food science

Question 1

why is food cooked

Answer 1

-to make it safe to eat
-to improve shelf life
-to develop flavours
-to improve texture
-to give variety to the diet

Question 2

what are the 3 ways heat can be transferred

Answer 2

conduction, convection and radiation

Question 3

how does conduction transfer heat

Answer 3

through the vibration of particles e.g a pan on a hob

Question 4

how does convection transfer heat

Answer 4

through gases or liquids e.g using ovens, hot air rises and cooler air falls in the same way

Question 5

how does radiation transfer heat

Answer 5

through waves of radiation e.g microwaves, which use radiation to heat up fat, sugar and water molecules in our food

Question 6

what is boiling

Answer 6

heating foods like rice and pasta in a pan of boiling water

Question 7

why is boiling classed as a healthy way of cooking foods

Answer 7

no fat is used, but colour, flavour and water-soluble vitamins can be lost in the water

Question 8

what is steaming

Answer 8

cooking foods like fish and rice with steam from boiling water or stock

Question 9

why is steaming classed as a healthy way of cooking

Answer 9

the veg keep more of their taste, texture, colour and nutrients

Question 10

what is blanching

Answer 10

part-cooking food in boiling water for a shirt time before putting it in iced water

Question 11

how does blanching work

Answer 11

the cold/iced water stops the cooking process - this helps retain colour, texture and minerals in the foods

Question 12

what is simmering

Answer 12

more gentle way of boiling, often used to make soups or curries

Question 13

what is poaching

Answer 13

cooking food like eggs in a pan of liquid below boiling point, usually around 80 degrees

Question 13

why is simmering classed as healthy

Answer 13

it preserves the nutrients better than boiling does

Question 14

what is braising

Answer 14

slowly cooking food like big joints of meat in an ovenproof pot that contains a liquid in it

Question 14

what is stir-frying

Answer 14

frying foods in a wok in a small amount of oil

Question 14

why is poaching not as good of a way to cook foods than other methods

Answer 14

nutrients and flavours of the foods can easily be lost in the water

Question 15

what is shallow frying

Answer 15

frying foods in a medium amount of oil in a pan

Question 15

what foods can you bake

Answer 15

bread, cakes, pies, tarts etc.

Question 16

why is baking a good method of cooking food

Answer 16

the oven heats up quicker and the food cooks quicker, using less energy

Question 17

what are the advantages of baking

Answer 17

gives the food a good appearance and no extra fat is added when baking

Question 18

what are the disadvantages of baking

Answer 18

can take a long time and the food can dry out

Question 19

how do foods get a golden exterior from grilling

Answer 19

the fats drip off the food as its grilled

Question 20

what are the advantages of grilling

Answer 20

-foods cook quickly
-no fat is added

Question 21

what are the disadvantages of grilling

Answer 21

-it is hard to cook the food evenly -risk of cross-contamination

Question 22

what are the advantages of roasting

Answer 22

-gives the food a great appearances and texture -the foods are moist

Question 23

what are the disadvantages of roasting

Answer 23

-not always healthy bc extra fat can be added -takes a long time

Question 24

what are the advantages of dry frying

Answer 24

-no fats are added -gives a more distinct aroma to nuts and seeds

Question 25

what are the disadvantages of dry frying

Answer 25

-takes longer than other methods of frying -can only be used for a small range of foods

Question 26

what are the 3 ways proteins can be denatured

Answer 26

-agitation (whisking, beating etc.) -changes in temp. -adding acids e.g lemon juice and marinades

Question 27

what happens to denatured proteins

Answer 27

they coagulate

Question 28

what is coagulation

Answer 28

-protein molecules collide with other protein molecules and join together -water is trapped between protein molecules -it changes the appearnce of foods as well (e.g whisking egg whites when making meringues)

Question 29

what happens if a food coagulates too much

Answer 29

-the proteins tighten -water molecules are pushed out -food becomes dry and chewy

Question 30

how are foams formed

Answer 30

-when liquids containing proteins are agitated (e.g whisking egg whites) -the proteins denature -air becomes trapped in the liquid -when the proteins coagulate, the air becomes trapped and a foam forms

Question 31

what happens if you overwhisk egg whites

Answer 31

-protein bonds break -air escapes -the foam collapses

Question 32

what is gluten

Answer 32

a protein found in wheat flours

Question 33

how is gluten formed

Answer 33

when water is mixed with flour to make dough

Question 34

why is dough needed

Answer 34

to stretch and strengthen the gluten strands

Question 35

what happens when gluten reaches a high temperature

Answer 35

it coagulates and the dough stays stretched

Question 36

what is gelatinisation

Answer 36

-mixing starch granules with liquids -when the granules are heated, the bonds start to break, allowing water molecules to enter -the starch granules begin to swell -between 62 and 80 degrees, the starch granules burst open and release starch into the liquid the sauce (e.g bechamel) thickens

Question 37

what is dextrinisation

Answer 37

-when starchy foods like bread are exposed to dry heat like toasting -the starch molecules in the food are broken down into dextrins

Question 38

what is caramelisation

Answer 38

when sugar molecules reach a high temperature and they begin to turn golden brown and become sweeter e.g creme brulee and onions

Question 39

what is aeration

Answer 39

when fats are beaten with sugar and air gets trapped in the mixture

Question 40

what is shortening

Answer 40

when fat is rubbed into flour and the flour particles get covered with fat, providing a waterproof coating e.g shortbread

Question 41

what is plasticity

Answer 41

when foods like fats are able to be spread

Question 42

how is plasticity possible

Answer 42

-because fats contain a mixture of triglycerides which melt and different temps.

Question 43

what is plasticity useful for

Answer 43

-decorating cakes -spreading butter

Question 44

what is emulsification

Answer 44

-when water and oils are mixed together e.g mayonnaise

Question 45

what are the two ends of a molecule in an emulsifier

Answer 45

-hydrophillic -hydrophobic

Question 46

what natural emulsifier do egg yolks contain

Answer 46

lecithin

Question 47

what are raising agents

Answer 47

substances that add gas to doughs and mixtures which expand when heated to create the rise

Question 48

what are examples of chemical raising agents

Answer 48

-bicarbonate of soda -baking powder -cream of tartar

Question 49

what are examples of biological raising agents

Answer 49

-yeast

Question 50

what are examples of mechanical raising agents

Answer 50

-beating -whisking

Question 51

how does steam make a food rise

Answer 51

as the steam rises, it raises the mixture up too