What Causes Physical Contamination of Food?

Instructor: Laura Foist

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

In this lesson we will learn how physical contamination of food occurs, including by natural, accidental, and intentional means. We will look at examples of physical contamination in each category.

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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