Avoiding Cross-Contamination in Restaurant Kitchens

By: Dahlia Snaiderman

12 Minute Read

Apr 04, 2019

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When you open a restaurant, you’re creating a space where you can give your customers a great experience – amazing service, exciting food, and beautiful design can all contribute. However, you also have the responsibility of providing a safe environment for your diners, and one big way that restaurants fail to do so is through a lax approach to food safety and cross-contamination.

What is Cross-Contamination?

Cross-contamination is when bacteria from one ingredient contaminates another ingredient (or dish), causing harm to the person who eats it.

Preventing cross-contamination is crucial in avoiding food poisoning and other food-borne illnesses like E. Coli and salmonella, and in preventing allergic reactions.

When training your employees, emphasize that cleanliness matters more than speed. It may be perceived as an odd request – few managers want to encourage anything but total efficiency from their staff. However, adding a minute of extra waiting time to your workflow is preferable to having to worry your staff is cutting corners that could make someone sick. You’ll also have less to worry about when the health inspector comes around.

If one of your customers gets sick from eating at your restaurant, not only will you have failed at your mission of providing a great experience for everyone, but you’ll probably be staring down a terrible Yelp review. You could also get shut down or sued if you’re found to be breaking health codes.

With that in mind, we’ve divided this guide in two: first, we’ll discuss allergen cross-contamination, and then we’ll explain how to avoid cross-contamination that leads to food poisoning.

Allergen Cross-Contamination

What makes dealing with allergies so difficult is that depending on the allergen, there’s a good chance that much of your kitchen is often cross-contaminated. For example, nuts aren’t a danger for most people, so it’s normal for your cooks to just brush off a surface where they chopped walnuts and move on – but this means anything prepped on that surface, until it’s thoroughly washed, is cross-contaminated with nuts. Same goes for wheat allergies – and flour goes everywhere.

Cross-contamination of allergens can happen everywhere in the kitchen – in prep table fridges where open containers of prepped foods are nestled together, on prep surfaces, in walk-in fridges or freezers, on utensils, on flat-top grills, in deep-fryers, and on the pass, to name a few. All foods leave behind traces in all these areas, unless you’re cleaning everything thoroughly between each dish, which is impossible in the rush of service.

It’s up to you to know which allergies you can accommodate, and to communicate it to your staff so they can confidently explain your allergy policy. Allergies exist on a spectrum of severity – some are life-threatening, while others can simply cause discomfort, which adds to the complicated nature of this issue. Sometimes, you will have to tell your customer you can’t guarantee there is no cross-contamination, and let them decide what to do.

Allergy-friendly restaurants, like Ming Tsai’s Blue Dragon, serve as a haven to guests with allergies. On Ming Tsai’s episode of our podcast, The Garnish, (Season 1, Episode 3) he told us he’s had customers come in with teenage children who had never been to a restaurant before, due to the dangers of cross-contamination and their severe allergies. Tsai’s own son was born with seven of the eight most common allergies (wheat, milk, eggs, soy, fish, tree nuts, peanuts, and shellfish), so he built his restaurant to give guests with allergies a place to dine without fear.

Tsai also developed a free framework, called the Food Allergy Bible, that any restaurant can put into place, downloadable on his website. Some tips he suggests:

  • Write “If you have any allergies, please alert your server or a manager” on your menu.
  • Train your servers to ask every guest about allergies.
  • Provide a booklet with the ingredient lists of every dish on the menu to any diner who requests it.
  • If a dish contains nuts in a hidden way (in a dressing, with peanut oil, in a sauce), garnish the dish with whole (or slightly chopped) nuts.
  • Servers must input allergies on the order ticket, and highlight any tickets with allergies on them to alert the kitchen.
  • When a server delivers the dish to the person, the server should repeat the allergies back to them, confirming the cooks have taken them into account and the food is safe to eat.

“Food allergies are a two-way street,” wrote Tsai in an essay for Allergy Amulet. “From the restaurant perspective, we need to have procedures in place to make sure customers can safely eat, but we also need to be made aware of any allergies and understand the severity so that we can accommodate.”

When preparing a dish for someone with an allergy, your cooks must understand they have to use only clean utensils, surfaces, and cooking vessels – and sometimes, further accommodations are necessary to prevent cross-contamination. The grill may need to be cleaned thoroughly between grilling shrimp and a steak for someone with a seafood allergy. A sponge can have residue from an allergen on it. Fryer oil could need to be switched out. In fact, Tsai uses the fryer question to gauge the severity of guest allergies.

