U2 Oxidation of food (course specification) Flashcards
define oxidation in terms of oxygen to hydrogen radio
oxidation is an increase in oxygen to hydrogen ratio (by adding oxygen atoms or removing hydrogen atoms)
define reduction in terms of oxygen to hydrogen radio
reduction is a decrease in oxygen to hydrogen ratio (by removing oxygen atoms or adding hydrogen atoms)
what substances can be used to oxidise alcohols? what is the name given to them?
acidified sodium dichromate solution and hot copper (II) oxide are oxidising agents
what happens to primary alcohols when oxidised?
they form aldehydes which can be oxidised to form carboxylic acids
what happens to secondary alcohols when oxidised?
they form ketones which cannot be oxidised
what happens to tertiary alcohols when oxidised?
tertiary alcohols are not readily oxidised
what happens to oxidising agents when they oxidise alcohols?
black copper(II) oxide forms a brown solid, and orange dichromate solution turns green
state three substances which oxidise aldehydes
Fehling’s/Benedict’s solution, acidified dichromate solution, Tollen’s solution
state the colour changes which occur when oxidising agents oxidise aldehydes
Fehling’s/Benedict’s solution turns brown, tollens reagent turns from clear to silver, acidified dichromate solution turns from orange to green
state examples of flavour molecules in foods
aldehydes + ketones
describe oxidation in food
Oxygen from the air causes the oxidation of food. The oxidation of aldehydes and ketones in food can give an unpleasant flavour.
describe the role of antioxidants in food
antioxidants are molecules that prevent unwanted oxidation reactions occurring. they are substances that are easily oxidised, and oxidise in place of the compounds they have been added to protect
