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What is Physical Contamination of Food?

Annakay Newell, Laura Foist
  • Author
    Annakay Newell

    Annakay Newell has taught in the biological and environmental science fields for over ten years. She has a PhD in plant pathology from the University of Georgia, a MSc in plant pathology from the University of Arkansas and a BSc in Biology from the University of Arkansas Pine Bluff.

  • Instructor
    Laura Foist

    Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

Learn about the physical contamination of food and how contamination happens. Discover the types and examples of physical contamination and ways to prevent it. Updated: 10/14/2021

What is Physical Contamination of Food?

Imagine going to a restaurant your friends have been recommending for months and ordering an elegant and expensive dish. When the dish arrives and you take the first bite, your teeth are in immediate and excruciating pain from biting into something hard. You immediately spit the food out to find a stone lodged in it. This is an example of the physical contamination of food. Physical contamination of food occurs when there is a foreign or unwanted object present. Physical contamination can occur at any time during food production and manufacture. Physical contamination can be metal, glass, plastic, rubber, bone, wood, or stones. Physical contamination of food is dangerous because it can damage the teeth, gums, throat, and other body parts or result in choking and death. The Food and Drug Administration (FDA) classifies physical contaminants by whether they are hard or sharp physical hazards or choking hazards.

Four Types of Food Contamination

There are four types of food contamination, namely physical, chemical, biological, and allergenic.

Chemical: chemical food contamination occurs when unwanted chemicals end up in food. Certain chemicals such as pesticides and cleaning supplies can contaminate fresh produce or foods during farming or preparation. It is therefore usually recommended that people properly wash fruits and vegetables before eating them and remove food from surfaces before cleaning. Chemical food contamination can also occur when people use household pesticides such as roach spray in areas where food is stored or prepared. Unsuitable pots and pans can also be a source of chemicals.

Biological: refers to the major groups of organisms (fungi, bacteria, viruses, and parasites) that can contaminate food and lead to serious illness and even death during any stage of food production or preparation. Many biological contaminants are found in fresh produce and meats. Biological contaminants are the main subjects that food recalls are issued to address. Many biological contaminants are opportunistic pathogens that cause a wide range of symptoms in humans.

Allergenic: is the contamination of food by allergens such as nuts, soy, wheat, and dairy. Allergens are strictly regulated by the FDA which requires that the major ones be added to food labels when products have them or when there is a possibility of cross-contamination. Many people are sickened by food allergens annually. Food allergens are serious because in many cases they can cause anaphylactic shock and sudden death.

Physical: when an unwanted object contaminates food. There is a wide range of physical contaminants that can end up in food. Stones, hair, metal, rubber, and insects can all be physical contaminants.

Physical Contamination

Most of the time when you open a can of peaches or a bag of cereal you find just what you expected: peaches (with syrup) in the can and cereal in the bag. But have you ever found something unexpected in your food, like a piece of plastic with the peaches or a piece of metal in the cereal bag? Finding random things in your food is called physical contamination of food.

Physical contamination comprises one of three categories of food contamination. There is also chemical contamination and biological contamination. The chemical category includes substances such as pesticides, antibiotics, cleaning agents, and allergens. Biological contamination includes salmonella, listeria, and any other microbes.

Physical contamination can happen in many different ways. Generally, we can group contamination as happening three ways: naturally, accidentally, or deliberately.

How Does Most Contamination of Food Happen

Contamination of food can occur at any stage of the production or preparation process. In the field, farmers use pesticides to manage pests and diseases. Residues from these pesticides can linger on fresh produce such as fruits and vegetables and if not properly washed before consumption can cause poisoning. Microorganisms can also be present in fresh foods or meat. One of the major reasons for food recalls is the contamination of foods with bacteria such as Salmonella spp, Escherichia coli, and Listeria monocytogenes which cause gastrointestinal illnesses and even death in severe cases.

Manufacturers also handle various kinds of foods during food processing. Food handlers usually have strict protocols regarding sanitation and the restriction of certain items like jewelry to prevent physical and microbial contamination of food. Biological contamination is by far the most common type that occurs.

Physical Contamination Types

Physical contamination of food can occur in different ways. Contamination can be natural, accidental, or intentional depending on how the contaminant was introduced into the food.

Natural Physical Contamination

Natural physical contamination of food is classified as contamination that occurs naturally without human contribution. For example, insects from the field can be found in certain vegetables. Although this is not usually a grave food safety concern, many consumers are more concerned about the quality of their food. Stones are also a natural physical contaminant that is found in food brought in from the field.

Many vegetables such as lettuce can have natural physical contaminants such as insects and stones from the farm

lettuce with natural physical contaminant

Accidental Physical Contamination

Accidental physical contamination occurs when food is contaminated with a physical object unintentionally or unexpectedly. During the manufacturing process, objects like metal or wood can be dislodged from equipment without anyone noticing. Rubber is also commonly used in manufacturing and can become fragmented, contaminating food.

Accidental physical contamination of food can occur when there is faulty manufacturing equipment

factory equipment as a source of physical food contamination

Natural Physical Contamination

Some physical contamination can occur naturally. This includes things such as insects entering your broccoli or bones appearing in 'boneless' fish. Food manufacturers try to eliminate all of these physical contaminants, but sometimes it is impossible to eliminate 100% of them.

