Guide to Gluten Cross Contamination

Separate - Don't Contaminate!

Basic kitchen safety rules tell us that we need to separate ready-to-eat foods from raw meats, poultry, seafood and eggs - and to use separate cutting boards and utensils to reduce the risk of food poisoning.

The same rules apply to gluten and gluten-free foods - they must be kept apart!

The recipes found on our website are made with gluten-free ingredients. The food must also be prepared properly so it remains gluten-free. If you are preparing foods for a gluten-free guest, you must be ever mindful of cross contact.

This guide will help you to understand and prevent gluten cross contamination.

The Basics

Before you start you need to know a few basics.

What is gluten?

Gluten is the generic term for the proteins found in grains. The proteins found in wheat, barley, rye and commercial/mainstream oats (think Quaker Oats) are not acceptable for those following a gluten-free diet. Commercial or mainstream oats are highly contaminated with gluten due to how they're grown, harvested, transported and processed. Certified gluten-free oats are acceptable for some celiacs.

Where is gluten found?

Just about everywhere! Bread, pizza, cake, cookies, crackers, pasta, cereal, soups, sauces, beer. - just to name a few foods. Many processed foods contain gluten in some form or another. It's very prevalent in the Standard American Diet.

What does gluten do?

Gluten provides the structure, the framework – it holds everything together. It provides that chewy texture that is desirable in many foods like bread & pizzas. It also makes a lot of people sick.

How much?

Think of gluten as a poison. How much arsenic would you like in your food? Very good, I thought you'd say zero.

Not only must the food be gluten-free, it must not come in contact with any gluten. Cross contamination and the concept of “a crumb will hurt you” is hard for people to wrap their brains around because it involves very small amounts.

How small? Literally, a very small crumb. A multicenter, double-blind, placebo-controlled, randomized study has shown that many celiacs can safely consume up to 10 milligrams (1/8th of a teaspoon of flour, or 18 slices of gluten-free bread) of gluten per day.

Yes, crumbs matter!

Here's a perfect illustration. An average grain of rice weighs 28 milligrams. Now, divide that grain into 3 pieces. Those pieces are 9.33 milligram each – just under 10 mg limit.

Mind blown? There's more...

Many can not consume even 10 mgs of gluten without getting sick. Many in the gluten-free community strive for and attain ZERO gluten.

ZERO gluten should be the ultimate goal for everyone following a gluten-free diet.

Where to find it and what to do about it

  • Condiments (spreadable) – jars of peanut butter, mayo, jelly, butter, margarine, etc. These guys are huge cross-contamination magnets!

  • You'll want to purchase and use new, fresh products that have not been contaminated.

    Double dipping is strictly prohibited. Master the fine art of “Gob Dropping” or using a couple of spoons & knives to accomplish the task.

    Some of these products can be gotten in squeezable containers.

  • Any foods like flours, starches, white or brown sugars, etc. that frequently use shared, unwashed utensils with gluten.

  • Do not use a measuring cup for gluten flour then use the same cup for anything else without a thorough cleaning; you could use a clean cup too.

    Same concept goes for stirring or serving. Always use a clean utensil for gluten-free foods.

  • Brown sugar has another risk factor. Some people will put a piece of bread in their container. This keeps the sugar soft.

  • Please purchase new products that use shared utensils or have been contaminated.

  • Deep fry oil or pasta water.

  • Do not deep fry gluten-free foods in oil that previously fried gluten-full foods. Use fresh oil, or fry GF foods in fresh oil before frying gluten-full foods.

    Do not boil gluten-free pasta in water that previously boiled gluten-full pasta. Use fresh water for GF pasta.

  • Kitchen surfaces with crumbs – whenever preparing gluten-free food, make sure work areas are clean and free of crumbs.

  • Use hot soapy water to wash then rinse with fresh, clean water. Bleach will not do anything to gluten to make it safe.

