Cross-Contamination: What It Is and How to Avoid It

According to the CDC, one in six Americans gets foodborne illness every year, killing over 3,000 people annually. Foodborne illness can happen at home, but approximately 60% of outbreaks trace back to restaurant service.

What can restaurants, food trucks, and other professional kitchens do to prevent foodborne illness? Cross-contamination is a common way for pathogens and other contaminants to end up on a customer's plate.

So, how does cross-contamination happen and how can you minimize its impact on your business?

What is Cross-Contamination?

Cross-contamination is the transfer of bacteria and other contaminants during food handling.

Cross-contamination can actually occur at any point along the production chain:

  • before or during harvest/slaughter
  • during processing and manufacturing
  • during transportation or storage
  • at market
  • during preparation or serving
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Types of Cross-Contamination

There are a few useful ways to classify cross-contamination. You can divide it by the type of contaminant and the method of transfer.

By Contaminant

The most common type of cross-contamination related to foodservice is the transfer of harmful microorganisms, but those aren't the only contaminants your operation needs to worry about.

Bacterial and Viral Cross-Contamination

The most common disease-causing microorganisms are bacteria. They represent four of the "Big 6" foodborne illnesses, including Shigella, E coli, and two types of Salmonella.

The remaining two of the "Big 6" pathogens are viruses: Hepatitis A and Norovirus. Bacteria and viruses are the biggest concerns because they multiply in food at certain temperatures and transfer between items easily. Parasites and fungi also cause foodborne illness but are less likely to transfer as you prepare or handle food.

Cross-Contamination with Allergens

Allergens are proteins that cause an allergic reaction in some people. These proteins can transfer easily during food handling, just like bacteria or viruses. The most common food allergens are found in:

  • Eggs
  • Milk
  • Soy
  • Peanuts
  • Tree nuts (like almonds, walnuts, or pecans)
  • Wheat
  • Fish
  • Shellfish (like crab, lobster, or shrimp)

Gluten represents a similar concern. Gluten intolerance isn't a true allergy, but the same preventative measures can spare people with certain medical conditions a painful (and in some cases life-threatening) reaction.

Chemical Cross-Contamination

Restaurants use a lot of cleaning products to reduce the chances of biological cross-contamination. Unfortunately, improper use or storage of these harsh chemicals can result in contaminated food, as well.

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Cross-Contamination By Transfer Method

Food-to-Food Cross-Contamination

If you mix food that has a high risk of contamination with other foods, you can cause food-to-food cross-contamination. This is a particular concern with bacterial or viral cross-contamination.

Some foods carry and support the growth of pathogens more easily than others. They're referred to as Potentially Hazardous Foods (or PHFs). The list of PHFs includes leafy greens, raw eggs or meat, unpasteurized milk, soft cheese, deli meat, or bean sprouts. Leftover foods should be handled and reused with caution.

You need to be careful with PHFs to prevent contamination of other ingredients or food that's ready to be served.

Equipment-to-Food Cross-Contamination

Equipment-to-food cross-contamination can happen when you use the same equipment, surfaces, or utensils for contaminated and uncontaminated foods without properly sanitizing the items in between. Certain microorganisms can survive on surfaces for long periods of time.

Allergens and chemicals can also linger. Any countertop, cookware, or tool that touches food can play a part in cross-contamination. These are referred to as food contact surfaces.

Person-to-Food Cross-Contamination

People can introduce or play a part in the transfer of pathogens or contaminants to food. A common source of foodborne illness is food service workers coming to work while they're ill. People can also contaminate food by not washing their hands in the right way at the right time.

How an Operation Can Prevent Cross-Contamination?

Educating staff and consistently enforcing certain rules can reduce or eliminate all kinds of cross-contamination.  However, it means you need to take precautions at every level of operations. So how can an operation prevent cross-contamination in a self-service area?

Tips to Avoid Cross-Contamination During Purchasing and Receiving

You have limited control over cross-contamination that takes place before the food arrives at your business. Your best defense is to be careful during purchasing and delivery. That includes:

  • Purchasing only from reputable suppliers
  • Checking expiration dates before accepting deliveries
  • Rejecting any food whose packaging is damaged or dirty, including dented or misshapen cans
  • Inspecting deliveries for any sign of pests
  • Monitoring food recalls and rejecting affected food

Tips to Avoid Cross-Contamination During Storage

Once you accept delivery, you need to store items in a way that prevents pathogen growth and minimizes the chance of accidental cross-contamination. You must:

  • Move food deliveries into appropriate storage areas right away
  • Never store food outside of designated storage areas
  • Never store food or food contact items near cleaning supplies
  • Cover all food items to prevent contaminants from falling inside
  • Store utensils and equipment to prevent contamination of food contact surfaces (for example, glasses upside-down, utensils handle-up, and cutting boards or napkins in covered containers)
  • Store equipment and implements for gluten-free/allergy-free service above regular equipment
  • Store all food and food contact items at least 6 inches off the ground
  • Separate ready-to-eat and raw food (or store ready-to-eat food above raw food)
  • Maintain the required temperature in all food storage areas
  • Discard any recalled food immediately
  • Discard any food storage containers that lose structural integrity
  • Never reuse chemical containers for food storage

Tips to Avoid Cross-Contamination During Food Preparation

Kitchen staff should take precautions to prevent cross-contamination during food preparation. That includes:

Cleaning Hands and Surfaces

Before handling food wash your hands with soap and water for 20 seconds. This should be done after you have handled a pet, used the bathroom, or changing diapers and before you eat/cook.

