water content
Chemical methods
Demonstration:
Compare the texture of meat being treated with baking soda and those with no
treatment.
2. Marinating
to steep food in a marinade which is a savory acidic sauce
Serve two purposes: a) enrich its flavor or b) to tenderize the meat
Marinades usually contain 3 components: acid, oil and herbs
Marinating
Demonstration: Marinating I
To compare the texture of marinated and un-marinated meat
Demonstration: Marinating II
To compare the effect of marinating on cut meat and whole piece of meat
3. Brining
The meats are immersed in a brine containing 3-6% salt by weight
Duration: from a few hours to two days (depending on the thickness)
Cooked as usual.
The action of brining
When meat is first placed in a brine, since the concentration of salt in the
brine is much higher than that of the cells in the meat, water is thus
being drawn out of the cells and salt flows in.
The salt dissolves some of the protein fibres, and the cell fluids of the
meat become more concentrated again, thus drawing water back in.
Two initial effects of brining
Salt disrupts the structure of the muscle filaments:
A 3% salt solution (2 tablespoons per quart/30 gm per liter) dissolves parts
of the protein structure that supports the contracting filament.
A 5.5% solution (4 tablespoons per quart/60 gm per liter) partly dissolves
the filaments themselves.
The interactions of salt and proteins result in a greater water holding
capacity in the muscle cells by creating a more concentrated medium in the
muscle cells, which then absorb water from the brine, due to osmosis.
Pros and Cons of using brining
Pros:
Counterbalance the lose of moisture during cooking
The dissolved protein filaments can’t coagulate into normally dense
aggregates, so the cooked meat seems more tender
Cons:
Makes both the meat and its drippings quite salty (saltiness can be balanced
by sugar or ingredients as fruit juices or buttermilk, which provide both
sweetness and sourness)
Brining
Demonstration:
Compare the texture of brining meat and non-brining meat
4. Meat tenderizer
Meat tenderizers are protein-digesting enzymes extracted from a number of
plant, such as pineapple, kiwi and ginger.
The enzymes act slowly at refrigerator or room temperature, and some five
times faster between 60-70oC
Disadvantages of meat tenderizer
Meat tenderizers penetrate into meat slowly, so that the meat surface tends
to accumulate too much while the interior remains unaffected.
The distribution can be improved by injecting the tenderizer into the meat.
Meat tenderizer Demonstration
Demonstration: Meat tenderizers
To demonstrate the effect of meat tenderizer
Demonstration: Improving the texture of meat
To compare different methods in improving the texture of meat
Physiology
1. Rigor mortis
Known as “Stiffness of Death”
Result in very tough meat when cooked in this state
Muscle fibers run out of energy and protein filament lock in place
Rigor mortis
It can greatly improves the texture and found that meat that does not go
through the process has a gummy texture
The increase in acidity slows spoilage of meat and also enhances the water-
holding capacity of meat proteins.
Aging
Occurs after rigor
The work of the muscle enzymes
The uncontrolled enzymatic activity after the animal is slaughtered
tenderizes meat by:
Weakening the supporting proteins that hold the contracting filament
together
Weakening the collagen fibres in connective tissue by breaking some of the
cross-link between them
Effects of aging on meat texture
Causes more collagen to dissolve into gelatin during cooking
→ making the meat more tender and succulent.
Reduces the squeezing pressure (strain) that the connective tissue exerts
during heating
→ more moisture can be kept during cooking.
Methods to modify the flavour of meat
Rigor and aging
The Maillard reactions
Rigor and aging
Uncontrolled enzymatic activity turns large flavourless molecules into
smaller, flavourful fragments:
Break proteins into savory amino acids;
Break glycogen into sweet glucose;
Break energy currency ATP into savory IMP (inosine monophosphate);
Break fats and fat-like membrane molecules into aromatic fatty acids
Maillard reaction/Browning reaction
A series of reactions which help to develop flavour during cooking
Louis Camille Maillard, a physician, work in investigating how the amino
acids would react with sugars and found that all the meaty flavours and
change of color that develop during cooking are caused by reactions of amino
acids with sugars.
Amino Acids + Carbohydrates → Meat Flavour
The Maillard reactions
Occurs most readily at around 300° F to 500° F
The first step of the reactions occurs between the carbonyl group of a sugar
molecule (in the chain form) and an –NH2 group, to eliminated a molecule
of water.
The Maillard reactions
The Maillard reactions
During Maillard reactions, proteins and carbohydrates are degraded into
smaller sugars and amino acids.
The sugar rings open and the resulting aldehydes and acids react with the
amino acids to produce a wide range of chemicals.
Molecules found in the Maillard reactions
Over 1000 different molecules have been identified as products of the
Maillard reactions.
Include polymers that are responsible for the brown colour of roast meat (
toast, etc.) and small molecules such as maltol that are responsible for
aroma.
