Food Safety Techniques
Senior 2 · Home Science
Food Safety Techniques
Lesson 1 of 4
18 min
Let's begin
Every year, large numbers of people in East Africa fall ill from food that looked, smelled and tasted normal. A pot of beans left out overnight, maize flour stored in a damp sack, or cassava leaves that were not cooked long enough can all make a family sick. Most of these illnesses can be prevented by a cook who knows what to look for.
A food hazard is anything in food that can harm the person who eats it. In this lesson you will learn the three main types of food hazard, where each one comes from in a Rwandan kitchen, and how each one is controlled. This is the first step of every food safety system, including the HACCP system you will meet later in this unit.
A biological hazard is a living thing, or a poison made by a living thing, that causes illness. The living things are usually too small to see.
Illness caused by eating contaminated food is called food poisoning or foodborne illness. Typical signs are stomach cramps, nausea, vomiting, diarrhoea and fever. Young children, elderly people, pregnant women and people who are already sick suffer most.
A chemical hazard is a harmful substance in food. Examples:
A physical hazard is a hard or sharp object in food that can cut the mouth, break a tooth or cause choking. Examples: small stones in dry beans and rice, fish bones, pieces of glass, hair, staples from sacks, and jewellery that falls from a cook's hand.
Allergens. Some food safety systems add a fourth group, allergens: foods such as groundnuts, eggs or milk that cause a dangerous reaction in some people. A cook must know what is in each dish so that a guest with an allergy can be warned.
Task: A school kitchen serves rice, beans and cabbage. Name one hazard of each type and say how the cook controls it.
| Type | Hazard | Control |
|---|---|---|
| Physical | Small stones in the dry beans and rice | Spread the grain on a tray and pick out stones before washing |
| Chemical | Pesticide on the cabbage | Buy from a trusted grower; remove outer leaves; wash well in safe water |
| Biological | Bacteria growing in cooked beans kept warm for hours | Cook thoroughly; serve hot; cool and refrigerate leftovers quickly |
Notice the pattern: for each hazard you name what it is, and then the action that stops it. Examiners award marks for both parts.
Tip
Memory hook: "B-C-P, Bugs, Chemicals, Pieces". Biological hazards are living "bugs" and their poisons, chemical hazards are substances, and physical hazards are pieces of something hard.
Exam technique: when asked to classify a hazard, ask whether it is alive (or made by something alive), a substance, or an object. Aflatoxin is a poison, but it is made by a mould, so most food safety systems place it with biological hazards; some list it as a chemical. Say which you are using and why.
Try each question before reading the solution.
Classify each hazard as biological, chemical or physical: (a) a hair in soup; (b) Salmonella in an undercooked egg; (c) insecticide sprayed near an open tray of bread.
Solution: (a) physical; (b) biological; (c) chemical.
Explain why maize grain should be dried well before it is stored in sacks.
Solution: Moulds grow on damp grain. Some moulds make aflatoxin, a poison that harms the liver and is not destroyed by cooking. Dry grain stops the mould growing.
A cook keeps paraffin in an empty soda bottle on the kitchen shelf. State the hazard and one control.
Solution: A chemical hazard: someone may drink it or pour it into food. Store chemicals in their original labelled containers, away from food.
Give two reasons why cassava leaves for isombe are pounded and cooked for a long time.
Solution: Pounding and long cooking release and drive off the cyanide-forming substances in the leaves (a chemical hazard), and thorough cooking also kills micro-organisms (a biological hazard). It also softens the tough leaves.
Summary
Sources and credits
The Rwandan examples, worked example and practice questions are written by Ganzaa.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
