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1
Chapter 34 Food Additives
34.1 Introducing food additives
34.2 Food colourings
34.3 Food flavourings
34.4 Food preservatives
34.5 Are food additives really safe?
CONTENTS OF CHAPTER 34
2
34.1 INTRODUCING FOOD ADDITIVES
34.1 INTRODUCING FOOD ADDITIVES
PROCESSED FOODS AND FOOD ADDITIVES
Some of the foods we eat are fresh. They are not processed.
Most foods, however, are processed.
3
Figure 34.1 Some unprocessed foods.
34.1 INTRODUCING FOOD ADDITIVES
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Figure 34.2 All the foods and drinks shown here have been processed.
34.1 INTRODUCING FOOD ADDITIVES
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In food processing, small amounts of certain chemicals are
often added — these are called food additives.
A FOOD ADDITIVE is a chemical added to food to improve it or
to preserve it.
The main reasons for using food additives are
to colour food
to flavour food
to change the texture (sponginess) of food
to add nutrients
to preserve food
34.1 INTRODUCING FOOD ADDITIVES
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Figure 34.3
A fruit juice with the additive
vitamin C.
34.1 INTRODUCING FOOD ADDITIVES
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Figure 34.4
Would you like this soft drink if no artificial flavouring and colouring had been added to it?
(a) The ‘normal’ look of the soft drink.
(b) What the soft drink would look like if no artificial colouring had been added.
(a) (b)
34.1 INTRODUCING FOOD ADDITIVES
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CONTROL OF FOOD ADDITIVES
The EU (European Union) countries have drawn a list of 314 safe
food additives. Each of them is given an E number.
Figure 34.5
The E number
identifies an
additive.
34.1 INTRODUCING FOOD ADDITIVES
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TYPES OF FOOD ADDITIVES
34.1 INTRODUCING FOOD ADDITIVES
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Table 34.1 Different types of food additives.
34.1 INTRODUCING FOOD ADDITIVES
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Figure 34.6 Can you list the basic foodstuff and food additives in this food?
34.1 INTRODUCING FOOD ADDITIVES
INSPECTING FOOD LABELS FOR ADDITIVES
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Figure 34.7 Can you list the food additives in these chocolate beans?
34.1 INTRODUCING FOOD ADDITIVES
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A34.1
E110 is used as an artificial colouring.
E201 is used as a preservative.
E320 is used as an anti-oxidant.
E322 is used as an emulsifier and stabilizer.
A34.2
Colouring, preservative and flavouring.
34.1 INTRODUCING FOOD ADDITIVES
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34.2 FOOD COLOURINGS
34.2 FOOD COLOURINGS
WHY USE FOOD COLOURINGS?
Food colourings are dyes. They are added to food for the
following purposes:
To give food an attractive colour, so as to make it more
appetizing and more saleable.
To restore the original colour which may be changed or lost
during food processing or storage.
To ensure colour consistency.
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Figure 34.8
When fruits are processed, their colours change. Artificial colourings are added to make
them look like fresh fruits.
34.2 FOOD COLOURINGS
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ARE FOOD COLOURINGS ESSENTIAL?
There is no definite conclusion to this. But one thing is certain —
most processed foods on market nowadays contain colourings.
NATURAL AND SYNTHETIC COLOURINGS
Synthetic colourings are more commonly used.
USE OF COLOURINGS WORLDWIDE
In most places nowadays, the use of food colourings is under
strict control by the government.
ANALYSING COLOURINGS BY CHROMATOGRAPHY
Food colourings can be analysed by chromatography.
34.2 FOOD COLOURINGS
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34.2 FOOD COLOURINGS
Paper chromatography of black ink..
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Figure 34.10
Colourful chocolate beans.
34.2 FOOD COLOURINGS
Figure 34.11
Chocolate beans become white
when the colourings are removed.
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Figure 34.12
A simple set-up for
paper chromatography
of colouring on
chocolate beans.
chromatography paper strip
stopper
spot of colouringstarting line
water
34.2 FOOD COLOURINGS
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34.2 FOOD COLOURINGS
To separate dyes in the colouring of a Smarties chocolate bean.
