1. © Food – a fact of life 2009 Carbohydrate and its functional and working properties in food products Extension Many foods contain some carbohydrate but the amounts of sugars, starch and fibre differ. Sugars are naturally present in foods such as milk, fruits, vegetables and honey. In the UK, sugar beet and sugar cane are the most common sources of sugar. Honey, treacle and golden syrup are also popular. Starch is present in foods such as potatoes, bread, rice and pasta. Fibre is present in whole grains, fruits and vegetables, especially the skin covering of seeds. It is a mixture of substances (mainly complex carbohydrates) which cannot be digested in the small intestine. Fibre, also known in the UK as non-starch polysaccharides (NSP), e.g. cellulose and pectin and guar gum is found in fruits, vegetables, beans and cereals.

2. © Food – a fact of life 2009 Functional properties Carbohydrates perform different functions in food products. They: Contribute to the chewiness, colour and sweet flavour of caramel Help cause the colour change of bread, toast and bakery products Thicken products such as sauces and custards Flavouring: sugar, e.g. sucrose, may be used to flavour many products such as drinks, cakes, tomato sauce and confectionary. It supplies sweetness and mouth feel. Preserving: sugar in high concentrations prevents the growth of micro-organism. It is used extensively in the production of jam, marmalade and some canned fruit. Sugar is an important ingredient in determining the shelf-life of a product. Jelling: some fruits, such as apples and blackcurrants, are rich sources of pectin. Pectin is used as a jelling agent in the production of jam. Dextrinisation Foods which are baked, grilled or roasted undergo colour, odour and flavour changes. This is due to a reaction involving protein and a reducing sugar. These polymerise to form complex brown coloured compounds called dextrins. These compounds contribute to the colour and flavour of many foods such as toast, bread and croissants. This is known as non-enzymic browning (Maillard reaction). Parts of amino acid and sugar molecules in food combine, when heated, to form brown compounds which change it’s colour, odour and flavour.

3. © Food – a fact of life 2009 Caramelisation When sucrose (sugar) is heated above its melting point it undergoes a physical change to produce caramel. This happens more readily without water, however syrups will caramelise with rapid heating. This process is used extensively in the production of confectionary. Overheating will cause the substance to become bitter and dark. The effect of dry heat on sugar is to cause melting, browning or caramelisation and eventually burning. Moist Grains Continued Forms a Caramelise Burn heat dissolve heat syrup e.g. browning of sugar on top of crème brulèe, production of spun sugar work. Crème Brulèe: http://www.youtube.com/watch?v=8nTcoAOyOvM&feature=related http://www.youtube.com/watch?v=8nTcoAOyOvM&feature=related Spun Sugar: http://www.youtube.com/watch?v=Qoe8UPvVe2U&feature=related http://www.youtube.com/watch?v=Qoe8UPvVe2U&feature=related

4. © Food – a fact of life 2009 Gelatinisation The process by which a gel is formed. It is usually associated with the thickening process of starchy foods in conjunction with a liquid and heat, in processes such as sauce making, cooking potatoes, pasta, rice. e.g. custard & other sauces which use flour or corn flour, pasta, rice, potatoes Starches absorb a large quantity of water and the starch eventually cross-links to form a three dimensional network. The temperature at which the starch gelatinises depends upon the starch used. When a suspension of starch in liquid is heated, the liquid penetrates the outer layers of the granules and the granules begin to swell and eventually rupture, absorbing liquid which thickens the mixture. This occurs from 60°C to 80°C The granules swell until they are as much as 5 times the original At 80°C the starch granules begin to break up dispersing the contents into the liquid The long chain molecules unfold and the mixture becomes more viscous (thicker) to become a sol On cooling, if enough starch is used, a gel forms and it becomes solid. This process is used in the production of blancmange Heat Starch grains soften Swell until Makes the mixture & absorb water they break thicker

5. © Food – a fact of life 2009 Retrogradation This is the reverse of gelatinisation and is usually seen in relation to the seepage of water from a thickened sauce. Water is expelled from the gel and the starch gradually changes its characteristics. In the case of bread, when it stales, it loses water and this can be considered a retrogradation. Starches containing amylose gel best, because the molecules are spiral shaped and form a network in which water is trapped. This produces a rigid gel. Amylose molecules tend to unwind in time however, producing a watery deposit, an opaque gel and a pulpy, spongy texture. It occurs mainly when foods are frozen and thawed. High amylopectin starches do not retrograde easily Some retrogradation can be reversed, e.g. the bread can be reheated to regain some of the original texture.

6. © Food – a fact of life 2009 Protein and its functional and working properties in food products Most foods contain protein, such as collagen in meat, gluten in wheat flour and albumin in egg white Some types of protein help with reactions – these are called enzymes, whilst others form part of the structure of the cells Protein performs different functions in food products. They: aerate foods, e.g. whisking egg whites; thicken sauces, e.g. egg custard; bind ingredients together, e.g. fish cakes; form structures, e.g. gluten development in bread; gel, e.g. lime jelly. Denaturation Denaturation is the change in structure of protein molecules. It is the break down of links in the chains of amino acids during heating. The process results in the unfolding of molecules. Factors which contribute to denaturation are heat, salts, pH and mechanical action. Denaturation is a partially reversible change. For example, when an egg white is whisked it incorporates air to form a foam. If the foam is left to stand, it will collapse back to form liquid egg white.

