Food Tech: Chapter 6 Flashcards
Define cooking
The transfer of energy from a heat source to food
Why do we cook food?
- cooking destroys harmful micro-organisms in food
- cooking destroys some of the enzymes that cause food to spoil and therefore extends the shelf life
- eating, digestion and adsorption of nutrients are made easier by the structural changes taken.
- the flavour is enhanced
- changes the texture
- aromas are released from food
- improve colour
- becomes less bulky
What is conduction ?
The process of cooking food by direct heat
How does conduction occur?
- Conduction of heat occurs when energy is moved from one particle to another by collision or movement.
e. g. Heat is conducted through the base of a saucepan when in contact with a gas flame, as the heat is transferred to the surface of the food, it is also transferred by conduction to the inside of the food, cooking it through.
What is convection?
- Convection is when the transfer of heat in liquids and air is brought about when the molecules move from a warmer area to a cooler one.
- It is a combination of conduction and mixing.
How does convection occur? (Liquid)
-Liquid: Convection takes place when cooking liquids are heated during the boiling and stewing of food. As the molecules absorb energy, they heat up and rise, sinking again when they cook off.
How does convection occur? (Air)
Convection currents are formed when an oven is heated. As the air in the oven is heated, it rises and forces the colder air at the top to flow down the sides of the oven, creating a current.
e.g. In an oven
What is radiation?
Radiation is the transmission of energy by wave motion in the form of electromagnetic waves.
e.g. cooking in a grill
How does radiation occur?
when the waves fall on food they cause the molecules in food to vibrate, which causes the food to heat up and subsequently cook.
- food does not come into contact with the heat source.
e. g. cooking under a grill or toaster
What is magnetic induction?
Heat in magnetic induction cooking is produced directly in the base of the saucepan, rather than on the cook top.
How does magnetic induction work?
An electric circuit supplies a current if power through a coil of copper wire, creating a magnetic field. When in contact with this magnetic field, the ferro-magnetic metal-based saucepan placed on the cooking zone is crossed by induction currents and heats up immediately.
-the saucepan heats up, rather than surface of the cook top.
Name the dry methods of cooking
- roasting
- baking
- grilling
- frying
Foods suitable for roasting
- red and white meats
- vegetables
Define roasting
Roasting is a method of cooking food in an oven using a minimum amount of fat or oil
Define Baking
Cooking food in an oven without the addition of fat or oil
Foods suitable for baking
- Fish
- Fruit
- Egg custard
- Combination dishes (lasagne, shepherd lie)
- Flour products
Safety practices for roasting and baking
- take care when lighting a gas oven
- use oven mitts to handle hot baking trays
- open the oven door completely
- do not leave the oven door open after removing food
- always check racks are in correct position before turning oven on
Define grilling
Grilling is a fast, dry methods of cooking that uses intense heat radiated by an electrical element, gas, flame, glowing charcoal or open wood fire.
Equipment for grilling
- Charcoal grills
- Grills I’m domestic ovens
- Overhead grills or salamanders
- Small appliance
Foods suitable for grilling
- Meats
- Fish
- Vegetables and fruits
- Other foods (toast, cheese topped dishes, crème brûlée)
Safety practices for grilling
- If using a separate grill leave grill door open while the grill is on to avoid build up of heat
- The door of a combination cooker/grill should be closed during cooking
- Turn food with tongs rather than a fork
- Check the grill is turned off when you finish
Define frying
Frying is cooking food by total or part immersion in fat or oil that is heated to temperatures between 150 degrees- 220 degrees.
Methods of frying
- Dry-frying
- Shallow-frying
- Stir-frying
- Deep-frying
What is Dry-frying
This uses only the fat that runs from the food as it is heated
What is shallow-frying?
Uses small quantities of fat or oil to cove the base of the pan
What is stir-frying?
A little oil is heated in a wok and the food is stirred and lifted during the short, hot cooking process
What is deep-frying?
Food is totally submerged in preheated fat or oil.
-The oil or fat is heated to a temperature twice that of boiling water and so the food cooks quickly
Foods suitable for frying
- Meats
- Vegetables
- Fish
- Fruit
- Other foods (eggs, omelettes, pancakes)
- Foods suitable for deep-frying
What is smoke point?
Smoke point is the temperature at which fats and oils begin to burn or denature.
- The ‘flash point’ is when the oil is heated so much that it is ready to burst into flames.
- animal fats have a smoke point of about 190 degrees
- natural butter “ “ “ 110 degrees
- vegetable oils “” “ 230 degrees
- rice bran boil has the highest smoke point of about 254 degrees
Safety practices for frying
- don’t leave the pan or deep-fryer unattended
- do not heat beyond the required temperature
- keep the pan handle turned to the side to prevent it being knocked over
- make sure any food placed in the oil is dry, or else it will be spitting
- if the oil catches fire,extinguish with a lid of fire blanket, not water.
Name the wet methods of cooking
- Boiling
- Blanching
- Poaching
- Steaming
- Stewing
Define boiling
Cooking food in water at 100 degrees
Define blanching
Blanching is a methods of partly cooking food by plunging it briefly into boiling water
Define simmering
Simmering is cooking at a lower temperature of 85 degrees, allowing bubbled to rise slowly at one side of the pan.
Foods suitable for boiling
- soups and stocks
- vegetables
- pulses
- cereals
- pasta
- meat and poultry
- fish and shellfish
- other foods (jams, jellies, sugar solutions, dumplings)
Define poaching
Poaching is a method of cooking delicate foods in liquid at a temperature just below simmering point 85 degrees.
Foods suitable for poaching
- Fish
- Fruits
- Eggs
Define steaming
Steaming is cooking food in the steam from boiling water
Methods of steaming
- Graduated or atmospheric steamer
- Sealed container
Foods suitable for stewing
- Meats, poultry, fish and game
- Fruits
Foods suitable for steaming
- Vegetable
- Fish
- other foods: puddings, pork buns, dumplings
Define stewing
Stewing is a long, slow methods of simmering food in a small amount of liquid
Safety practices for using the cook top
- turn saucepan handles so that they face away from the walkway
- use oven mitts to handle hot handles
- when opening the lid to saucepans or steamers, open it away from your face
- take care of moving saucepans filled with liquid
- use wooden spoons to stir boiling liquids
Microwaving
In microwaving cooking, energy is transferred to the food by electromagnetic radiation.
How does a microwave work?
The microwave oven contains a magnetron, which converts electricity to microwaves by rapidly switching electromagnets on and off to set up a wave pattern. The microwaves are channelled into the oven space by the waveguide, they bounce off the sides of the oven and return to the magnetron for recharging. A fan called a mode stirrer and the turntable ensure even distribution of microwaves through the oven.
How food is cooked in a microwave
The food absorbs the microwaves and the molecules of eater vibrate at a high speed, which knocks into the protein and fat molecules and transfer energy to them. This vibration produces heat, which cooks the food.
Safety practices for cooking in a microwave oven
- only use microwave safe containers
- do not place metal in the microwave
- only plastic designed for microwaving should be used
- If covering food with plastic film, avoid direct contact with food
- do not turn microwave on, unless there is food in it
- turn microwave off at source before cleaning or moving it
What is the difference between boiling and simmering?
Boiling is cooking food at 100degrees, the water has big bubbles. Simmering is cooking food at 85 degrees, allowing small bubbles to rise slowly on one side of the pan.
