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Unit 2 Higher Chemistry > 2.7 Oxidation of Food > Flashcards

2.7 Oxidation of Food Flashcards

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1
Q

What are the 3 types of oxidation

A
  • Loss of electrons
  • Gain of oxygen
  • Loss of hydrogen
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2
Q

What does oxidation always result in

A

An increase in the oxygen to hydrogen ratio

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3
Q

When oxidation is occurring what is also occurring

A

Reduction

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4
Q

Name 3 oxidising agents

A

Acidified sodium dichromate
Potassium permanganate
Copper (II) oxide

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5
Q

What are the only types of alcohols that can oxidise

A

Primary and Secondary

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6
Q

What happens when potassium permanganate is reduced

A

Purple permanganate ion turns to colourless Mn2+ ions

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7
Q

What happens when sodium dichromate is reduced

A

Orange dichromate ion turns to green Cr3+ ions

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8
Q

What happens when hot copper oxide is reduced

A

Black oxide turns to reddish copper metal

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9
Q

What happens when primary alcohols are oxidised

A

It forms an aldehyde

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10
Q

What happens when you oxidise a secondary alcohol

A

It forms a ketone

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11
Q

What is the functional group for aldehydes and ketones

A

Carbonyl group

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12
Q

Where is the carbonyl group in an aldehyde

A

At the end of the carbon chain

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13
Q

Where is the carbonyl group in a ketone

A

It is attached` to other carbon atoms

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14
Q

What is the general formula for aldehydes and ketones

A

CnH2nO

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15
Q

What compounds can Acidified potassium dichromate oxidise

A

Primary and Secondary alcohols

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16
Q

What is the colour change for acidified potassium dichromate

A

Orange > blue/green

17
Q

What compounds will Fehling’s solution oxidise

A

Only aldehydes

18
Q

What is the colour change for Fehling’s solution

A

Blue > orange/red

19
Q

What compounds will Tollens reagent oxidise

A

Only aldehydes

20
Q

What is the colour change for Tollens reagent

A

Colourless > silver mirror

21
Q

What is a useful way of determining weather oxidation has occurred

A

Calculating the oxygen to hydrogen ratio (It decreases when oxidation has occurred)

22
Q

When cooking vegetables how is flavour released

A

Flavour is usually trapped inside the cell wall, cooking damages the cell wall letting it out

23
Q

Give two examples of aldehydes of ketones used in food

A

Limonene and Vanillin

24
Q

What can happen when vitamin C is cooked in water

A

Since vitamin C is polar, it may dissolve in the water

25
Q

Why should something be cooked in a solvent that is the opposite of its polarity

A

So the flavour molecules do not dissolve

26
Q

What happens when proteins are heated during cooking

A

They denature, allowing them to change shape

27
Q

Give an example of a protein that denatures when cooking meat

A

Collagen

28
Q

When can oxidation of food occur

A

When food is exposed to oxygen in the air

29
Q

What kind of foods are at the greatest risk of oxidisation

A

Foods containing fats or oils

30
Q

How can oxidation of food be avoided

A

Packing it with nitrogen, an inert gas that will not react with the food

31
Q

Name effects of oxidisation on food

A

Loss of colour
Deterioration of flavour
Loss of nutritional value

32
Q

What is an antioxidant

A

A substance that slows down or prevents the oxidation of another chemical

33
Q

What type of agent are antioxidant molecules

A

Reducing agents

34
Q

What can oxidation reactions produce

A

Free radicals

35
Q

How can free radicals damage food

A

By removing electrons

36
Q

How does an antioxidant cancel a free radical

A

The antioxidant donates an electron and stabilises the free radical as a stable electron pair is formed. The antioxidant itself is then oxidised

37
Q

Give an example of an antioxidant

A

Vitamin C

Unit 2 Higher Chemistry (9 decks)

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