What To Know About Canned and Bottled Goods Contamination

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bottled foods and canned foods

The canning process vastly increases the shelf life of delicate foods while retaining their quality. It gives communities all over the world access to foods that may not grow anywhere nearby. It enables people to continue to enjoy foods well into the off-season, long after the supply of fresh food may have run out.

Just because humans have been canning fruits, vegetables, and meats for generations, however, doesn’t mean it’s always safe. Whether from poor hygiene practices or inadequate quality control measures, contamination of canned and bottled goods can threaten food quality and stability.

In this post, we discuss everything you need to know about contamination in the canning process, including what kind of contaminants to look out for, common causes of contamination, and what you can do to prevent contaminants from wreaking havoc on your production line.

Metal Contamination

Risks of contamination in canned and bottled items come from various sources, including physical contaminants like wood, bone, glass, rock, and metal. Also called physical hazards or foreign matter, these contaminants can cause choking as well as cuts in the mouth, throat, esophagus, stomach, and intestines.

Metal is one of the most common foreign objects found in the food production industry. Shards or pieces of metal can enter the food supply from agricultural activities, transportation, or machines and utensils during processing. Therefore, quality control for canned and bottled goods must include detection systems for the following types of metal contaminants.

Ferrous Metals

Ferrous metals contain iron. Common ferrous metals include cast iron, wrought iron, steel, alloy steel, and carbon steel. Because metals containing iron are magnetic, they are typically easy for metal detectors to find.

Non-Ferrous Metals

Non-ferrous metals, on the other hand, do not contain iron. Common ferrous metals include aluminum, copper, lead, zinc, and tin. Precious metals like gold and silver are also non-ferrous. While non-ferrous metals aren’t strongly magnetic, they can conduct electricity. Therefore, metal detection systems can also identify non-ferrous metal contamination fairly easily.

Stainless Steel Fragments

Because of its low magnetic and electrical properties, stainless steel is among the most challenging contaminants for metal detection systems to find. Complicating the matter is that moist conditions and high salt content can interfere with detection. Thankfully, RXP x-ray inspection systems for bottles, cans, and jars can detect stainless steel particles down to 0.3mm.

Microbial Contamination

canned food contaminated by clostridium botulinum

Detecting contaminants in canned products also involves looking for less visible impurities like microorganisms. Bacteria, viruses, yeasts, and molds can make their way into food at almost any step of the food production line.


While some bacteria are beneficial and even essential for final food products — like yogurt, cheese, and sauerkraut — not all bacteria are so friendly. E. coli, listeria, campylobacter, and salmonella can all cause illness in consumers of canned goods. However, you can destroy most of these contaminants by heating foods to the proper temperature during the canning process.

The most significant threat to most canning operations comes from heat-resistant Clostridium botulinum. While not everyone has heard the name of the bacteria, many have heard of the disease that it causes: botulism. Botulism can cause difficulty breathing, muscle paralysis, and even death, which makes preventing Clostridium botulinum contamination in canned goods essential to food safety.


Like bacteria, molds are difficult to remove from food surfaces. While washing fresh foods has little impact on the amount of mold they contain, peeling root vegetables, underground stem crops, and tomatoes greatly reduces microbial contaminants. Mold dies below the temperature of boiling water, which makes it relatively easy to kill with proper heating processes.


Similarly, washing fresh foods only slightly decreases the number of yeast microorganisms. Peeling and blanching can also help, but the best way to control canned and bottled goods contamination from pathogens is to follow proper canning methods, sterilization procedures, and thermal processing times.

Chemical Contaminants

unapproved adulterants and food additives on test tubes

The third type of contamination in the food supply comes from potentially hazardous chemicals. Research has shown that a variety of chemicals can contaminate canned food items, including the following:

  • Unapproved adulterants and food additives
  • Environmental contaminants like dioxins, pesticides, and heavy metal residues
  • Unwanted compounds formed during baking, roasting, canning, heating, fermentation, or hydrolysis
  • Chemicals that leach from the packaging, such as the chemical bisphenol A (BPA) from the coating inside of many food cans


Melamine is a man-made substance widely used in manufacturing plastic goods, industrial coatings, and paper products. One of its common uses is to produce the coating of metal containers, such as three-piece tin cans. Like BPA, melamine may migrate into food products and harm the health of consumers. Migration tends to occur particularly when acidic foods — like tomatoes — are heated for long periods.

Common Causes of Contamination

Chemical, physical, and biological contaminants can enter the food supply at almost any point of the long processing chain, from growing and harvesting raw ingredients to producing, transporting, and storing food products. These are some of the most common causes of canned and bottled goods contamination:

Equipment and Facility Issues

Improper sterilization or heating procedures allow microorganisms to survive the canning process. Worn or defective machinery can shed metal fragments into the food during processing. Poor facility design can allow cross-contamination of one product with another, which can cause a problem known as allergenic contamination.

Poor Hygiene Practices

man not wearing proper protective equipment in production facility

When factory floor workers are sick, don’t wash their hands, or don’t wear the proper personal protective equipment, viruses and bacteria can easily enter the food product. Another cause of contamination is poor facility hygiene, including not having a one-way production line, not having easy-to-clean surfaces, or not properly sterilizing equipment.

Supply Chain Issues

Contaminants can enter the food supply before they ever come inside your facility. You may receive ingredients contaminated with chemical residues, small pieces of stone, glass, or wire, or biological materials like insects, bacteria, and molds.

Lack of Quality Control Measures

You can’t always control what enters your facility, but strong quality control measures can help ensure that the food leaving your facility is safe. If your quality control systems falter, you lose the opportunity to address issues with contaminants before they become a problem.

Technologies for Detecting Contaminants in Canned and Bottled Goods

Ensuring safety in bottled goods and canned products requires strong safety and sanitation plans, good manufacturing practices, and robust food inspection systems, such as the following.

Food metal detectors can find ferrous metals, non-ferrous metals, and even stainless steel. Different types of x-ray systems can detect physical contaminants and even identify defects in glass jars and other containers.

Modern x-ray inspection systems don’t require an operator to monitor, which means the system will automatically detect contaminants. If you opt for a rejection conveyor, it can also automatically remove any packages suspected of having contaminants or any other quality issues.

Another advantage of x-ray systems is that they can check for fill levels and proper lid sealing, helping you detect bottled goods safety issues.

For more information about how x-ray systems can help your business detect canned and bottled goods contamination or even recover from it, check out our blog on how x-ray systems work. To discuss which food inspection systems are right for your needs, contact the professionals at TDI Packsys today!

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