Molecules identified in the Maillard reactions
Di-sulphides have pungent and even unpleasant smells.
Bis-2-methyl-3-furyl-disulphide is responsible for the meaty odor and is now
widely used in flavour industry.
Conditions necessary for Maillard reaction
Protein
With an exposed amino group (-NH2) from protein
Reducing sugars
Glucose (corn syrup) with an aldehyde (-CHO) are most reactive
Nonacidic environment:
Acid prevent Maillard reaction
at pH 7 and above, browning occur
at pH 6.5-6.8 some browning occurred
at pH 5 or lower, no browning occurred.
Conditions necessary for Maillard reaction
High temperature:
The Maillard reactions only take place at temperatures above 140℃.
Since high temperature only occurs at the surface of the meat, flavour will
develop more quickly with an increase in surface area.
However, some of the new molecules formed at 200℃ can be carcinogenic,
polyaromatic hydrocarbon (PAH)
Changes in appearance of meat during cooking
Initially the appearance of meat is translucent:
because its cells are filled with a relatively loose meshwork of protein
suspended in water.
When heated to 50℃, it develops a white opacity:
as heat-sensitive myosin denatures and coagulates into clumps large enough
to scatter light, causes red meat colour to lighten from red to pink
Around 60℃, red myoglobin begins to denature into a tan-coloured version
called hemichrome. As this change proceeds, meat colour shifts from pink to
brown-grey
Fe2+ (Oxidation) Fe3+
Learning Outcome
How to judge the doneness of meat?
Change in meat texture during cooking
Types of Cooking methods
Ways of meat preservation
Judging doneness of fresh meat by colour
The denaturation of myoglobin parallels the denaturation of fibre proteins,
making it possible to judge the doneness of fresh meat by colour:
Little-cooked meat and its juices are red;
Moderately cooked meat and its juices are pink;
Thoroughly cooked meat is brown-gray and its juices clear
Misleading redness by myoglobin
If myoglobin has already been denatured by prolonged by exposure to air,
light or to freezing temperature, it’s possible for undercooked meat to
look brown and well-done
Effect of heat on meat texture
Change in water-holding capacity
Change in muscle fibres
Change in connective tissue
Change in water-holding capacity
Initially during heating, meat still remains juicy even though the water-
holding capacity is reduced.
Reason: there is a conversion of bound water to free water. This conversion
of water offsets the water lost during cooking.
Rate of free water lost = Rate of conversion of bound water
At 74-80℃, too much bound water is converted to free water, result in
reduced juiciness.
Change in muscle fibres
Muscle proteins in meat become less tender/tough
Reason:
When fibres are heated to 40-50℃, myosin becomes less soluble, and
hydration of myosin and other muscle proteins decreases.
When further heating to temperature 65-75℃, this affect the tenderness of
muscle proteins occurs.
Change in connective tissue
Collagen is converted to gelatin under heating
The length of time that meat is held above 65 ℃ is important in promoting
collagen conversion to gelatin
The opposing effect of collagen and muscle proteins
The tenderizing effect of heating collagen for an extended period is opposed
by the toughening effect of heat on muscle proteins:
If collagen content is high, classified as less tender, extended heating is
desirable to permit considerable conversion of collagen to gelatin. This
tenderizing action will more than compensate for the toughening of the
muscle proteins that is occurring at the same time.
The opposing effect of collagen and muscle proteins
Tender cut of meat will become less tender with extended heating if the meat
reaches temperatures above 60℃, it is due to the toughening of the muscle
proteins, a change that cannot be offset by the conversion of limited
amounts of collagen to gelatin.
The opposing effect of collagen and muscle proteins in fish
Since only a small amount of collagen is found in fish, the major effect of
heating is change in muscle proteins.
By heating fish just until it flakes, some softening of collagen occurs to
permit easy separation of fibres while some denaturation of the muscle
proteins also occurs. The meat at this stage is still tender.
Similarly, prolonged heating increases toughness because change in the
muscle proteins occurs.
Effect of temperature
Maillard reactions occur only at above about 140 ℃, without the occurrence
of Maillard reactions, the meat will not taste “meaty”.
The combination of attempting not to heat those muscles that contain little
connective tissue above about 40℃, while heating those parts where there is
lots of connective tissue to temperatures above 70℃; and at the same time
ensuring that some parts are heated to above 130℃ for the meaty flavour
makes the cooking of meats a complex process.
Cooking methods for meat
High temperature and short cooking time:
allow the occurrence of Maillard reactions and at the same time keeps the
meat tender.
Low temperature and long cooking time:
can melt the connective tissue of the meat; but Maillard reaction will not
occur.
