Gluten-Free Foods: Shared Fryers, Safe Eating?

People with celiac disease or gluten intolerance are often advised against consuming gluten-free foods cooked in shared fryers with wheat-containing foods. This recommendation stems from the potential risk of gluten cross-contact, which can occur even with proper oil filtration. Studies have detected varying levels of gluten in fries cooked in shared fryers, and it is challenging to determine the exact gluten content in fryer oil. The lack of clear data and the possibility of invisible cross-contact contribute to confusion among consumers, especially when gluten-free options cooked in shared fryers are offered on restaurant menus.

Can you eat gluten-free foods cooked in shared fryers?

Gluten cross-contact

People with celiac disease or gluten intolerance must avoid gluten for medical reasons. Due to the risk of gluten cross-contact, dietitians advise against consuming gluten-free foods cooked in shared fryers. This recommendation is based on the presumed risk of gluten exposure, as gluten exposure, even in microscopic amounts, can trigger an autoimmune response in individuals with celiac disease.

A study on gluten cross-contact in shared fryers found that out of 20 orders of fries from 10 different restaurants, 9 orders (45%) tested positive for gluten using the sandwich ELISA method, while 3 orders (15%) tested positive using the competitive ELISA method. These results indicate that gluten cross-contact may occur when gluten-free foods are cooked in shared fryers, reinforcing the need for caution when consuming fried foods for those with gluten sensitivities.

The gluten level in a shared fryer can vary depending on factors such as previously cooked foods, oil change frequency, and the filtration system used. However, it is challenging to completely eliminate gluten from fryer oil, even with proper filtration. The lack of visible gluten in fried foods does not guarantee its absence, and even minuscule amounts of gluten can be harmful to those with gluten-related disorders.

To ensure the safety of gluten-intolerant diners, foodservice operators should consider implementing dedicated gluten-free fryers and strict protocols for their use. Certification by organizations like the Gluten-Free Food Service (GFFS) helps instill confidence in gluten-intolerant individuals that their dietary needs are being accommodated and their health protected.

Gluten-free labelling

The U.S. Food and Drug Administration (FDA) has established a federal definition of the term "gluten-free" for food manufacturers that voluntarily label FDA-regulated foods as "gluten-free". The definition was intended to provide a reliable way for people with celiac disease to avoid gluten, and, given the public health significance of gluten, restaurants’ use of gluten-free labelling should be consistent with the federal definition.

The FDA's gluten-free food labelling rule specifies what the claim actually means on a food label. Manufacturers that label their foods as free of gluten are responsible for using the claim in an accurate and not misleading manner, and for complying with all requirements established by the regulation and enforced by the FDA. The rule specifies, among other criteria, that any foods that carry the label “gluten-free,” “no gluten,” “free of gluten,” or “without gluten” must contain less than 20 parts per million (ppm) of gluten. This level is the lowest that can be reliably detected in foods using scientifically validated analytical methods.

The FDA does not require manufacturers to test for the presence of gluten in ingredients or in the finished gluten-free-labelled food product. However, they are responsible for ensuring that the food product meets all labelling requirements. Manufacturers will need to determine how they will ensure this. The FDA may perform food label reviews, follow up on consumer and industry complaints, and analyse food samples.

In 2017, the FDA released the results of an analysis of 702 samples from more than 250 products labelled “gluten-free”. Only one of the products did not comply with the labelling requirements. That product was recalled and subsequent testing did not find any products that violated the regulation.

In a 2021 study, 20 orders of fries were purchased from 10 different restaurants. Restaurants confirmed that the fries and oil were free of gluten-containing ingredients. All restaurants confirmed that their fryers were used to cook wheat-containing foods. The sandwich R5 ELISA test found gluten in 9/20 fry orders (7 to > 80 ppm). The competitive R5 ELISA test found gluten in 3/20 fry orders (14 to > 270 ppm). In the microwave control (60-ppm gluten mixture of wheat flour and canola oil), the unheated mixture tested at a mean level of 64 ppm gluten using the sandwich ELISA and 137 ppm gluten using the competitive ELISA. The mixture heated to 190°C tested at a mean level of 55 ppm gluten using the sandwich ELISA and < 10 ppm and 16 ppm gluten using the competitive ELISA. Based on these test results, 25% of fry orders would not be considered gluten-free.

The study concluded that gluten cross-contact may occur when gluten-free foods are cooked in shared fryers with wheat. Dietitians have long been discouraging consumers with celiac disease from ordering gluten-free foods cooked in the same deep fryer as gluten-containing foods at restaurants. This recommendation is based on presumed gluten exposure vs. evidence-based research that gluten cross-contact occurs.

