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foodtech > food science > Flashcards

food science Flashcards

1
Q

name 5 reasons why food is cooked?

A

-make it safe to eat
-improve shelf life
-develop flavours
-improve texture
-varies diet

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2
Q

how does cooking food make it safe to eat?

A

-kills bacteria = abouve 75 degrees
-prevents you from getting food poisoning etc

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3
Q

how does cooking food improve shelf life?
give an example x

A

-cookes to high temps to destroy mould & bacteria
-milk = pasteurised (heated to 72 degrees form 15 secs) = preseves it for longer

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4
Q

how does cooking food develop flavours?

A

-chemical reactions occur = caramilastion - makes food sweeter
-brasing/roasting = allows meat to absorb flavours of stock,veg etc
-crisper

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5
Q

how does cooking food improve textures?

A

-easier to chew, swallow & digest
-gelatanisation = thickens starchy soucces & starch swells in rice and pasta = become soft
-egg whites = protein coagualtes = becomes firm
(from proteins denaturing and joining together

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6
Q

name the 3 ways heat can be transferred when cooking?

A

conduction
convection
radiation

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7
Q

how does conduction transfer heat?

A

-solid (pan) placed on hob
-causes particles in pan to vibrate, more heat energy = more KE = more collisions, collide w near by particles e.g food
transfers heat to food by vibrations

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8
Q

how is heat transfered by convection? (through gasses/ liquids)

A

-pan on hob = warm water rises & cold water simks this repeats creating a CONVECTION CURRENT = after abit heats the food

SAME OCCURS W HOT AIR IN OVENS

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9
Q

how is heat energy transfered through radiaition?

A

-waves of radioton pass through food = absorbes - heats food
e.g toasters and microwaves

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10
Q

how do proteins de nature name 3 ways?

A

mechanical agitation = whisking etc
heat
acid

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11
Q

how do proteins de nature?

A

-chemical bonds break
-protein unravell

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12
Q

how do denatured proeins coagulate?

A

-denatured proetins join together , water gets trapped betwen protein molecules

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13
Q

using the e.g of egg whites what changes occur from coagulation?

A

-firmer texture
-white colour
-

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14
Q

what happens if food is overcooked?

A

protein molecules tighten = water forced out = hard and chewy eww

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15
Q

how are foams formed?
using egg whites

A

-proteins in whites denature, casusing them to stretch = air becomes trapped
-proteins coagulate
=gas in liquid foam

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16
Q

what happens if you over whisks

A

-proteins break = air released = foam colappses

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17
Q

why does gluten need kneading?

A

-develop strands, longer, stronger, strechier

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18
Q

what happens to gluten (coiled for elasitity) at high tmeps?

A

-coagulate, dough stays stretch , ligh airy texture

19
Q

expalin the process off gelatinasation?

A

60 degrees - starch molecules start to swell (absorbs water)
80 degrees - starch molecules burst relaesing starch into liquid
100 degrees = strach evenly distributed & gelatinisation complete

20
Q

whats is dextrinsioation?
what does it produce?

A

-breaks down starch molecules into simple sugar = dextrins

21
Q

affect of dextriniasation?

A

-browner colour
-crispier texture

22
Q

what is caramlaisation?

A

sugar breaks down - sugar goes brown & chnages flavour

23
Q

affects of caramalisation?

A

-adds sweetness and brown colour

24
Q

what are the processes of sugar?

A

-very sweet and runny
-smooth caramel
-cools = becomes hard brittle candy

25
Q

what is aeration?
e.gs?

A

when fats e.g butter is beaten with sugar
-light, fluffy texture
-whisking egg whites

26
Q

whats shortnening?
-gives food crumbly texture

A

-rub fat into flour
-flour gives fat waterproof coating
-prevents long gluten strands forming
=short crumbly texture

27
Q

what does plasticty mean?

A

abilty to spread and shape foods
more placsticity = easier to spread

28
Q

what do fats contain hic allws plasiticty?

A

triglycerides

29
Q

what type of fat has a more plasticty?

A

unsaturated = liquid at room temp(healthier)

30
Q

advantages of plasiticy?

A

-decorating cakes
-rubbing in fat
-spreading butter oon toast
-cream cheese on crackers

31
Q

name to ends of emulsifiers? (needed to keep water and oil together)

A

hydrophilic-attacted to water
hydrophobic-repulsed by water

32
Q

what happens when u add an emulsier to water & oil?

A

hydrophilic bonds to water
hydrophobic bonds to oil = holds mixture together in a stable emulsion

33
Q

what emulsifier does egg yolks contain?

A

lecithin

34
Q

name an exampple of an emulsion?

A

sauces =hollandaise sauce

35
Q

how is hollandaise sauce made?

A

-melt buuter
-mix yolk and lemon jucie - heat gently
-add together and whisk

36
Q

what happens if u add fat to fast in emulsiation?

A

-wont bond to hydrophilic/phobic ends xx

37
Q

how does bioligical rasing agent yeast work?

A

e.g in bread the process of FERMENTATION occurs - yeast reales carbon dioxide & alchol
-when heated CO2 mkaes bread rise

38
Q

name a chmical raising agent?
how does it work?

A
  • bicarbonate of soda = rleases CO2 bubbles to make food rise
39
Q

con of BOS?

A

-alkaili = leavs soapy tatse
-need to be made in strong things
e.g choclate cake

40
Q

pros of using baking powder?

A

-mix of cream of tatar(acid) and BOS(base) = neutralisation reaction

41
Q

how does steam make food rise?

A

-crossiants and shoux pastry
-when bakes
-steam rises
-water evaporates

42
Q

when cooking crossiabts why cant u open the oven?

A

-cold air = makes thing sink

43
Q

name 5 methos we can phycally add air to food?

A

-folding cake traps air or pastry air in between layers is trapped
-beating (vigouros)
-whisking
-seiving
-creaming & rubbing

foodtech (2 decks)

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