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Blocks of cheese with blue mould on it
Mouldy Cheese

Food Contaminants

Food can become contaminaited in a number of ways across the entire food chain, from farm to fork. There are four main types of contamination: microbiological, chemical, physical and allergenic.

A food contaminant is defined as:

Any substance not intentionally added to food, which is present in such food as a result of the production (including operations carried out in crop husbandry, animal husbandry and veterinary medicine), manufacture, processing, preparation, treatment, packing, packaging, transport or holding of such food or as a result of environmental contamination. (Codex Alimentarius).

Biological Contaminants

Biological contaminants are organisms or substances produced by organisms that pose a threat to human health. They are a major concern in the food sector because they cause foodborne illness outbreaks. These organisms can affect human health including infection, intoxication and even death. The effect can vary in the degree of severity. Examples include Salmonella, E. coli and Listeria and Escherichia coli.

Microorganism Symptoms Likely source Control Measures
Salmonella spp. Abdominal Pain, Diarrhea, Fever, Nausea and Vomitting, Raw or undercooked poultry, eggs, meat Proper storage conditions, Adequate cooking of meat to core temperatues of 75 degrees celcius, Avoiding cross contamination of raw and cooked meats, Washing fruit and vegetables, Keep animals out of the kitchen and way from food and Personal hygiene
Campylobacter spp. Abdominal Pain, Diarrhea, Nausea, Vomitting and Fever Poultry, Red meat, Unpasteurised milk, Untreated water Adequate hygiene, Cook food thoroughly, Adequate storage, Avoid cross contamination and only drink pasteurised or boiled milk
Listeria monocytogenes Diarrhea, Abdominal Cramps, Nausea, Fever, Vomitting Soft cheese, cold cuts of meat, smoked fish, ready to eat refrigerated and prepared meals, salads, raw vegetables Cook food thoroughly, Follow storage instructions and expiry dates, Keep cooked food and utensils away from raw food, Wash salads, fruits and vegetables thoroughly, Throw away left over reheated food
Escherichia coli 0157 Severe gut infection with bloody diarrhea, Abdominal Cramps, Fever Undercooked Meat, Unpasteruised Milk, Cheese, Yoghurt, Raw vegetables Wash hands after toilet, Personal hygiene, Regularly clean toilets with disinfectant

Please have a look at the ‘Microbial Contamination’ Fact File developed by CCEA in the ‘See Also’ section below to find out more about these biological contaminants

Chemical Contaminants

A chemical food hazard is any chemical agent that has the potential to cause illness or injury. Food chemical hazards can be classified into chemicals that occur naturally, chemicals that may be used in the formulation of your finished product, or chemicals that are unintentionally or incidentally present in your finished product. Chemical contaminants include undesirable substances like acrylamide, arsenic in rice, Bisphenol-A (BPA), dioxins and heavy metals (e.g. mercury, lead and cadmium).

Table 2: Examples of Chemical Hazards

Chemical Contaminant What is it? Potential health risk Main dietary sources
Acrylamide Chemical produced natrually in food as a result of cooking starch rich food at high temperatures (above 120 degrees celcius) as a consequence of The Maillard reaction EFSA concluded, based on animal studies, acrylamide and glycidamide (one if its breakdown products in the body) are genotoxic (can damage DNA) and carcinogenic (can cause cancer) Fried potato products, coffee, biscuits, crackers and breads
Arsenic in rice Arsenic is a naturally occuring element present in food due to its absorption from the soil and water Immediate symptoms include vomitting, abdominal pain and diarrhoea; followed by numbness and tingling of the extemities, muscle cramping, and in extremeities, muscle cramping, and in extreme cases death. Long term exposure can cause cancer (of the skin, bladder or lungs) and skin lesions. It has been associated with developmental effects, heart disease, diabetes and damage to the nervous system and brain Rice takes up more aresenic than other foods and due to its high consumption can contribute significantly to arsenic exposure
Bisphenol-A (BPA) A chemical used to make plastics including materials that come into contact with food, such as refillable water bottles, food storage containers or protective coatings and linings for foods and drinks cans The amount of BPA consumers actually abosrb from food and drink is not considered to be harmful and independent studies have show that BPA is rapidly detoxified and eliminated from humans. Although, there is a lot of controversy surrounding its effects because some studies claim to show BPA cuases hormonal changes Very small amounts of BPA can transfer from packaging into food and drinks
Dioxins A group of chemicals formed as a by-product of chemical processes. These range from natural events such as forest fires to man-made processes, such as manufacturing of chemicals, pesticides, steel and paint Long term exposure to high levels have been shown to cause cancer, adverse reproductive and developmental effects, birth defects, immune system abnormalities, endometriosis, heart related conditions, skin diseases and other skin effects Meat, fish, poultry, cheese, milk, butter, free range eggs and oily fish

Please have a look at the ‘Chemical Contamination’ Fact File developed by CCEA in the ‘See Also’ section below to find out more about these chemical contaminants

  • Physical Hazards

A physical hazard is any extraneous object or foreign matter in a food item which may cause illness or injury to a person consuming the product. These foreign objects include, but are not limited to: bone or bone chips, glass, wood, faeces, plastic, sewages, waste, sand, gravel, soil, packaging, metal or any foreign material not normally present in food products. Sources for such contaminants include raw materials, badly maintained facilities and equipment, improper production procedures, and poor employee practices.

Table 3: Examples of Physical Hazards

Physical Hazard Example
Unnatural Metal fragments, pieces of plastic, wood chips and glass
Natural Stems in blueberries, microscopic airborne debris, dirt on potatoes, or minute insect fragments in figs
  • Allergenic Contaminants

Allergenic contamination occurs when a food that causes an allergic reaction comes into contact with another food. The 14 main allergens are: Celery; Cereals containing gluten – including wheat (such as spelt and Khorasan), rye, barley and oats; Crustaceans – such as prawns, crabs and lobsters; Eggs; Fish; Lupin; Milk; Molluscs – such as mussels and oysters; Mustard; Tree nuts – including almonds, hazelnuts, walnuts, brazil nuts, cashews, pecans, pistachios and macadamia nuts; Peanuts; Sesame seeds; Soybeans; and Sulphur dioxide and sulphites (if they are at a concentration of more than ten parts per million).

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This article is from the free online course:

Introduction to Food Science

EIT Food