What is cross-contamination

What is Cross-Contamination?

Cross-contamination occurs when pathogens – microorganisms like bacteria that can cause disease – are transferred from one food product or surface to another, potentially resulting in foodborne illness. 

There are several ways this could happen:

  • Contaminated ingredients are added to food that receives no additional cooking.
  • Ready-to-eat food comes into contact with a contaminated surface.
  • A contaminated food touches, or drips fluid, onto a cooked or ready-to-eat food.
  • A food handler touches contaminated food and then touches ready-to-eat food.
  • A contaminated wiping cloth touches the food-contact surface.
  • Pathogens can transfer easily, spread from food or unwashed hands to prep areas, equipment, utensils, or other food. 
  • This can occur throughout any point of the flow of food – the path that food takes through your operation, from receiving to storing, prepping, cooking, holding, serving, etc. 
  • Knowing how and where it can happen is half the battle. Master that, and it becomes much easier to prevent.

Types of Cross-Contamination:

There are three broad types of contaminants: biological, chemical, and physical.

Biological Contamination:

  • Biological contamination occurs when harmful microorganisms, pathogens, are consumed. There are four types of pathogens that can contaminate food and cause foodborne illness: bacteria, viruses, parasites, and fungi (mold and yeast). The FDA reports more than 40 kinds that can occur in food and cause illness. The Big Six – dubbed because they are highly contagious and can cause severe illness – include:
  • Shigella – often transferred from flies
  • Salmonella Typhi – lives only in humans, transferred from person to person
  • Nontyphoidal Salmonella – lives in animals, transferred from poultry, eggs, meat, dairy products, and produce
  • Shiga toxin-producing Escherichia coli (E. Coli) – found in ground beef and contaminated produce
  • Hepatitis A
  • Norovirus
  • If a food handler has been diagnosed with any one of these six, they must be excluded from the operation until symptoms disappear and a doctor says they can come back. In order to prevent these, it is essential to know how each of the four pathogen types occurs.
  • Bacteria
  • Bacteria require six conditions to grow: food, acidity, temperature, time, oxygen, and moisture (FATTOM). To prevent bacteria growth, the best course of action is to control time and temperature, always doing your best to ensure that food mandating time and temperature control is kept out of the temperature danger zone (between 41°F and 135°F).
  • Viruses
  • Viruses need a living host to survive, thus why they are carried and transmitted by humans and animals. People can contract a virus from food, water, or contaminated surfaces. Unlike bacteria and parasites, viruses cannot be destroyed by cooking food to minimum internal temperatures. The best way to prevent a virus is by practicing good personal hygiene and mandating staff stay home when they’re ill.
  • Parasites
  • Parasites are commonly associated with seafood, wild game, and food processed with contaminated water, like produce. They require a host to thrive. To prevent this, always ensure your food products are purchased from an approved, reputable supplier and that cooked food meet the required minimum internal temperatures.
  • Toxins
  • Many biological toxins are associated with certain plants, mushrooms, and seafood. Histamine is a prominent toxin produced by pathogens, occurring when fish is time-temperature abused. It can often be found in tuna, mackerel, mahi-mahi, and bonito.
  • Ciguatera is another common toxin that is transferred when a large fish eats a smaller fish and then passed onto humans if appropriate preventative measures are neglected. This is often observed in barracuda, snapper, grouper, and amberjack.
  • Onset times for symptoms of biological contamination vary; however, with toxins, symptoms typically occur within minutes of consumption. The most commonly observed symptoms of biological contamination include nausea and an upset stomach. Though these may be present in contamination caused by toxins, one key distinguisher is the onset of neurological symptoms. In addition to nausea, many experience hot and cold sensations, tingling in the extremities, flushing of the face, difficulty breathing, heart palpitations, and hives.
  • The most important way to prevent toxins in your foodservice is ensuring all plant-based or seafood products are purchased from approved suppliers, and adequately controlling time and temperature when handling raw fish.

Chemical Contamination:

  • If not correctly utilized, everyday chemicals like cleaners, sanitizers, and polishers can contaminate food and cause illness. Ensure that chemicals are approved for use in a foodservice operation and purchased from approved suppliers. Store away from prep areas, food storage areas, and service areas, and separate from food and food-contact surfaces with proper spacing and partitions. Never store chemicals above food or food-contact surfaces, and always use only for their intended use, following the manufacturer’s directions. Also, be sure to handle food only with equipment and utensils approved for foodservice. All chemicals should be clearly labeled.

Physical Contamination:

  • Physical contamination occurs when physical objects find their way into foods. These could include dirt, hair, bandages, metal shavings, glass, jewelry, etc. Natural objects, such as fish bones, are also considered physical contaminants. These could cause mild to fatal injuries such as cuts, dental damage, and choking. To help prevent, carefully inspect all food you receive, and take steps to make sure food handlers are aware of their surroundings. Jewelry should be removed and hair nets donned before handling food.
  • How to Prevent Cross-Contamination During the Flow of Food

Several steps should be implemented and followed to reduce the risk of cross-contamination when handling food.

  • 1. Use separate equipment for raw and ready-to-eat food
  • While there is no substitute for thorough cleaning and sanitizing equipment and supplies after every use, color coding your food prep supplies is a great way to reduce the risk of cross-contamination. 
  • Separate types of food mandate the use of different equipment and utensils. 
  • Colored cutting boards and utensil handles can help keep everything separate and organized while keeping awareness top of mind.
  •  The color tells the food handler what type of food should be prepped. Traditionally, green has been used to indicate use for produce, yellow for raw poultry, blue for cooked food, white for dairy products, brown for seafood, and red for raw meat.
  • Color-coded knives and cut-resistant gloves can be coordinated with your cutting boards to ensure certain colors are only used for particular food items.
  • A green cutting board is traditionally used for prepping fresh produce.
  • Use a yellow cutting board and utensils for handling raw poultry.
  • Use blue cutting boards and supplies for cooked foods.
  • White cutting boards and supplies are ideal for dairy products.
  • Brown cutting boards and supplies are used when dealing with seafood.
  • Traditionally, red cutting boards and supplies have been used to indicate use for raw meat.
  • As food allergies become increasingly more common, many have taken to using purple color-coded supplies to prep allergen special orders.
  • Properly clean and sanitize before and after tasks
  • To ensure pathogens are properly killed and to reduce the risk of being transferred to ready-to-eat foods, all work surfaces, equipment and utensils need cleaned and sanitized before and after each task. It’s not enough to simply rinse.
  • And, as always, hands should be washed thoroughly as well to ensure there’s no trace of contaminants before starting on the next task.
  • Prep raw and ready-to-eat-food at separate times
  • If you need to use the same prep table to prepare different types of food, especially raw foods that need to be cooked to minimum internal temperatures, do so at different times than ready-to-eat food. You can reduce the potential for cross-contamination by prepping ready-to-eat foods before raw foods.
  • Buy food that’s already been prepared
  • For example, bagged chopped lettuce or pre-cooked chicken. Improper handling of food is a prominent contributor to cross-contamination, so it stands to reason that purchasing foods that do not require handling dramatically reduces risk.
  • Don’t forget, proactivity is key. You can achieve this by incorporating active managerial control in your operation. When it comes to food safety, there is no shortage of vital practices.
Marius Joubert
Author: Marius Joubert

Founder of Restauranthub.co the first true community for the restaurant and hospitality industry.

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