FOOD SAFETY AND QUALITY ASSURANCE: CONTAMINATION AND ADULTERATION
Diagram
Two ways food goes wrong
Contamination
Something that should not be there arrives by accident or through poor practice: germs, chemicals, or stones and glass.
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Adulteration
Food is deliberately changed for money: something added, something valuable removed, or a cheaper material substituted.
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The difference
Contamination is an accident; adulteration is deliberate. One is stopped by control at each stage, the other by buying, testing and watching prices.
Figure 1: Contamination arrives by accident; adulteration is done on purpose for money. Drawn in our own style from the FTN Quality Control and Assurance notes, Unit 4, and from Bee Wilson, Swindled.
Introduction
Adulteration and contamination are the two ways something unwanted gets into food, and both mean the food is not what it should be, but they differ in intent. Contamination is the presence in food of something that should not be there, arriving by accident or through poor practice. Adulteration is deliberate: adding something to a food, removing something valuable from it, or substituting a cheaper material for a dearer one, in order to gain money while deceiving the buyer. One is stopped by control at each stage of processing, and the other by buying from approved suppliers, testing every delivery, and watching prices.
The FTN Quality Control and Assurance notes, Unit 4, explain all three ways food goes wrong, contamination, adulteration and extraneous matter, and Wilson, Swindled, tells the history of adulteration, from leaded wine to bogus milk powder. This article follows those two sources.
Quick comparison
Table 1: Adulteration compared with contamination
| Aspect | Adulteration | Contamination |
|---|---|---|
| Intent | Deliberate, done for money while deceiving the buyer | Accidental, arriving by accident or through poor practice |
| What happens | Adding something to a food, removing something valuable, or substituting a cheaper material for a dearer one | Something that should not be there is present in the food |
| Examples | Water added to milk, starch added to a spice, a cheap oil mixed into a dear oil, fat skimmed from milk sold as whole | Bacteria from dirty equipment in milk, mould in damp grain, stones in wheat, glass or metal from a broken screen |
| Kinds | One kind: deliberate change for gain | Three kinds: biological, chemical and physical |
| Biological kind | Not the point: the adulterant may be harmless in itself | Bacteria, yeasts, moulds, viruses and parasites, and the toxins some of them make |
| Chemical kind | A toxic colour or a banned chemical used to fake a better appearance | Pesticide residues, cleaning chemicals, heavy metals and lubricants that leak into food |
| Physical kind | Not the point: the adulterant blends in | Stones, glass, metal, wood, hair, plastic and insects |
| Harm | The buyer is cheated, the food is worth less than its label claims so its nutrition falls, and sometimes the added substance is harmful | Illness from germs and toxins, poisoning from chemicals, and injury from solid objects |
| Detection | Tests that see what the eye cannot: freezing point of milk, fat content, iodine for starch, fatty acid pattern of an oil | Inspection and testing at intake, during processing and at the end, with a metal detector as the last layer |
| Prevention | Buying from approved suppliers, testing every delivery, keeping raw materials under lock and key, auditing suppliers, and watching prices | Layered control: approved suppliers, clean areas separate from dirty ones, cleaning on a schedule, tested water, and hygiene rules |
Scientific explanation
Definition
Contamination is the presence in food of something that should not be there, arriving by accident or through poor practice, and contaminants fall into three kinds: biological, chemical and physical. Adulteration is different from contamination because it is deliberate: it means adding something to a food, removing something valuable from it, or substituting a cheaper material for a dearer one, in order to gain money while deceiving the buyer.
