FN7: Functional Properties of Food
How food ingredients behave during cooking: gelatinisation, coagulation, emulsification, foaming, browning, and shortening.
Functional Properties of Food
How food ingredients behave during cooking: gelatinisation, coagulation, emulsification, foaming, browning, and shortening.
Key Fact: Functional properties are the characteristics of food components that affect how they behave during preparation and cooking — they determine the texture, appearance, and structure of food products.
Key Fact: Gelatinisation: starch granules absorb water, swell, and burst when heated in liquid (above 60°C), thickening the mixture. The starch molecules (amylose and amylopectin) gelatinise, creating a gel on cooling. Used in: sauces (white sauce, gravy), soups, custard.
Key Fact: Dextrinisation: dry heat breaks down starch into dextrins (smaller carbohydrate molecules), producing browning and a sweeter taste. Used in: toast, bread crust, roasted vegetables. Over-dextrinisation produces bitter flavours (burnt toast).
Key Fact: Coagulation: proteins change from liquid to solid when heated (above 60°C for egg white, 70°C for egg yolk). The protein molecules denature (unfold) and then form new bonds, creating a solid network. Over-coagulation makes proteins tough and rubbery. Used in: egg custard, scrambled egg, cooked meat.
Key Fact: Emulsification: combining two immiscible liquids (oil and water) using an emulsifier. The emulsifier has a hydrophilic head and hydrophobic tail, allowing it to sit between oil and water droplets. Used in: mayonnaise (egg yolk as emulsifier), salad dressings, sauces.
Key Fact: Foaming: incorporating air into a liquid to create a foam. Egg whites form stable foams because denatured proteins form a network around air bubbles. Key factors: clean bowl (no fat/grease), room temperature eggs, acid (cream of tartar) stabilises. Used in: meringues, soufflés, mousses.
Key Fact: Browning reactions: Maillard reaction (amino acids + reducing sugars, above 140°C) and caramelisation (sugars heated above 160°C, producing golden colour and toffee flavour). Both create complex flavour compounds.
Key Fact: Shortening: fat coats flour particles during rubbing in, preventing gluten formation and creating a short, crumbly texture. Used in: pastry, biscuits, shortbread. The more fat, the shorter (more crumbly) the texture.
Key Fact: Gluten formation: when flour is mixed with water, glutenin and gliadin proteins form gluten — an elastic network that traps gas for rising. Strong flour (bread) has more gluten; weak flour (cake/pastry) has less. Over-kneading makes gluten tough.
Key Fact: Plasticity: fats can be shaped and spread at room temperature — important for pastry-making and cake creaming. Butter has good flavour but poor plasticity (too hard when cold). Margarine has better plasticity.
Key Fact: Gelation: setting of a liquid into a gel when cooled. Gelatine (from animal collagen), agar (from seaweed), and pectin (from fruit) form gels. Used in: jelly, set desserts, jams.
Key Fact: Aeration: incorporating air into mixtures to increase volume and create light texture. Methods: creaming (fat + sugar), whisking (eggs + sugar), folding (flour into whisked eggs), raising agents (baking powder, bicarbonate of soda).
📋 Key Vocabulary and Concepts
For Functional Properties of Food, you must know:
- Gelatinisation
- Dextrinisation
- Coagulation
- Denaturation
- Emulsification
- Emulsifier
- Foaming
- Maillard reaction
- Caramelisation
- Shortening
- Gluten
- Plasticity
- Aeration
- Gelation
❓ Practice Questions
Q: Explain the process of gelatinisation and its role in sauce-making.
Q: What is the difference between the Maillard reaction and caramelisation?
Q: Explain how emulsification works, using mayonnaise as an example.
✅ Answers
- Gelatinisation occurs when starch granules are heated in liquid above 60°C. The granules absorb water and swell. As temperature increases, the granules burst, releasing amylose and amylopectin which thicken the liquid. On cooling, the starch molecules form a gel network, setting the sauce. This process thickens white sauce, gravy, and custard. The ratio of starch to liquid determines the final consistency.
- The Maillard reaction involves amino acids and reducing sugars reacting at temperatures above 140°C, producing browning and complex savoury flavours. It requires protein (amino acids). Caramelisation involves only sugars heated above 160°C, producing browning and sweet toffee-like flavours. It doesn't require protein. Both produce browning but have different reactants and flavour profiles.
- Mayonnaise is an oil-in-water emulsion. Oil and water are immiscible, but egg yolk contains lecithin — an emulsifier with a hydrophilic (water-loving) head and hydrophobic (water-hating) tail. The hydrophobic tail embeds in oil droplets while the hydrophilic head faces the water, creating a stable barrier around each oil droplet that prevents them from coalescing. Oil must be added slowly to allow the emulsifier to coat each droplet.