“Over the years, I’ve developed a useful and effective way to better determine the severity of people’s food allergies. I ask, ‘Is using the same fryer okay?’ The point we are getting at here is if shrimp is fried in a fryer, could the customer eat fries out of that same fryer? Depending on the answer we then have a better understanding as to the severity of the food allergy, which we use as a directive to the kitchen staff,” explained Tsai in the same essay.

Preventing Food Poisoning from Cross-Contamination

The most insidious culprits behind food poisoning caused by cross-contamination are improperly handled and prepared poultry, meat, seafood, and fish. All four of these groups can contain dangerous bacteria like the famous salmonella and E.Coli, but also listeria, campylobacter, norovirus, and parasites, explains FoodSafety.gov.

Here’s how to keep your diners safe, divided by some of the areas of your kitchen.

On Prep Surfaces

Switching out your cutting board is not enough. Often, whatever raw meat product you’re handling produces liquid that drips over the sides of the cutting board, even if you’re careful, especially when dealing with defrosted meat. A swipe of a paper towel after removing the dirty cutting board is not enough to prevent bacteria from hopping onto other foods – surfaces must always be thoroughly cleaned after preparing raw meat, seafood, or poultry, says the USDA. Even if there wasn’t any visible dripping, it’s always better to be safe than sorry.

Example Scenario:

A cook slices 30 chicken breasts on a cutting board. A few little slices fall off the cutting board and onto the counter, but the cook grabs them quickly and puts them back on the cutting board. When the cook is done, they place the chicken in a container, wrap it, and store it in the fridge. They give the dirty cutting board to the dishwasher, who washes it with hot water and soap, and runs it through the dishwasher. The cook’s next task is to prep carrots for salad, so they wipe the counter with a wet paper towel, put down a fresh cutting board, and get to work. A bunch of peeled carrots roll away and hit the counter, right where the rogue slices of raw chicken landed.

The salads that those carrots end up in are now cross-contaminated with bacteria from the raw chicken. Does that mean that a guest will 100% get sick? No - but it significantly increases the likelihood that they could.

The cook should have washed the counter with hot, soapy water, and/or sprayed it with a bleach solution: Industry standard is 1 tablespoon chlorine bleach dissolved in 1 gallon of water, according to the USDA. Then, they could put down the new cutting board and get working on the carrots.

At the Sink

Sometimes people don’t think they need to wash a sink - believing it’ll just get rinsed and washed while being used – but especially in restaurant kitchens, sinks are frequently exposed to raw meat, seafood, fish, and poultry, especially if anything is being defrosted.

Most kitchens are too cramped to have a dedicated defrosting sink, so it’s important to wash out a sink with soap and hot water after doing a task when a contaminant was present. You should also wash surrounding areas, especially if there’s a prep area attached, because splashing water can carry bacteria.

Example Scenario:

Several pounds of raw shrimp are defrosting in a bowl of water with a steady stream of cold water dripping over it. In theory, the shrimp should be in a leakproof plastic bag, but in practice, this takes longer, so the shrimp are left floating directly in the water. After about an hour, the shrimp is defrosted and the cook who will prepare it drains it, puts the container in the dishwasher, and moves onto seasoning and cooking the shrimp. Another cook comes by and places a large colander full of parsley directly in the sink to be rinsed. As he’s rinsing the parsley, water splashes around and carries bacteria from the raw shrimp onto the parsley. For an allergy, this is more than enough to cause an allergic reaction, and it could make anyone sick.

The cook should have quickly washed the sink with hot, soapy water after finishing with the shrimp, instead of leaving a shrimp-covered sink for the next person to use.

In the Fridge and Freezer


I shudder to think of the fridges I have seen full of raw meat packages stacked on top of veggies.

In the walk-in fridge, any foods that could cause cross-contamination should be stored as low to the ground as possible, so no raw meat, poultry, fish, or seafood ever drips on any produce or prepped foods.

In the freezer, the same logic applies, with meat, poultry, fish, and seafood on the bottom and everything else on top, or ideally, in a different section altogether. If your power goes out and meat stored on top defrosts and drips all over the other foods, the chance of cross-contamination goes way up, even if everything is packaged.

Cleaning Messes

Spills (of all kinds) should be taken care of promptly, not at the end of a shift, especially if the spilled food could have contaminated anything else in the fridge. A salad that had chicken juice splashed into it – gross, but it happens – needs to be thrown out.

Now you know about the many ways that cross-contamination can happen in your kitchen, train or retrain your staff and make cleanliness a priority.

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