Food Additives and Emulsifiers

Learning ObjectiveDescribe the role of different food additives.Explain what an emulsion is and how it works.

KeywordsSodium hydrogencarbonate, emulsion, emulsifier, antioxidant, hydrophobic, hydrophilic, food additives.

Role of Food Additives

• colours to make food look more attractive• antioxidants like ascorbic acid to prevent

foods reacting with oxygen• emulsifiers like egg yolk lecithin to stop oil and

water separating• flavour enhancers like monosodium glutamate

to improve the taste.

food additives

antioxidants food colours

emulsifiersflavour enhancers

a. Take-away meals that will leave customers wanting more

1. antioxidants

b. A food that contains oil and vinegar like mayonnaise

2. food colourings

c. Fruit salad that turns brown if oxygen reacts with it

3. flavour enhancers

d. Sweets designed to attract young children

4. emulsifiers

REVIEW OF LEARNING

Practical

limewater turns milky when carbon dioxide bubbles through it

bakingpowder

HEAT

•Clamp the test tube of baking powder at an angle above an unlit Bunsen.•Use a test tube holder to keep the tube of limewater in the position shown. •Light the Bunsen and heat the baking powder.•Let the gas released bubble through the limewater.•Remove the limewater before turning off the Bunsen.•Record your observations.•Deduce what role baking powder plays in cooking.

Baking powder

Baking powder is used in making cakes.

It contains sodium hydrogencarbonate.

This breaks down (decomposes) when heated and makes carbon dioxide.

Carbon dioxide makes the cake rise.

Baking powder

This is a chemical change. The word equation is:

sodium hydrogencarbonate

sodium carbonate

carbon dioxide

water+ +

The test for carbon dioxide:Carbon dioxide turns _____ water ______.

lime cloudy

baking powder used (g)

amount Kasia’s cake rose (mm)

0 2

0.5 5

1.0 16

2.0 13

3.0 18

4.0 21

5.0 12

6.0 6

•Kasia plans to make a special cake for her mum’s birthday. She has an idea. Her hypothesis is that the cake will rise higher if she adds more baking powder to the mixture.

She tests her hypothesis by making 8 small cakes. The table on the right shows her results.

Plot a graph to display the results.•Explain what the results show.________________________________________________________________________________________________________________________________________________________•Do the results support Kasia’s hypothesis? ________________________________________________________________________________________________________________________________________________________

What do the results show? From 0-4g, the more baking powder used the more the cake rose, but from 4-6g, the more baking powder used the less the cake rose.

Do the results support the hypothesis? The results support Kasia’s hypothesis from 1-4g but optimum results are achieved between 3 and 5g, so adding extra makes the results worse

Emulsifiers

Oil and water do not mix. When an emulsifier is added, they mix and

do not separate. Emulsifiers are used in mayonnaise and ice

cream. One important emulsifier is lecithiin (E322)

How emulsifiers work

Emulsifiers have molecules with two parts:

A water-loving or hydrophilic end

A fat-loving or hydrophobic end

How emulsifiers work

The hydrophilic end bonds with water molecules.

The hydrophobic end bonds with oil molecules

In this way, the oil droplets stay mixed with the water.

Review of Learning

Five key points from the lesson are:1.2.3.4.5.