Topic 1: Food Science Flashcards
why do we cook food?
- destroy harmful bacteria
- make food less bulky
- improve the keeping quality
- easier to eat and digest
- flavour is improved
- destroy natural poisons in food
- hot food in cold weather
- attractive and colourful
- adds variety to diet
- aroma released
how does cooking food make it less bulky?
volume is reduced
how does cooking food improve the keeping quality?
preserved to last longer
how does cooking food make it easier to digest?
changes its structure, soften
how does cooking food improve its flavour?
flavours develop as ingredients cook together
how does cooking food make it more colourful and attractive?
changes colour, method of cooking affects the colour of the food
how does cooking food provide variety to the diet?
cook foods in different ways
how does cooking food release aroma?
gets digestive juices working
what are the three basic methods of transferring heat?
conduction, convection and radiation
what methods of cooking use conduction?
boiling, simmering, blanching, poaching, baking, frying, microwaving, roasting, braising casserole
how is heat transferred in conduction?
contact with heat
what methods of cooking use radiation?
barbequing, grilling, microwaving, chargrilling
how is heat transferred in radiation?
direct rays pass from the heat source to the food
what methods of cooking use convection?
baking, boiling, simmering, blanching, poaching, frying, roasting, steaming, braising, casserole
how is heat transferred in convection?
heat moves through convection currents, hot air rises and cool air falls
what factors influence the cooking method used?
type of food, facilities available, time, needs of individual, skills of cook, consumer choice
what are examples of moist-heat cooking methods?
boiling, simmering, poaching and steaming
what are examples of dry-heat cooking methods?
roasting, frying, stir-frying
what is boiling?
uses large amounts of rapid bubbling liquid to cook food, conduction and convection, suitable for rice, pasta, potatoes and vegetables
what is simmering?
cooked in a hot liquid (85-99ºC) but require a gentler treatment than boiling, to prevent fish or meat from toughening and vegetables disintegrating
what is poaching?
temperature of the liquid should be just below simmering (85ºC) and foods do not need a long cooking time, suitable for eggs, fruit and fish
what is blanching?
cooked and then cooled very quickly to stop the cooking process, put food in iced water. Blanched before frozen to stop enzymatic reaction, does not decay while frozen
what is steaming?
food does not come in contact with boiling water, but cooked with the steam rising from it. Convection currents used, suitable for puddings, fish and vegetables
what is baking?
temp used depends on the food being cooked. Moisture can be added to develop certain textures in the food, top is hottest in gas ovens as warm air rises by convection
what is roasting?
small amount of fat used to prevent the food from drying out and to develop the flavours, heat transferred through conduction as well as convection in oven, vegetables and meat
what is braising?
to cook meat, first browned in pan using a small amount of fat, put in a container with some liquid and covered
what is casserole?
food cooked in small amount of liquid which simmers, cooked in container with fitted lid so liquid does not evaporate
what is frying?
heat transferred by conduction in pan and convection through hot fat, highly discouraged, fat can easier catch fire. water causes fat to split and separate when heated so fat used must be suitable to heat to 200ºC and cannot burn or change taste.
4 different types:
- dry-frying
- shallow-frying
- stir-frying
- deep-frying
what is dry-frying?
fried without any fat, usually use non stick frying pans to prevent food from sticking, food that use method usually have a high fat content (sausage and bacon)
what is shallow-frying?
cooked in a shallow layer of fat or oil, comes up halfway to the food.
Very quick and not suitable for tough cuts of meat
Suitable for eggs, fish and meat
what is stir-frying?
small pieces of finely chopped food in a wok with high temp oil, food is constantly moved around the pan
- quicker
- energy saving
- only small amount of fat used
what is deep frying?
food is totally covered in fat during frying process
what is grilling?
- heat conducted through radiation
- heat comes from both above and below the food
- turned to ensure even cooking
how do microwaves oven work?
- penetrating the food and causing the molecules to vibrate by radiation
- molecules cause friction when vibrating against each other, produces heat
- water molecules continue to vibrate when out of the oven, generates heat, centre of food will gain temp
pros and cons of boiling
Advantages
- quick
- not likely to burn
- simple
Disadvantages
- food disintegrates if boiling is not carefully timed
- flavour leaches into water
- water-soluble vitamins lost
pros and cons of steaming
Advantages
- light in texture, easier to digest
- can cook different foods at once
- retains natural vitamins
Disadvantages
- can take long, depends on product
- care taken with timings so delicate foods aren’t overcooked
pros and cons of grilling
Advantages
- quick, reduces energy costs
- possible to trim excess fat before cooking
Disadvantages
- not suitable for tough cuts of meat
- careful timing so food isn’t over or undercooked
frying pros and cons
Advantages
- quick
- attractive in colour
Disadvan
- fats need straining and changing regularly
- more difficult to digest
- can be unsafe
- heat-sensitive vitamins destroyed
- fatty, doesn’t follow guidelines
microwave pros and cons
Advantages
- cooked quickly, saves energy
- useful for busy people
- useful for defrosting
- less loss and destruction of heat-sensitive and water soluble vitamins
Disadvantages
- easy to overcook
- flavours may not develop due to short cooking time
- may be pale in appearance
How is protein affected by cooking processes?
Unaffected
How are carbohydrates affected by cooking processes?
- NSP softened, particularly when using moist cooking methods
- starch reduced when cooked in water as it dissolves
How are fats affected by cooking processes?
- fat content reduced
- cooking in fat will increase the fat content
How is Vitamin A affected by cooking processes?
not affected
How is Vitamin D affected by cooking processes?
not affected
How is Vitamin E affected by cooking processes?
not affected
How is Vitamin K affected by cooking processes?
not affected
How is Vitamin B1 affected by cooking processes?
easily destroyed in heat
water-soluble, so cooking liquid should be used in the dish
How is Vitamin B2 affected by cooking processes?
destroyed by heat in the presence of an alkali
soluble in water
How is Vitamin B3 affected by cooking processes?
most resistant B group vitamin to heat
water-soluble, so cooking liquid should be used in the dish
How is Vitamin B9 affected by cooking processes?
less sensitive to heat, but destroyed if food is reheated
How is Vitamin B12 affected by cooking processes?
soluble in water
How is Vitamin C affected by cooking processes?
destroyed by moist and dry heat
dissolved in water so cooking methods use minimum amount of water
How are minerals affected by cooking processes?
nutritional value of minerals is not affected by normal cooking process
What is a colloidal structure?
when two substances are mixed together
What is the function of starch?
used to thicken mixtures
What is shortening?
what fat coasts the flour grains to prevent the gluten from developing and absorbing water, crumbly mixture
What is the function of cornflour
alternative for flour in sauces, tasteless,
What starch sources are used to thicken mixtures?
potatoes
rice
other root vegetables
arrowroot
What is aeration?
trapping air in a mixture
What is caramelisation?
process of changing the colour of sugar from white to brown when heated
What is dextrinisation?
dry heat applied to flour and it browns as starch changes into sugar
What is the Maillard Reaction?
when foods containing proteins and carbohydrates are cooked by dry methods
What is plasticity?
consistency of fats
