Food additives are substances added to food to solve a particular problem. The fastest way to answer questions on them is to start from the problem, then name the additive that fits.
This lesson is part of SPM Chemistry and sits with the other consumer and industrial chemistry lessons. Check your own textbook for the examples your school expects.
Which additive solves which problem?
Keep one line per additive type, with the problem it solves.
| Additive type | Problem it solves | Example |
|---|---|---|
| Preservative | Microorganisms make food spoil | Sodium benzoate |
| Antioxidant | Oxidation causes browning or rancidity | Ascorbic acid |
| Flavouring | Food tastes weak or plain | Monosodium glutamate |
| Dye | Food looks dull or uneven in colour | Tartrazine |
| Stabiliser or thickener | Food is too thin or separates | Gelatin |
| Emulsifier | Oil and water layers separate | Lecithin |
Always link the type to its function in your sentence. “It is a preservative” is not enough, but “it slows the growth of bacteria” is.
Worked example: starting from the problem
Here is an original question. A fictional fruit drink is sold in a clear bottle. Within two weeks the sides of the bottle grow a cloudy layer, and a separate batch of sliced fruit on the same shelf turns brown in a day.
Read the two problems separately.
The cloudy layer suggests microorganisms are growing, so the matching additive is a preservative. The browning of the cut fruit is an oxidation problem, so the matching additive is an antioxidant.
| Observation | Problem | Additive |
|---|---|---|
| Cloudy growth in the drink | Microorganisms | Preservative |
| Cut fruit turning brown | Oxidation | Antioxidant |
The mistake that loses marks
The pair students swap most is preservative and antioxidant, because both “keep food fresh”. The safe test is to ask which process is being slowed.
| If the process is… | Write |
|---|---|
| Growth of bacteria or fungi | Preservative |
| Reaction with oxygen | Antioxidant |
A second slip is to write “to make food healthier” as the function of a dye or flavouring. A dye changes colour and a flavouring changes taste, so name exactly that.
Check yourself
A fictional salad dressing separates into an oil layer and a watery layer after a day. Which additive would fix this, and how does it work?
Answer
An emulsifier, such as lecithin. Each emulsifier particle has one end that attaches to oil and one end that attaches to water, so it holds small droplets of one liquid spread through the other and stops the layers from separating.
What to study next
Practise the matching on new foods in the consumer and industrial chemistry practice set. The emulsifier idea connects to interpreting soap and detergent chemistry.
For a teacher to drill the matching with unfamiliar foods, see online one-to-one Chemistry tuition.