Food- Mid term assessment

  • Created by: erp2002
  • Created on: 16-10-16 13:26

Why we cook food?

To give people a variety of foods in their diet - Foods like potatoes can be cooked in different ways to give people a variety.

To make food safe to eat - Some foods are likely to contain food poisoning bacteria so muct be thoroughly ccooked through to destroy them. Some foods can contain natural toxins and of the food was eaten raw they would be harmful, so cooking makes the food safe to eat.

To develop flavours in the food - Cooking causes chemical reactions so develops flavour. Cooking will concentrate and intensify flavour by causing water to evaporate.

To improve its shelf like - Cooking will destroy micro-organisms like bacteria and moulds so the food will last longer. For example long life milk has been heated so it will last longer.

To improve the texture and appearance - Cooking causes starch granules to swell, gelatinise and thicken or soften a food. Meat becomes tenderised when cooked, making it softer so it is easy to chew and digest. Fat melts when cooked making it smooth (chocolate). Cooking will soften the cell structure in vegetables to make them easier to eat. When raw dough is cooked it is turned into bread. Cooking will develop a crisp texture on some foods.

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Conduction, Convection and Radiation

Conduction - When a metal pan is heated on the hob, or a baking tin in the oven, it heats up and transfers heat energy to the food inside. The atoms making up metals are packed tightly in a lattice. As the heat energy from the hob or oven is transferred into the pan, it makes the metal atoms vibrate. As they vibrate, they knock againstadjoining atoms and pass on heat energy. Something like baked beans would be cooked like this. 

Convection - When a pan of cold water is heated the energy passes through the pan by conduction and then is transferred to the water. As the amount of heat energy increases the water molecules move upwards to where the water is cooler. They collide with other molecules passing on the heat energy, The more energy, the faster they move. When they reach the surface they slow down and sink to the bottom where it is repeated. This sets up convection currents which eventually makes the water boil. Vegetables may be cooked like this.

Radiation - Infared rays travel through the air and when they come into contact with a solid object, they are absorbed into the surface of the object and heat it up. Toast is cooked by radiation.

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Palatability and Cooking methods

Palatability - What makes a food acceptable and good to eat.

Water based - boiling (eggs and rice), steaming (green vegetables and white fish), poaching (fish and eggs), braising (meat and poultry), simmering (vegetables and soup), and stewing (meat and poultry). All of these are conduction and convection.

Dry methods - bake (cakes and breads, conduction), grilling (meat joints and fish, radiation), toasting (bread and buns, radiation), and dry frying (minced meats and nuts, conduction and convection).

Fat based - frying (shallow (eggs and fish, conduction) and deep fat (fish and scotch egg, conduction and convection)), roasting (meat joints and roast vegetables, convection), sauteing (onions and leeks, conduction), and stir frying (finely cut vegetables, conduction).

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Micro-organisms - (bacteria, germs) can't be seen.

Where can we find micro-organisms? - Clothes, dust, pets, insects, finger nails, hair, gone off food, door handles, public transport, rubbish, bins, unwashed vegetables, taps, toilets, water

What do micro-organisms need to multiply and grow? - Time, moisture, food, warmth, bacteria likes neutral; not acidic or alkaline; why lemon juice, salt etc is used for presering foods.

How to control growth and multiplication - Temperature: Heat food to 75C, don't leave warm food out for long. 0-5C in fridge, -18C in freezer, micro-organisms become dormant. Moisture: Preserve food by drying it. Preserve foods with a high concentration of sugar or salt. Food: Keep food covered and away from sources of micro-organisms. Time: Store, cook and cool foods thoroughly and correctly so micro-organisms don't have time to multiply and grow. Use foods by their use-by-date. pH level: Preserve foods in acid to stop micro-organisms growing and multiplying.

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Enzymic browning and Mould

Enzymic browning - The discolouration of a fruit or vegetable due to the reaction of enzymes with plant cell substances and oxygen from the air. Enzymes cause fruit to rippen. Ways we cause enzymic browning: cutting, grating, biteing, peeling, and bruising. Foods this is common to: apples, bananas, carrots, potatoes, avocado, mushrooms, and aubergines. How we can prevent it: eat whole, cut into large chunks, add acid (lemon juice), cook the food, put the food in cold water, and blanching the food.

Mould - Some types of mould will contaminate foods and give off toxins. Moulds multiply by sending out airborne spores that land on food and germinate if conditions are right.

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Factors which influence food choice

Factors which influence food choice - Medical condition, nutrition, palatability, culture/tradiation, food preferences/eating habits, availability/seasonability, age, cost, health/physical activity level, lifestyle, time of day/time available to prepare and cook food, enjoyment/celebration/occaision, ethics/moral beliefs/relgion. 

To improve nutrition - The nutrition may need to be improved in a recipe. If someone's nutrition isn't good they may develop health problems in later life. It is particularly important for children and teenagers as they are still growing. It is also important for food labels to have the correct information so people know what nutritious ingredients they are consuming.

To make vegetarian - Some people will not eat meat or other foods for various reasons. E.g. animal welfare, fairtrade, local produce, organic food, genetically modified food. Some people will only eat free range eggs, or fairtrade bananas.

To be reflective of a season - When choosing a recipe to make people may use ingredients reflective of the seasons, because these will generally be cheaper and from the UK. Strawberries are harder to get in the winter, as they do not grow in the UK at that time.

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Bacteria that causes food poisoning

Campylobacter This can be found in raw or undercooked meat (particularly poutry), unpasteurised milk or untreated water. The incubation period is usually between two and five days. The symptoms include: diarrhoea, nausea and vomiting, abdominal pain and fever. The symptoms will usually last no longer than a week.

E-coli This can be found in raw beef (particularly mince, burgers and meatballs), or unpasteurised milk. The incubation period is usually between one and eight days. The symptoms include: diarrhoea (this can be mild and watery or severe and bloody), abdominal pains, nausea and vomiting.These symptoms cam last from a couple of days to a couple of weeks.

Salmonella - This can be found in raw or undercooked meat, raw eggs, milk or other dairy products. The incubation period can be anything between tweleve and seventy-two hours. The symptoms include: diarrhoea, fever and abdominal cramps.. These symptoms usually last around seven days.

Listeria - This can be found in chilled ready-to-eat foods like, pre-packed sandwiches, cooked sliced meats and pate of soft cheese.The incubation period can vary between a couple of days and several weeks. The symptoms include: fever, muscle aches, nausea and diarrhoea. These symptoms will usually pass in three days.

Staohylococus aureus - This can be found in foods which are made with hand contact and then have no further cooking. Foods like salads, bakery products and sandwiches. The incubation period is between one and six hours. The symptoms include: nausea, vomiting, diarrhoea, loss of appetite, severe abodinal crampls and mild fever.These symptoms usually last between twelve and twenty-four hours.

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