Key points in cooking meats
Always ensure the outside of the meat is cooked at a high temperature until
it is a dark brown color. – i.e. start cooking meats at high temperatures
Cook meats with little connective tissue for only a short time so that the
outside is browned, but the inside does not become tough – i.e. grill, fry
or roast these meats
Cook meats with lots of connective tissue for very long times so that all
the connective tissue denatures and the bundles of coagulated muscle
proteins fall apart making the meat tender again. – i.e. make stews with
gristly meats
Grilling and broiling
Advantages:
Intense heat gets the surface of the meat to high temperature fast
→ occurrence of Maillard reactions
Cooking time is short
→ keeps the interior of the meat at a relatively low temperature
to prevent toughening and excessive shrinkage and moisture loss.
Grilling and broiling
Disadvantages:
Methods only work best for thin, tender cuts and fish.
Heat cannot be conducted to the centre of a thick cut.
Less powerful grill will cause fish muscle to coil up and expel water,
resulting in a dry and tough meat.
Roasting
Low temperature slow roasting:
produces even cooking and juiciness and tenderness texture
High temperature roasting:
creates flavourful browning and is fast
Roasting of fish involves exposing it to the fierce heat of a hot oven
the fish skin will crisp up well, providing a good combination of textures
from the crisp outer layer to the moist and tender flesh inside the fish.
Baking
Fish is often baked with vegetable:
so that some of the steam that rise from the fish and vegetables remains
above and around the fish, which helps to reduce the overall loss of water
Frying
Shallow frying:
pieces of meat are cooked in enough melted fat or oil to bathe the bottom
and sides of the meat.
Deep-frying:
there is enough oil to immerse the meat completely
A rapid cooking method
Applied to thin, tender cuts best suited for grilling and broiling
Role of fats and oils in frying
Fat and oil used can be heated to temperature well above the boiling point
of water, producing dry, crisp and brown texture of meat
Sautéing
Sautéing in butter or oil.
Common method of cooking fish in home.
The outside of the fish is hot enough for Maillard reactions to occur to
develop new flavour.
Poaching, stewing, braising and boiling
Advantages of using water to cook meat:
Transmits heat rapidly and evenly
The temperature of water can be easily adjusted
Carry and impart flavour and become a sauce
Disadvantages of using water:
Cannot get hot enough to generate browning flavours at the meat surface
→ meats can be browned first in a frying pan to develop flavour
Poaching, stewing, braising and boiling
A prolonged time cooking is one useful strategy in cooking meat with water-
based liquids:
→ The time that the meat spends below 50℃ amounts to a period of
accelerated aging that weakens the connective tissue and reduces the time
needed at fiber-drying temperature.
→ Allow meat enzymes to tenderize and flavour the meat
→ Allow more of the myoglobin pigment to remain intact
Poaching, stewing, braising and boiling
Meats cooked in liquid should be allowed to cool in that liquid:
→ The capacity of the meat tissue to hold water increases as it cools, so
it will actually reabsorb some of the liquid it lost during the cooking.
Steaming
Suitable for thin, tender cuts of meat, and seafood
Advantages:
The fastest method for pouring heat into food
Disadvantages:
Does not guarantee moist meat: ∵muscle fibres heated to the boiling point
shrink and squeeze out much of the moisture, and steamy atmosphere cannot
replace it.
Maillard reactions do not occur
Cooking methods
Demonstration:
Compare the texture and flavour of meat being cooked with different cooking
methods: boiling, frying, deep frying, sautéing and microwaving.
Preserving methods
Curing
Smoking
Freezing
Drying fish
Curing and its effect on meat
A treatment of meat with salt, sodium nitrates (NaNO3), and heat to achieve
colour and flavour changes:
The original nitrate is reduced to nitrite, which then reacts with myoglobin
in the meat to produce the familiar red colour and prevent botulism
Promote shelf life and reduce spoilage
E.g. corned beef and ham
Smoking and its effect on meat
Enhance flavours and to promote shelf life
Done using sawdust from hardwoods
Dries the surface
Adds distinctive flavours (depends on the types of wood being used)
Cause protein denaturation
Freezing and its effect on meat
Sharp frozen or quick freezing
Sharp frozen:
Holding meat in a storage room with rapidly moving air and a temperature of
-23℃
Slow method when compared to quick freezing
Ice crystals in meat tend to be quite large
Freezing and its effect on meat
Quick freezing:
Any technique that results in extremely fast freezing
Methods can be immersion (use of a brine solution to achieve temperatures
below the point of freezing water), contact and convection (use of a blast
of cold air).
Result in a frozen meat with small ice crystals and with extremely low
bacterial, yeast, or mold growth
Freezing and its effect on meat
Drip loss will be comparatively less for thin pieces of frozen meat:
∵Thick pieces will freeze slowly in the center, moisture will tend to be
drawn out and frozen between the fibers, while the thin pieces will freeze
so rapidly that the moisture is trapped within the fibers.
