Oxidation of Food Flashcards
Oxidation and Reduction
Oxidation - Increase in the oxygen to hydrogen ratio
Reduction - Decrease in the oxygen to hydrogen ratio
Oxidation of alcohols
Primary alcohols = aldehydes = carboxylic acids
Secondary alcohols = Ketones
What are the oxidising agents and their colour changes?
- Hot copper (II) oxide - black to brown solid
- Acidified dichromate (VI) solution - orange to green
- Fehlings solution - blue to brick red
- Toilens reagent - forms a silver mirror
What are oxidising agents used to identify?
Aldehydes (NOT ketones)
Why can tertiary alcohols not be oxidised?
Due to the position of the hydroxyl group, due to there being a branch a =0 bond cannot be formed.
What are the functional groups that are found in aldehydes and ketones?
Aldehydes - CHRO
Ketones - CRRO
Carbonyl - C=O
What are the first 8 Aldehydes called?
Methanal (CH2O) , Ethanal (C2H4O) , Propanal (C3H6O) , Butanal (C4H8O) , Pentanal (C5H10O) , Hexanal (C6H12O) , Heptanal (C7H14O) , Octanal (C8H16O)
What are the first 6 Ketones?
Propanone (C3H6O) , Butanone (C4H8O) , Pentanone (C5H10O) , Hexanone (C6H12O) , Heptanone (C7H14O) , Octanone (C8H16O)
What are the Oxidation & Reduction reactions of aldehydes & Ketones?
Oxidation:
Aldehydes = Carboxylic acids
Ketones = no oxidation
Reduction:
Aldehydes = Primary Alcohol
Ketones = Secondary Alcohol
Uses of Aldehydes
They often have distinct flavours or aromas so are used in food products or essential oils.
What happens when food reacts with oxygen?
Food reacts with oxygen in the air, this then reacts with edible oils giving them a rancid flavour (the food goes off)
Antioxidant
Antioxidants are molecules that prevent unwanted oxidation reactions to occur by being oxidised in their place (they are reducing agents).
Vitamin C is an example of an antioxidant. Other antioxidants are found in food products, skin care, cosmetics etc.