7. © Food – a fact of life 2009 Coagulation Coagulation follows denaturation. It is the setting of proteins during heating. For example, when egg white is cooked it changes colour and becomes firmer or sets. This change is irreversible. Another form of coagulation occurs in the production of cheese. Rennin (an enzyme from a calf’s stomach) is added to milk causing the protein casein to clot, producing curds (solid) and whey (liquid). Other applications of coagulation are: yogurt making thickening of sauces with beaten egg binding ingredients together, e.g. fish, cakes providing a coating for products, e.g. scotch eggs Temperature raised slowly (kept at around 66°C) = protein will set gradually (coagulate) & not become too hard. e.g. poached egg Temperature raised above 100°C = protein will set quickly (coagulate) and harden. e.g. fried egg DENATURATION COAGULATION (break down when heated) (quickly/slowing depending on temperature) High temperatures also cause protein foods to brown, giving added flavour to meat & look more appealing/appetising.

8. © Food – a fact of life 2009 Gluten formation Two proteins, gliadin and glutenin, found in wheat flour, form gluten when mixed with water. Gluten is strong, elastic and forms a 3D network in dough. In the production of bread, kneading helps untangle the gluten strands and align them. Gluten helps give structure to the bread and keeps in the gases that expand during cooking. The amount and type of protein present depends on the flour type and quality. Strong flour contains a maximum of 17% protein, plain flour 10%. A cross section is shown below of under developed dough and weak or soft flour 8% respectively. Products that require short or non-elastic textures, such as biscuits and cakes, use flours with lower protein contents. https://www.youtube.com/watch?v=zDEcvSc2UKA

9. © Food – a fact of life 2009 Gelation Gelatine is a protein which is extracted from collagen, present in connective tissue in meat. When it is mixed with warm water the gelatine protein molecules start to unwind. Although on cooling a stable network is formed, trapping the liquid. Gelation is reversible. Syneresis is the shrinkage of a gel and the subsequent loss of liquid Gels affected by syneresis can be based upon protein An example of syneresis is scrambled egg, which if overcooked, shrinks and produces a liquid Another example is jelly left to stand, producing a pool of water around the base Syneresis

10. © Food – a fact of life 2009 Fat and its functional and working properties in food products All fats and oils have unique flavours and odours. Some are more suited for particular purposes than others, e.g. olive oil for salad dressing (for flavour) and lard for pastry (due to its blandness). They can also contribute to the texture of the food, for example increasing succulence. Retention of moisture : Some fats can help retain a bakery product’s moisture and increase its shelf-life. They may also be used to baste food being cooked by dry heat, e.g. roast beef. Glaze : Placed on hot vegetables, some fats give glossy appearance, e.g. butter or margarine. Fats also add shine to sauces. Sensory attributes: All fats and oils have unique flavours and odours. Some are more suited for particular purposes than others, e.g. olive oil for salad dressing (for flavour) and lard for pastry (due to its blandness). They can also contribute to the texture of the food, for example increasing

11. © Food – a fact of life 2009 Shortening Shortcrust pastry, biscuits and shortbread rely on fat to give them their characteristic crumbly texture. The fats coats the flour particles and prevents them from absorbing water. This reduces the formation of gluten development, which would cause the dough to become elastic. Fats such as pure vegetable fats or lard are suitable for shortening because of their low water content. There are distinctive colours associated with the type of fat used. Margarine produces a golden colour and lard produces a pale yellow. A compromise is sometimes reached by using a combination of the two. Plasticity Fats do not melt at fixed temperatures, but over a range. This property is called plasticity. It gives all fats unique character. The plasticity is due to the mixture of triglycerides, each with it’s own melting point. Some products are formulated with fats with lower melting points so they can spread from the fridge, e.g. margarine, or melt on the tongue, e.g. chocolate. Other fats have a higher melting point and are used for cooking.

12. © Food – a fact of life 2009 Aeration Products such as creamed cakes need air incorporated into the mixture in order to give a well risen texture. This is achieved by creaming a fat, such as butter or margarine, with caster sugar. Small bubbles of air are incorporated and form a stable foam. Flakiness Flaky and puff pastry use fat to help separate layers of gluten and starch formed in the dough. The fat melts during cooking, leaving minute layers. The liquid present produces steam which evaporates and causes the layers to rise. The fat prevents the layers sticking together. Retention of moisture Some fats can help retain a bakery product’s moisture and increase its shelf-life. They may also be used to baste food being cooked by dry heat. Glaze Placed on hot vegetables, some fats, e.g. butter or margarine, give glossy appearance. Fats also add shine to sauces.

