Functional and Chemical properties of food

Question 1

Definition of protein denaturation

Answer 1

when food is cooked proteins denature, meaning the chemical bonds holding their structure together break down

-proteins unravel and their shape changes

Question 2

Name 4 ways proteins can be denatured

Answer 2

• Physical agitation
• Changes in temperature
• Acids
• Heat

Question 3

Name the process that occurs once protein molecules have been denatured

Answer 3

protein coagulation

Question 4

Definition of protein coagulation

Answer 4

-once they have been denatured protein molecules collide with other protein molecules and coagulate (join together)

Question 5

What does protein coagulation change in a food

Answer 5

The appearance and texture

Question 6

Definition of foam formation

Answer 6

Foams form when gas becomes trapped (aeration) inside a liquid

Question 7

Definition of gluten formation

Answer 7

Gluten is formed when water is mixed with flour to make dough

Question 8

What foods is gluten found in

Answer 8

bread

pasta

cakes

pastries

Question 9

What is gelatinisation

Answer 9

It helps to thicken foods containing starch

Question 10

Describe the steps of gelatinisation

Answer 10

• starch molecules become suspended when first mixed with liquid
• starch molecules then start to break when heated with water, allowing water molecules to enter
• water is absorbed and starch granules swell in size and soften
• between 62 and 80 degrees starch granules burst open and release starch into liquid causing it to thicken
• when it cools liquid solidifies and a solid gel is formed

Question 11

When does dextrinisation occur

Answer 11

It occurs when starch is exposed to dry heat

Question 12

How does dextrinisation occur

Answer 12

When starchy foods are cooked with dry heat starch molecules in food break down into dextrins

Question 13

How does dextrinisation change food

Answer 13

gives food a browner colour

crispier texture

different taste

Question 14

What is caramelisation

Answer 14

The browning and change in flavour of sugar when heated

Question 15

Describe the steps of caramelisation- what food is like when it is first caramelised

Answer 15

• at first the liquid is runny and has a very sweet taste
• as time passes it becomes more like a smooth caramel
• then it turns harder and as it cools becomes more like candy

Question 16

How does caramelisation change food

Answer 16

gives desserts like crème brulee and apple pie extra sweetness

Question 17

What is shortening

Answer 17

When a fat coats starch and prevents the water from lengthening the gluten

-Gives food a crumbly texture

Question 18

How does shortening occur

Answer 18

• Rub fat into flour and cover flour particles with fat giving the flour particles a waterproof coating
• This waterproof coating prevents long gluten molecules forming
• So dough can’t become stretchy and so keeps a short texture

Question 19

What is plasticity

Answer 19

The ability to be spread and shaped

Question 20

How does plasticity occur

Answer 20

• Fats contain a mixture of different triglycerides
• These different triglycerides all melt at different temperatures so fats gradually soften over a range of temperatures rather than just melting on

Question 21

What does emulsification do

Answer 21

Emulsification keeps oil and water in a stable emulsion

Question 22

How does emulsification occur

Answer 22

• Molecules in an emulsifier have two different ends one is hydrophilic (attracted to water) and the other is hydrophobic (repulsed by water)
• when you add an emulsifier the water molecules bond to the hydrophilic side and the oil molecules bond to the hydrophobic side
• this holds water and oil together in a stable emulsion preventing them from separating

Question 23

What are examples of emulsions

Answer 23

Milk, margarine, mayonnaise

Question 24

Which types of raising agents produce carbon dioxide

Answer 24

• Chemical

- Biological

Question 25

How do chemical raising agents produce carbon dioxide

Answer 25

-when heated bicarbonate of soda breaks down to produce carbon dioxide bubbles that expand to make the mixture rise

Question 26

How do biological raising agents produce carbon dioxide

Answer 26

- Yeast is a microorganism that causes fermentation- a process that releases alcohol and carbon dioxide - When carbon dioxide is released and trapped in dough, it causes the dough to rise

Question 27

Name a chemical raising agent

Answer 27

Bicarbonate of soda

Question 28

Name a biological raising agent

Answer 28

Yeast

Question 29

Which types of raising agents add steam or air to the mixture

Answer 29

- Steam | - Mechanical

Question 30

How does the steam raising agent add steam to the mixture

Answer 30

- when using a very hot oven to cook a mixture it contains lots of liquid - this water leaves the mixture as steam and as it rises it raises the mixture up and food becomes more solid

Question 31

How do mechanical raising agents add air to the mixture

Answer 31

-Air can be folded into mixtures and doughs: using a spoon, repeatedlty folding the mixture over itself trapping the air pastry doughs can be folded in layers traping the air - Whisking - Beating - Sieving flour - Creaming

Question 32

Name 5 reasons why food is cooked

Answer 32

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

Question 33

Name the 3 ways heat can be transferred

Answer 33

- convection - conduction - radiation

Question 34

Definition of convection

Answer 34

-transfer of heat energy through the vibration of particles

Question 35

Describe what happens in convection when a pan is placed on the hob

Answer 35

- when a pan is placed on the hob heat energy from hob causes particles to vibrate and gain heat energy - these particles collide with nearby particles passing some of their extra heat energy to them - when food is placed in pan- heat energy is transferred from the pan to particles in the food

Question 36

Definition of conduction

Answer 36

-transfer of heat energy through gases/ liquids

Question 37

Describe what happens in conduction when you heat up a liquid

Answer 37

- when you heat a liquid, liquid near heat source heats up fast - As warm air rises, colder liquid takes its place - as process continues you end up with convection currents resulting in whole fluid being heated

Question 38

Definition of radiation

Answer 38

-transfer of heat energy through waves of radiation

Question 39

Describe what happens in radiation when using a grill/ toaster

Answer 39

-they emit waves of radiation which are absorbed and heat food up

Question 40

Name 6 water-based cooking methods

Answer 40

- boiling- healthy method - steaming-healthy - simmering - blanching - poaching - braising

Question 41

Name 2 fat-based cooking methods

Answer 41

- shallow frying | - stir fry

Question 42

Name 4 dry-methods of cooking

Answer 42

- baking - roasting - grilling - dry frying

Question 43

definition of aeration

Answer 43

-adding air to a mixture through baking/ whisking

Question 44

name a food which shows visible denaturation and coagulation

Answer 44

frying an egg