Chemistry Of Cooking Flashcards
What holds polypeptide chains together
Intermolecular bonding between the side chains of amino acids and hydrogen bonding between.
Why does the texture of protein change when it is cooked
The heat involved in cooking breaks intermolecular bonds within proteins and consequently changes the shapes and structure. This is called denaturing and is irreversible
Cooking proteins changes the texture of the food
.
3 types of alcohols
Primary secondary and tertiary
Which alcohols can be oxidised
Primary and secondary
What occurs when primary alcohol oxidised
An aldehyde
Carboxylic acid
What happens when secondary alcohol oxidised
Ketone
What is definition of oxidation
Increase in oxygen to hydrogen ratio
Name two oxidising agents that can be used to oxidised primary and secondary alcohols
Hot copper(II) oxide Acidified potassium dichromate solution
Why does dichromate oxidising agent need to be acidified
To provide hydrogen ions for the reaction
Why are aldehydes an important group of food chemicals
Many flavour and aroma molecules are aldehydes
Functional group in aldehydes and ketones
Carbonyl
Aldehyde is on the … of molecule and ketone is on the …. of molecule
Aldehyde end
Ketone middle
Ending of aldehyde
Ending of ketone
Al
One
Name the 3 oxidising agents that can oxidised alcohols into ketones and there colour change
- tollens colourless to silver mirror
- fehlings/benedicts blue to brick red
- acidified potassium dichromate orange to green
Describe an experiment which could be used to distinguish between an aldehyde and a ketone
Place substances in test tube with suitable oxidising agent.
Warm water bath and observe colour change
Why does an apple go brown when the skin is removed
Substances in the apple are reacting with oxygen in the air causing oxidation
How can manufacturing prevent oxidation
Packed in vacuum
What are antioxidants
Molecules that are added to foodstuffs to prevent them from undergoing reactions
(Reducing agents or free radical scavengers)
Edible oils react with oxygen to form compounds that give food a rancid flavour
.
What reaction does vitamin c undergo when it acts as an antioxidant in food
Oxidation
What is votality
How easily a substance vaporises
What do volatile molecules contained within food we eat do
Give the food flavour
Why do some food taste better when cooked in oil rather than water
Some of the flavour molecules are soluble in oil than water
How does size of flavour molecule affect …
- boiling point
- volatility
The larger the molecule the higher the boiling point
The larger the molecule the less volatile the molecule is
Explain why size affects boiling point volatility
Increased van der waals (intermolecular)
How does the functional group present in flavour molecules affect….
- boiling point
- volatility
In general the more polar the functional group present ….
The higher the boiling point
The less volatile the molecule
Explain why the functional groups affect boiling point and volatility
Increased van der waals forces. The more polar the functional group in the molecule the stronger the intermolecular bonding
