Cross Contamination Action Ideas
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1 A Leading Cause of FBI
If you work in the area of food and health, you already know that foodborne illness (FBI) is a major public health issue.
It affects 1 in 6 Americans annually, according to Centers for Disease Control and Prevention (CDC) data published in 2011. You may also know that at least two out of three FBI outbreaks trace back to food prepared outside the home—as in a restaurant, an institution, or a retail establishment.
Why? We can talk about causes, and you can probably name culprits straight out of media headlines: E. coli, Salmonella, Clostridium, Listeria, Norwalk virus, and many other pathogens. These pathogens are everywhere, yet not every meal leads to illness (thankfully). In analyzing FBI outbreaks, the CDC identifies contributing factors. These are not the pathogens. Rather, they are the factors that allow pathogens to thrive and persist through the flow of food, ultimately causing an outbreak.
According to the CDC, the top five contributing factors to FBI in foodservice and retail food establishments are:
- Food from Unsafe Sources
- Poor Personal Hygiene
- Inadequate Cooking
- Improper Holding/Time and Temperature
- Contaminated Equipment/Not Protected from Contamination
During the past 10 years, the FDA has been conducting on-site research regarding compliance with specific FDA Food Code guidance related to these five factors. In its 2009 report, Report on the Occurrence of Foodborne Illness Risk Factors in Selected Institutional Foodservice, Restaurant, and Retail Food Store Facility Types, FDA analysts cited personal hygiene, time and temperature control, and protection from contamination (#2, #4, and #5) as “areas most in need of improvement.”
They noted, “Foodservice and retail food store operators must ensure that their management systems are designed to achieve active managerial control over the risk factors.” In this short CE program, you will learn more about contributing factor #5.
Sources: Centers for Disease Control & Prevention (CDC). 2011 Estimates of Foodborne Illness in the United States.
Food and Drug Administration (FDA). FDA Report on the Occurrence of Foodborne Illness Risk Factors in Selected Institutional Foodservice, Restaurant, and Retail Food Store Facility Types (2009)
3 What is Cross Contamination?
Cross contamination is the transfer of pathogens to food.
The word “cross” sometimes confuses people. Why “cross”? It’s the idea that something dangerous crosses from any item to food. For example, when your hands are unclean and you touch a slice of bread, bacteria cross from your hands over to the bread.
In food safety, most people use “cross contamination” to describe pathogens passing to a food. Technically, contamination can be anything that makes the food unsafe—even a cleanser or a food allergen.
Consider the flow of food. As each food ingredient and recipe moves through the process defined in your organization, it has multiple opportunities to become contaminated. The job of a foodservice manager is to anticipate and control each of these opportunities, or “risks”. A typical flow of food begins with food being received and checked in, then transferred to storage. Later, it may be retrieved from storage and used in a recipe. Later still, the food may undergo transportation and/or holding in a service area. Finally, it may be stored again for future use.
Even a home kitchen has a flow of food. Someone brings home groceries, places them in storage, and uses foods to make meals.
While a food is following its flow in any kitchen, contamination can occur at any point. (Remember, it can even enter your doors contaminated.) Once contamination occurs, pathogens in food pose a food safety risk.
One of today’s most respected food safety models, the Hazard Analysis and Critical Control Point (HACCP) system, targets controls where risks are highest and interventions can have the greatest impact. For example, foods that risk being contaminated undergo cooking to defined time and temperature standards. This mitigates the food safety risk.
However, other foods are ready-to-eat. This means they will undergo no cooking (or further cooking). An example is a sliced turkey and avocado deli sandwich. If it becomes contaminated with Staphylococcus bacteria from a foodservice worker’s skin, the bacteria are likely to live on. Upon cross contamination, odds of causing an illness are higher when the food involved is ready-to-eat. Typically, there are no further controls to mitigate this hazard.
4 Types of Cross Contamination and Examples
There are two typical ways that cross contamination occurs:
- Pathogens cross from one food to another food.
- Pathogens pass from food-contact surfaces of equipment or utensils to food.
Let’s look more closely. First, Pathogens cross from one food to another food. Here are some examples:
- Someone places raw ground beef above a tray of ready-to-eat sandwiches in a refrigerator. Meat drippings are contaminated with E. coli bacteria. The drippings contaminate the sandwiches with E. coli bacteria.
- A chef is breading fish in an egg batter and then frying it. Also on the counter is a bowl of coleslaw to be scooped and served with the fried fish. The egg batter is contaminated with Salmonella bacteria. As he lifts a piece of batter-dipped fish, he drips the egg mixture over the coleslaw.
