Food Contaminants, Food Contamination – Sources and Their Control


A food contaminant is “Any biological or chemical agent, foreign matter and other substances not intentionally added to food which may compromise its safety and appropriateness” (FAO). Based on nature, contaminants can be categorized into three groups; biological, chemical, and physical.

Table of Contents (toc)

A. Biological Contaminant

A biological contaminant means a microbial contaminant (bacteria, viruses, fungi, and parasites) in food. Contamination by microbe may occur by miss handling at any stage during production, harvesting, processing, storage, or distribution to the consumer. Lack of training of field workers about good personal hygiene and poor sanitation control during post-harvest handling activities are the way for biological contamination to food. Following are the ways to prevent biological contaminants:

• Follow Good Agricultural Practices.

• Maintain good personal hygiene.

• Maintain cleanliness and sanitize facilities including equipment.

• Use only quality potable water.

• Clean can openers regularly.

B. Chemical Contaminant

The chemical contaminant is a chemical substance that makes its way into food. Poor agronomic practices along with non-judicious use of agrochemicals and application of improperly composted animal manure as fertilizer could contribute significantly to the chemical. contamination. Chemical substances are normally found in restaurants like pesticides, cleaning. products, lubricants may also contaminate the fresh food when handled improperly. However, contamination of heavy metals in food occurs mainly through pollution of air, water, and soil. Methods adopted for preventing chemical contaminants are as follows:

• Follow Good Agricultural Practices.

• Wash foods in cold running water.

• Do not use wild mushrooms as they contain toxins.

• Make sure labels clearly identify chemical contents of chemical containers and store them in original containers to prevent accidental misuse as well as leakage into food.

• Wash hands thoroughly after working with chemicals.

• Rinse the utensils properly after washing.

• Monitor pest control operator and confirm chemicals don’t contaminate foods.

C. Physical Contaminant

Any foreign object that accidentally finds its way into food is called a physical contaminant. It may occur mainly because of improper product handling at harvesting, processing, storage, or distribution to the consumers. Example dust, stone or gravel, hair, wire, insect parts, dropping of rats, etc. Physical contaminants can be prevented in the following ways:

• Follow Good Agricultural Practices.

• Store the food properly.

• Storage and cooking area should be separate especially at food service establishments.

• Observe good personal hygiene like wear a headscarf during preparing, cooking, and serving food.

• Also avoid wearing ornaments and jewelry when preparing, cooking, and holding foods.

• Place shields on lights during processing or storage.

• Control pests.



Food contamination refers to the presence of any unwanted material in the food, which should not normally be there. While there are many scenarios that might cause food contamination, most fall under one of the two of the following:

1. Direct Contamination

When any of the physical, biological, or chemical contaminants directly contaminate the food. the process is called direct contamination. The control methods of this type of contamination lie in the fact that what is the type of contaminant and the method has already been discussed in this chapter.

2. Cross-Contamination

It occurs when contaminants are transferred from contaminated surfaces, hands, or equipment to food and are primarily absent in raw material. It can be :

(i) Human to food Contamination

It occurs when contaminated hands, clothing, or personnel handle cooked or ready to eat foods.

How to prevent it?

• Cover cuts, sores, and wounds.

• Keep fingernails short, unpolished, and clean.

• Avoid wearing ornaments and jewelry.

• Always wear a clean apron and headgear while working on food.

• Wash hands properly.

When to wash hands?


(a) Beginning food preparation;

(b) Putting on disposable gloves;

(c) Serving customers.


(a) Arriving at work and after break;

(b) Using the restroom, washing sinks;

(c) Eating, drinking, smoking, chewing tobacco and gums;

(d) Using mobile or handkerchief;

(e) Handling inventory;

(f) Handling raw foods;

(g) Touching or scratching a part of the body;

(h) Coughing, sneezing:

(i) Handling garbage or touching dirty surfaces.

How to Wash Hands?

(a) Use the handwashing sink with water running at approximately 38°C and liquid soap; 

(b) Lather hands and exposed arms; 

(c) Rub hands for at least 20 seconds; 

(d) Wash hands thoroughly, paying attention to fingernails; 

(e) Rinse in clean running water. Turn off the faucet with a paper towel in your hands; 

(f) Dry hands using a paper towel or air dryer, not cloth or apron.

(ii) Food to Food Contamination

When harmful organisms transferred from one contaminate food to other foods.

How to prevent it?

• Store cooked foods that will not be cooked in the refrigerator on a higher shelf than raw foods.

• Do not put raw meat, thawing meat on top of the shelf where it can drip on the other foods.

• Best not to practice mix leftover foods with fresh foods.

• Wash meat and fruits and vegetables in a cold running separately.

• Do not let raw meat and raw vegetables be prepared on the same surface at the same time.

(iii) Equipment to Food Contamination

Improperly washed/maintained equipment may cause food contamination.

How to prevent it?

• Use separate cutting boards for different foods like meat and vegetables.

• Prepare raw foods in a separate area from fresh and ready-to-eat foods.

• Clean and sanitize equipment, work surfaces, and utensils after preparing each food.

• Use specific containers for various food products. Make sure cloth and paper towels used for wiping spills are not used for any other purposes.

(iv) Processing Contamination 

Processing contaminants are generated during the processing of foods formed by the chemical reactions between natural and or added food constituents. They are absent in raw materials and maybe physical (metal chips from the processing equipment) or chemical like polycyclic aromatic hydrocarbons (PAH), heterocyclic amines (HCA), trans fat and ethyl carbamate. Technological processes can be adjusted and/or optimized, to reduce the levels of formation of processing contaminants.

Read More Topics of the Same Course – ABT 5211 – Food Safety and Standards

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