Working principle
Each kind of contamination has its own route into food. Biological contamination comes from soil, water, air, people, animals and equipment: a worker with unwashed hands, a cracked pipe that lets in dirty water, a store that is warm and damp. Chemical contamination comes from the field, from the factory and from the pack: a pesticide applied too close to harvest, a cleaning chemical not rinsed away, a printing ink that migrates through a pack. Physical contamination comes from the raw material itself, such as stones in grain, and from the factory, such as a broken screen or a chipped blade. Contamination is controlled in stages: at intake, raw materials are inspected and tested; during processing, clean areas stay separate from dirty ones, equipment is cleaned on a schedule, water is tested, and staff follow hygiene rules; at the end, the finished product is checked. Adulteration is hard to fight because the person doing it tries to hide it: the added water in milk is invisible, the starch in a spice looks like the spice, and the cheap oil blends with the dear one. Detection therefore depends on tests that see what the eye cannot: measuring the freezing point of milk, which falls when water is added; measuring the fat content; testing for starch with iodine, which turns blue black in the presence of starch; and checking the fatty acid pattern of an oil, which differs between oils.
Apparatus
The books used here name no laboratory apparatus for telling the two apart, so no apparatus list is given.
Measurement procedure
For contamination, the check is inspection and testing at each stage: at intake, during processing, and at the end, with a metal detector as the last layer, not the only one. For adulteration, the check is the test that sees what the eye cannot: the freezing point of milk, the fat content, the iodine test for starch, and the fatty acid pattern of an oil. Each test exploits a property that the adulterant changes, and each test must be sensitive enough to catch the addition at the level where it pays the adulterator to do it.
Factors affecting readings
For contamination, the route decides the risk: knowing the route is the first step to blocking it, because a control that blocks the wrong route wastes effort while the real route stays open. For adulteration, price decides the risk: a raw material offered far below the market price is a warning sign, because honest material cannot be sold that cheaply, and a quality system treats a bargain that is too good to be true as a risk, not a gift. Hiding decides the difficulty: the adulterant is chosen to be invisible, so the test must be sensitive enough to catch it.
Formulas and calculations
The books used here give no formula for this comparison, so no formula or worked calculation is given.
Industrial applications
- Adulteration: water added to milk, found by the freezing point of milk, which falls when water is added.
- Adulteration: starch added to a spice, found by iodine, which turns blue black in the presence of starch.
- Adulteration: a cheap oil mixed into a dear oil, found by the fatty acid pattern, which differs between oils.
- Contamination: bacteria from dirty equipment in milk, stopped by cleaning on a schedule and tested water.
- Contamination: stones in grain, found by washing, sieving and spreading the sample on a white tray.
- Contamination: metal from a broken screen, caught by a metal detector at the end of the line.
Advantages and limitations
- Adulteration control, advantage: buying from approved suppliers, testing every delivery and watching prices make adulteration harder and riskier.
- Adulteration control, limitation: the adulterant is hidden on purpose, so detection needs tests that see what the eye cannot.
- Contamination control, advantage: layered control at intake, during processing and at the end backs each layer up, so no single layer must catch everything.
- Contamination control, limitation: the routes are many, from soil, water, air, people, animals and equipment, and each needs its own control.
FAQ
What is the main difference between adulteration and contamination?
Contamination is the accidental presence of something that should not be in the food, such as bacteria from dirty equipment or stones in grain. Adulteration is deliberate: adding water to milk or mixing a cheap oil into a dear one to gain money while deceiving the buyer.
What are the three kinds of contamination?
Biological, chemical and physical: germs and toxins, substances such as pesticide residues and cleaning chemicals, and solid objects such as stones, glass and metal.
How is water added to milk found?
By measuring the freezing point of milk, which falls when water is added.
How is starch in a spice found?
By testing with iodine, which turns blue black in the presence of starch.
Why is adulteration harder to detect than contamination?
Because the person doing it tries to hide it: the added water in milk is invisible, the starch in a spice looks like the spice, and the cheap oil blends with the dear one.
References and further reading
- FTN subject: Quality Control and Assurance, Unit 4: Contamination, Adulteration and Extraneous Matter: Finding What Should Not Be There.
- Bee Wilson, Swindled: The Dark History of Food Fraud, from Poisoned Candy to Counterfeit Coffee, Princeton University Press, 2020 (Google Books page read)
