Food Science Flashcards
Why do we cook food?
- To make it safe to eat
- To improve shelf life
- To develop flavour
- To improve texture
- To give variety in the diet
How does different cooking methods change food?
Change their sensory properties (appearance, favour, texture and smell) and nutritive value.
How does cooking food improve shelf life?
- At high temperatures, mould and bacteria are destroyed.
- Food can be preserved like this through manufacturing process.
- E.g. milk is pasteurised so it stays fresh for longer.
How does cooking food develop flavour?
- Chemical reactions take place that change flavour (caramelisation).
- Roasting meats and veg create more intense flavour and food becomes browner and crispier with more fat added to it as water evaporates.
- Allows allows the flavours of different foods to combine (braising a meat in a pot of liquid and veg).
How does cooking food improve texture?
- Usually makes it easier to chew, swallow and digest food.
- Some foods become softer (carrots and broccoli become flexible and rice when starch molecules soften).
- Meats become more tender as solid fats melt and proteins denature.
- Other foods become firm (coagulation in eggs).
- Can also make food more pleasant to eat (roast potato with soft centre and crispy outside).
How does cooking food give variety in the diet?
- Foods can be cooked in different ways to create variety.
What are three ways heat is transferred to cook food?
- Conduction
- Convection
- Radiation
What is conduction?
The transfer of heat energy through the vibration of particles. In a solid, particles are held tightly together, so when one particle vibrates, it bumps to other particles around them and passes the vibrations on.
What is convection?
The transfer of heat energy through a liquid or a gas.
When a liquid is heated, the warmer fluid rises above its colder surroundings. As the warmer fluid rises, colder liquid takes it place. Liquid at the bottom heats up and liquid at the top cools down. As this continues, this causes a circulation of fluids.
What is radiation?
Transfer of heat energy through waves of radiation (no direct contact). When the waves reach the food, they absorb and heat the food up.
How does conduction help to cook food?
When a pan is placed on a hob, heat energy from the hob causes particles in the pan to vibrate more and gain heat energy.
When food is placed in the pan, heat energy is transferred from particles to the pan in the food (and its particles vibrate and pass on heat energy through it) until the food is cooked through.
How does convection help to cook food?
Convection occurs in ovens - hot air rises and cool air falls as convection currents.
- Modern ovens are fan-assisted - they have a a fan that helps circulate the air around the oven.
How does radiation help to cook food?
- Cookers like grills and toasters use radiation to cook food.
- Microwaves use radiation to heat up the fat, sugar, and water molecules in food.
What are six ways water can used to cook food?
- Boiling
- Steaming
- Braising
- Blanching
- Simmering
- Poaching
What is boiling?
Cooking food by heating it in a pan of boiling liquid, usually water.
What is steaming?
Cooking food with steam from boiling water or stock.
What is braising?
Slowly cooking food in an ovenproof pot that has the lid on and contains liquid (usually water, stock or wine), and often herbs and vegetables.
What is blanching?
Involves part-cooking food in boiling water for a very short time before putting in in cold/iced water.
What is simmering?
Foods is cooked in hot liquids kept just below the boiling point of water and above poaching temperature.
A liquid is brought to a boil, then its heat source is reduced to a lower, constant temperature.
What is poaching?
Cooking food in a pan of liquid, below boiling point, usually around 80°C.
What are the two types of frying that use different amounts of fat?
- Stir-Frying
- Shallow frying
- Dry frying
What is sweating?
The gentle heating of vegetables in a little oil or butter, with frequent stirring and turning to ensure that any emitted liquid will evaporate.
This releases moisture from the food, making it more tender and sweet tasting.
While food is sweating, it’s usually covered with a lid to help moisture (in the form of steam) circulate around the food.
What are some examples of food that are boiled?
- Tougher cuts of meat
- Potatoes
- Rice
- Pasta
- Veg
What are some examples of food that are steamed?
- Fish
- Rice
- Vegetables
What are some examples of food that are braised?
- Big or tough joints of meat (gentle cooking helps tenderise)
What are some examples of food that are blanched?
- Tomatoes and almonds (make them shrivel up, making skins easier to remove).
What are some examples of food that are simmered?
Soups and curries