food science

Question 1

name 5 reasons why food is cooked?

Answer 1

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

Question 2

how does cooking food make it safe to eat?

Answer 2

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

Question 3

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

Answer 3

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

Question 4

how does cooking food develop flavours?

Answer 4

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

Question 5

how does cooking food improve textures?

Answer 5

-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

Question 6

name the 3 ways heat can be transferred when cooking?

Answer 6

conduction
convection
radiation

Question 7

how does conduction transfer heat?

Answer 7

-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

Question 8

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

Answer 8

-pan [heat transfer to pan = conduction] 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

Question 9

how is heat energy transfered through radiaition?

Answer 9

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

Question 10

how do proteins de nature name 3 ways?

Answer 10

mechanical agitation = whisking etc
heat
acid

Question 11

how do proteins de nature?

Answer 11

-chemical bonds break
-protein unravell

Question 12

how do denatured proeins coagulate?

Answer 12

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

Question 13

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

Answer 13

-firmer texture
-white colour
-

Question 14

what happens if food is overcooked?

Answer 14

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

Question 15

how are foams formed?
using egg whites

Answer 15

-proteins in whites denature[form mechanical agiatation -whisking] casusing them to stretch = air becomes trapped
-proteins coagulate
=gas in liquid foam

Question 16

what happens if you over whisks

Answer 16

-proteins break = air released = foam colappses

Question 17

why does gluten need kneading?

Answer 17

-develop strands, longer, stronger, strechier

Question 18

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

Answer 18

-coagulate, dough stays stretch , ligh airy texture

Question 19

expalin the process off gelatinasation?

Answer 19

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

Question 20

whats is dextrinsioation?
what does it produce?

Answer 20

-breaks down starch molecules into simple sugar [heat] = dextrins

Question 21

affect of dextriniasation?

Answer 21

-browner colour
-crispier texture

Question 22

what is caramlaisation?

Answer 22

sugar breaks down - sugar goes brown & chnages flavour

Question 23

affects of caramalisation?

Answer 23

-adds sweetness and brown colour

Question 24

what are the processes of sugar?

Answer 24

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

Question 25

what is aeration? e.gs?

Answer 25

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

Question 26

whats shortnening? -gives food crumbly texture

Answer 26

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

Question 27

what does plasticty mean?

Answer 27

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

Question 28

what do fats contain hic allws plasiticty?

Answer 28

triglycerides

Question 29

what type of fat has a more plasticty?

Answer 29

unsaturated = liquid at room temp(healthier)

Question 30

advantages of plasiticy?

Answer 30

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

Question 31

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

Answer 31

hydrophilic-attacted to water hydrophobic-repulsed by water

Question 32

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

Answer 32

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

Question 33

what emulsifier does egg yolks contain?

Answer 33

lecithin

Question 34

name an exampple of an emulsion?

Answer 34

sauces =hollandaise sauce

Question 35

how is hollandaise sauce made?

Answer 35

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

Question 36

what happens if u add fat to fast in emulsiation?

Answer 36

-wont bond to hydrophilic/phobic ends xx

Question 37

how does bioligical rasing agent yeast work?

Answer 37

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

Question 38

name a chmical raising agent? how does it work?

Answer 38

- bicarbonate of soda = rleases CO2 bubbles to make food rise [heat needed for reaction to occur]

Question 39

con of BOS?

Answer 39

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

Question 40

pros of using baking powder?

Answer 40

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

Question 41

how does steam make food rise?

Answer 41

-crossiants and shoux pastry -when bakes - fat pockets = relase steam it rises -water evaporates

Question 42

when cooking crossiabts why cant u open the oven?

Answer 42

-cold air = makes thing sink

Question 43

name 5 methos we can phycally add air to food?

Answer 43

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