1. Protein Protein is one of the macronutrients that is essential for growth and repair of body tissue. It is also crucial to the healthy functioning of the body. Protein is made up of complex chains of molecules called amino acids. There are 20 different types of amino acid, each with a specific function in the body.

3. Key Terms

4. The functions of protein in the diet: Used for growth especially in children and pregnant women. Used to repair body tissue after illness, accidents and surgery; renewal of cell proteins for people of all ages. Enzymes vital for metabolism are composed of proteins. Hormones, which regulate some important bodily functions, are composed of protein. They provide a secondary source of energy. When the body has used all the amino acids it needs for construction, the remainder are ‘burnt’ for energy.

5. Where can we get it from? The human body needs all 20 amino acids for the maintenance of health and growth. Eleven of these can be made up by the body itself, but the others have to be obtained through the food we eat – these are called essential amino acids.

6. Sources of protein in the diet Animal sources include all meats, such as poultry, offal and game, as well as fish, cheese, milk, eggs and gelatine. Vegetable sources include soya beans and soya products, pulses, beans, cereal grains and cereal products, nuts and Quorn.

7. High biological value proteins The foods that contain all the essential amino acids are said to have a high biological value. Most of these come from animal sources (meat, fish, poultry and dairy products) plus the vegetable source of soya. As the vegetarian market grows, there is a large range of food products made from soya, such as soya mince, textured vegetable protein (TVP) and tofu. Another HBV protein is Quorn, which is a brand name for a food product made from mycoprotein.

8. There are 3 main types of meat eaten in the UK… These are called red meats (though pork is sometimes classed as white meat). They’re all great sources of protein, but too much can cause health problems like heart disease. Meat can be tenderised. You have to partly break down the fibres in the meat, you can do this by hitting it with a mallet, marinating it in something acidic or by cooking it very slowly (this is what makes casseroles so lovely and tender). Meat can dry out during cooking. To avoid this you can seal the outside of the meat (by cooking it at a high temperature for the first couple of minutes)- this keeps the juices in.

9. Three main types of poultry… These are white meats – although duck’s often called red meat. Poultry is good source of protein and B Vitamins and is fairly low in saturated fat (especially without the skin!) But it can be contaminated with salmonella bacteria, which can make you seriously ill.

10. And three main types of fish… Fish is very nutritious – it contains loads of vitamins, plus omega 3 oils which are great for health.

11. Low biological proteins Vegetable sources of protein include cereals, peas, beans, pulses, nuts and seeds. As these do not contain all the essential amino acids they are said to have low biological value (LBV). They can easily be combined in a meal or product to provide all the essential amino acids. This is called food combining or complementary proteins.

12. Meat Analogues Meat analogues use either naturally occurring ingredients (e.g. Soya bean) or fermentation technology to manufacture a food which has been altered to perform a particular function i.e. act as an alternative to meat.

13. Some people choose not to eat meat because of a variety of ethical, social and value issues and obtain all their protein from other sources. In recent years, manufacturers have produced many meat-like products, called ‘meat analogues’, which mimic the sensory properties of meat and can be used to replace or extend meat in traditional products, e.g. textured vegetable protein (TVP), myco-protein and tofu. Many of these analogues are also fortified with vitamins and minerals, e.g. vitamin B12 and iron.

14. Textured Vegetable, Protein (TVP) What is it? It is composed of bundles of short fibres of extruded soya protein. The globular soya protein is gelled by heat and shear to form a fibrous structure. Plain TVP may have a ‘beany’ taste, so needs to be flavoured. Varieties of flavoured TVP are available. Uses It is used in sausages, pies, Cornish pasties, burgers and pasta and dishes.

15. Tofu What is it? It is produced from ground soya beans, which have been sieved. The proteins are coagulated, producing a soft cheese-like product. Tofu is semisolid and is available in plain and smoked forms. As it is quite soft, it absorbs flavours well. Uses It does not have a meaty texture, yet may be used for many dishes as a substitute for meat, e.g. in stir -fries and steamed dishes.

16. Myco-protein What is it? It is produced by fermentation of a particular organism (Fusarium graminearum) to produce fine fibres, which are formed together to produce a meat analogue. It has similar textural properties to meat and contains a small amount of fibre. The myco-protein undergoes forming, cutting and texturising according to the nature of the product to be made. Uses Myco-protein absorbs flavours well and may be cooked in many different ways. It is easily formed into many different shapes. e.g. mince, burgers, fillets and sausages.

