1
Q
What are additives and what are some?
A
- substances added to foods improve flavour, colour or prolong expiry
- food colours make food look more appetising
- flavour enhancers bring out the taste and smell of food without adding their own taste
- antioxidants help to preserve food
- emulsifiers help oil and water blend together in foods
2
Q
What is the structure of an emulsifier?
A
- hydrophobic (likes oil) tail
- hydrophilic (likes water) head
3
Q
What is an emulsion?
A
- a mixture of oil and water
- made up of lots of droplets of one liquid suspended in another liquid
4
Q
How do emulsifiers work?
A
- stops oils and water separating
- when you shake a oil and water together the oil with an emulsifier the oil forms droplets, bonded to a coating of emulsifier
- the hydrophobic end is bonded to the oil, and the hydrophilic end is facing onward
- other oil droplets are repelled by the hydrophylic head, while water latches on
- the emulsion won’t separate
5
Q
Why are many foods cooked?
A
- better texture and taste
- easier to digest cooked
- high temperature kills microbes that cause diseases
- some foods are poisonous raw, e.g. kidney beans
6
Q
How are eggs and meat changed in cooking?
A
- egg and meat are proteins
- energy from cooking breaks some chemical bonds in the protein and allows its molecules to change shape
- this is denaturing
- a chemical change and irreversible
- giving food a more edible texture
7
Q
How are potatoes changes during cooking?
A
- potato cells have rigid cell walls made of cellulose
- human’s cannot digest cellulose
- cooking potatoes ruptures the cell walls and the starch grains inside the cell swell up and spread out
- making the potato softer, more flexible and easier to digest
8
Q
What happens when baking powder is is heated?
A
- thermal decomposition
- sodium hydrogencarbonate—>sodium carbonate+carbon dioxide+water
9
Q
What is thermal decomposition?
A
- a substance breaking down into a simpler substance when heated
- many thermal decomposition need catalyst
