Source: https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-1-reasons-for-cooking-and-heat-transfer [Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [GCSE](https://senecalearning.com/en-gb/revision-notes/gcse.md) › [Food Preparation](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation.md) › [AQA](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa.md) › Reasons for Cooking & Heat Transfer # Reasons for Cooking & Heat Transfer Food Preparation & Nutrition: AQA GCSE, topic 3.1.1 ## Why Do We Cook Food? Cooking food in different ways alters the texture, smell, flavour, appearance and nutritional value. Here are some explanations for _why_ we cook: ### To enhance flavours ![To enhance flavours](https://image-v2.cdn.app.senecalearning.com/2018-05/510f0df8-8fb9-4577-96ec-083f98fca74c/shutterstock_384426301.jpg) - Cooking involves chemical reactions. The chemical reactions that take place alter the flavour of the food. - When cooking different foods together, their flavours combine. - Roasting intensifies flavours. When we roast meats and vegetables, they brown and become crispier (because of added fat). This happens because the water within the foods evaporates. ### To preserve food for longer ![To preserve food for longer](https://image-v2.cdn.app.senecalearning.com/2018-05/ba2cccd8-6176-4e18-85a3-a4102280434a/shutterstock_627314192.jpg) - Cooking food at high temperatures helps to kill any bacteria and mould present. - Pasteurising milk involves heating milk to a high temperature before cooling so that it stays fresher for longer. ### To make sure it's safe to consume ![To make sure it's safe to consume](https://image-v2.cdn.app.senecalearning.com/2018-05/1a72aa61-9753-49be-8733-1d6705c4bae1/shutterstock_327673388.jpg) - Lots of foods contain dangerous toxins (e.g. rhubarb) or bacteria (e.g. sprouts and poultry) that are destroyed during the cooking process. - For example, it's important to cook chicken properly (for long enough at a high enough temperature) to kill any Salmonella bacteria present. ### To enhance texture ![To enhance texture](https://image-v2.cdn.app.senecalearning.com/2018-09/a44bae33-3c25-43a6-85be-efd6780598c0/cauliflower-vegetables-.jpg) - Many foods are harder to swallow, chew or digest pre-cooking. - Cooking softens some foods (e.g. cauliflower becomes less rigid and couscous expands as it's starch molecules become softer). - Cooking makes meats more tender because the solid fats in the meats melt and the proteins become softer. But, overcooking meats can make them tough. - Some people may prefer the textures of foods cooked in certain ways (e.g. brownies can have a soft interior and crusty exterior). ### To vary a diet ![To vary a diet](https://image-v2.cdn.app.senecalearning.com/2018-05/2cb0f90f-444a-4259-b960-09d16ae7b85d/shutterstock_788702059.jpg) - Cooking allows you to enjoy foods in many different ways. - For example, you could enjoy chicken through eating: - Roast chicken. - Barbecued chicken skewers. - A chicken curry. - A chicken stew. - A grilled chicken breast. ## Methods of Heat Transfer We use heat energy to cook. Heat energy is transferred in three ways: ### Conduction ![Conduction](https://image-v2.cdn.app.senecalearning.com/2018-05/f9031e31-4b7d-45cc-895d-861caeb03f7b/shutterstock_413329057.jpg) - Heat energy is transferred through vibrating particles. Particles are tightly packed in solids, so vibrations pass quickly from one particle to another when they collide. - When you put a pan on a stove (hob), heat energy transfers to the pan, causing the particles in the pan to start vibrating more. - Pans are often made of metal because metal conducts heat well. - The particles pass on heat energy by colliding with other particles until heat energy has transferred throughout the pan. - When food is added to the hot pan, the particles in the pan transfer heat energy to those in the food. This process happens until the food in the pan is cooked all the way through. ### Convection ![Convection](https://image-v2.cdn.app.senecalearning.com/2018-05/71fe00eb-8ba9-4da8-b55d-1e36db4ceea3/shutterstock_654140512.jpg) - Heat energy is transferred through liquids and/or gases. - When liquids are heated, the liquid closest to the heat source heats up first. - The warmer liquid rises and the cooler liquid flows beneath it. - The cooler liquid then starts to heat up as it is closer to the heat source. It rises and even cooler liquid falls beneath it. - The movement of water in this way creates convection currents. Eventually, all of the fluid is heated. - This process also takes place in ovens - where hot air rises and colder air replaces it below. ### Radiation ![Radiation](https://image-v2.cdn.app.senecalearning.com/2018-05/73cc0570-99e0-4511-8b93-f91b5a93022f/shutterstock_694624951.jpg) - Heat energy is transferred through radiation waves. - The heat source and food don't come into direct contact. - Microwaves warm up the water molecules, fat and sugar in food via radiation. - Toasters and grills also heat up food using radiation. - They send out radiation waves. Food absorbs these waves and heats up. ## Test yourself on Reasons for Cooking & Heat Transfer - Which of the following is NOT a method of heat transfer? - How do toasters and grills heat food? [Practise