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Preparing Food © ORCA Education Limited 2005 New Words Why Cook Food? Cooking destroys harmful bacteria: it is more appetizing improves appearance, flavour, texture and smell aids digestion makes food easier to eat preserves food to stop it decaying improves and enhances flavour gives variety in the diet reduces bulk so more can be eaten. What different ways are there to cook potato? * © ORCA Education Limited (2005) and suppliers, all rights reserved The Transfer of Heat Heat energy is used for cooking. It can be transferred in three ways: Conduction; heat is conducted from one molecule to another. Convection; liquids and gases create convection currents transferring heat to the food. Radiation; heat travels from one object to another in waves or rays e.g. barbeque, grill or microwave. Most food is cooked using more than one method of heat transfer. How is heat transferred for baking bread? * © ORCA Education Limited (2005) and suppliers, all rights reserved Conduction from the hot grill bars cook food stripes Conduction on the fish surface against the hot casserole pan Convection of stock The frying pan conducts heat directly to the fish Convection Heat from Heatof from thecoals fire hotthe air radiates the food heats thetofrying pan Moist Methods of Cooking Food can be cooked in four ways according to how heat is applied. Moist methods involve heat being applied through liquid such as water, milk, steam, stock, wine, etc. This method uses relatively low temperatures over a long period. Prolonged moist cooking causes water soluble vitamins C and B to be leached into the cooking liquid. Some moist cooking examples are: What type of foods would be suitable for this method? * © ORCA Education Limited (2005) and suppliers, all rights reserved pressure cooking stewing & braising. poachin g simmerin g steaming boilin g Dry Methods of Cooking In dry cooking, as with these sausages in a commercial oven, heat is applied directly onto food. Other examples are roasting, grilling and barbecuing. During dry methods of cooking e.g. grilling (toasting) or baking, heat turns starch a light golden colour known as dexrinisation. When sugar is heated under the grill, it turns brown called caramelisation. © ORCA Education Limited (2005) and suppliers, all rights reserved How does dry cooking change the nutrients in food? * Frying Heat is applied through fats or oils. Some fat is absorbed increasing the the fat content of the food cooked. In frying high temperatures destroy heat sensitive nutrients. In deep frying the food is immersed in fat or oil at up to 200ºc. Butter or margarine can be used for shallow frying as temperatures are not as high. Foods high in fat can be dry fried using non-stick pans. What other method of frying is more healthy? * © ORCA Education Limited (2005) and suppliers, all rights reserved Microwave Cookery Microwaves generate heat by electro-magnetic rays from a magnetron valve. Microwaves are reflected off the metal walls of the cooker and are absorbed by the food. They vibrate millions of times a second causing friction and heat in the food molecules Paper china and some plastics allow microwaves to pass through them. This method of cooking is very quick, therefore there is less destruction of nutrients. © ORCA Education Limited (2005) and suppliers, all rights reserved Which foods are not suitable for microwave cooking? * Preserving Nutrients Vegetables and fruit contain the water soluble vitamins B and C which dissolve into cooking water. This loss can be minimised by careful preparation and cooking. Cook with a lid on and cook for the minimum amount of time. Vegetable water can be used for gravy. Eat cooked vegetables immediately. Steaming vegetables reduces loss of nutrients from leaching. Oxygen in air and water encourages the destruction of vitamin C. Avoid peeling as vitamins and minerals are under the skin. Vegetables should be chopped quickly and leaf vegetables torn not cut to avoid tissue damage. What is the best way to cook cabbage? * © ORCA Education Limited (2005) and suppliers, all rights reserved Which Method of Cooking? You have a chicken and some vegetables to cook. Your choice of cooking method will depend on: time for cooking and preparation facilities available nutrient loss and healthy eating need the needs of the individual e.g. small child or adult individual preference on taste, texture, smell and flavour. From the points above decide on a set of circumstances.. © ORCA Education Limited (2005) and suppliers, all rights reserved ..how would you then cook the chicken and vegetables? * Macro-Nutrients & Heat How has an increase in temperature caused these foods to change? Protein foods like the meat are permanently changed called denaturation. Meat like this chicken hardens and darkens. Other proteins like eggs coagulate and set. The starch grains in the stew break open and form a gel with the liquid called gelatinisation which thickens the liquid. When toasting or baking as with the roll the dry heat turns starch to dextrin. The fats in the meat melt to a liquid when heated. Fats can decompose at a high temperature, give off a bluish haze and burst into flames called the flash point. * © ORCA Education Limited (2005) and suppliers, all rights reserved Acids in Cooking Acids effect flavour, appearance, texture and nutritional value of food. There are several kinds of acid used in these foods. Citric acid (lemon juice) helps pectin make a gel for the jam. It also prevents enzymatic browning of cut fresh fruit and coagulates protein in cold desserts using cream. Acetic acid (vinegar) is used in preserves like chutney, it marinates meat to tenderise it and gives a sharp flavour to salad dressing. Ascorbic acid (Vitamin C) is used as flour treatment for yeast fermentation. Tartaric acid(cream of tartar) is used with bicarbonate of soda in baking. Lactic acid starter is used to coagulate milk in cheese making. * © ORCA Education Limited (2005) and suppliers, all rights reserved Alkalis These scones rely on alkalis for their light open texture. Alkalis are used in cooking as raising agents. When these are mixed with other ingredients and heated, a chemical reaction takes place and carbon dioxide is produced. There are 3 types of chemical raising agents: bicarbonate of soda bicarbonate of soda and acid (sour milk or cream of tartar) baking powder. © ORCA Education Limited (2005) and suppliers, all rights reserved How are these 3 types different? * Vocabulary Some words or terms to learn bacteria pressure cooking poaching leached water soluble tissue damage coagulate tenderise raising agents © ORCA Education Limited (2005) and suppliers, all rights reserved conduction convection radiation braising microwaves gelatinisation marinate* The Task You can enter here a task for your students. © ORCA Education Limited (2005) and suppliers, all rights reserved End End Show Acknowledgements All images used in these presentations are the property of their owners, ORCA Education Limited and suppliers inc. Hemera Images, Jupiter Media Corp. and Animation Factory All rights are reserved. The Licence agreement applies to all elements of these presentations. ORCA.VT is a trademark of ORCA Education Limited Microsoft Agent is the property of Microsoft Corporation, Redmond WA. ORCA Education Limited are licensed distributors of Microsoft Agent technology Licence 276899. The Microsoft Agent Technology elements including Peedy character may not be distributed beyond the constraints of this product licence Microsoft Agent characters Susan and Tom are packaged with this product as part of the Vox Proxy development tools used by ORCA Education. They are not for resale or distribution beyond their use in these products © ORCA Education Limited (2005) and suppliers, all rights reserved