🎯 Exam Tips
- Always describe the science AND give a practical food example
- Use correct scientific terminology (denaturation, not 'unfolding'; coagulation, not 'setting')
- Explain the process step-by-step for maximum marks
📝 Exam Technique
Food Preparation & Nutrition Exam Tips — Functional Properties of Food:
1. For Functional Properties of Food questions, show every step of your working clearly — method marks count even if the final answer is wrong
2. Check your answer makes sense in context (estimation, units, reasonableness)
3. Use correct mathematical notation and state formulae before substituting values
4. If a Functional Properties of Food question asks you to 'prove' or 'show', write a logical chain of reasoning with a conclusion line
5. For problem-solving, identify the topic first, then recall the relevant method
1. For Functional Properties of Food questions, show every step of your working clearly — method marks count even if the final answer is wrong
2. Check your answer makes sense in context (estimation, units, reasonableness)
3. Use correct mathematical notation and state formulae before substituting values
4. If a Functional Properties of Food question asks you to 'prove' or 'show', write a logical chain of reasoning with a conclusion line
5. For problem-solving, identify the topic first, then recall the relevant method
⚠️ Common Errors
✗ Gelatinisation and gelation are the same process. ✓ Gelatinisation involves starch granules absorbing water and swelling when heated. Gelation involves a liquid setting into a gel when cooled (e.g. gelatine setting a jelly). They are different processes with different mechanisms.
✗ Caramelisation and Maillard reaction are the same. ✓ Caramelisation involves only sugar breaking down under heat. The Maillard reaction involves amino acids AND reducing sugars reacting together. They produce different flavours — caramelisation gives sweet toffee flavours; Maillard gives savoury, complex flavours.
✗ Eggs coagulate at a single fixed temperature. ✓ Egg white begins to coagulate at around 60°C and is fully set by 65°C. Egg yolk begins at around 65°C and is fully set by 70°C. This is why eggs can be cooked with a runny yolk but set white — the different proteins coagulate at different temperatures.
✍️ Model Answer
Full-Mark Response
Explain how the functional properties of protein are used in cooking, using specific examples. [12 marks]
Proteins have several key functional properties that are exploited in cooking: denaturation, coagulation, foaming, emulsification, and gelation. Denaturation is the unfolding of protein molecules due to heat, acid, or mechanical action. This is the first stage before coagulation. Whisking egg whites denatures the proteins, uncoiling them so they can form a network around air bubbles. Coagulation follows denaturation — the unfolded proteins form new bonds, creating a solid network. In scrambled eggs, heating causes egg proteins to denature and then coagulate, transforming liquid egg into solid curds. Over-coagulation (excessive heat or time) makes proteins tough and rubbery — this is why overcooked eggs become rubbery and overcooked meat becomes dry and chewy. Foaming exploits the ability of denatured proteins to trap air. In meringues, egg white proteins denatured by whisking form a stable network around air bubbles. Acid (cream of tartar) stabilises the foam. Sugar strengthens the foam but must be added gradually. Baking sets the foam permanently through coagulation. Emulsification uses proteins as emulsifiers. Egg yolk contains lecithin, which stabilises oil-in-water emulsions like mayonnaise. The lecithin's hydrophilic head and hydrophobic tail sit between oil and water, preventing separation. Gelation occurs when proteins form a three-dimensional network that traps liquid. Gelatine (denatured collagen) forms a gel on cooling — used in jelly, panna cotta, and trifles. Understanding these properties allows cooks to control texture and structure: gentle heat for tender coagulation, correct technique for stable foams, and gradual addition for successful emulsification.
📊 AO Deep Dive
Assessment Objective Analysis
AO1 (Knowledge & Understanding): Demonstrate knowledge and understanding of functional properties of food, including nutritional principles, food science, and food safety regulations.
AO2 (Application): Apply knowledge and understanding of functional properties of food to practical cooking contexts, recipe adaptation, and food choice decisions.
AO3 (Analysis & Evaluation): Analyse and evaluate functional properties of food in relation to nutritional needs, food safety, sustainability, and cultural factors. Justify decisions with reasoned arguments and evidence.
📝 Exam Questions by Topic
- AQA Past Papers - Topic Questions -- AQA
- Edexcel Past Papers - Topic Questions -- Edexcel
- OCR Past Papers - Topic Questions -- OCR
- Eduqas Past Papers - Topic Questions -- Eduqas
🎬 Video Resources
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