    It's best to designate a gluten-zero prep area where no gluten is allowed.

  • Silverware drawers – take a look in there – lots of crumbs!

  • Clean out the entire drawer and re-wash the utensils. This goes for any other drawers too.

  • Toasters - if you’ve ever toasted glutened products in it, there is no way to effectively clean it.

  • Do not use a glutened toaster. Purchase a new one.

    Toaster bags could be used in a pinch. You put your bread in a bag, then inside the toaster

  • Toaster Ovens – are easier to work with than toasters.

  • Fixed racks - line with foil. Might not work well for actual toasting, but works well for heating.

    Removable racks - Purchase another rack for GF use. Foil existing rack or clean.

  • Convection Ovens – they circulate the air inside the oven to shorten cooking times.

  • Either turn off the convection feature or make sure you have tight fitting lid on your gluten-free dish

  • Colanders/Strainers/Flour Sifters – Since pastas/gluten often get stuck in the small little holes and slits, cleaning them fully is a nightmare if not impossible.

  • Wooden utensils/boards/rolling pins – Porous item can harbor gluten.

  • Cutting boards [plastic or wood] – due to the deep cuts and grooves, it’s best to get a new one.

  • Purchase new colanders, wooden/porous items & cutting boards.

  • Any utensil, pot, pan, dish, etc that has come in contact with gluten. They must be clean prior to gluten-free use.

  • Do not re-use these items for gluten-free foods without thoroughly washing them or grabbing a clean one. For example: Don't use the gluten-full pasta salad spoon to serve the gluten-free pasta salad.

    Those living in a mixed house will have dedicated gluten-free utensils, cutting boards, colanders, etc. It helps to have them color coded.

  • Cake pans – these pans typically have a lot of very deep cuts/grooves in them.

  • Purchase new or use disposable aluminum cake pans.

  • Cookie sheets

  • Line with parchment paper when baking GF cookies.

    Some have dedicated GF cookie sheets

  • Non-stick pots & pans

  • Replace if there are any cuts or scratches in the surface - do no use it; gluten can get caught. As long as it can be well cleaned, it should not be a problem.

  • Cast iron skillets – the “seasoning” develops from years of use.

  • Replace. Some have heated their old skillets to 600-700 degrees to burn off any residue.

  • Ceramic bake or cookware – it's porous.

  • Foil it or purchase new.

  • Dishtowels/sponges/dishrags

  • It helps to use paper towels to do initial clean up, then use clean/unused items to finish cleaning.

  • Grill grates

  • If cleaning or replacing the grates are not an option – grill your GF items on tinfoil.

  • Shared bowls/bags of your favorite GF snack food - Think about when someone makes a gluten-full sandwich, then they dig their gluteny paws into the potato chip bowl/bag.

  • Bags of snacks must be poured out into an individual bowl.

  • Family-Style or Buffet-Style service – these styles of food service is a gluten-free nightmare; inevitably, someone will grab the spoon from the pasta salad to dish out the gluten-free coleslaw.

  • If you are serving foods buffet style have the gluten-free foods separate from the gluten foods. This will lessen the cross contamination risks.

    Also ask if your GF guest to go thru the line first – before any of the GF dishes have a chance of getting contaminated.

  • TV Remotes, Phones, Keyboards, Mice...anything that has been touched by glutened hands.

  • Clean these items the best you possibly can - it's tough.

For more cross contamination information see Gluten Intolerance Group's educational bulletin:

“Producing Gluten-Free Products in a Non-dedicated Kitchen” -

For more information on accommodating gluten-free guests, see GIG of ECW's webpage:

“Educating Family and Friends about Gluten-Free” -

For a collection of cross contamination articles, see webpage:

Daily Living: Cross Contamination

Printer Friendly

01/31/15 - Added Cross Contamination page link
06/21/14 - Add convection oven
12/27/13 - Fix broken links
10/20/2013 - Clarify terminology