Food is cooked to make it safe by destroying harmful bacteria, to make it easier to digest, to improve its flavour, colour, texture and aroma, to give variety in the diet, and to keep it longer in some cases. Heat reaches the food in three ways: conduction (heat passing through a solid such as a pan), convection (heat carried by moving liquid or air, as in boiling or baking) and radiation (heat rays, as in grilling).

What is gelatinisation and why does it matter?

Gelatinisation is what happens when starch is heated with liquid: the starch grains absorb the liquid, swell and burst, and the mixture thickens into a gel as it cools. It is the science behind thickening a sauce, gravy or custard with cornflour or plain flour. Knowing it lets you explain why a sauce thickens, why it must be stirred to stay smooth, and why too much starch makes it too thick.

What are coagulation and denaturation of protein?

Denaturation is when protein unfolds and changes shape because of heat, acid or beating; coagulation is the next stage, when the unfolded proteins set firm. Together they explain why an egg white turns from runny and clear to firm and white when cooked, why meat firms up, and why milk curdles with acid. This is the science behind setting custards, baking and frying eggs.

What do raising agents do and what are the main types?

Raising agents make baked products rise and become light by introducing a gas that expands when heated. The three types are air (beaten in by whisking eggs or rubbing fat into flour), steam (from the water in a wet mixture, as in choux pastry and Yorkshire pudding), and carbon dioxide (from chemical raising agents such as baking powder, or from yeast in bread). The gas expands in the heat and is then set in place as the mixture cooks.

How can cooking be done to keep the most nutrients?

Water-soluble vitamins (B group and vitamin C) are lost into cooking water and destroyed by long heating, so steam or stir-fry vegetables quickly in little water, cut them just before cooking, and serve straight away. Use the cooking water in soups or sauces to save dissolved nutrients, and avoid keeping food hot for a long time. Fat-soluble vitamins (A, D, E, K) are more stable, but overcooking still wastes nutrients and spoils texture and colour.

SingaporeNutrition & Food Science

Food science and the effects of cooking: why we cook, methods of cooking, effects on nutrients, functional properties of carbohydrates, proteins and fats, and raising agents

An N(A)-Level Nutrition and Food Science (SEAB 6073) overview of food science and the effects of cooking: why food is cooked and how heat is transferred, the effects of cooking on nutrients, the functional properties of carbohydrates, proteins and fats, and raising agents, with links to every dot point and a worked recipe-science walkthrough.

Generated by Claude Opus 4.87 min readSEAB-6073Updated 2026-06-13

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

What this module demands
Why we cook and what cooking does
The functional properties cooks use
How this module is examined
Check your knowledge

What this module demands

This is the science of what actually happens when you cook. SEAB (6073) wants you to explain why we cook food and how heat travels, what cooking does to nutrients, and the functional properties that cooks rely on, such as starch thickening a sauce, egg setting a custard and a raising agent making a cake rise. The written Paper 1 tests this with explanation questions ("explain why a flour-thickened sauce thickens when heated"), and the coursework food study expects you to choose and justify methods using this science. This overview links every dot point in the module.

You can see the full set of dot points at /sg-n-level/nutrition-and-food-science/syllabus/food-science-and-the-effects-of-cooking.

Why we cook and what cooking does

Start with why food is cooked and methods of cooking. Food is cooked to make it safe, easier to digest, and better in flavour, colour, texture and aroma, and to give variety. Heat is transferred by conduction (through solids), convection (through moving liquid or air) and radiation (heat rays), and each cooking method uses one or more of these.

Effects of cooking on nutrients explains the trade-off: cooking improves safety and digestibility but can destroy nutrients, especially the water-soluble vitamins B and C. The practical lesson is to cook vegetables quickly in little water and serve them straight away to keep the most goodness.

The functional properties cooks use

Functional properties of carbohydrates covers gelatinisation (starch swelling and thickening a sauce), dextrinisation (starch browning under dry heat, as in toast) and caramelisation (sugar browning when heated). These explain how sauces thicken and how foods brown.

Functional properties of proteins and fats covers denaturation and coagulation (protein unfolding then setting, as in a cooked egg), foam formation (whisking egg white traps air) and emulsification (fats helping oil and water mix, as in mayonnaise). These are the science behind setting, aerating and binding.

Raising agents explains how baked goods rise: air, steam and carbon dioxide (from baking powder or yeast) each expand in the heat and are then set in place as the mixture cooks.

How this module is examined

Explain a process in steps. Questions ask you to explain gelatinisation, coagulation or how a raising agent works. Give the cause, the change and the result.
Choose a method with reasons. Questions ask which cooking method suits a food and why, linking the method to heat transfer, nutrient retention and the result you want.
Link cooking to nutrients. Explain how a method affects vitamins and how to reduce loss.

The science of cooking a steamed egg custard with a side of greens

A student makes a steamed egg custard served with stir-fried greens and explains the science.

step Choose the methods and heat transfer

Steaming cooks the custard gently by convection of hot steam, which suits a delicate egg mixture; stir-frying cooks the greens quickly by conduction from the hot pan, keeping them crisp and bright.

step Explain how the custard sets

As the egg and milk mixture is heated, the egg proteins first unfold (denaturation) and then join together and set firm (coagulation), turning the runny mixture into a soft, set custard. Gentle steaming avoids overheating, which would make the custard rubbery and weepy.

step Explain the greens and nutrients

Stir-frying the greens for a short time in a little oil cooks them fast, so less vitamin C is lost than in long boiling; serving them straight away keeps the most of this water-soluble vitamin.

step Judge the result

The dish is safe and easy to digest, the custard is smooth from controlled coagulation, and the greens keep their colour, texture and vitamin C, showing how choosing the right method protects both quality and nutrients.

Check your knowledge

Attempt these, then check against the solutions.

State three reasons why food is cooked. (3 marks)
Name the three ways heat is transferred in cooking and give one cooking example of each. (3 marks)
Explain what happens during gelatinisation. (3 marks)
Explain why a whisked egg white becomes a stiff foam. (2 marks)
Name the three types of raising agent and give one example of a food raised by each. (3 marks)

Solutions

Q1: Any three of: to make food safe by destroying harmful bacteria; to make it easier to digest; to improve flavour, colour, texture and aroma; to give variety; and to keep some foods longer.
Q2: Conduction (e.g. frying or pan-cooking), convection (e.g. boiling or baking) and radiation (e.g. grilling or toasting). (Any one valid example for each.)
Q3: When starch is heated with liquid, the starch grains absorb the liquid, swell and burst, releasing starch that thickens the mixture; as it cools it sets into a gel. This is how a flour or cornflour sauce thickens.
Q4: Whisking egg white traps tiny bubbles of air; the egg protein unfolds (denatures) and forms walls around the bubbles, holding the air and turning the liquid white into a stiff foam.
Q5: Air (e.g. in a whisked sponge cake), steam (e.g. in choux pastry or Yorkshire pudding) and carbon dioxide (e.g. in bread from yeast, or scones from baking powder).

Sources & how we know this

Singapore-Cambridge GCE N(A)-Level Nutrition and Food Science (Syllabus 6073) — Singapore Examinations and Assessment Board (2026)
My Healthy Plate and dietary guidelines — Health Promotion Board, Singapore (2026)