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GCSE Food Tech AQA > Functional and Chemical properties of food > Flashcards

Functional and Chemical properties of food Flashcards

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1
Q

Definition of protein denaturation

A

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

-proteins unravel and their shape changes

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2
Q

Name 4 ways proteins can be denatured

A
  • Physical agitation
  • Changes in temperature
  • Acids
  • Heat
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3
Q

Name the process that occurs once protein molecules have been denatured

A

protein coagulation

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4
Q

Definition of protein coagulation

A

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

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5
Q

What does protein coagulation change in a food

A

The appearance and texture

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6
Q

Definition of foam formation

A

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

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7
Q

Definition of gluten formation

A

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

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8
Q

What foods is gluten found in

A

bread

pasta

cakes

pastries

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9
Q

What is gelatinisation

A

It helps to thicken foods containing starch

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10
Q

Describe the steps of gelatinisation

A
  • 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
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11
Q

When does dextrinisation occur

A

It occurs when starch is exposed to dry heat

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12
Q

How does dextrinisation occur

A

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

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13
Q

How does dextrinisation change food

A

gives food a browner colour

crispier texture

different taste

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14
Q

What is caramelisation

A

The browning and change in flavour of sugar when heated

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15
Q

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

A
  • 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
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16
Q

How does caramelisation change food

A

gives desserts like crème brulee and apple pie extra sweetness

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17
Q

What is shortening

A

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

-Gives food a crumbly texture

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18
Q

How does shortening occur

A
  • 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
19
Q

What is plasticity

A

The ability to be spread and shaped

20
Q

How does plasticity occur

A
  • 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
21
Q

What does emulsification do

A

Emulsification keeps oil and water in a stable emulsion

22
Q

How does emulsification occur

A
  • 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
23
Q

What are examples of emulsions

A

Milk, margarine, mayonnaise

24
Q

Which types of raising agents produce carbon dioxide

A
  • Chemical

- Biological

25
Q

How do chemical raising agents produce carbon dioxide

A

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

26
Q

How do biological raising agents produce carbon dioxide

A
  • 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
27
Q

Name a chemical raising agent

A

Bicarbonate of soda

28
Q

Name a biological raising agent

A

Yeast

29
Q

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

A
  • Steam

- Mechanical

30
Q

How does the steam raising agent add steam to the mixture

A
  • 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
31
Q

How do mechanical raising agents add air to the mixture

A

-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
32
Q

Name 5 reasons why food is cooked

A
  • make it safe to eat
  • improve shelf life
  • develop flavours
  • improve texture
  • give variety in diet
33
Q

Name the 3 ways heat can be transferred

A
  • convection
  • conduction
  • radiation
34
Q

Definition of convection

A

-transfer of heat energy through the vibration of particles

35
Q

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

A
  • 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
36
Q

Definition of conduction

A

-transfer of heat energy through gases/ liquids

37
Q

Describe what happens in conduction when you heat up a liquid

A
  • 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
38
Q

Definition of radiation

A

-transfer of heat energy through waves of radiation

39
Q

Describe what happens in radiation when using a grill/ toaster

A

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

40
Q

Name 6 water-based cooking methods

A
  • boiling- healthy method
  • steaming-healthy
  • simmering
  • blanching
  • poaching
  • braising
41
Q

Name 2 fat-based cooking methods

A
  • shallow frying

- stir fry

42
Q

Name 4 dry-methods of cooking

A
  • baking
  • roasting
  • grilling
  • dry frying
43
Q

definition of aeration

A

-adding air to a mixture through baking/ whisking

44
Q

name a food which shows visible denaturation and coagulation

A

frying an egg

GCSE Food Tech AQA (6 decks)

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