FOOD SAFETY AND QUALITY ASSURANCE: HAZARD TYPES
Diagram
Biological
Living things, or the poisons they make: bacteria, viruses, moulds, yeasts, and parasites. The most common cause of foodborne illness.
Chemical
Substances that can harm health: natural toxins, mould poisons, pesticide and drug residues, cleaning chemicals, heavy metals, and additives used in the wrong amount.
Physical
Objects that should not be in food: stones, glass, metal fragments, wood splinters, hair, bone pieces, plastic pieces, and insects.
Figure 1: The three hazard groups. Every food safety worker learns to sort every danger into one of these three groups.
Introduction
Every danger in food falls into one of three groups, and sorting them correctly decides what control to use. Biological hazards are living things, or the poisons they make: bacteria, viruses, moulds, yeasts, and parasites, and they are the most common cause of foodborne illness. Chemical hazards are substances that can harm health, from natural toxins to pesticide residues and cleaning chemicals left on equipment. Physical hazards are objects that should not be in food, such as stones, glass, and metal fragments. In short: biological hazards grow, chemical hazards poison by dose, and physical hazards hurt by being there.
Table 1: Quick comparison of biological, chemical, and physical hazards
| Aspect | Biological | Chemical | Physical |
|---|---|---|---|
| What it is | Living things, or the poisons they make | A substance that can harm health | An object that should not be in food |
| Examples | Salmonella, Campylobacter, norovirus, moulds, parasites | Natural plant and fish toxins, mould poisons, pesticide residues, veterinary drug residues, cleaning chemicals, lead, additives in the wrong amount | Stones, glass, metal fragments, wood splinters, hair, bone pieces, plastic pieces, insects |
| How harm happens | Infection: germs grow inside the body; or intoxication: the poison they made is eaten | Dose decides safety: a small amount may be safe, a large amount harms | Cutting the mouth, breaking a tooth, or choking, often a child |
| Onset | Often 12 hours to several days for infection, as germs need time to multiply | Minutes to hours for some toxins; days to years for low level exposure | At once, when the object is bitten or swallowed |
| Can cooking fix it? | Cooking kills most germs, but not always the toxins they already made | Often not: heat does not remove lead, pesticide residues, or most toxins | No: heat does not remove a stone or a piece of glass |
| Main control | Cooking, chilling, clean hands, and keeping raw and cooked food apart | Supplier checks, correct additive amounts, safe cleaning, and residue limits | Sieves, filters, metal detectors, and X-ray checks, plus careful handling |
| Most common? | Yes: the most common cause of foodborne illness | Less common, but serious when limits are missed | Less common, but visible and costly when found |
Scientific explanation
Definition
Biological hazards are living things, or the poisons they make: bacteria, viruses, moulds, yeasts, and parasites. Chemical hazards are substances that can harm health: natural toxins in plants and fish, poisons made by moulds, pesticide residues, veterinary drug residues, cleaning chemicals left on equipment, heavy metals such as lead, and food additives used in the wrong amount. Physical hazards are objects that should not be in food: stones, glass, metal fragments, wood splinters, hair, bone pieces, plastic pieces, and insects.
Working principle
Biological hazards work in three ways: infection, where a living germ is eaten, survives the stomach, and grows inside the body; intoxication, where the poison the germ made is eaten; and allergy, where the immune system reacts to a food protein. Cooking kills most germs, so infection is often a sign that food was undercooked, cross contaminated, or handled by a person carrying the germ. Chemical hazards work by dose: a preservative at the allowed level is a safety tool, while the same preservative at ten times the level can harm health and hide spoilage. Physical hazards work by being there: they cut the mouth, break a tooth, or choke a child.
Apparatus
Biological hazards are found by microbiological testing, such as plate counts and sampling plans. Chemical hazards are found by chemical analysis, such as residue and heavy metal testing. Physical hazards are found by sieves, filters, metal detectors, and X-ray checks.
Measurement procedure
Microbiological testing follows a sampling plan: take a set number of samples, test by the stated method, and compare with the microbiological criteria for that food. Chemical testing measures the amount in the food, such as milligrams in each kilogram, and compares it with the limit. Physical checks run while food flows: metal detectors and X-ray units check every pack, and a failed pack is rejected.
Factors affecting readings
Biological growth changes with temperature, time, pH, and water activity: warm food left for hours grows far more germs than cold fresh food. Chemical results change with dose and with body weight: the same amount is a larger dose for a small child. Physical results change with the size and hardness of the object and with who eats it: a small hard object is a greater danger to a small child.
Formulas and calculations
Exposure, for chemical hazards: daily intake = concentration in the food x amount eaten per day, then divide by body weight. Worked example from the FTN notes: a spice carries lead at 0.5 mg in each kilogram. A person eats 5 g of that spice a day, which is 0.005 kg. Step 1: daily intake is 0.5 x 0.005 = 0.0025 mg of lead a day. Step 2: for a 60 kg adult, divide 0.0025 by 60, which gives 0.000042 mg for each kilogram of body weight per day. Step 3: compare that number with the tolerable intake set by experts. Biological and physical hazards have no standard formula of this kind in the books used here.
Industrial applications
- Biological: pasteurisation, cooking, chilling, hand washing, and separation of raw and cooked food in dairies, meat plants, and kitchens.
- Chemical: supplier checks for residues, measured additive use, safe cleaning and rinsing, and label declarations for substances such as sulphur dioxide, SO2.
- Physical: sieving of flour, filtering of liquids, metal detection, X-ray inspection, and glass control in factories.
Advantages and limitations
Biological control advantages: cooking and chilling are strong, proven controls. Limitations: germs can grow again after cooking if food is held warm, and some toxins survive cooking.
Chemical control advantages: limits and measured use keep useful substances safe. Limitations: heat does not remove most chemical hazards, so prevention at the source matters most.
Physical control advantages: detectors check every pack and reject the bad one at once. Limitations: a detector cannot find every material, so good handling and glass control must come first.
FAQ
Which hazard group causes most foodborne illness?
Biological hazards: bacteria, viruses, and parasites are the most common cause.
Can cooking make a chemically contaminated food safe?
Usually not. Cooking kills most germs, but it does not remove lead, pesticide residues, or most toxins.
Why does slow cooking of red kidney beans fail where full boiling works?
Lectins need high heat to be destroyed. Slow cooking warms the beans without reaching the heat that breaks the lectins down, so the poison stays active.
A loaf without preservative goes mouldy in three days. Is the loaf with preservative safer?
It depends on the amount and the rules. A preservative at the allowed level is a safety tool; at ten times the level it can harm health, so dose and the label decide.
References and further reading
- FTN subject Food Safety and Security, Unit 1: What Food Safety Means, Hazards and Risk; Unit 2: Biological Hazards; Unit 3: Chemical and Physical Hazards; Unit 7: Microbiological Criteria, Sampling Plans and Testing.
- Book on disk: Food Microbiology; and Food Quality Assurance: Principles and Practices.
- Google Books: Food and Drink: Good Manufacturing Practice, books.google.com/books?id=KugWswD7ESQC, for cleaning chemical control and GMP setting.