17. Protein deficiency Not eating enough protein can cause various problems: In children, growth slows down or stops. Digestive upsets are caused as enzymes are not produced. The liver fails to function normally. Muscles become weak, so limbs are thin and the tummy is soft and may look distended.

18. Apply it! Answer the following questions: List four functions of protein in the diet. (4 marks) Explain the difference between HBV and LBV proteins. (4 marks) Explain why you would combine protein foods to complement each other. (4 marks) Give two examples of complementary proteins. (2 marks)

19. Key points Protein is needed for growth and repair of body tissues. Protein is made up of amino acids. Good sources of high biological proteins are meat, fish, cheese, eggs and soya. Good sources of low biological value protein are pulses, cereals and nuts.

20. Function  Growth and repair of muscles, tissues and organs During digestion, proteins are broken into amino acids. The amino acids are absorbed into the blood made into new proteins in the cells of the body. There are 20 different amino acids which can combine together to make proteins such as muscle ; hormones; skin; haemoglobin The body can make 11 of the amino acids, the other 9 have to come from the food we eat. These are known as essential amino acids. Meat Poultry Oily Fish White Fish Shellfish Essential amino acids are found in protein from animal tissue and soya bean. These foods are called High Biological Value (HBV). Protein from plant sources are said to be Low Biological Value (LBV) as they are lacking in one or more of the essential amino acids. Meats (lamb, beef & pork) can be high in saturated fats but are a good source of Vitamin B, Iron and Zinc. Poultry (chicken, duck & turkey) is low in saturated fat and is a good source of Vitamin B. Fish (Oily fish, white fish & shellfish) is very nutritious as it contains a range of vitamins and omega 3 oils. Vegetarians don’t eat meat so get their protein from beans, lentils, nuts and alternative proteins like Quorn or Tofu.

21. Practice Questions 1 1.What do we need proteins for? 2.List 3 examples of foods that contain all the essential amino acids. 3.Name two vitamins or minerals that are contained in each of the following: a) beef b)pork 4.Mary is going to cook a steak for dinner. Before she fries it, she bashes it with a mallet. Explain why she does this. 5.Give 1 advantage and 1 disadvantage of eating white meats. 6.What are the three main types of fish? Give an example of each type. 7.How can someone on a vegetarian diet ensure they get the required amount of protein? 8.a) what does ‘marinate’ mean? b) why are alternative protein foods often marinated?

23. Eggs We mainly eat hens’ eggs, but goose, duck and quail eggs are popular with some people.

24. Eggs have lots of uses and functions in cooking… Binding, e.g. in burgers – coagulation sticks the ingredients together as they cook. Coating or enrobing – eggs help dry ingredients like breadcrumbs to stick to food Glazing, e.g. on bagels – brushing egg over bread gives it a glossy finish when it’s cooked. Emulisifcation, e.g. in salad dressings – oil and water mixed together form an emulsion. But the emulsion usually separates after a while. Lecithin, found in egg yolk, keeps the emulsion stable (stops it separating again). That’s why egg yolks are used in mayonnaise. Aeration, e.g. in cakes – egg white traps air when it’s beaten, because the protein stretches. Thickening, e.g. in custard or quiche – egg white coagulates (becomes solid) at 60ºC and yolk at 70ºC, so when it reaches these temperatures it sets and stays ‘thickened’.

25. Eggs may contain Salmonella 1.Raw eggs may contain the bacteria salmonella – which causes severe food poisoning. (You can also get it from chicken that isn’t cooked properly!) 2.It’s very important that eggs are cooked thoroughly so that all bacteria are destroyed. 3.You should be extra careful when cooking eggs to be eaten by pregnant women, babies and elderly or frail people. 4.Manufacturers often use dried or pasteurised egg to be on the safe side, like for mayonnaise.

26. Be careful with how you cook your eggs… The way you cook an egg can make a lot of difference to how healthy it is. Boiled and poached eggs are nice and healthy because they’re cooked using no fat. Scrambled eggs are healthy – and if you do them in the microwave you don’t need any fat. A lot of people like fried eggs though – and these can absorb a lot of fat from oil. It’s best to use oils with unsaturated fat and drain off as much of the oil as possible before eating them.

27. Practice Questions 2 1.List 5 nutrients contained in all eggs. 2.Explain how eggs can be used in each of the following ways and give an example product or food for each: a) aeration b) binding c) thickening 3. a) what part of an egg does lecithin come from? b) Why is it used in mayonnaise? 4. Describe 3 ways you can reduce the risk of getting salmonella. 5. Why are fried eggs less healthy than boiled eggs?