5 Types of Cross Contamination and Examples - continued
Now we’ll look more closely at the second kind of cross contamination:
Pathogens pass from food-contact surfaces of equipment or utensils to food. Here are some examples:
- A grill cook uses the same spatula to put raw sausage patties onto the grill—and to remove cooked patties. The sausage patties are contaminated with Listeria bacteria. Every time he touches the raw meat, he gets bacteria onto the spatula. When he uses the same spatula to handle cooked meat, he re-contaminates the cooked sausage patties. (From a HACCP perspective, the risk that was controlled by proper cooking is now back all over again.)
- A kitchen worker is slicing deli turkey meat in the slicer. It happens to be contaminated with Campylobacter bacteria. Later, she slices American cheese for sandwiches. The bacteria cross from the turkey to the slicer, and from the slicer to the cheese.
- A person assembling tacos in a food court is wearing gloves to prevent bare-hand contact with ready-to-eat food. She drops an empty taco shell box into the trash. The trash is overflowing, so she pushes it down with her gloved hand. Then she continues assembling tacos. In this case her glove is the food-contact surface. It’s been contaminated by the trash. Now any pathogens present in the trash are transferring to the tacos she serves.
Cutting boards are often a focus of equipment contamination, simply because they are used so extensively in pre-preparation procedures. This is why some managers choose color-coded cutting boards. At a minimum, if a cutting board is reserved for meat or for fresh produce, the risk is reduced. However, all food contact surfaces are at play. This includes cutting boards, knives, countertops, blenders, mixers, utensils, storage containers, serving pans, and even potholders and aprons. Needless to say, proper cleaning and sanitizing between processes are the key weapon against this kind of cross contamination.
It’s important to focus on entire work areas, not just a bowl or a utensil. British researchers demonstrated that simple food preparation tasks like cracking an egg can contaminate work surfaces as far away as 40 cm (about 16 inches) with Salmonella. When eggs are mixed or whisked as part of a recipe, they said, “contamination of surfaces around the mixing bowl was a common occurrence.” They also noted, “Once present on formica work surfaces, S. enteritidis survived well.” Bacteria were still present after 24 hours.
Source: Cambridge University Press. Contamination of hands and work surfaces with Salmonella enteritidis PT4 during the preparation of egg dishes
6 Hands and Handwashing
Some systems also describe a third kind of contamination—from people to food. In the CDC and FDA research cited previously, this is the contributing factor named as personal hygiene. And this factor does indeed contribute to foodborne illness.
The facts are alarming. The FDA study on FBI risk factors indicates that “proper, adequate handwashing” was the food safety control most “out of compliance” with FDA Food Code standards. Only 36% of the the items that related to handwashing passed the audit. Among retail meat departments, the number dipped to 18%.
According to the FDA, “Handwashing reduces the spread of pathogenic microorganisms that are transmitted through food. The hands of food employees can be colonized with microorganisms such as Staphylococcus aureus or contaminated with organisms from human fecal material, such as Norovirus, Shigella spp., hepatitis A virus,E. coli O157:H7, or Salmonella Typhi, or contaminated from raw animal foods, with E. coli O157:H7 and Salmonella spp. These and other pathogenic microorganisms can get on the hands from a number of sources and then move from hands to food during preparation and service.
“An infected food employee and/or food employees with unclean hands, and exposed portions of arms or fingernails, can contaminate food. If a consumer eats contaminated food, foodborne illness may result.”
While reasons, triggers, and procedures for handwashing are well known, compliance is an ongoing concern in both foodservice and healthcare industries. As reported in Cracking Edge newsletter, compliance with handwashing protocols in hospitals stands at less than 50 percent. Typical handwashing messages tell healthcare workers to wash their hands to avoid illness. But many healthcare workers are better motivated by messages that focus on patients, according to recent research, They suggest that routinely refreshing messages may improve compliance, too. Example: “Did you wash your hands? What if your mother was the next patient you saw?”
Sources: Food and Drug Administration (FDA). FDA Report on the Occurrence of Foodborne Illness Risk Factors in Selected Institutional Foodservice, Restaurant, and Retail Food Store Facility Types (2009)
Safest Choice™. Cracking Edge Newsletter Sep. 2011
7 FDA Study on Cross Contamination by Foodservice Segment
The 2009 FDA Report provides highly actionable information for any foodservice manager.
Using the targeted contributing factors and Food Code standards as a guide, researchers actually inspected 850 foodservice operations around the nation and directly measured compliance with best practices. They included a range of foodservice segments—hospitals, nursing homes, elementary schools, fast food restaurants, full service restaurants, and departments of retail food stores.
