Meat

Meat is an important food commodity which provides nutrients essential for health.

A variety of different textures, colours and flavours of meat are available for you to choose.

This unit contains an overview of the origin, structure and composition of different types of meat.

Meat

Types of meatMeat is the flesh of animals and birds that is eaten by humans.

Red meat includes flesh from

•Cattle (beef)

•Sheep (lamb)

White meat encompasses flesh from

•Pigs (pork)

•Calves (veal)

•Poultry (chicken, turkey, duck)

Game meat is dark meat that may come from

•Rabbits

•Kangaroo

•Crocodiles

•Deer

•Wild birds

The structure of meatAnimal flesh consists of muscle tissue or fibres, connective tissue and fatty (adipose) tissue.

Lean meat is the muscle tissue of animals.

Meats are composed of a combination of

• water 75%

• proteins 20% (actin and myosin in muscle fibres) (elastin and collagen in connective tissue).

• vitamins and minerals 5%

• Fat 5-40%

What’s the connection?Meat muscle is made up of bundles of long muscle fibres held together by creamy white connective tissue.

Tendons join the muscle (made up of bundles of muscle fibres, surrounded by connective tissue and fatty tissue) to the bones of animals.

meatandeducation.com 2011

Component 1: MuscleIndividual muscle fibres are made up of cells which contain the proteins actin and myosin.

In live animals, actin and myosin work together to make the muscle contract and relax.

Muscle fibres

Fine muscle fibres These tend to come from the muscles of young animals, or in older animals from the muscles which do least work.

They contain little collagen and are tender even when cooking times short, e.g. grilling.

Muscle fibres are very small – and can only be seen under a microscope. The length of muscle fibres varies.

Thick muscle fibresThese tend to be from older animals and also muscles which do the most ‘work’ – such as neck and shin.

They have more connective tissue to prevent muscle damage.

This type of meat is tougher and needs long, slow cooking with moisture to make it tender, e.g. casserole.

Component 2: Connective TissueConnective tissue is made up of two proteins called collagen and elastin.

CollagenThe connective tissue in and around the muscle fibres and tendons is mostly collagen. When meat is cooked, the collagen becomes soft and soluble, and forms gelatine.

Elastin (gristle) This is much more elastic connective tissue.

It is yellow in colour and remains tough, even when cooked. The ligaments which join two bones together are mostly made up of elastin.

Component 3: Fatvisible fat

Fat is found in meat underneath the skin (subcutaneous fat) and between the muscles (intermuscular fat) and is a creamy-white colour.

Visible fat (called suet) is also found around the animal’s organs, such as the kidneys.

Visible fat

Invisible Fat

A small amount of fat is also found in connective tissue surrounding the bundles of muscle fibres. This is usually not obvious to the eye, so it is known as invisible fat. Sometimes these lines of fat can be seen and give meat a ‘marbled’ look.

The colour of meatThe colour of meat is largely due to the red protein called myoglobin and some haemoglobin (blood) left in the muscle. Some muscles contain more of these red pigments than others.

Colour differences can be due to age and exercise, but are mainly due to the metabolism of the species and the function of the particular muscle.

Meat from muscles which have been used a lot and are from older animals is usually a darker colour. For example, chicken breast is much whiter in colour than the leg or wing. Also chicken is much lighter than duck due to the fact that they are not a bird of flight; whereas duck is a darker meat due to the fact that it moves more.

meatandeducation.com 2011

The colour of meatDuring the time meat is stored the colour changes to a darker brown-red because of the formation of metmyoglobin.

When meat is cut and exposed to oxygen in the air, it takes about twenty minutes for myoglobin to change to oxymyoglobin, which is brighter red in colour.

After some time, the meat becomes a browner colour again as metmyoglobin is formed.

These colour changes do not make any difference to the taste or texture.

Tenderness of MeatsOverall , natural meat tenderness is due to factors such as the cut, age, and fat content.

Cut. The toughest cuts of meat come from the hardest working muscles that do more exercise and have greater amount of connective tissue e.g neck, shoulder, chest (beef, lamb, pork) wings, legs (poultry). Parts of the animal which do greater exercise are also darker due to increased blood flow. Tender cuts are from the parts that are not worked as hard and have less connective tissue e.g the beef rump, sirloin and chicken breast.