Meats are made more tender by freezing
∵Formation of ice crystals disrupt the components of muscle fibres
Drying
A common, and probably original method of preserving fish.
Made from leaving out in the sun, drying on racks over an open fire and
salting
Salting of fish
Principle:
Salt will draw moisture out of the fish, and also out of any micro-organisms
that might attack it.
Disadvantages:
Re-hydration of the dried fish is needed before consumption
Excess salt need to be get rid of to make the fish palatable
==================================
Part 3: Arts and Methods of Kitchen Arts
TOPIC: MEAT
Cooking meat
Cooking meat is all about producing the right texture and flavours.
Texture concerns the structure of meat.
Flavours are all about chemistry –the Maillard reaction.
Components of muscle
Water: 75%
Protein: 18%
Fat: ~4-10%, varies among different types of meat
Carbohydrate: just over 1%
Vitamins, minerals, various organic compounds…
Sliding-filament model of muscle contraction
Contraction and relaxation of muscles
Both muscle contraction and relaxation require energy, which they get from
the energy-carrying molecule ATP
The most efficient generation of ATP requires oxygen, which muscles get from
circulating blood.
What will happen when an animal is slaughtered?
ATP regeneration stops, and the actin and myosin remain locked in a
permanent contraction
Resulting in very tough meat!
Effect of heating on muscle fibres
When muscle fibres are heated above about 40 ℃ the proteins start to
denature, and they change their shape irreversibly.
When the protein molecules are denatured
muscles shrink
meat becomes harder
the meat becomes tough.
Muscle structure in fish
Fish muscles vs. poultry muscles
No tough connective tissue between the muscles and the bones in fish
→ no need to cook fish for any length of time to make it tender
Two types of muscle fibres and meat colour
Specialize in exerting force rapidly and briefly
Use oxygen to burn glycogen
When they generate energy faster than they blood can deliver oxygen, a waste
product, lactic acid, accumulates until oxygen arrives
Two types of muscle fibres and meat colour
Used for prolonged efforts
Fueled primarily by fat, whose metabolism requires oxygen
Red colour contributed by a pigment proteins called myoglobin, which adpot a
purple colour when they give up oxygen
Heavily used muscles need lots of myoglobin and hence darker, e.g. legs
Effect of sodium nitrite
Gives meat the red color
By prohibiting oxidation of iron (II) to iron (III) in the myoglobin
Summary on two types of muscle fibres
Muscle fibre and meat colour
Cows and pigs are both sources of dark meat, though pig is often called "the
other white meat." Pigs' muscles do contain myoglobin, but the
concentration is not as heavy as it is in beef.
Chickens have a mixture of both dark and white meat, and fish is mainly
white meat.
Connective tissue
Holds the muscles together and connect them to the bones
Usually is tough and strong
Mainly has 3 kinds of tissue:
Collagen
Reticulin
Elastin
Collagen
A complex molecule made up from 3 strands of amino acids that are twisted
together
Collagen in poultry
Mostly found around bundles of muscle fibres and helps to hold them together
. The muscles are then joined to the bones with yet more sinews, which cooks
recognize as tough “gristly” material.
Collagen in fish
Fish with little collagen (e.g. trout, bass) is relatively drier when cooked
than those with more (e.g. halibut, shark)
Because the motion for steady swimming comes mostly from the back end of the
fish, the tail region contains more connective tissue than the head end,
and seems more succulent.
Comparison of Connective Tissues
Connective tissue of fish is weak because its collagen contains less
structure-reinforcing amino acid
Connective tissues in land animal is progressively reinforced with age
Meat collagen is relatively tough and must be cooked for some time near the
boil to be dissolved into gelatin
Fat
A special form of connective tissue
Can also serve as energy storage
Found in 3 different parts of the body:
Under the skin (provide insulation and energy)
Body cavity (often around kidneys, intestine and heart)
In connective tissue separating muscles and the bundles within muscles
Role of fat in meat cooking
Provide flavour
Act as lubricant which soften the meat when we eat –marbling in meat
Role of fat in meat cooking
Demonstration:
Compare the texture of meat with and without marbling.
Demonstration- Role of fat in meat cooking
Rib Eye Steak
Sirloin Steak
Fat in fish
Fat content of fish muscle runs a tremendous range from 0.5% in cod and
other white fish to 20%
Fat storage cells are found primarily in distinct layers under the skin, and
then in the visible sheet of connective tissue that separate the myotomes
Both gelatin and fat can contribute an impression of moistness to fish
texture
Role of water in meat
Determine texture and taste:
Trapped by some of the proteins in the meat
Locked in a piece of meat - “bound water”
Will escape when the proteins are denatured by heating
If significant amounts of water are lost in this way, the cooked meat will
seem to be rather dry.
Why frozen meats often seem to be drier than fresh ones?
