Oxidation of food

For carbon compounds what is oxidation?

an increase in the oxygen to hydrogen ratio

For carbon compounds what is reduction?

a decrease in the oxygen to hydrogen ratio

What solutions can be used to oxidise?

• hot copper(II) oxide

• acidified dichromate(VI)

hot copper(II) oxide or acidified dichromate(VI) solutions can be used to oxidise what?

• primary alcohols to aldehydes and then to carboxylic acids;

• secondary alcohols to ketones

During these reactions _____ copper(II) oxide forms a ____ _______, and ______ dichromate solution turns _____

• Black

• Brown solid

• Orange

• Green

tertiary alcohols cannot be ________ using these oxidising agents

Oxidised

What are aldehydes and ketones?

molecules containing a carbonyl functional group C=O

How can you differentiate aldehydes and ketones?

• Aldehydes have carbonyl at the end of the molecules

• Ketones have carbonyl somewhere near the middle of the molecules

Which type of molecules can be oxidised to carboxylic acids: ketones or aldehyde’s

Aldehydes

Oxidising agents can be used to what?

differentiate between an aldehyde and a ketone

Reactions of solutions with an aldehyde?

• blue Fehling's solution forms a brick red precipitate;

• clear, colourless Tollens' reagent forms a silver mirror;

• orange acidified dichromate solution turns green

Many ________ and _________ molecules are aldehydes

• Flavour

• Aroma

What causes the oxidation of food?

Oxygen from the air

The oxidation of edible oils gives what?

Food a rancid flavour

Features of Antioxidants

• are molecules that prevent unwanted oxidation reactions occurring;

• are substances that are easily oxidised, and oxidise in place of the compounds they have been added to protect

• can be identified as the substance being oxidised in a redox equation