this topic for free](https://app.senecalearning.com/classroom/course/d59d0e60-4fa8-11e8-bbba-738ab127bed6/section/e5f77270-582a-11e8-9504-0b16557bc3b5/session) - Previous topic: [2.3.8 End of Topic Test - Nutritional Needs & Health](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-8-end-of-topic-test-nutritional-needs-and-health.md) - Next topic: [3.1.2 Water-Based Cooking Methods](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-2-water-based-cooking-methods.md) ## Food Preparation & Nutrition: AQA GCSE contents ### 1 Food Preparation Skills - 1.1 Food Preparation Skills - [1.1.1 General Practical Skills](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-1-general-practical-skills.md) - [1.1.2 Knife Skills](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-2-knife-skills.md) - [1.1.3 Preparing Fruit, Vegetables & Using Equipment](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-3-preparing-fruit-vegetables-and-using-equipment.md) - [1.1.4 Cooking Methods: Prepare, Shape & Combine](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-4-cooking-methods-prepare-shape-and-combine.md) - [1.1.5 Sauce Making, Tenderising & Marinating](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-5-sauce-making-tenderising-and-marinating.md) - [1.1.6 Dough & Pastry](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-6-dough-and-pastry.md) - [1.1.7 Shaping & Finishing Dough](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-7-shaping-and-finishing-dough.md) - [1.1.8 Raising Agents & Mixtures](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-8-raising-agents-and-mixtures.md) - [1.1.9 End of Topic Test - Food Preparation Skills 1](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/1-1-9-end-of-topic-test-food-preparation-skills-1.md) ### 2 Food, Nutrition & Health - 2.1 Macronutrients - [2.1.1 Proteins](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-1-1-proteins.md) - [2.1.2 Proteins 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-1-2-proteins-2.md) - [2.1.3 Fats](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-1-3-fats.md) - [2.1.4 Carbohydrates](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-1-4-carbohydrates.md) - [2.1.5 Carbohydrates 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-1-5-carbohydrates-2.md) - 2.2 Micronutrients - [2.2.1 Fat-Soluble Vitamins](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-2-1-fat-soluble-vitamins.md) - [2.2.2 Water-Soluble Vitamins](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-2-2-water-soluble-vitamins.md) - [2.2.3 Minerals & Water](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-2-3-minerals-and-water.md) - [2.2.4 Minerals & Water 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-2-4-minerals-and-water-2.md) - [2.2.5 End of Topic Test - Macro & Micronutrients](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-2-5-end-of-topic-test-macro-and-micronutrients.md) - 2.3 Nutritional Needs & Health - [2.3.1 Informed Choices for a Balanced Diet](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-1-informed-choices-for-a-balanced-diet.md) - [2.3.2 Informed Choices for a Balanced Diet 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-2-informed-choices-for-a-balanced-diet-2.md) - [2.3.3 Energy Needs](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-3-energy-needs.md) - [2.3.4 Nutritional Analysis](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-4-nutritional-analysis.md) - [2.3.5 Diet Modifications](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-5-diet-modifications.md) - [2.3.6 Diet-Related Problems](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-6-diet-related-problems.md) - [2.3.7 Diet-Related Problems 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-7-diet-related-problems-2.md) - [2.3.8 End of Topic Test - Nutritional Needs & Health](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/2-3-8-end-of-topic-test-nutritional-needs-and-health.md) ### 3 Food Science - 3.1 Cooking of Food & Heat Transfer - [3.1.1 Reasons for Cooking & Heat Transfer](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-1-reasons-for-cooking-and-heat-transfer.md) - [3.1.2 Water-Based Cooking Methods](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-2-water-based-cooking-methods.md) - [3.1.3 Fat-Based Cooking Methods](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-3-fat-based-cooking-methods.md) - [3.1.4 Dry Cooking Methods](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-4-dry-cooking-methods.md) - [3.1.5 Dry Cooking Methods 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-1-5-dry-cooking-methods-2.md) - 3.2 Functional & Chemical Properties of Food - [3.2.1 Proteins & Carbohydrates](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-2-1-proteins-and-carbohydrates.md) - [3.2.2 Fats & Oils](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-2-2-fats-and-oils.md) - [3.2.3 Raising Agents](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-2-3-raising-agents.md) - [3.2.4 End of Topic Test - Food Science](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/3-2-4-end-of-topic-test-food-science.md) ### 4 Food Safety - 4.1 Food Spoilage & Contamination - [4.1.1 Microorganisms & Signs of Food