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34.3 FOOD FLAVOURINGS
34.3 FOOD FLAVOURINGS
WHY USE FOOD FLAVOURINGS?
Flavourings are added to food for the following purposes:
To enhance flavour of food
To restore the original flavour which may be lost during food
processing
To add flavour to foods which are tasteless themselves (e.g.
ice cream, jelly)
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Figure 34.14
The flavour of an ice cream is
due to the flavourings added.
34.3 FOOD FLAVOURINGS
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COMMON FLAVOURINGS
Flavourings make up the largest class of food additives.
Both natural and artificial flavourings are used.
34.3 FOOD FLAVOURINGS
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Figure 34.15 Common flavourings.
34.3 FOOD FLAVOURINGS
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A34.3
Synthetic esters are widely used as fruit flavours in drinks,
ice creams and sweets.
Monosodium glutamate
Monosodium glutamate is a white solid. It possesses little flavour
of its own, but it can ‘bring out’ the flavour of foods. It is therefore
actually a flavour enhancer.
34.3 FOOD FLAVOURINGS
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Figure 34.16 Monosodium glutamate is a widely-used flavour enhancer.
34.3 FOOD FLAVOURINGS
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Figure 34.17 Instant noodle supplied with the packet of flavouring (mainly MSG).
34.3 FOOD FLAVOURINGS
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34.4 FOOD PRESERVATIVES
34.4 FOOD PRESERVATIVES
TO PRESERVE FOOD
Food spoilage is mainly due to micro-organisms (microbes). Thus
there are two ways to preserve food:
Kill the microbes in food
Keep food in conditions where the microbes cannot multiply
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(a) (b) (c)
Figure 34.19
Three main types of micro-organisms:
(a) Bacteria (b) Mould (c) Yeast
34.4 FOOD PRESERVATIVES
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Common methods to preserve food
Common methods to preserve food include:
Canning Cook food and then seal it in tin cans under
sterile conditions.
Drying Dry food in the sun or in special ovens. Drying
takes away the water needed by microbes.
Freezing and refrigeration Freeze food quickly. Freezing
turns liquid water into ice, thus controlling the growth of
microbes. Refrigeration slows down biochemical changes of
microbes.
34.4 FOOD PRESERVATIVES
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Irradiation Expose food to gamma rays from certain
radioactive isotopes for a short time. The microbes are killed
at once.
Using preservatives
34.4 FOOD PRESERVATIVES
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(a)
(d)
(b)
Figure 34.20
Foods preserved by different methods:
(a) Canned foods.
(b) Dried fruits.
(c) Frozen foods.
(d) Irradiated strawberries (compared with
non-irradiated ones)
(c)
34.4 FOOD PRESERVATIVES
33
A34.4
(a) Drying
(b) Canning
PRESERVATIVES AND THEIR FUNCTIONS
We add preservatives to food to kill microbes or inhibit their
growth, so that the food spoils less quickly.
Common food preservatives are common salt, sugar, vinegar,
sulphur dioxide, benzoic acid and sodium nitrite.
34.4 FOOD PRESERVATIVES
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Common salt and sugar
Salting and sugaring are two of the oldest methods of preserving
food.
Figure 34.21
Using salt to preserve fish.
34.4 FOOD PRESERVATIVES
35
Figure 34.22 Fruits preserved in strong sugar solution.
34.4 FOOD PRESERVATIVES
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A34.5
(a) Osmosis.
(b) Salting and sugaring.
Vinegar
Pickling in vinegar is a common method of preserving onions,
cucumbers and beetroot.
34.4 FOOD PRESERVATIVES
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Figure 34.23 Onion is pickled in vinegar.
34.4 FOOD PRESERVATIVES
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Sulphur dioxide
Sulphur dioxide has been used in wine-making for hundreds of
years to control the growth of unwanted microbes.
A wide range of other foods, such as fruit juices and dried
fruits, also have sulphur dioxide added as a preservative.
