What jobs do ingredients do when we cook, and why do recipes work?
The functional and chemical properties of ingredients, including aeration, coagulation, gelatinisation, shortening, emulsification, denaturation, dextrinisation and caramelisation.
A focused CCEA GCSE Food and Nutrition answer on the functional and chemical properties of ingredients, covering aeration, coagulation, gelatinisation, shortening, emulsification, denaturation, dextrinisation and caramelisation, with examples in real dishes.
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What this dot point is asking
CCEA wants you to know the functional and chemical properties of ingredients, that is, the science of what happens when you cook, including aeration, coagulation, gelatinisation, shortening, emulsification, denaturation, dextrinisation and caramelisation, with an example of each.
Why these properties matter
The key properties
| Property | What happens | Example |
|---|---|---|
| Gelatinisation | Starch grains swell and burst in hot liquid, thickening it | White sauce, custard |
| Dextrinisation | Starch browns in dry heat | Toast, bread crust |
| Coagulation | Protein sets and firms on heating | Fried egg, quiche |
| Denaturation | Protein structure unravels (heat, whisking, acid) | Whisked egg white for meringue |
| Aeration | Air is trapped to make a mixture light | Creamed cake mixture, whisked sponge |
| Shortening | Fat coats flour, giving a crumbly texture | Shortcrust pastry |
| Emulsification | Oil and water held together by an emulsifier | Mayonnaise, salad dressing |
| Caramelisation | Sugar browns and changes flavour on heating | Caramel, toffee |
Pairing properties in one dish
Many dishes use several at once. A quiche uses shortening in the pastry and coagulation of egg in the filling; a Victoria sponge uses aeration (creaming) and coagulation (the egg setting in the oven).
Linking to the rest of the course
These properties underpin cooking and heat transfer (heat triggers most of them) and the practical tasks in Unit 2, where you explain and use them in the dishes you make.
Examples in context
- Example 1. Why pastry is "short"
- In shortcrust pastry, fat coats the flour and limits gluten forming, so the cooked pastry crumbles rather than being tough. This is shortening, and it explains the rub-in method, a practical skill assessed in the course.
- Example 2. Mayonnaise that does not split
- Egg yolk contains lecithin, a natural emulsifier that holds tiny oil droplets in vinegar so the mixture stays creamy instead of separating. This is emulsification, and it shows why a specific ingredient (egg yolk) is chosen for a function.
- Example 3. The brown crust on bread
- As bread bakes, the dry heat browns the starch on the surface (dextrinisation) and any sugars caramelise, giving the golden crust and flavour. This links two chemical properties to a familiar result.
Try this
Q1. Name the property that thickens a sauce as starch swells in hot liquid. [1 mark]
- Cue. Gelatinisation.
Q2. Explain what shortening does in pastry. [2 marks]
- Cue. Fat coats the flour so it absorbs less water and forms less gluten, giving a crumbly, short texture.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA past-style6 marksExplain the terms gelatinisation, coagulation and aeration, giving an example of each in cooking.Show worked answer →
Six marks: a definition and an example for each (two marks each).
Gelatinisation is when starch grains swell and burst in hot liquid, thickening it into a sauce or gel. Example: making a white sauce, where flour thickens the milk as it heats.
Coagulation is when protein sets or becomes firm on heating (or whisking). Example: an egg setting when fried, or eggs setting a baked custard or quiche.
Aeration is trapping air in a mixture to make it light and risen. Example: whisking egg whites for meringue, or creaming butter and sugar in a cake.
Markers reward a correct definition and a valid example for each term.
CCEA past-style4 marksExplain what shortening and emulsification mean, naming a dish that relies on each.Show worked answer →
Four marks: definition plus dish for each (two marks each).
Shortening is when fat coats flour particles and stops them absorbing water, giving a crumbly, short texture. Dish: shortcrust pastry, which is crumbly because the fat shortens the gluten.
Emulsification is mixing two liquids that normally separate, such as oil and water, using an emulsifier to hold them together. Dish: mayonnaise, where egg yolk (lecithin) emulsifies oil and vinegar; also salad dressings and cake batters.
Markers reward a correct definition and a valid dish for each property.
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