Food science Flashcards
Why is food cooked?
- texture,
- easier to digest(fibres softened)
- flavour improved
- destroys harmful bacteria
- making it less bulky, volume reduces
- foods can be preserved to last longer
what is conduction?
when heat is transferred from molecule to molecule
what is convection?
where warm molecules rise and cooler molecules fall closer to the source of heat
*in air and liquids
eg: boiling, simering, baking ,frying ,braising ,caserole
what is radiation?
heat is transferred through electro magnetic radiation.
direct rays into food
eg: barbequeing, grilling,microwaving
what factors influence the method of cooking?
- economical staus
- time
- special equipment
- skill
- type of food
what are some methods of dry cooking?
- baking,
- roasting
- frying
- saueting
- stir frying
what are some sources for animal fat?
lard
butter
suet
dripping
what are some sources of plant fats?
oil
margarine
avocados
nuts
seeds
What are the functions of fat in the body?
a source of energy
insulating the body
protecting organs
carries fat soluble vitamins
what are the functions of protein in the body?
growth/repair
secondary source of energy
what are the functions of fat in food?
flavour
glossiness
texture
creamy mouthfeel
what are some methods of moist heat cooking?
- boiling
- simmering
- poaching
- steaming
describe boiling
and pros and cons
conduction and convection
Bubbling water to 100
✗food may disintergrate
✗flavour from the foods leaching into the water
✗water soluable vitamins lost
✓quick
✓simple method of cooking (less skill required)
✓ food will not burn
simmering 95, poaching <85
describe blanching
food is cooked and then quickly cooled,( put into iced water)
describe steaming
pros and cons
cooked by steam rising from the boiling water . Convection
✓food is light in texture and easily digestible
✓tired steamers can reduce electrical costs
✓ reatins the natural vitamins
✗can take a long time
✗can become overcooked easily
describe baking and roasting
baking: warm air rises to the top of the oven by convection.
roasting: small amount of fat also added to prevent the food from drying out
what are some methods of dry heat - fat based?
- **dry-frying **: no fat added to the pan, coz food has a high fat content
- shallow frying : small layer of fat/oil
- ** stir frying**: high temperature oil and food then moved around the pan, fast and cost efficent
- deep frying : food completely coverd in fat
describe grilling
pros and cons
heat conducted through radiation. For fods that are not thick
✗not suitable for tough cuts of meat
✗ careful timing so that food is not left under or overcooked
✓quick method of cooking, reduced energy costs
✓possible to trim excess bits of fat off
describe frying
pros and cons
✓quick
✓attractive golden colour
✗need straining and changing regularly
✗fried food is difficult to digest
✗ can be dangerous , great care has to be taken
✗heat sesnitive vitamins are destroyed
✗ high fat content
describe microwaing
pros and cons
radiation of microwaves. conduction
✗can be overlooked
✗ flavours may not develop as food is cooked quickly
✗colour of food pale
✓food cooked quickly, saves energy
✓bright colours retained as quick cooking
✓ useful for defrosting foods
✓more heat sensitive vitamins retained as cooking time is short
✓less loss of water soluable vitamins
how are carbohydrates, fat, vitamins affected by cooking
- NSP softens in water. starch content reduced as dissolves into liquid
- fat can be increased -frying or decreased roasting
- B &C affected as are water soluable and so are lost in the liquid
what are the working and chemical properties of carbohydrates?
- gelatinsation
- dextrination
- caramelisation
describe gelatinisation
- when flour is mixed in a liquid and heated, the mixture will thicken
- the strach grains cannot dissolve the liquid and so form a suspension
- as the liquid is heated, the strach grains swell at 60 degreess
- more heat applied maks the grains burst open and amalose and amylospectin are relaeed, cauing it to thicken
describe dextrinsisation:
- browning causes by dry heat
- starch in flour chnaged to sugar
describe caramalisation
the colour of sugar changes from white to brown when heated
1. the sugar melts and becomes syrup
2. at 154 the sugar starts to change colour
3. teh longer the sugar is heated, the deeper th colour of the caramel and the harder it will set once cooled
what are the working charctertistics of fats and oils?
- shortning
- aeration
- plasticity
- emulsification
describe shortning
creats a short, crumbly texture
* the fat grains are coat the flour and give it a waterproof coating
* therfore it prvents gluten from developing
describe aeration
the process of trapping air in a mixture to cause it to rise
* fat and sugar creamed together, air is trapped
* when the product is heated the air will expand, causing it to rise
describe plasticity
solid fat melting over a range of temperatures
* fats deisnged to have a lower melting temperature, creating spreads
ability to be spread
describe emulsification
the emulsfier stops mixture of oil and and liquid from seperating
attract oil and liquid, holding the two together
what are the characteristics of protein
- coagulation
- foam formation
- gluten formation
- acid denature
describe coagulation
when the protein in foods set
describe gluten formation
- gluten used to provide structure in the bread
- the gliadin and glutenin form gluten
- the gluten is then kneaded to create structure
describe acid denature
when acids change the shape and structure of protein foods, to tenderise meat for soft texture, white vinegar added to meringue
* the long chains of amino acids unravel
functions of fruits and vegtables
- enzymic browning
- oxidation
describe enzymic browning/oxidation
- chemical reaction when cells are exposed to oxygen
- when the fruit/ veg go broen because it reacts with oxygen producing a brown colour
describe rasing agents charctertistics
- yeast
- chemical rasining agents
- air
- steam
describe yeast
- usd in bread for lightness and causes it to rise
- yeast given preferable conditions: food, warmth, moisture,time
- breaks down food into carbon dioxide (fermenation)
- causes bread to rise
describ chemical raising agents
make baked products ris e(baking powdr)
* produces carbon dioxide when heated
dscribe air
whisked into roulades, souffls
air incoroperted by whisk
describe steam
causes products thst contsin lots of)
liquid to rise (choux, puff/flaky pastry
* steam produced from the liquids presnt in the mixture , allowing it ot rise
what are the 5 senses in foods?
- sight (size, shape, colour)
- sound (sizzling of bacon, crunch of crisps)
- smell (aromas- stimulate digestive juices and make it seem more appetising)
- taste (bitter, sweet, sour, salt, umami, flavours developed when chewing and mixed with saliva)
- touch (mouth feel- crumbly, soft, mushy, creamy, gritty)
how do you set up a testing panel?
- in a quiet area, testers not allowed to communicate with each other
- give testers lemon flavoured water to clear the palette
- small quantities of food on identicle plates
- serve at correct temperature
- use codes to prevent testers being aware of the product name
what are the different types of testing?
- comparison testing (triangle test)
- rating testing (ranking, profilling)
describe traingle testing
two samples are the same and are asked to identify the odd one out
describe a ranking test
sort variety of foods into preffered order
* presented with a set of codes
* rank in terms of an attribute (sweetness)
describe profilling tests
can be used to find out what consumers particulary enjoy about the product, according to a range of sensory qualities
* give a score out of 5
* star profile
describe meat
- muscls and fibres bundled together stored by connective tissue
- connective tissue: collagen, elastin
- myglobin gives a red colour
- fat between connective tissue: moist