34.4 FOOD PRESERVATIVES
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Figure 34.24 Sulphur dioxide is a common preservative for dried fruits.
34.4 FOOD PRESERVATIVES
40
Benzoic acid
Benzoic acid (or sodium benzoate) is a preservative commonly
used in fruit juices and other drinks. It is able to stop the growth of
bacteria and yeasts.
34.4 FOOD PRESERVATIVES
41
Figure 34.25
Fruit juices usually contain small amounts of benzoic acid (or sodium benzoate) as
preservative.
34.4 FOOD PRESERVATIVES
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Sodium nitrite
In the process of manufacturing ham, bacon and sausages, the
meats are soaked in a solution containing sodium chloride,
sodium nitrate and sodium nitrite. This is called curing.
34.4 FOOD PRESERVATIVES
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Figure 34.26 Luncheon meat and ham contain sodium nitrite as preservative.
34.4 FOOD PRESERVATIVES
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Table 34.2 Main functions of food preservatives.
34.4 FOOD PRESERVATIVES
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A34.6
(b) B, C (c) B (d) A, D
(e) A, C (f) D
34.4 FOOD PRESERVATIVES
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34.5 ARE FOOD ADDITIVES REALLY SAFE?
34.5 ARE FOOD ADDITIVES REALLY SAFE?
DIFFERENT OPINIONS ON SAFETY OF FOOD
ADDITIVES
It is hard to draw general rules to control food additives which
would apply to all people.
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34.5 ARE FOOD ADDITIVES REALLY SAFE?
Activity 4
Some guiding questions for this discussion are:
Selecting one or two food items, try to decide what the food
would be like without the additives. For example, what would
vanilla-flavoured ice cream be like without colouring? Without
flavouring? Without emulsifiers and stabilizers?
For the same food items, would you still buy them without the
additives? Or would you buy another different food instead?
Are some types of additives more useful than others? If so,
which ones? Could we do without any additives?
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Should we worry about the possible effect of food additives on
health?
Without food additives, the variety of food available in shops
would be much smaller (just imagine potato crisps with no
flavour). Would this have a great impact on sales?
A list of ingredients is not found in some foods, e.g. fresh fruit,
vegetables and alcoholic drinks. Why do you think this is so?
Should all foods have ingredient lists?
34.5 ARE FOOD ADDITIVES REALLY SAFE?
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POSSIBLE HAZARDS OF FOOD ADDITIVES
Possible hazards of some food additives to our health are:
Hazards of colourings
Food colourings permitted by law may not be really safe.
Hazards of MSG
Some people are allergic to MSG.
34.5 ARE FOOD ADDITIVES REALLY SAFE?
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Figure 34.27 All these contain much MSG.
34.5 ARE FOOD ADDITIVES REALLY SAFE?
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Hazards of preservatives
Sulphur dioxide would cause breathing difficulties and
stomach upset in some asthma patients. Besides, sodium
nitrite is suspected of causing cancer.
34.5 ARE FOOD ADDITIVES REALLY SAFE?
52
SUMMARY
1. A food additive is a chemical added to food to improve it or to
preserve it.
2. The main reasons for using food additives are:
To colour food (by colourings)
To flavour food (by flavourings)
To keep oils and water mixed in food (by emulsifiers
and stabilizers)
To add nutrients
To preserve food (by preservatives)
SUMMARY
53
SUMMARY
3. Food additives approved by the EU countries often have an
E number. (See Table 34.1 on p. 305.)
4. Paper chromatography can be used to separate the dyes in
food colourings.
5. Common food flavourings include common salt, sugar,
vinegar and synthetic esters. MSG is a flavour enhancer.
6. Food spoilage is mainly due to micro-organisms (bacteria,
fungi, yeast).
7. Food preservatives include common salt, sugar, vinegar,
sulphur dioxide, benzoic acid and sodium nitrite.
8. Food preservatives can function as such because they either
kill microbes or inhibit their growth.
54
SUMMARY
9. Some food additives such as tartrazine (E102) and sodium
nitrite are hazardous to health.