13. © Food – a fact of life 2009 Functional properties overview Foundation Ingredients have a range of different properties. Sometimes these are called functions. The main nutrient provided by an ingredient gives it a range of properties during cooking. Carbohydrate, protein and fat all have a range of different properties.

14. © Food – a fact of life 2009 Aerating Product / IngredientHow do you aerate?Why does it aerate? Meringue / Egg white Whisk egg white to produce a foam. Fold foam with other ingredients to create light mixture, e.g. sugar. Protein in egg white denature and trap air in a stable network Scone / Self raising flour Combine self raising flour with other ingredients and bake. Raising agents in the flour react with water to produce carbon dioxide which expands on heating. Cake / Baking powder Add baking powder to flour, mix with other ingredients and bake. Baking powder reacts with water to produce carbon dioxide which expands on heating. Wholemeal bread / Yeast Sprinkle dried yeast into flour mixture and add liquid, knead the dough and leave to rise then bake. Yeast releases carbon dioxide and alcohol during rising and baking, causing the dough to expand - the alcohol and water evaporate during baking.

15. © Food – a fact of life 2009 Binding Product / IngredientHow do you bind?Why does it bind? Nann bread / Yogurt Combine yogurt with main ingredients and stir. Liquid present in yogurt is absorbed by the starch granules and hydrates proteins in the flour to form a network. Pancake / Milk Whisk milk gradually into other ingredients until smooth. Milk disperses the protein from the egg and suspends the starch granules from the flour in a smooth batter mixture. Fish cake / Egg Mix egg with other ingredients. Raw egg combines the other ingredients and during cooking the protein in the egg coagulates keeping the fish cake together. Pastry / Water Stir water into flour mixture until a dough is formed. Water is absorbed by the starch granules, hydrating proteins in the flour to form a network.

16. © Food – a fact of life 2009 Bulking Product / IngredientHow do you bulk?Why does it bulk? Fruit Pie Filling / Sugar Boil sugar with fruit juice, reduce mixture to thickness required, add prepared fruit, assemble pie and bake. Water evaporates and the mixture caramelises producing a syrup or a thick puree. Vegetable Samosa / Potato Prepare filling using potato as the main ingredient, add extra liquid and seasoning if needed, assemble and cook. Potato absorbs flavours and liquid, retaining its shape and texture - forming the body of the filling. Nut Roast / Breadcrumbs Stir breadcrumbs with other ingredients, add extra liquid and seasoning if needed, bake. Breadcrumbs absorb flavours and liquid and bind to other ingredients. Cottage Pie / Textured Vegetable Protein (TVP) Mix reconstituted TVP with minced meat and vegetables, add extra liquid and seasoning if needed, layer mashed potato on top. TVP absorbs flavours and liquid, mimics the sensory properties of meat - forming the main part of the filling.

17. © Food – a fact of life 2009 Glazing Product / IngredientHow do you glaze?Why does it glaze? Sausage Roll / Egg Brush beaten egg over the surface of the sausage roll before baking. The surface of the sausage roll takes on a shiny golden brown appearance due to coagulation of egg proteins and the Maillard browning reaction. Bun / Sugar Boil sugar with water or milk, brush over the surface of the bun after baking. The liquid evaporates and caramelises producing a syrup, which gives the buns a shiny and sticky appearance. Pie / Milk Brush milk over the surface of the pie before baking. The surface of the pie takes on a matt light brown appearance due to the Maillard browning reaction. Gammon / Honey Spread honey over the gammon before roasting. The honey caramelises giving a shiny brown appearance.

18. © Food – a fact of life 2009 Setting Product / IngredientHow do you set?Why does it set? Blancmange / Cornflour Blend cornflour with a little milk and sugar to a smooth paste, gradually add to hot milk, stir and heat to boiling point - allow to cool. The corn starch grains swell and rupture, releasing starch which absorbs the liquid, the mixture sets on cooling. Cold Soufflé Mix gelatine with a little warm water until it has dissolved, add to remaining mixture slowly to avoid lumps forming. The gelatine swells, forming a network which traps water forming a gel. Quiche Mix egg with other fillings, pour mixture into pastry case and bake. On heating the egg protein coagulates, setting the mixture. Jam Heat fruit and sugar, add extra pectin, water and citric acid if needed - boil until setting point is reached - allow to cool. The pectin, sugar and acid form a gel which traps the water.

19. © Food – a fact of life 2009 Thickening Product / IngredientHow do you thicken?Why does it thicken? Sauce / Flour Blend the flour with melted fat, gradually add the liquid, stir and heat to boiling point. Starch granules in the flour swell, rupture and release starch which absorbs the liquid causing the mixture to gelatinise. Egg custard / Egg Add beaten egg slowly to the milk and sugar mixture, heat gently, stirring continuously until thick. The egg coagulates on heating and thickens the mixture. Soup / Potato Combine chunks of potato with other solid ingredients, add liquid and heat. Potato starch is released from the cells on heating and absorbs liquid which gelatinise and thicken the soup. Syrup / Sugar Heat sugar and water (or fruit juice) together, reduce the mixture to the thickness required. The water evaporates and the mixture caramelises producing a syrup.