Washing All Surfaces and Utensils After Use

Wash vegetables and fruit before using them and even after you peel them. However, don’t wash eggs, beef, or poultry as that can help bacteria spread rapidly. The juices of the meat can splash on you or the counter as well which will create unhygienic conditions.

Maintaining Proper Refrigeration

Keep cold food from thawing by keeping it in the refrigerator at all times. Unsafe temperatures can result in illnesses. All perishable food should be kept in the refrigerator within 2 hours. Avoid thawing or marinating foods on the counter at room temperature. That surface becomes a breeding ground for bacteria then. Thaw it in the fridge and only take it out when you need to cook it.

In short, all kitchen staff should abide by the following guidelines:

  • Handwashing thoroughly for at least 20 seconds
    • After going to the bathroom
    • After coughing or sneezing
    • After using their phone or other non-sanitized items
    • After touching raw meat, unwashed leafy greens, and other PHFs
    • Before preparing an allergen-free order or touching any allergen-free equipment
  • Washing and sanitizing food contact surfaces properly, especially after PHF contact
  • Using separate cutting boards for PHFs and other foods
  • Washing produce in slightly warm water before mixing or serving
  • Observing all Time/Temperature Control measures while storing, heating, cooling, or holding PHFs
  • Preparing PHFs at a different time or place than ready-to-eat foods, and never letting ready-to-eat foods touch the same food contact surfaces
  • Allergen-free orders can't touch any of the same gloves, equipment, cookware, utensils, cooking oils, or food contact surfaces as the allergen
  • If allergen-free dishes are prepared improperly, you can't serve them as allergen-free. Trace allergens can remain and cause a reaction. Never just "pick" the allergen out.

Tips to Avoid Cross-Contamination While Serving Food

Front-of-house staff also need to take steps to prevent cross-contamination while serving food. They must:

  • Never touch the food contact surfaces of utensils, dishes, or glassware
  • Never stack glasses or dishes – use a rack or tray, instead
  • Never touch ready-to-eat foods with bare hands
  • Never use hands or glassware to scoop up ice
  • Use separate utensils for handling different food items, especially ready-to-eat food and PHFs
  • Clearly communicate allergen-free orders to kitchen staff
  • Deliver allergen-free orders directly to the affected guest, separately from other food
  • Provide separate utensils for each food item in self-service areas and remove utensils that customers use improperly
  • Ensure customers only use clean plates and utensils when serving themselves at a buffet or salad bar

Tips to Avoid Cross-Contamination While Cleaning

Regular cleaning is an important part of food safety in the front and back of the house, but you risk cross-contamination if servers and kitchen staff don't take precautions. Make sure all staff:

  • Store cleaning products and implements separately from food and in a designated area. This prevents chemicals or dirty cleaning tools from contaminating food or food contact surfaces
  • Store chemicals in original or clearly marked containers
  • Dispose of mop water and other cleaning fluids in a designated service sink, away from food or food contact surfaces. Also, avoid toilets or urinals – cleaning equipment contaminated with fecal bacteria can contaminate everything you clean.
  • Only wipe up food spills with designated towels – don't reuse them for any other purpose
  • Keep towels for cleaning food spills in sanitizer solution, never an apron or pocket
  • Only using clean sponges and dishcloths

Additional Food Safety Principles to Follow

Here are some additional safety rules to maintain clean food habits while handling food in the kitchen:

  • Keep your food and kitchen by cleaning, separating, cooking, and chilling ingredients/dishes.
  • Never place food such as groceries and cooked items out at room temperature for more than 2 hours if you don’t want it to get spoiled. It takes less than an hour for food to spoil in hot weather. If it is left in temperatures between 40 and 140° F it will enter the danger zone.
  • Marinades cannot eliminate bacteria so make sure you keep marinated meat in the fridge till you need it.
  • Vegetables should be washed and even after they are peeled. Bacteria from the peeler or rind can contaminate veggies.
  • Salmonella has no scent so make sure meat is cooked through or to the right temperature.
  • Bacteria grows rapidly on meat that is left on the counter to thaw.
  • Just because leftovers don’t smell bad doesn’t mean they are safe to eat.

The Bottom Line on Cross-Contamination

Whether it's pathogens, allergens, or chemicals, it's critical to the safety of all guests that food service workers use protocols that prevent cross-contamination. That's why many states require or incentivize Food Handler Training for certain employees. Even when it isn't required by law, training employees who handle food or food contact surfaces can protect your business interests.

Our food handler courses are state-specific to comply with local regulations. In jurisdictions with less specific requirements, our food handler training is ANSI-accredited to meet the highest national standards. To train your staff for less, check out our business solutions.

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