1 chapter 34food additives 34.1introducing food additives 34.2food colourings 34.3food flavourings...

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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

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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.

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Figure 34.1 Some unprocessed foods.


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Figure 34.2 All the foods and drinks shown here have been processed.


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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


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Figure 34.3

A fruit juice with the additive

vitamin C.


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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)


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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.


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TYPES OF FOOD ADDITIVES


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Table 34.1 Different types of food additives.


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Figure 34.6 Can you list the basic foodstuff and food additives in this food?


INSPECTING FOOD LABELS FOR ADDITIVES

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Figure 34.7 Can you list the food additives in these chocolate beans?


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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.


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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.


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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.


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Paper chromatography of black ink..

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Figure 34.10

Colourful chocolate beans.


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


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To separate dyes in the colouring of a Smarties chocolate bean.

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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.


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COMMON FLAVOURINGS

Flavourings make up the largest class of food additives.

Both natural and artificial flavourings are used.


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Figure 34.15 Common 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.


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Figure 34.16 Monosodium glutamate is a widely-used flavour enhancer.


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Figure 34.17 Instant noodle supplied with the packet of flavouring (mainly MSG).


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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


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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.


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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


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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)


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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.


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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.


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Figure 34.22 Fruits preserved in strong sugar solution.


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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.


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Figure 34.23 Onion is pickled in vinegar.


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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.


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Figure 34.24 Sulphur dioxide is a common preservative for dried fruits.


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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.


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Figure 34.25

Fruit juices usually contain small amounts of benzoic acid (or sodium benzoate) as

preservative.


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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.


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Figure 34.26 Luncheon meat and ham contain sodium nitrite as preservative.


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Table 34.2 Main functions of food preservatives.


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A34.6

(b) B, C (c) B (d) A, D

(e) A, C (f) D


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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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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?


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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.


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Figure 34.27 All these contain much MSG.


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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.


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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

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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.

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SUMMARY

9. Some food additives such as tartrazine (E102) and sodium

nitrite are hazardous to health.

1 chapter 34food additives 34.1introducing food additives 34.2food colourings 34.3food flavourings...

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food food spoilage

food processing

introducing food additives

food preservatives

food labels

food colourings figure

control of food additives

safe food additives