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© Boardworks Ltd 20051 of 26 These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates that.

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Presentation on theme: "© Boardworks Ltd 20051 of 26 These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates that."— Presentation transcript:

1 © Boardworks Ltd 20051 of 26 These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates that the slide contains activities created in Flash. These activities are not editable. For more detailed instructions, see the Getting Started presentation. © Boardworks Ltd 2005 1 of 26 Product Design Food Products

2 © Boardworks Ltd 20052 of 26 Learning objectives To understand that food products require the right proportions of ingredients. To learn about the physical and chemical properties of starch, sugar, protein and fat. To understand about the role of raising agents in food production. © Boardworks Ltd 2005 2 of 26

3 © Boardworks Ltd 20053 of 26 Food groups

4 © Boardworks Ltd 20054 of 26 Food groups

5 © Boardworks Ltd 20055 of 26 Which foods are high in protein?

6 © Boardworks Ltd 20056 of 26 The main property of proteins is that they coagulate on heating – they become solid. The protein in the white and the yolk of an egg both set when cooked (the yolk takes longer to set than the white as it contains less protein). Properties of proteins The protein in meat and fish coagulates too. Acid sets protein. If acid is added to milk, it curdles. These curds make cheese.

7 © Boardworks Ltd 20057 of 26 binding – the egg coagulates and sticks the dry ingredients together as they are cooked (used for burgers and cakes) coating – egg and breadcrumbs coat fish before frying; the egg coagulates and provides a barrier to stop oil seeping in glazing – the egg sets during baking and turns golden brown as it reacts with the starch (Maillard reaction) thickening – egg can be used instead of starch to thicken custard and soup. It also sets the sauce in a quiche foaming – the protein in the white of the egg unravels when beaten and holds lots of air; it can increase to eight times its original volume. Eggs Eggs can be used in a number of useful ways since they coagulate. They can be used for:

8 © Boardworks Ltd 20058 of 26 Using eggs

9 © Boardworks Ltd 20059 of 26 The muscle tissues of meat and fish mainly contain protein which coagulates during cooking. The length of the muscle fibres and how they are grouped together determines how much cooking time is needed for the meat or fish to become tender. Meat and fish Meat has longer muscle fibres than those of fish, which are bundled together with collagen and elastin. Elastin is tough and yellow in colour and binds the muscle fibres to the bone in addition to binding the muscle fibres together. Fish needs a shorter cooking time than meat because it is made up of short muscle fibres held together in bundles with a small amount of collagen (which dissolves when heated). Fish can easily become overcooked with the liquid in the muscle being evaporated away, leaving the fish dry and chewy.

10 © Boardworks Ltd 200510 of 26 The tenderness of meat is dependent on the length and size of the muscle fibres. The length of the fibre and amount of connective tissue varies according to which part of the animal the muscle tissue comes from. The more the muscle works, the longer the fibres are and the more connective tissue there is, meaning that the meat is tougher and needs more cooking time. Why does meat vary in tenderness? Which is the toughest meat out of these examples? breast? thigh? fillet steak? leg joint?

11 © Boardworks Ltd 200511 of 26 How can meat be tenderized?

12 © Boardworks Ltd 200512 of 26 Which foods are high in carbohydrates?

13 © Boardworks Ltd 200513 of 26 Carbohydrates are divided into three groups – starch, sugar and non-starch polysaccharides (NSP), more commonly known as fibre. They all have different functions. Which foods are high in carbohydrates? Fibre can affect the way starch works. It absorbs more water and creates a heavy texture. Compare wholemeal bread with white bread! starch sugar fibre

14 © Boardworks Ltd 200514 of 26 When starch is dry and heated it dextrinizes – it goes golden brown. Properties of starch When starch is wet and heated, it gelatinizes – it absorbs liquid and swells to give a good open texture, especially if a raising agent is used. Starch has the property of being a filling ingredient. Flour is used as a bulk ingredient in all baked products and creates the structure of a product.

15 © Boardworks Ltd 200515 of 26 Flour can be made from starchy foods other than wheat – cornflour (from maize), rice flour, potato flour and rye flour are some examples. The higher protein content of wheat flour, however, makes it an important ingredient in baked products as it mixes with liquid to form gluten. Making bread is an example: Flour Strong flour contains more protein than ordinary flour and is therefore better for making bread. The varying amounts of protein in different wheats makes them suitable for different food products. The flour is mixed with liquid to produce gluten. By kneading the dough, the protein strands are untangled and more gluten is produced. The gluten is not only strong and elastic, holding the bread together, but also traps the gases that form in bread when you cook it.