Role of water in meat
Demonstration:
Compare the texture and taste of fresh meat and frozen meat.
This is not recommended !!
Each time meat is frozen there is some deterioration of quality
Ice crystals tend to rupture the muscle fibre, breaking down texture and
letting juices escape
Water-holding capacity of meat
Water-holding capacity is responsible for the sensation of juiciness of meat.
Treatment that may reduce the water-holding capacity of the meat:
Grinding
Proteolysis
Freezing
Salting,
Heating and
pH alternation
Two phases of juiciness perception
The initial release of juices from the meat with early chews;
Further release of serum and increased flow of saliva resulting from the
stimulation by fat in the meat.
The composition of different meat
Eating quality of meat
It is determined by muscle tissue texture and flavours.
For texture and flavours of meats, they are controlled by the following
factors:
Water
Protein,
Fat,
Carbohydrate
Texture of meat (Toughness)
It is determined by the following factors:
Parts of the animal’s body
Animal’s age and activity
Marbling fats
Cut of Beef
1. Parts of the animal’s body
The neck, shoulders, and legs are used continually in walking and standing,
and include a number of different muscles and their connective-tissue
sheaths. They are therefore relatively tough.
The tenderloin is appropriately named because it is a single muscle with
little internal connective tissue that runs along the back and gets little
actions; it is tender.
Poultry legs are tougher than breasts: the protein in chicken legs is 5-8%
collagen compared to 2% in the breast.
2. Animal’s age and activity
Younger animals – veal, limb, pork and chicken all come from younger
animals than beef does – have tenderer muscle fibres because they are
smaller and less exercised.
Collagen in their connective tissue is more rapidly and completely converted
to gelatin than older, more cross-linked collaged.
3. Marbling fats
Tenderize the
sheet of connective tissue
and the mass of muscle fibres by creating liquid;
Melts when heated rather than drying out and stiffening as the fibres do;
Lubricates the tissue, helping to separate fibre from fibre.
Learning Outcomes
Factors that affect the meat flavour
Ways to improve meat texture
Ways to improve meat flavour
Flavour of meat
Major consideration in meeting cooking
Arise from the proteins in energy-generating machinery of the muscle fibres.
Red muscle fibres and its flavour
A high proportion of red fibres are more flavourful because it contains more:
fat droplets and fat-like components of the membrane that house the fat
oxidizers.
substances that help break flavour precursors down into flavourful pieces,
including iron atoms in myoglobin
Fat and flavour
It is considered as one of the important sources of flavour, contributing
the unique flavour of different types of meat.
Fat cells are essentially storage tissue, and any sort of fat-soluble
material, especially aroma molecules, are trapped in them (like dissolve
like!)
The flavor carried in fat gets stronger as animals get older, as more of the
flavor compounds are put into storage.
Fishy Smell
The unique smell of “fishiness” in fish is largely due to the saltwater-
balancing compound TAMO (trimethylamine oxide), which bacteria on the fish
surfaces slowly break down to smelly TMA.
Ways to remove fishy smell
TMA on the surface can be rinsed off with tap water
React with acidic substances such as lemon juice, vinegar, tomatoes :
Contribute a hydrogen ion, which thereby take on a positive electrical
charge, and becomes non-volatile to go into our nose.
Methods to modify the texture of meat
Physical methods
Chemical methods
Physiology
Physical method
Demonstration:
Compare the texture of meat being treated with and without pounding.
Physical Method
Sliced with the grain (i.e., parallel to these fibres) will result in a long
, tough, uninterrupted fibre that may be unchewable
Sliced thinly across the grain will result in tiny length of fibre and is
easy to chew
Slicing and craving
Slicing across the grain is also important when the meat is raw:
When a piece of raw chicken breast or flank steak is sliced lengthwise with
the grain, when it cooks it will shrink into a tough wad.
In chicken or turkey breasts, the grain runs along the length of the breast.
Slicing and craving
Demonstration:
Compare the texture of meats being sliced across the grain and those being
sliced along the grain.
Slicing and flavour
Shaved ham seems more flavorful than the same ham cut thicker:
it is because there is much more surface exposed to oxygen and more surfaces
in the mouth to influence taste.
Chemical methods
Increase the water content and prevent the meat to dry out during cooking,
resulting in meat tendering.
Increase disruption of the structure of muscle fibre so as to open up “
tunnels” in meat structure to hold more water content
Chemical methods
Demonstration:
Compare the texture of meat being treated with baking soda and those with no
treatment.
2. Marinating
to steep food in a marinade which is a savory acidic sauce
Serve two purposes: a) enrich its flavor or b) to tenderize the meat
Marinades usually contain 3 components: acid, oil and herbs
Marinating
Demonstration: Marinating I
To compare the texture of marinated and un-marinated meat
Demonstration: Marinating II
To compare the effect of marinating on cut meat and whole piece of meat
3. Brining
The meats are immersed in a brine containing 3-6% salt by weight
Duration: from a few hours to two days (depending on the thickness)
Cooked as usual.
