Topic 4 of 6 · Form 5
Food microbiology and food safety
Food, moisture (water activity), temperature (danger zone about 5–63 °C), time, pH and oxygen.
Notes for this topic 1 file, in order
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Micro-organisms
- Bacteria: pathogenic (Salmonella, Escherichia coli O157, Staphylococcus aureus, Clostridium perfringens, Clostridium botulinum, Listeria, Bacillus cereus in rice) and spoilage bacteria.
- Moulds (some produce mycotoxins, e.g. aflatoxin from Aspergillus in poorly stored maize and groundnuts) and yeasts.
- Useful microbes: fermentation of mahewu, maheu, amasi (sour milk), yoghurt, bread and beer.
Factors affecting growth
Food, moisture (water activity), temperature (danger zone about 5–63 °C), time, pH and oxygen.
Food-borne illness
Infection versus intoxication; symptoms; high-risk foods (cooked meats, dairy, eggs, cooked rice); vulnerable groups. Cholera and typhoid spread through contaminated water and food.
Food safety management
- HACCP (Hazard Analysis and Critical Control Points): identify hazards, determine critical control points, set critical limits, monitor, take corrective action, verify and keep records.
- Good hygiene and manufacturing practices; cleaning and disinfection; pest control; staff training.
Legislation
Zimbabwe's Food and Food Standards Act sets standards for composition, labelling and hygiene; local authorities inspect food premises; the Standards Association of Zimbabwe (SAZ) certifies products.
Exam tip: For HACCP questions, give a named product and a specific critical control point with a measurable limit (e.g. core temperature at least 75 °C).
Check yourself
- Which mould toxin is a concern in stored groundnuts?
- Name the seven principles of HACCP.
- Why is cooked rice a high-risk food?
Show answers
- Aflatoxin.
- Hazard analysis, critical control points, critical limits, monitoring, corrective actions, verification, record keeping.
- Spores of Bacillus cereus survive cooking and multiply if rice is left warm, producing toxins.
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