16 © Boardworks Ltd 200516 of 26 Different wheats

17 © Boardworks Ltd 200517 of 26 Properties of sugar Sugar makes foods sweet and is also an important bulking agent. When sugar is caramelized – heated to a temperature above its melting point – it adds colour, flavour and texture. Sugar can preserve a product if used in large amounts. Sugar helps food products stay moist because it is hydroscopic – attracted to water. When sugar is heated in the presence of proteins, non-enzymic browning takes place – it turns a product brown. Most importantly, sugar aerates a mixture – increases its size.

18 © Boardworks Ltd 200518 of 26 When sugar is beaten with fat, air gets incorporated into the mixture and sticks to the sugar crystals. The fat surrounds the air bubbles and traps them in the mixture, making the mixture lighter and more aerated. In a sponge cake, the butter and sugar should be beaten for eight minutes! Aeration Caster sugar is the best sugar to use because it has a large number of fine crystals, which means more air bubbles and better aeration. Granulated sugar has fewer and bigger crystals. The crystals in icing sugar are too small for aeration to work.

19 © Boardworks Ltd 200519 of 26 Which foods are high in fat? Butter has a low smoking point with lots of flavour; it is a saturated fat. Sunflower oil has very little flavour but a very high smoking point; it is a polyunsaturated fat which is better for the heart. Olive oil has lots of flavour, quite a high smoking point and is a monounsaturate which is best for the heart.

20 © Boardworks Ltd 200520 of 26 Properties of fats Fats can be animal or vegetable and solid or liquid. They have different properties and other functions in addition to adding flavour and being used in cooking. They are used for spreading (on bread), aerating (they help sugar to trap the air on account of their plasticity – they are mouldable and pliable) and shortening (they make baked products crumbly). Shortening creates the crumbly soft texture of cakes, rather than the chewy texture which is desired in bread. A high fat content stops the protein in flour from absorbing liquid by surrounding the flour particles and forming a waterproof coating. This prevents gluten from forming which would make the mixture elastic and stretchy and creates a crumbly and ‘short’ mixture instead.

21 © Boardworks Ltd 200521 of 26 Enzymic browning occurs in fruit and vegetables when they are cut open and their cut surface is exposed to the air. The enzymes in the fruit and vegetables react with the oxygen in the air, gradually turning the surface brown. Enzymic browning To stop enzymic browning taking place, vegetables can be coated in a dressing and fruit can be covered in an acid such as lemon juice.

22 © Boardworks Ltd 200522 of 26 All sorts of ingredients are used for their sensory or nutritional function, such as herbs in a sauce or peppers on a pizza. There is one other group of ingredients, however, which has an important physical function in food products – these are raising agents. Raising agents are used to make baked products rise. They are gases which expand on heating and push up the surrounding mixture. Three different gases can be used: What are raising agents? air – added mechanically by whisking, creaming or sieving steam – requires a lot of liquid being present, such as in batters and choux pastry, or a very high temperature, such as in cooking bread carbon dioxide – added chemically or biologically.

23 © Boardworks Ltd 200523 of 26 Baking powder is the chemical raising agent most commonly used to produce carbon dioxide; liquid and heat are also needed. Baking powder is a commercial mix of bicarbonate of soda, acid and flour (to add bulk). Bicarbonate of soda can be used on its own but leaves an aftertaste and yellow colour – in gingerbread this does not matter! Carbon dioxide Carbon dioxide is produced chemically or biologically. Yeast is a biological raising agent. Yeast needs food, warmth, liquid and time to ferment and produce carbon dioxide. It is used in most breads, getting its own food from the sugar in the flour.

24 © Boardworks Ltd 200524 of 26 The properties of bread

25 © Boardworks Ltd 200525 of 26 Properties of food quiz

26 © Boardworks Ltd 200526 of 26 Key points Successful food products are made by using the right proportions of ingredients. Starch, sugar, protein and fat all have important functions in food production. Raising agents are used in food production to make baked products rise. © Boardworks Ltd 2005 26 of 26


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