Spoilage](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-1-1-microorganisms-and-signs-of-food-spoilage.md) - [4.1.2 Enzymes & Signs of Food Spoilage](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-1-2-enzymes-and-signs-of-food-spoilage.md) - [4.1.3 Food Poisoning](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-1-3-food-poisoning.md) - [4.1.4 Bacterial Contamination](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-1-4-bacterial-contamination.md) - [4.1.5 Microorganisms in Food Production](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-1-5-microorganisms-in-food-production.md) - 4.2 Principles of Food Safety - [4.2.1 Temperature Control](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-2-1-temperature-control.md) - [4.2.2 Ambient Foods & Food Labels](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-2-2-ambient-foods-and-food-labels.md) - [4.2.3 Preparing, Cooking & Serving Food](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-2-3-preparing-cooking-and-serving-food.md) - [4.2.4 End of Topic Test - Food Safety](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/4-2-4-end-of-topic-test-food-safety.md) ### 5 Food Choice - 5.1 Factors Affecting Food Choice - [5.1.1 Factors Which Influence Food Choice](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-1-factors-which-influence-food-choice.md) - [5.1.2 Food Choices](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-2-food-choices.md) - [5.1.3 Religious Food Choices](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-3-religious-food-choices.md) - [5.1.4 Food Labels](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-4-food-labels.md) - [5.1.5 Mandatory Food Labels](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-5-mandatory-food-labels.md) - [5.1.6 Optional Food Labels](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-6-optional-food-labels.md) - [5.1.7 Marketing Influences](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-7-marketing-influences.md) - [5.1.8 End of Topic Test - Food Choice](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-1-8-end-of-topic-test-food-choice.md) - 5.2 British & International Cuisines - [5.2.1 British Cuisine](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-2-1-british-cuisine.md) - [5.2.2 Japanese Cuisine](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-2-2-japanese-cuisine.md) - [5.2.3 Japanese Ingredients & Dishes](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-2-3-japanese-ingredients-and-dishes.md) - [5.2.4 Spanish Cuisine](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-2-4-spanish-cuisine.md) - [5.2.5 Spanish Ingredients & Dishes](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-2-5-spanish-ingredients-and-dishes.md) - 5.3 Sensory Evaluation - [5.3.1 Taste Receptors & Olfactory Systems](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-3-1-taste-receptors-and-olfactory-systems.md) - [5.3.2 Sensory Testing Methods](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-3-2-sensory-testing-methods.md) - [5.3.3 Sensory Testing Methods 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-3-3-sensory-testing-methods-2.md) - [5.3.4 End of Topic Test - Cuisines & Senses](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/5-3-4-end-of-topic-test-cuisines-and-senses.md) ### 6 Food Provenance - 6.1 Environmental Impact & Sustainability of Food - [6.1.1 Food Sources - Intensive & Organic Farming](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-1-food-sources-intensive-and-organic-farming.md) - [6.1.2 Food Sources - Genetically Modified Crops](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-2-food-sources-genetically-modified-crops.md) - [6.1.3 Food Sources - Reared Food](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-3-food-sources-reared-food.md) - [6.1.4 Food Sources - Caught Food](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-4-food-sources-caught-food.md) - [6.1.5 Food & The Environment](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-5-food-and-the-environment.md) - [6.1.6 Food & The Environment 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-6-food-and-the-environment-2.md) - [6.1.7 Sustainability of Food](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-7-sustainability-of-food.md) - [6.1.8 Sustainability of Food 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-8-sustainability-of-food-2.md) - [6.1.9 End of Topic Test - Environmental Impacts](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-1-9-end-of-topic-test-environmental-impacts.md) - 6.2 Food Processing & Production - [6.2.1 Primary Food Processing](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-2-1-primary-food-processing.md) - [6.2.2 Primary Food Processing 2](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-2-2-primary-food-processing-2.md) - [6.2.3 Secondary Food Processing](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-2-3-secondary-food-processing.md) - [6.2.4 Fortification](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-2-4-fortification.md) - [6.2.5 Additives](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-2-5-additives.md) - [6.2.6 End of Topic Test - Food Processing & Production](https://senecalearning.com/en-gb/revision-notes/gcse/food-preparation/aqa/6-2-6-end-of-topic-test-food-processing-and-production.md)