AgeThe more younger the animal, the more tender it is as the muscle fibres thicken as the animal ages. Aging also means the animal exercises more causing a greater development of connective tissue.

Fat contentIncreased fat throughout the meat (marbling) can increase tenderness as the fat melts during cooking to give increased moisture and juiciness. However as an animal gets older, the visible fat increases which provides toughness.

Tenderness of MeatsOverall , natural meat tenderness is due to factors such as the cut, age, and fat content.

Meats can also be treated to make them more tender.•Enzymes are sometimes injected to the animal before slaughter or used in many ‘meat tenderiser’ products. The enzymes used include:

Papain- PapayaFicin- figsBromelain- Pineapple.

•Mechanical methods such as chopping, grinding, pounding etc

•Marinades containing acids chemically break the meat fibers.

•Preparation temperatures and times also have an influence on tenderness.

Choice of cut and method? Tender cuts suit quick dry cooking as they have little fat and connective tissue. e.g. Grilling, deep frying, pan frying,

Tougher cuts suit longer cooking times as the connective tissue needs time to break down. They can be cooked dry (roasting) but are mostly suited to slow, wet cooking methods. e.g. stewing, braising.

Justify with reasons what cut you would choose for… a chicken casserole? a steak sandwich? a beef bourguignon? A chicken parmigana ?

Changes that occur to the properties on cooking meatTexture

• Protein solidifies and becomes firm (coagulates). If overcooked the protein shrinks and releases water leaving a dry meat.

• Collagen denatures and converts to gelatin over long times• Meat goes from soft and mushy to firm, moist and easy to bite

Color• Surface browning is due to the maillard reaction. • Myoglobin pigment denatures and changes colour from red to

brown.Flavor

• Cooking intensifies flavor and enhances aroma. Dry heat develops best flavor due to surface browning in maillard reaction.

Nutritive value• No loss of protein• Some loss of B-vitamins

Why is it important to cook meat?

Safe to eat• Meat is a high protein and high water food, making it a very high

risk for bacteria and food poisoning. Cooking meat above 70 degrees destroys bacteria.

More palatable• Easier to chew as cooking changes texture.

Develop flavours• Cooking intensifies flavor and enhances aroma. Intense heat

develops flavoured crust in maillard reaction.

SeafoodThe three main types of seafood can be classified as White fish •less 5% fat •delicate flesh•tropical waters •whiting, flathead, perch, john dory,

Oily fish •between 10-25% fat •darker flesh colour•salmon, sardines, tuna,•good source of omega-3 oils

Shellfish•have an outer shell •not as easily digested as fish •two types

• Crustaceans – have a hard outer shell that turns orange when cooked. Example: prawns, crayfish, crab

• Molluscs – have a shell that opens when cooked. Example: oysters, mussels, clams, scallops

Seafood

Nutritional benefits (chemical properties)

•Contains complete protein (all essential amino acids)•Fat in fish and seafood is good a source of Omega-3 oil - assists in reducing heart disease •B group vitamins •A and D vitamins (oily fish only)•Minerals

PhosphorusCalciumIodineFluorine (salt water only)

Fish

Properties of fish

•70 % water•20% protein•Muscles of fish are arranged in layers of short fibres surrounded by very thin sheets of delicate connective tissue. •Very little amount of connective tissue. Only 3% compared with meat having 15% of body weight. •Fat in fish is good a source of Omega-3 oil - assists in reducing heart disease •In its raw state, fish is translucent, firm to touch and juices are clear and watery. •Fish when cooked becomes opaque, the flakes begin to separate and the juices are milky white.

EXAM QUESTIONS

1.The tenderness of meat is influenced by a number od factors including the age of the animal, the muscle from which the meat comes from, the activity levels of the animal, the use of acid marinades, preparation techniques and fat content.

Select 3 of the factors above and describe how each one contributes to the overall tenderness when it is cooked. 9 marks

2.There are a number of changes that occur to the properties of meat when it is cooked.

Describe these changes in detail. 6 marks

1.Meat is usually cooked before it is eaten. Provide a detailed explanation of why it is important to cook meat prior to consumption. 3 marks

2.Japan has one of the highest life expectancies of any population in the world. This has been attributed to the fact that Japanese people eat a large amount of deep sea fish such as Salmon.

Explain why this high consumption of fish may contribute to a greater life expectancy and explain why fish is a healthy choice. 2 marks