In the fields where fruits and vegetables are grown, we can't prevent every insect from deciding that broccoli looks like a good home. This is especially true with the growing trend of organic foods, where the absence of pesticides makes it difficult to ensure that insects are not in that broccoli. If you buy broccoli directly from a farm, chances are good that you'll find an insect or two in your food item. Producers typically wash their produce prior to selling it in order to wash away even more of the insects. However, insects can still escape all attempts at removal and end up on the consumer's table.

Insects in food aren't typically considered a safety concern, unless they carry diseases that can impact human health. Insects generally pose more of a quality concern as consumers do not like finding them in their food.

Accidental Physical Contamination

Accidental physical contamination includes things like a piece of plastic from a bag of sugar breaking off and getting mixed into a cake. Another example would be a metal shaving from equipment breaking off and ending up in the macaroni. Since some of these issues can be dangerous to the consumer, food producers implement a variety of procedures to ensure that this does not occur. For example, many food producers require that all product be passed through a metal detector in order to detect any metal that may be present.

Accidental physical contamination may be caught before it reaches the consumer, in which case producers will not sell the product. However, if the product is still sold, the contamination can be considered intentional (we will talk about that in a moment). For example, if an employee accidentally drops a plastic bucket into a mixer, the physical contamination is accidental and that product has now been contaminated. If the facility can ensure that all pieces of the plastic bucket are retrieved, it can sell the product to the consumer. However, if pieces of plastic remain in the product, it will probably not be sold to consumers . This would still be considered a physical contamination, but the product would never reach the consumer.

Intentional Physical Contamination

Intentional physical contamination is the type that we hear about most frequently. This happens when someone sticks a needle into an apple or adds rodent hair to the bread dough. This can occur at any point of the production process. The perpetrator can be anyone from an employee to a random stranger.

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Additional Info

Physical Contamination

Most of the time when you open a can of peaches or a bag of cereal you find just what you expected: peaches (with syrup) in the can and cereal in the bag. But have you ever found something unexpected in your food, like a piece of plastic with the peaches or a piece of metal in the cereal bag? Finding random things in your food is called physical contamination of food.

Physical contamination comprises one of three categories of food contamination. There is also chemical contamination and biological contamination. The chemical category includes substances such as pesticides, antibiotics, cleaning agents, and allergens. Biological contamination includes salmonella, listeria, and any other microbes.

Physical contamination can happen in many different ways. Generally, we can group contamination as happening three ways: naturally, accidentally, or deliberately.

Natural Physical Contamination

Some physical contamination can occur naturally. This includes things such as insects entering your broccoli or bones appearing in 'boneless' fish. Food manufacturers try to eliminate all of these physical contaminants, but sometimes it is impossible to eliminate 100% of them.

In the fields where fruits and vegetables are grown, we can't prevent every insect from deciding that broccoli looks like a good home. This is especially true with the growing trend of organic foods, where the absence of pesticides makes it difficult to ensure that insects are not in that broccoli. If you buy broccoli directly from a farm, chances are good that you'll find an insect or two in your food item. Producers typically wash their produce prior to selling it in order to wash away even more of the insects. However, insects can still escape all attempts at removal and end up on the consumer's table.

Insects in food aren't typically considered a safety concern, unless they carry diseases that can impact human health. Insects generally pose more of a quality concern as consumers do not like finding them in their food.

Accidental Physical Contamination

Accidental physical contamination includes things like a piece of plastic from a bag of sugar breaking off and getting mixed into a cake. Another example would be a metal shaving from equipment breaking off and ending up in the macaroni. Since some of these issues can be dangerous to the consumer, food producers implement a variety of procedures to ensure that this does not occur. For example, many food producers require that all product be passed through a metal detector in order to detect any metal that may be present.

Accidental physical contamination may be caught before it reaches the consumer, in which case producers will not sell the product. However, if the product is still sold, the contamination can be considered intentional (we will talk about that in a moment). For example, if an employee accidentally drops a plastic bucket into a mixer, the physical contamination is accidental and that product has now been contaminated. If the facility can ensure that all pieces of the plastic bucket are retrieved, it can sell the product to the consumer. However, if pieces of plastic remain in the product, it will probably not be sold to consumers . This would still be considered a physical contamination, but the product would never reach the consumer.

Intentional Physical Contamination

Intentional physical contamination is the type that we hear about most frequently. This happens when someone sticks a needle into an apple or adds rodent hair to the bread dough. This can occur at any point of the production process. The perpetrator can be anyone from an employee to a random stranger.

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Frequently Asked Questions

What is the difference between physical and chemical contamination?

chemical food contamination occurs when unwanted chemicals contaminate food. Physical food contamination, however, occurs when unwanted objects end up in food.

What is physical contamination in a restaurant?

Physical contamination in a restaurant can occur if employees are not careful or do not follow safety protocols. Many restaurants require that employees wear hairnets, no jewelry, and not use glass dishware. Physical contamination in a restaurant can be anything from broken glass, hair, stones, or even bones in a meal.

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