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

Every year, according to the CDC, one in six Americans contracts a foodborne illness, and over 3,000 people die. Foodborne illness can happen at home, but approximately 60% of outbreaks can be traced back to food service.

In this article, we’ll explain what cross-contamination is, why it’s a common source of foodborne illness, how it happens, and how food businesses can prevent it at every stage of operations.

What Is Cross-Contamination?

Cross-contamination is the invisible transfer of bacteria and other foodborne illness-causing agents during food handling.

Cross-contamination can happen anywhere food is handled along the production chain:

• Before or during harvest/slaughter
• During processing and manufacturing
• During transportation or storage
• During retail and market handling
• During preparation and service

Why Cross-Contamination Is a Serious Food Safety Risk

Cross-contamination is the leading cause of foodborne illness outbreaks in restaurants and other food service operations. While kitchens are often aware of undercooking or time-temperature lapses, cross-contamination often goes unnoticed until customers become sick. Restaurants must actively combat cross-contamination in their everyday practices to avoid disaster.

Cross-contamination with allergens can be especially prone to slipping through even a strong kitchen safety system, because allergenic proteins aren’t destroyed or eliminated through the same methods as common pathogens. This is unfortunate because even small traces of allergenic proteins can trigger anaphylaxis in some customers, leading to emergency room visits, lawsuits, and irreversible harm to both the customer and the restaurant. This is why restaurants should carefully consider the effort they’re willing to put into avoiding allergen cross-contamination and avoid making promises about allergy-free food they can’t keep.

Beyond the chance of making customers ill, cross-contamination is a regulatory risk. Health inspectors cite it as a critical violation under the FDA Food Code, and repeat offenses can lead to fines, mandatory closure, license suspension, or permanent revocation of operating permits.

That’s just for technical violations. If cross-contamination leads to a foodborne illness outbreak, the costs are even higher, including:

• Legal settlements and litigation expenses
• Increased insurance premiums
• Criminal negligence charges in severe cases
• Lost customer trust and declining sales
• Negative media coverage that can persist for years
• Potential permanent shutdowns

Types of Cross-Contamination

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

Cross-Contamination by Contaminant Type

There are three categories of food contaminants that transfer easily between sources with simple contact: biological agents, allergens, and chemicals.

Biological Cross-Contamination (Bacteria, Viruses, Parasites)

The most common type of cross-contamination related to food service is the transfer of harmful microorganisms.

Bacteria and viruses are the biggest concerns because they multiply in food at certain temperatures and transfer between items easily. Of the “Big 6” foodborne illnesses, most are caused by bacteria: Shigella, E coli, and two types of Salmonella. The remaining illnesses are caused by viruses: Hepatitis A and Norovirus.

Parasites and fungi also cause foodborne illness, but are less likely to be transferred as you prepare or handle food.

Allergen Cross-Contamination

Allergens are proteins that cause an allergic reaction in some people. These proteins transfer easily during food handling, and, just like bacteria or viruses, they’re invisible but dangerous.

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)
• Sesame

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

Cleaning and sanitizing are key food safety processes in food service, but the required chemicals are dangerous when ingested. Improper storage and misuse of cleaning products can result in chemical cross-contamination of food.

Cross-Contamination by Transfer Method

Contaminants get transferred in one of three ways.

Food-to-Food Transfer

• When pathogens or allergens (and more rarely, chemicals) are transferred directly between items of food
• Potentially Hazardous Foods (PHFs) carry and support the growth of bacteria and viruses more easily than others, so they require more caution

Equipment-to-Food Transfer

• When equipment, surfaces, or utensils are reused without properly sanitizing between items
• Certain microorganisms can survive on surfaces for long periods, but allergens and chemicals can also linger
• Items that touch food are collectively referred to as “food contact surfaces,” including countertops, cookware, or tools

Person-to-Food Transfer

• When people introduce or transfer pathogens or contaminants to food
• Food service workers coming to work while ill is a common source
• Hygiene lapses, like a lack of or inadequate handwashing, also contribute

How Food Operations Can Prevent Cross-Contamination

Since food can arrive at your facility contaminated or become contaminated on-site, you need to take precautions against cross-contamination at every stage of normal operations.

Cross-contamination prevention requires as systemic and dedicated an approach as all food safety does.

Below, we’ll detail step-by-step tips for preventing cross-contamination in restaurants.

Preventing Cross-Contamination During Purchasing and Receiving

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

• Purchasing only from reputable suppliers
• Checking use-by or expiration dates before officially accepting deliveries
• Inspecting packaging integrity
• Looking for any sign of pests
• Monitoring food recalls

Staff should always reject food deliveries when:

• Expiration or use-by dates have passed
• Items have been recalled
• Documentation is missing or incomplete, including:
  • Invoices
  • Health certificates
  • Shellstock tags
• The packaging is damaged or appears tampered with, including:
  • Holes or tears
  • Broken seals
  • Missing labels
  • Dents or bulging ends for cans
• There are signs of temperature control breaches, including:
  • Cold food arriving above 41ºF
  • Hot foods arrive below 135ºF
  • Frozen foods are not solidly frozen
  • Frozen foods have ice crystals or fluid stains, indicating thawing and refreezing
• Food shows signs of spoilage or contamination, including:
  • Dry foods arrive moist
  • Moist foods arrive dry
  • Abnormal or rotten odor
  • Unusual color
  • Unusual texture (soft/mushy)
• Visible signs of pests or pest damage

Special care should be taken with seafood, poultry, and meat.

