Section Revision: Food Safety

This lesson provides a comprehensive revision of food safety content for the AQA GCSE Food Preparation and Nutrition exam (8585), covering bacteria, temperatures, storage, cross-contamination and hygiene.

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Key Temperatures

These are the most frequently tested facts in the food safety section:

Temperature	Significance
-18°C	Freezer — bacteria dormant (NOT killed)
0–5°C	Fridge — bacterial growth very slow
5–63°C	DANGER ZONE — bacteria multiply rapidly
37°C	Optimum for most pathogenic bacteria (body temperature)
63°C	Hot holding minimum (top of danger zone)
72°C	Pasteurisation (72°C for 15 seconds)
75°C	Core cooking and reheating minimum
100°C	Boiling point
135°C	UHT treatment (135°C for 1–4 seconds)

Exam Tip: These temperatures appear in almost every food safety exam. Learn them so thoroughly that you can recall them instantly.

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The Five Food Poisoning Bacteria

Bacterium	Main Source	Onset	Key Symptom	Serious Complication	Unique Feature
Campylobacter	Raw poultry	2–5 days	Bloody diarrhoea	Guillain-Barré syndrome	Most common in UK; do NOT wash chicken
Salmonella	Poultry, eggs	12–72 hrs	Diarrhoea, vomiting	Septicaemia	Lion mark eggs; egg vaccination
E. coli O157	Raw beef (mince)	1–4 days	Bloody diarrhoea	HUS (kidney failure)	Very low infective dose (~10 bacteria)
Listeria	Soft cheese, pâté	1–70 days	Flu-like; meningitis	Miscarriage/stillbirth	Grows at fridge temperatures
S. aureus	Human skin, nose, cuts	1–6 hrs	Violent vomiting	Dehydration	Heat-resistant toxins

Quick Onset Order (fastest to slowest)

flowchart LR
    A["S. aureus<br/>1-6 hrs"] --> B["Salmonella<br/>12-72 hrs"]
    B --> C["E. coli O157<br/>1-4 days"]
    C --> D["Campylobacter<br/>2-5 days"]
    D --> E["Listeria<br/>1-70 days"]

    style A fill:#e74c3c,color:#fff
    style E fill:#2c3e50,color:#fff

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Cross-Contamination Prevention

Method	How It Prevents Cross-Contamination
Raw meat on bottom shelf	Prevents drips falling on ready-to-eat food
Separate chopping boards	Red = raw meat; Blue = raw fish; Green = salad; Yellow = cooked meat
Separate utensils	Different knives and tongs for raw and cooked food
Handwashing	Removes bacteria between handling different foods
Clean and disinfect surfaces	Two-stage process: clean (remove dirt) then disinfect (kill bacteria)
Do not wash raw chicken	Washing splashes bacteria around the kitchen
Cover foods	Prevents bacteria from one food reaching another

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Personal Hygiene

Requirement	Detail
Handwashing	Hot soapy water; at least 20 seconds; between fingers, under nails, wrists
When to wash	Before food prep; after raw meat; after toilet; after touching face/hair; after pets
Hair	Tied back; hair net in commercial kitchens
Clothing	Clean apron; remove outdoor clothing
Nails	Short, clean; no nail polish or false nails
Jewellery	Remove rings, watches, bracelets
Cuts	Blue waterproof plaster (visible; contains metal strip for detection)
Illness	48-hour rule: symptom-free for 48 hours before returning to food handling
Temperature probes	Insert into thickest part; avoid bone; clean before and after use

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Storage Principles

Principle	Detail
Fridge at 0–5°C	Check with thermometer; do not overload
Raw meat bottom shelf	Prevents cross-contamination
Cover all foods	Prevents contamination and moisture loss
FIFO (First In, First Out)	Use oldest items first
Use-by dates	SAFETY — do not eat after
Best-before dates	QUALITY — safe after, but quality declines
Freezer at -18°C	Bacteria dormant; label and date food
Thaw in fridge	Safest method; never at room temperature
Reheating	Core temperature 75°C; only reheat once
Cooling	Cool within 90 minutes; do not put hot food straight in fridge

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Microorganisms: Key Points

Type	Reproduction	Key Feature
Bacteria	Binary fission (double every 10–20 min)	Main cause of food poisoning; pathogenic vs spoilage
Yeasts	Budding	Cause fermentation; beneficial in bread/beer
Moulds	Spores	Visible fuzzy growth; some produce mycotoxins; beneficial in blue cheese

FATTOM Conditions for Growth

Factor	Detail
Food	Nutrients, especially protein
Acidity	Most bacteria prefer neutral pH (6.6–7.5)
Temperature	Danger zone 5–63°C; optimum 37°C
Time	Bacteria double every 10–20 minutes
Oxygen	Aerobic (need O₂), anaerobic (don't), facultative (either)
Moisture	High water activity supports growth

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Food Spoilage vs Food Poisoning

Feature	Food Spoilage	Food Poisoning
Caused by	Spoilage bacteria, yeasts, moulds, enzymes	Pathogenic bacteria or their toxins
Visible signs	Yes — slime, mould, discolouration, off-smells	No — contaminated food looks, smells and tastes normal
Danger	Unpleasant but usually not dangerous	Can be life-threatening (especially for YOPI)
Key point	You CAN tell food is spoiled	You CANNOT tell food is contaminated

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Quick Revision: 10 Essential Facts

1. Danger zone = 5°C to 63°C
2. Core cooking temperature = 75°C
3. Fridge = 0–5°C; Freezer = -18°C
4. Campylobacter = most common food poisoning in UK
5. Never wash raw chicken (splashes bacteria)
6. Raw meat on bottom shelf (prevents drips)
7. Pathogenic bacteria do NOT change appearance/taste/smell
8. S. aureus and Bacillus cereus produce heat-resistant toxins
9. Listeria can grow at fridge temperatures
10. E. coli O157 has a very low infective dose (~10 bacteria)

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Common Exam Mistakes

• Saying freezing kills bacteria. It makes them dormant — they resume growth when thawed.
• Confusing pathogenic and spoilage bacteria. Pathogenic = food poisoning (no visible changes). Spoilage = visible deterioration.
• Wrong temperatures. Danger zone is 5–63°C, not 5–75°C. Cooking is 75°C, not 63°C.
• Vague prevention methods. "Cook food properly" → "Cook to a core temperature of at least 75°C."
• Forgetting YOPI. Always mention vulnerable groups: Young, Old, Pregnant, Immunocompromised.
• Confusing onset times. S. aureus = fastest (1–6 hrs). Listeria = slowest (up to 70 days).

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Summary