The action of brining
When meat is first placed in a brine, since the concentration of salt in the
brine is much higher than that of the cells in the meat, water is thus
being drawn out of the cells and salt flows in.
The salt dissolves some of the protein fibres, and the cell fluids of the
meat become more concentrated again, thus drawing water back in.
Two initial effects of brining
Salt disrupts the structure of the muscle filaments:
A 3% salt solution (2 tablespoons per quart/30 gm per liter) dissolves parts
of the protein structure that supports the contracting filament.
A 5.5% solution (4 tablespoons per quart/60 gm per liter) partly dissolves
the filaments themselves.
The interactions of salt and proteins result in a greater water holding
capacity in the muscle cells by creating a more concentrated medium in the
muscle cells, which then absorb water from the brine, due to osmosis.
Pros and Cons of using brining
Pros:
Counterbalance the lose of moisture during cooking
The dissolved protein filaments can’t coagulate into normally dense
aggregates, so the cooked meat seems more tender
Cons:
Makes both the meat and its drippings quite salty (saltiness can be balanced
by sugar or ingredients as fruit juices or buttermilk, which provide both
sweetness and sourness)
Brining
Demonstration:
Compare the texture of brining meat and non-brining meat
4. Meat tenderizer
Meat tenderizers are protein-digesting enzymes extracted from a number of
plant, such as pineapple, kiwi and ginger.
The enzymes act slowly at refrigerator or room temperature, and some five
times faster between 60-70oC
Disadvantages of meat tenderizer
Meat tenderizers penetrate into meat slowly, so that the meat surface tends
to accumulate too much while the interior remains unaffected.
The distribution can be improved by injecting the tenderizer into the meat.
Meat tenderizer Demonstration
Demonstration: Meat tenderizers
To demonstrate the effect of meat tenderizer
Demonstration: Improving the texture of meat
To compare different methods in improving the texture of meat
Physiology
1. Rigor mortis
Known as “Stiffness of Death”
Result in very tough meat when cooked in this state
Muscle fibers run out of energy and protein filament lock in place
Rigor mortis
It can greatly improves the texture and found that meat that does not go
through the process has a gummy texture
The increase in acidity slows spoilage of meat and also enhances the water-
holding capacity of meat proteins.
Aging
Occurs after rigor
The work of the muscle enzymes
The uncontrolled enzymatic activity after the animal is slaughtered
tenderizes meat by:
Weakening the supporting proteins that hold the contracting filament
together
Weakening the collagen fibres in connective tissue by breaking some of the
cross-link between them
Effects of aging on meat texture
Causes more collagen to dissolve into gelatin during cooking
→ making the meat more tender and succulent.
Reduces the squeezing pressure (strain) that the connective tissue exerts
during heating
→ more moisture can be kept during cooking.
Methods to modify the flavour of meat
Rigor and aging
The Maillard reactions
Rigor and aging
Uncontrolled enzymatic activity turns large flavourless molecules into
smaller, flavourful fragments:
Break proteins into savory amino acids;
Break glycogen into sweet glucose;
Break energy currency ATP into savory IMP (inosine monophosphate);
Break fats and fat-like membrane molecules into aromatic fatty acids
Maillard reaction/Browning reaction
A series of reactions which help to develop flavour during cooking
Louis Camille Maillard, a physician, work in investigating how the amino
acids would react with sugars and found that all the meaty flavours and
change of color that develop during cooking are caused by reactions of amino
acids with sugars.
Amino Acids + Carbohydrates → Meat Flavour
The Maillard reactions
Occurs most readily at around 300° F to 500° F
The first step of the reactions occurs between the carbonyl group of a sugar
molecule (in the chain form) and an –NH2 group, to eliminated a molecule
of water.
The Maillard reactions
The Maillard reactions
During Maillard reactions, proteins and carbohydrates are degraded into
smaller sugars and amino acids.
The sugar rings open and the resulting aldehydes and acids react with the
amino acids to produce a wide range of chemicals.
Molecules found in the Maillard reactions
Over 1000 different molecules have been identified as products of the
Maillard reactions.
Include polymers that are responsible for the brown colour of roast meat (
toast, etc.) and small molecules such as maltol that are responsible for
aroma.
Molecules identified in the Maillard reactions
Di-sulphides have pungent and even unpleasant smells.
Bis-2-methyl-3-furyl-disulphide is responsible for the meaty odor and is now
widely used in flavour industry.
Conditions necessary for Maillard reaction
Protein
With an exposed amino group (-NH2) from protein
Reducing sugars
Glucose (corn syrup) with an aldehyde (-CHO) are most reactive
Nonacidic environment:
Acid prevent Maillard reaction
at pH 7 and above, browning occur
at pH 6.5-6.8 some browning occurred
at pH 5 or lower, no browning occurred.