Preventing 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.

For food items, you must:

• Move deliveries into appropriate storage areas right away
• Never store food outside of designated storage areas or near cleaning supplies
• Store all food at least 6 inches off the ground
• Cover all food items to prevent contaminants from falling inside
• Make sure all items are labeled with name, prep date (if applicable), discard date, and staff initials
• 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
• Never reuse chemical containers for food storage

Non-food items should also be stored with care. You should:

• Store all food contact items at least 6 inches off the ground
• 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 to prevent allergenic proteins from cross-contaminating them
• Never reuse chemical containers for food contact items

Storage integrity should be maintained by:

• Abide by discard dates with routine auditing
• Discarding any recalled food immediately
• Discarding any food storage containers that lose structural integrity

Preventing Cross-Contamination During Food Preparation

Kitchen staff should take precautions to prevent cross-contamination during food preparation. That involves careful attention to both personal hygiene and food/surface handling.

Staff are often vehicles for cross-contamination in food service, so the following hygiene measures are critical. Food service staff must:

• Wash their hands thoroughly for at least 20 seconds with soap
  • Before starting work or handling ready-to-eat food
  • After touching raw meat, unwashed leafy greens, and other PHFs
  • After taking out the trash, touching cleaning chemicals, or handling dirty equipment
  • After going to the bathroom, coughing, sneezing, touching the hair or face, eating, drinking, or otherwise taking a break
  • After using their phone or other non-sanitized items
  • Between different tasks
  • Before preparing an allergen-free order or touching any allergen-free equipment
• Remove all hand and arm jewelry before work
• Use hair and beard restraints
• Bathe regularly and wear clean clothing
• Cover cuts with waterproof bandages and single-use gloves
• Call out from work if they have vomiting, diarrhea, jaundice, a sore throat with a fever, or an infected wound.

Food contact items – any surface or implement that touches food – also must be handled and cleaned in a way that prevents cross-contamination. That includes:

• Using separate cutting boards for Potentially Hazardous Food (PHF) and other food
• 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
• Sanitizing food contact surfaces properly between tasks, especially after PHF contact
• Washing produce in slightly warm water before mixing or serving
• Never rinsing meat
• Observing all Time/Temperature Control measures while storing, heating, cooling, or holding PHFs

For allergen-free service, there are additional and careful considerations, including:

• 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 "pick" the allergen out.

Preventing Cross-Contamination While Serving Food

Front-of-house staff are often overlooked when discussing ways to avoid cross-contamination, but they also play an important role.

Front-of-house staff, like servers and bussers, 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
• Clearly communicate the restaurant’s limitations for allergy-free orders to allergic customers
• 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

Preventing Cross-Contamination During Cleaning

Cleaning obviously plays a key role in preventing restaurant cross-contamination, but it can also be a source of cross-contamination if not done correctly.

First, cleaning chemicals need to be stored responsibly to prevent cross-contamination. This means you must:

• Never store cleaning supplies near food or food contact items
• Store chemicals in original or clearly marked containers
• Accurately label cleaning supplies according to OSHA’s HazCom standard
• Always place liquid cleaning supplies into spill trays or bins to catch leaks
• Store incompatible chemicals separately
• Place powdered cleaning supplies on elevated shelves in a dry location

Precautions also must be taken during, between, and after use, including:

• Use appropriate cleaning agents and follow the recommended procedures to ensure adequate decontamination
• Clean equipment and surfaces thoroughly after applying chemicals to remove any residues or potential contaminants
• Follow appropriate handling techniques for each chemical, including proper pouring, transferring, and mixing procedures
• Avoid direct contact between containers or tools to prevent cross-contamination.
• 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
• 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.

Additional Food Safety Best Practices

All the recommendations in this article have been about how to prevent cross-contamination. All other food safety protocols must be followed during restaurant operations, including:

• Maintaining an awareness of time-temperature danger zones
• Using safe thawing and reheating methods to bring foods through the temperature danger zone within acceptable amounts of time
• Cooling and reheating leftovers according to safe time/temperature practices; take extra care to cool and reheat large batches evenly and on schedule
• Never reheating leftovers more than once; only reheat the portion needed
• Holding hot and cold foods at safe temperatures; never leave perishable leftovers at room temperature for more than 2 hours
• Discarding ready-to-eat Time/Temperature Control for Safety (TCS) foods within 7 days
• Not re-serving any food that has been served to a customer (buffet items, plate leftovers, breadbasket rolls) unless it is prepackaged and intact
• Never mixing old leftovers with fresh batches; package separately and apply first-in, first-out (FIFO) practices
• Following best practices for produce washing

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’s not required by law, training employees who handle food or food contact surfaces can protect your business and guests.

Food Handler Training and Cross-Contamination Prevention

Food handler training isn’t just a compliance checkbox; it’s an important tool for reducing risk and improving consistency of food safety practices.

As a trusted compliance training provider with over twenty years of experience, we offer online food handler training to teach front- and back-of-house staff to follow food safety best practices. We also offer food safety manager training to teach persons in charge how to maintain a food-safe system.

Our food safety compliance courses are state-specific in line 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.