Therefore, it is not advisable to eat gluten-free foods cooked in shared fryers, as there is a risk of gluten cross-contact.

Celiac disease

One common source of gluten cross-contact is the shared fryer, often used in restaurants and fast-food chains. In a busy kitchen, it can be challenging to prevent cross-contamination, especially at the fry station. Even if the oil in a fryer is changed, and gluten-free foods are cooked, particles of gluten can remain in the crevices of the fryer, contaminating the food. This is because gluten cannot be "killed off" or "disinfected"—high heat has no effect on it. The gluten proteins will remain in the fryer, ready to contaminate the next batch of food.

A study by Celiac.com found that gluten was present in 9 out of 20 fry orders from restaurants, ranging from 7 to over 80 ppm gluten. A further 3 out of 20 fry orders were found to contain gluten at levels ranging from 14 to over 270 ppm. These results suggest that one out of four French fry orders would not be considered gluten-free, which poses a risk to individuals with celiac disease.

Therefore, it is recommended that people with celiac disease avoid eating gluten-free foods cooked in shared fryers. Cross-contact with gluten can cause an autoimmune response, even if symptoms are not visible or noticeable. To prevent cross-contact, people with celiac disease should inquire about the fryer status when dining out and consider other options if a dedicated gluten-free fryer is not available. Maintaining a gluten-free household and using separate utensils, shelves, and labels for gluten-free items can also help prevent cross-contact.

Gluten-free dining out tips

Dining out when you're gluten intolerant can be a source of anxiety. Many restaurants offer gluten-free options, but it's hard to be sure that procedures are being followed to avoid cross-contact with gluten. One way to feel more confident is to choose a restaurant that has gone through a programme like GIG's Gluten-Free Food Services (GFFS) Validation Program. Restaurants that have completed this programme are considered Gluten Free Safe Spots.

If you're dining at a restaurant that hasn't been validated, there are still steps you can take to help ensure your meal is gluten-free. It's a good idea to research the restaurant in advance and look at the menu online. Call ahead to discuss your requirements and ask questions about how the food is prepared. Be prepared to explain your dietary needs and ask if they understand what that means. You may want to let them know how severe your reaction can be.

When you're at the restaurant, ask your server about the risk of cross-contact. Find out if gluten-containing foods have been cooked on the same surface or in the same oil. You can also ask about specific ingredients and request that your meal is prepared without gluten, for example, a salad without croutons or a hamburger without the bun. It's important to double-check that your instructions have been followed when your meal arrives.

Other tips for gluten-free dining include choosing simple dishes that are naturally gluten-free, like plain meat, chicken, or fish. Be cautious when ordering fried foods, as the oil may be used for both breaded and non-breaded items, which can lead to cross-contact with gluten. In large restaurants where multiple fryers are used, there may be a lower risk of cross-contact.

Finally, remember that you can always bring your own gluten-free food to a restaurant and ask the chef to cook it for you.

Gluten-free certification

Various organizations offer gluten-free certification, each with its own set of standards and requirements. One of the prominent organizations is the Gluten-Free Certification Organization (GFCO), which is currently the largest and fastest-growing certification body in North America. GFCO requires tested foods to contain a maximum of 10 ppm of gluten, which is even stricter than the FDA requirement of less than 20 ppm. The GFCO certification process includes an annual ingredient review, plant inspection, and product testing.

Another well-known certifying body is the Celiac Support Association (CSA) or the Celiac Sprue Association, which sets an even lower threshold of 5 ppm of gluten for certified products. The CSA conducts detailed facility inspections and product packaging reviews to ensure the absence of gluten-containing ingredients.

The Allergen Control Group (ACG) is another reputable organization that offers the Gluten-Free Certification Program (GFCP). They require tested foods to contain less than 20 ppm of gluten, aligning with the FDA's gluten-free food labeling rule.

The process of obtaining gluten-free certification can be lengthy and expensive, involving annual inspections, audits, and testing. However, it is essential to provide consumers with confidence in the safety of their food choices, especially those with gluten-related conditions.

While gluten-free certification primarily focuses on packaged foods, restaurants should also adhere to the FDA's definition of gluten-free when making gluten-free claims on their menus. It is important to note that gluten cross-contact can occur when gluten-free foods are cooked in shared fryers with wheat-containing foods, as evidenced by studies. Therefore, individuals with celiac disease are generally advised to avoid fried foods cooked in shared fryers to prevent potential gluten exposure.

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