Conditions necessary for Maillard reaction
High temperature:
The Maillard reactions only take place at temperatures above 140℃.
Since high temperature only occurs at the surface of the meat, flavour will
develop more quickly with an increase in surface area.
However, some of the new molecules formed at 200℃ can be carcinogenic,
polyaromatic hydrocarbon (PAH)
Changes in appearance of meat during cooking
Initially the appearance of meat is translucent:
because its cells are filled with a relatively loose meshwork of protein
suspended in water.
When heated to 50℃, it develops a white opacity:
as heat-sensitive myosin denatures and coagulates into clumps large enough
to scatter light, causes red meat colour to lighten from red to pink
Around 60℃, red myoglobin begins to denature into a tan-coloured version
called hemichrome. As this change proceeds, meat colour shifts from pink to
brown-grey
Fe2+ (Oxidation) Fe3+
Learning Outcome
How to judge the doneness of meat?
Change in meat texture during cooking
Types of Cooking methods
Ways of meat preservation
Judging doneness of fresh meat by colour
The denaturation of myoglobin parallels the denaturation of fibre proteins,
making it possible to judge the doneness of fresh meat by colour:
Little-cooked meat and its juices are red;
Moderately cooked meat and its juices are pink;
Thoroughly cooked meat is brown-gray and its juices clear
Misleading redness by myoglobin
If myoglobin has already been denatured by prolonged by exposure to air,
light or to freezing temperature, it’s possible for undercooked meat to
look brown and well-done
Effect of heat on meat texture
Change in water-holding capacity
Change in muscle fibres
Change in connective tissue
Change in water-holding capacity
Initially during heating, meat still remains juicy even though the water-
holding capacity is reduced.
Reason: there is a conversion of bound water to free water. This conversion
of water offsets the water lost during cooking.
Rate of free water lost = Rate of conversion of bound water
At 74-80℃, too much bound water is converted to free water, result in
reduced juiciness.
Change in muscle fibres
Muscle proteins in meat become less tender/tough
Reason:
When fibres are heated to 40-50℃, myosin becomes less soluble, and
hydration of myosin and other muscle proteins decreases.
When further heating to temperature 65-75℃, this affect the tenderness of
muscle proteins occurs.
Change in connective tissue
Collagen is converted to gelatin under heating
The length of time that meat is held above 65 ℃ is important in promoting
collagen conversion to gelatin
The opposing effect of collagen and muscle proteins
The tenderizing effect of heating collagen for an extended period is opposed
by the toughening effect of heat on muscle proteins:
If collagen content is high, classified as less tender, extended heating is
desirable to permit considerable conversion of collagen to gelatin. This
tenderizing action will more than compensate for the toughening of the
muscle proteins that is occurring at the same time.
The opposing effect of collagen and muscle proteins
Tender cut of meat will become less tender with extended heating if the meat
reaches temperatures above 60℃, it is due to the toughening of the muscle
proteins, a change that cannot be offset by the conversion of limited
amounts of collagen to gelatin.
The opposing effect of collagen and muscle proteins in fish
Since only a small amount of collagen is found in fish, the major effect of
heating is change in muscle proteins.
By heating fish just until it flakes, some softening of collagen occurs to
permit easy separation of fibres while some denaturation of the muscle
proteins also occurs. The meat at this stage is still tender.
Similarly, prolonged heating increases toughness because change in the
muscle proteins occurs.
Effect of temperature
Maillard reactions occur only at above about 140 ℃, without the occurrence
of Maillard reactions, the meat will not taste “meaty”.
The combination of attempting not to heat those muscles that contain little
connective tissue above about 40℃, while heating those parts where there is
lots of connective tissue to temperatures above 70℃; and at the same time
ensuring that some parts are heated to above 130℃ for the meaty flavour
makes the cooking of meats a complex process.
Cooking methods for meat
High temperature and short cooking time:
allow the occurrence of Maillard reactions and at the same time keeps the
meat tender.
Low temperature and long cooking time:
can melt the connective tissue of the meat; but Maillard reaction will not
occur.
Key points in cooking meats
Always ensure the outside of the meat is cooked at a high temperature until
it is a dark brown color. – i.e. start cooking meats at high temperatures
Cook meats with little connective tissue for only a short time so that the
outside is browned, but the inside does not become tough – i.e. grill, fry
or roast these meats
Cook meats with lots of connective tissue for very long times so that all
the connective tissue denatures and the bundles of coagulated muscle
proteins fall apart making the meat tender again. – i.e. make stews with
gristly meats
Grilling and broiling
Advantages:
Intense heat gets the surface of the meat to high temperature fast
→ occurrence of Maillard reactions
Cooking time is short
→ keeps the interior of the meat at a relatively low temperature
to prevent toughening and excessive shrinkage and moisture loss.