The study was designed to:
- Measure trends over time in regulatory and industry efforts to reduce the occurrence of FBI risk factors
- Assess the occurrence of FBI risk factors and management practices essential to their control
- Identify employee practices and behaviors that contribute to the occurrence of foodborne illness that are in need of priority attention
Researchers concluded, “Improper cleaning and sanitizing of food-contact surfaces before use was the item most commonly observed to be Out of Compliance in eight out of the nine facility types. Percent Out of Compliance values for this data item ranged from 18% in seafood departments to 64% in full service restaurants.” Take a look at the FDA summary graphs below to see details for hospitals, nursing homes, fast food, and full-service restaurants. For more details on finding by foodservice segment, see the complete FDA report online.
The FDA researchers used five audit points derived from the FDA Food Code. These are targeted takeaway points for foodservice operators as well.
- Food is protected from cross contamination by separating raw animal foods from raw ready-to-eat food and by separating raw animal foods from cooked ready-to-eat food
- Raw animal foods are separated from each other during storage, preparation, holding, and display
- Food is protected from environmental contamination
- After being served or sold to a consumer, food is not re- served
- Food-contact surfaces and utensils are clean to sight and touch and sanitized before use
Source: Food and Drug Administration (FDA). FDA Report on the Occurrence of Foodborne Illness Risk Factors in Selected Institutional Foodservice, Restaurant, and Retail Food Store Facility Types(2009)
8 Findings on Buffets
According to Colin Caywood, writing in Food Safety News, the self-service model of buffet dining “practically invites… cross contamination issues.” This is because patrons are now practicing food service, but without the requisite training in foodservice sanitation.
Caywood cites examples of FBI outbreaks that traced back to buffet dining. One involved E. coli bacteria in Minnesota, linked to a Chinese buffet. Victims suffered severe infection and had to be hospitalized.
Another involved Salmonella Heidelberg at a buffet restaurant in North Carolina. Not one, but three meat entrees tested positive for the bacteria. Two employees were infected as well. Researchers could not determine whether the employees were sources or victims of a pathogen spread through the buffet.
Yet another case Caywood cites involved the breakfast buffet of a hotel in Colorado. Multiple groups of guests (and staff) became ill with Shigellosis.
Caywood emphasizes controlling risk factors such as temperature control and protecting food from contamination.
Source: Caywood, C. Buffets and Cross-contamination, Food Safety News, July 20, 2010
9 Video Findings
A study conducted by Benjamin Chapman and colleagues at North Carolina State University collected actual video footage of employees’ foodservice sanitation practices in eight commercial kitchens.
As reported by the University, “Chapman’s study found approximately one cross-contamination event per food handler per hour. In other words, the average kitchen worker committed eight cross-contamination errors, which have the potential to lead to illnesses, in the course of the typical eight-hour shift.”
Chapman also found that the rate of error in personal hygiene and cross contamination increased dramatically during peak meal times.
The researchers’ conclusions:
"The prevalence of cross contamination is a hidden problem for food service, as food handlers acting in a multi-user environment may not see themselves as part of a team. Many of the recorded indirect cross contamination events occurred when multiple food handlers used common food contact surfaces, utensils, or equipment.”
Chapman and colleagues have been testing interventions for improving food-safe practices.
Their suggestions include:
- Highlighting the “team-like nature of a food service system,” showing workers how their own actions affect others, and training for a system (rather than an individual)
- Re-structuring foodservice systems to create a more even workflow, such as in a commissary-like system
- Using food safety “infosheets” to compel behavioral change
Source: Chapman, B. Video Study Finds Risky Food-Safety Behavior More Common Than thought, NC State University Newsroom, June 08, 2010
10 Cross Contamination – Considerations Related to Food Allergies
The concept of cross contamination has taken on new meaning in light of the Food Allergen Labeling and Consumer Protection Act of 2004, which took effect in 2006.
It’s estimated that 12 million Americans (4% of the population) have one or more food allergies, which are responsible for 30,000 emergency room visits and 150 deaths in the US each year.
Accordingly, the 2009 edition of the FDA Food Code rolled out new guidance regarding food allergies. The “person in charge” at a foodservice establishment is now accountable for being able to identify common food allergens and recognize symptoms of an allergic response to food. Common food allergens, those most frequently involved in serious allergic reactions, are: milk, eggs, fish (e.g. bass, flounder, cod), shellfish (e.g. crab, lobster, shrimp), tree nuts (e.g. almonds, walnuts, pecans), peanuts, wheat, and soybeans.
