Cooking and food additives

Question 1

Why is cooking a chemical change?

Answer 1

• A new substance is made
• It cannot be reversed
• An energy change takes place in the food

Question 2

How does a potato change when cooked?

Answer 2

• Taste is better
• Texture changes (softer&fluffy)
• This is because the cell walls break down/ rupture resulting in a loss of rigid structure and a softer texture
• Starch grains burst, swell up and spread which makes it easier to digest

Question 3

How do proteins change during cooking?

Answer 3

• Proteins are chemicals in food
• They are large molecules with definite shapes
• The white of an egg is made of a protein called albumin.
• Albumin molecules change shape when cooked
• So does the protein in meat
• This is called denaturing

Question 4

How does baking powder affect food?

Answer 4

• It is a chemical called sodium hydrogencarbonate
• When heated it decomposes to give sodium carbonate, carbon dioxide and water
• The carbon dioxide causes cakes to rise

Question 5

What are the 4 main food additives and why are they used?

Answer 5

> Antioxidants stop the food reacting with oxygen
Food colourants improve colour
Flavour enhancers improve flavour
Emulsifiers help oil and water mix in foods and stop them separating

Question 6

What is an emulsifier?

Answer 6

> Has 2 parts to the molecule
The hydrophilic head is water-loving
The hydrophobic tail is water-hating and attracts to the oils and fats