Food functions

How do ingredients change? Egg yolk and white mixed together. Liquid state. Bread is toasted – goes brown / crunchy. Butter melts on toast – due to heat. Egg sets during cooking. Stirring breaks up the egg – gives the scrambled look.

Introducing different roles of ingredients

How do you aerate? Whisk egg white to produce a foam. Fold foam with other ingredients to create light mixture, e.g. sugar. Why does it aerate? Protein in egg white denature and trap air in a stable network.

How do you bind? Combine yogurt with main ingredients and stir. Why does it bind? Liquid present in yogurt is absorbed by the starch granules and hydrates proteins in the flour to form a network.

Thicken How do you thicken? Blend the flour with melted fat, gradually add the liquid, stir and heat to boiling point. Why does it thicken? Starch granules in the flour swell, rupture and release starch which absorbs the liquid causing the mixture to gelatinise.

How do you bulk? Boil sugar with fruit juice, reduce mixture to thickness required, add prepared fruit, assemble pie and bake. Why does it bulk? Water evaporates and the mixture caramelises producing a syrup or a thick puree.

How do you set? 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. Why does it set? The corn starch grains swell and rupture, releasing starch which absorbs the liquid, the mixture sets on cooling.

How do you glaze? Brush beaten egg over the surface of the sausage roll before baking. Why does it glaze? The surface of the sausage roll takes on a shiny golden brown appearance due to coagulation of egg proteins and the Maillard browning reaction.

Bread is made from flour, water and yeast. Yeast produces CO2 (bubbles), which expand on cooking – making the dough rise. The flour produces the structure (protein). Grilling (heat) ‘toasts’ the bread – changing its colour. Proteins in the egg denature (unfold) forming a solid network. This is not reversible. (You can’t un-fry an egg!)

Gelatine forms a gel (the protein unfolds and forms a network) – the network traps the water inside. This is reversible, i.e. is you add heat the jelly melts.

Egg white is whisked – this mechanical process denatures the protein (it unfolds) – forming a network, trapping the air. Egg yolk, and cornflour help thicken the mix.

Milk has hot air pumped in Milk has hot air pumped in. The heat partially denatures the milk proteins – forming a network – this traps the air, resulting in a foam.

Sugar, with a little water, is heated. This forms a thick syrup Sugar, with a little water, is heated. This forms a thick syrup. On further heating the sugar caramelises (colour changes). The syrup can be formed into different shapes (colours and flavours can be added).

Victoria Sandwich Cake Making a… Victoria Sandwich Cake September 2003

Ingredients 150 grams self raising flour 150 grams soft margarine 150 grams castor sugar 3 eggs 1x 5ml spoon baking powder All measurements are in metric units. It is helpful to gather and weigh or measure all ingredients before starting to make the recipe.

Equipment 2 sandwich cake tins pastry brush grease proof paper mixing bowl electric hand whisk measuring spoons palette knife cooling rack sieve Equipment lists are important to help prepare for making.

Method The method gives step-by-step instructions, in a logical order, for example: preheat the oven first, if needed; sequence the task to ensure effective use of time; do other steps while food is cooking; specific skills, such as sift, whisk, mix, fold, beat, line or cream are included.

What is happening? Preheat oven Preheat the oven to 180oC or gas mark 4. Why? Before baking, the oven should be preheated to the correct temperature, to ensure that the cake will start to rise as soon as it is placed inside.

What is happening? Lining Grease and line 2 sandwich cake tins. Why? Greaseproof paper must be cut to the right size and greased as well as the tin to prevent the cake from sticking. Oil should be applied thinly with a pastry brush.

What is happening? Creaming Mix the fat and sugar until light and fluffy in texture. Why? This will trap air in the form of tiny bubbles, to act as a raising agent.

What is happening? Mixing Beat eggs until well mixed and add a little at a time to the fat and sugar, beating well at each addition. Why? This will ensure that the fat becomes emulsified by the egg yolk and is prevented from separating out or curdling. Air is also trapped at this stage, which is important for raising the mixture.

What is happening? Sift Sift flour and baking powder. Why? This incorporates air into the flour and removes any unwanted particles.

What is happening? Folding Fold the flour gently into the mixture a little at a time using a metal spoon. Why? A metal spoon will cut through the mixture and cause minimum disturbance to the air bubbles. It is important not to beat the flour in as this will cause trapped air to escape and reduce the volume of the mixture.

What is happening? Divide Place a spoonful of mixture alternatively into each cake tin until all the mixture is used. Why? This ensures the same amount of cake mixture is in each cake tin which in turn will result in two cakes of equal size.

What is happening? Remove Once the cakes are cooked, remove from the tins immediately, remove the paper and allow to cool on a a cooling rack. Why? Removing the cake tin and the paper allows the cake to cool down quickly. The cooling rack allows air to circulate around the cake.

What is happening? Spread Once completely cooled, spread jam over the base of one sponge and place the other sponge on top. Why? If the cake is warm, the jam will become runny and drip over the side.

This resource was developed for the DfE Teach Food Technology programme. The information provided is provided under the Open Government Licence. Terms can be found at: http://www.nationalarchives.gov.uk/doc/open-government-licence.