For individuals who are highly susceptible to allergic reactions, cross contamination is a critical issue. Controls extend beyond simply choosing (or avoiding) foods on a menu. Cross contamination of foods and/or work surfaces with allergens from other foods can trigger a life-or-death response. Says the FDA in its Food Code Annex, “The person in charge establishes an important barrier to food contamination.”
The Wisconsin Department of Public Instruction provides these guidelines for preventing cross contamination with food allergens:
During Food Preparation:
- Handle products and prepare items that do not contain the allergen(s) first.
- Prior to working with these items, wash hands with soap to remove any potential allergen residue.
- Put on clean gloves if coming in contact with a ready to eat food items.
- Thoroughly wash any food contact surfaces with detergent solution that will come in contact with the non-allergen items to remove any residue. These surfaces include the cutting boards, and equipment such as slicers and can openers.
- If disposable gloves are worn during cleaning, discard after cleaning surfaces.
- Rinse cleaned surface with water.
- Sanitize surfaces and allow to air dry.
- Designated color coded cutting boards for allergen and non-allergen products to minimize cross contamination. Clean, rinse and sanitize the color codes cutting boards separately.
Meal Service and Clean up:
- Set up serving line to prevent cross contamination of non-food allergen products with allergen containing products.
- Appropriately label items to prevent mix ups and to help students with diagnosed food allergy recognize what items may contain allergens.
- Keep protective covers on key boards and key pads clean. Clean with detergent solution (not sanitizer) to remove food residue.
- Clean allergen free table prior to meal service with detergent solution.
Sources: The Wisconsin Department of Public Instruction. Preparation of Foods with Potential to Cause Allergic Reaction Standard Operating Procedure.
Food and Drug Administration (FDA).
Food Code 2009
Food and Drug Administration (FDA). FDA Report on the Occurrence of Foodborne Illness Risk Factors in Selected Institutional Foodservice, Restaurant, and Retail Food Store Facility Types(2009)
11 How to Prevent Cross Contamination During Food Storage
Food storage is one of the steps in the flow of food in which food is subject to cross contamination. Here are some tips for preventing cross contamination from the National Food Service Management Institute.
To prevent food-to-food cross contamination:
- Separate raw animal foods such as eggs, fish, meat, and poultry from ready-to-eat foods such as lettuce, cut melons, and lunch meats during storage.
- Separate different types of raw animal foods such as eggs, fish, meat, and poultry from each other except when combined in recipes.
- Store raw animal foods in refrigerators or walk-in coolers by placing the raw animal foods on shelves in the following order of cooking temperature: whole beef or pork on top shelf, raw ground meats on middle shelf, and poultry on bottom shelf.
- Separate unwashed fruits and vegetables from washed fruits and vegetables and other ready-to-eat foods.
- Place food in covered containers or packages except during cooling and store in the refrigerator or cooler.
- Designate an upper shelf of a refrigerator or walk-in cooler as a “cooling” shelf. Uncover containers of food during the initial quick cool-down phase to facilitate cooling.
- Store damaged goods in a separate location.
To prevent equipment and food contact surface-to-food cross contamination:
- Use only dry, cleaned, and sanitized containers for food storage.
- Clean and sanitize shelves in the storage unit on a routine basis.
- Cover all foods well and label and date them.
To prevent chemical contamination:
- Store all chemicals away from food products, preferably in a separate storeroom.
- Limit access of chemical storage areas to designated personnel.
Source: National Food Service Management Institute. Food Safety Fact Sheet, Preventing Cross Contamination During Food Storage (2009).
12 How to Prevent Cross Contamination During Food Preparation
One of the most crucial food-safe procedures in a foodservice operation is to begin each process with clean, sanitized work surfaces and equipment.
It takes more time to thoroughly sanitize work surfaces and equipment adequately than it does to use one item to wipe down everything. It is up to the foodservice manager to practice what the FDA Food Code calls “active managerial control” to implement practices, train team members, monitor compliance, and coach employees in actions that protect customers from FBI.
The National Food Service Management Institute offers these additional tips for preventing cross contamination during preparation.
- Use only dry, cleaned, and sanitized equipment and utensils for food preparation.
- Clean and sanitize work tables, equipment, and cutting boards after each use and before beginning a new task. For example, after slicing ham, the slicer should be cleaned and sanitized before slicing turkey.
- Clean and sanitize surfaces that are handled often, such as refrigerator and freezer handles.
- Maintain a fresh bucket of cleaning solution and a fresh bucket of sanitizing solution in the work area so that cleaning and sanitizing can be done easily.
- Check the concentration of the sanitizing solution to make sure it is at appropriate levels to sanitize.