Grilling and broiling
Disadvantages:
Methods only work best for thin, tender cuts and fish.
Heat cannot be conducted to the centre of a thick cut.
Less powerful grill will cause fish muscle to coil up and expel water,
resulting in a dry and tough meat.
Roasting
Low temperature slow roasting:
produces even cooking and juiciness and tenderness texture
High temperature roasting:
creates flavourful browning and is fast
Roasting of fish involves exposing it to the fierce heat of a hot oven
the fish skin will crisp up well, providing a good combination of textures
from the crisp outer layer to the moist and tender flesh inside the fish.
Baking
Fish is often baked with vegetable:
so that some of the steam that rise from the fish and vegetables remains
above and around the fish, which helps to reduce the overall loss of water
Frying
Shallow frying:
pieces of meat are cooked in enough melted fat or oil to bathe the bottom
and sides of the meat.
Deep-frying:
there is enough oil to immerse the meat completely
A rapid cooking method
Applied to thin, tender cuts best suited for grilling and broiling
Role of fats and oils in frying
Fat and oil used can be heated to temperature well above the boiling point
of water, producing dry, crisp and brown texture of meat
Sautéing
Sautéing in butter or oil.
Common method of cooking fish in home.
The outside of the fish is hot enough for Maillard reactions to occur to
develop new flavour.
Poaching, stewing, braising and boiling
Advantages of using water to cook meat:
Transmits heat rapidly and evenly
The temperature of water can be easily adjusted
Carry and impart flavour and become a sauce
Disadvantages of using water:
Cannot get hot enough to generate browning flavours at the meat surface
→ meats can be browned first in a frying pan to develop flavour
Poaching, stewing, braising and boiling
A prolonged time cooking is one useful strategy in cooking meat with water-
based liquids:
→ The time that the meat spends below 50℃ amounts to a period of
accelerated aging that weakens the connective tissue and reduces the time
needed at fiber-drying temperature.
→ Allow meat enzymes to tenderize and flavour the meat
→ Allow more of the myoglobin pigment to remain intact
Poaching, stewing, braising and boiling
Meats cooked in liquid should be allowed to cool in that liquid:
→ The capacity of the meat tissue to hold water increases as it cools, so
it will actually reabsorb some of the liquid it lost during the cooking.
Steaming
Suitable for thin, tender cuts of meat, and seafood
Advantages:
The fastest method for pouring heat into food
Disadvantages:
Does not guarantee moist meat: ∵muscle fibres heated to the boiling point
shrink and squeeze out much of the moisture, and steamy atmosphere cannot
replace it.
Maillard reactions do not occur
Cooking methods
Demonstration:
Compare the texture and flavour of meat being cooked with different cooking
methods: boiling, frying, deep frying, sautéing and microwaving.
Preserving methods
Curing
Smoking
Freezing
Drying fish
Curing and its effect on meat
A treatment of meat with salt, sodium nitrates (NaNO3), and heat to achieve
colour and flavour changes:
The original nitrate is reduced to nitrite, which then reacts with myoglobin
in the meat to produce the familiar red colour and prevent botulism
Promote shelf life and reduce spoilage
E.g. corned beef and ham
Smoking and its effect on meat
Enhance flavours and to promote shelf life
Done using sawdust from hardwoods
Dries the surface
Adds distinctive flavours (depends on the types of wood being used)
Cause protein denaturation
Freezing and its effect on meat
Sharp frozen or quick freezing
Sharp frozen:
Holding meat in a storage room with rapidly moving air and a temperature of
-23℃
Slow method when compared to quick freezing
Ice crystals in meat tend to be quite large
Freezing and its effect on meat
Quick freezing:
Any technique that results in extremely fast freezing
Methods can be immersion (use of a brine solution to achieve temperatures
below the point of freezing water), contact and convection (use of a blast
of cold air).
Result in a frozen meat with small ice crystals and with extremely low
bacterial, yeast, or mold growth
Freezing and its effect on meat
Drip loss will be comparatively less for thin pieces of frozen meat:
∵Thick pieces will freeze slowly in the center, moisture will tend to be
drawn out and frozen between the fibers, while the thin pieces will freeze
so rapidly that the moisture is trapped within the fibers.
Meats are made more tender by freezing
∵Formation of ice crystals disrupt the components of muscle fibres
Drying
A common, and probably original method of preserving fish.
Made from leaving out in the sun, drying on racks over an open fire and
salting
Salting of fish
Principle:
Salt will draw moisture out of the fish, and also out of any micro-organisms
that might attack it.
Disadvantages:
Re-hydration of the dried fish is needed before consumption
Excess salt need to be get rid of to make the fish palatable