Source: National Food Service Management Institute. Food Safety Fact Sheet, Preventing Contamination During Food Preparation (2009).
13 How to Prevent Cross Contamination During Transportation and Meal Service
Here are some tips for preventing contamination during transportation and service:
- Cover foods to protect them from contamination.
- Ensure that transport and service equipment (e.g., carts, steamtables) are cleaned and sanitized on an established schedule.
- Provide utensils for handling any ready-to-eat food that is not pre-packaged.
- Use only cleaned, sanitized utensils and service ware.
- Keep utensils in the food (not laying them down on a counter).
- Monitor glove usage among employees. Ensure that every incident that should trigger handwashing (e.g., handling trash, sneezing, using the restroom) leads to changing gloves.
- Monitor activity in self-service areas, such as salad bars and buffets, and remove any food that may have become contaminated.
- Label foods to discourage touching or tasting.
- Provide fresh plates and service ware for each service, and collect soiled service ware from tables promptly.
- Use sneeze guards.
- Wash linens (e.g., aprons, potholders) on an established schedule.
14 Cross Contamination: Consumer Education Points
The principle of preventing cross contamination applies in home kitchens, too.
Consumer education can include messages that closely parallel those of foodservice. The USDA, in its fact sheet, “Be Smart. Keep Food Apart,” offers tips for consumers that address all steps in the flow of food.
David L. Williams and colleagues, reporting in Food Protection Trends, determined that a growing consumer trend—reusable grocery bags—presents a cross contamination risk. The researchers found that about half of bags were contaminated with coliform bacteria. Coliform bacteria, a general category identifying bacteria that are common in feces, are used as a marker of biological contamination. E. coli is one example of a coliform bacteria, and in fact, 8% of the bags were contaminated with E. coli.
Researchers also noted, “When meat juices were added to bags and stored in the trunks of cars for two hours, the number of bacteria increased 10-fold.” Fortunately, there is a simple solution: washing the bags on a regular basis. They recommend public educational efforts around this message.
NSF identifies the 10 “germiest” places in the home as documented by household swabs and cultures in 2011. Clearly, many relate to food handling in the home kitchen.
10 Germiest Places
- Kitchen Sponge/Dish Rag
- Kitchen Sink
- Toothbrush Holder
- Pet Bowl
- Coffee Reservoir
- Faucet Handles
- Pet Toys
- Countertops
- Stove Knobs
- Cutting Boards
One microbiology expert, Charles Gerba, PhD of the University of Arizona, was quoted by Philly.com as saying, ``You'd be better off eating a carrot stick that fell in your toilet than one that fell in your sink.'' He has also pointed out that cutting boards used for raw meat can carry 200 times more bacteria than a toilet seat. (Consumer Reports, March 2012).
Note that 30% of homes reviewed by NSF tested positive for coliform contamination on the countertops. NSF said that this can come from a variety of foods passing through the food preparation process in a home kitchen, as well as pet toys and bowls. Consumer advice offered by NSF includes:
- For the sponge/dish rag: “Place wet sponges in the microwave for two minutes once per day and replace often - every two weeks or more as needed. Better options for kitchen cleaning are dishcloths, towels and rags. These items can be sanitized by washing on the clothes washer's hot water cycle with bleach. Replace every 1-2 days.’
- For the sink: “Wash and disinfect the sides and bottom of the sink 1-2 times per week with a disinfecting cleaner. Sanitize kitchen drains and disposals monthly by pouring a solution of one teaspoon household bleach in one quart of water down the drain. Wash kitchen sink strainers in the dishwasher weekly.”
- For the coffee reservoir: “Follow the manufacturer's recommended cleaning instructions.”
- For faucet handles: “Clean daily with disinfecting cleaner or disinfecting wipes.”
- For countertops: Wash daily. "Once all food prep activities have been completed, wash the surface with hot soapy water, rinse with clean water, then apply a bleach/water solution. For specialty countertops, use the manufacturer's recommended cleaning/sanitizing agent.”
- For stove knobs: “Remove knobs, wash in hot soapy water, rinse well, let dry, then re-install once per week.”
- For cutting boards: “Thoroughly wash them after each use and between food types.”
Sources: United States Department of Agriculture, Food Safety and Inspection Service. Be Smart. Keep Foods Apart. Don't Cross-Contaminate., December 15, 2010
Williams, David L. et al. Assessment of the Potential for Cross-contamination of Food Products by Reusable Shopping Bags. Food Protection Trends, vol. 31, no. 8, 2011.
NSF International, Top Ten Germiest Places in the Home