As of August 2021, finalized rules are in effect for gluten-free claims on fermented and hydrolyzed foods regulated by FDA. If a fermented or hydrolyzed food (or a food containing fermented or hydrolyzed ingredients) bears a gluten-free label, the manufacturer must maintain records demonstrating that the food or ingredient met the FDA definition of gluten free prior to fermentation or hydrolysis and that gluten cross-contact was controlled after fermentation or hydrolysis. While this regulation seems straightforward on paper, challenges remain for food manufacturers trying to interpret the rule for their products. This article reviews the development of the current gluten-free regulations and the impact of the recently finalized rule for fermented and hydrolyzed foods.
Gluten and Celiac Disease
Celiac disease, also known as gluten-sensitive enteropathy, a lifelong condition affecting an estimated 1% of the U.S. population, is characterized by a chronic immune-mediated inflammatory response to the gluten proteins found in certain cereal grains, including wheat, rye, barley, and sometimes oats. The inflammatory process in celiac disease primarily impacts the intestinal tract, creating a chronic malabsorption syndrome unless treated. The symptoms of celiac disease, which are reflective of an inability to absorb nutrients including weight loss, anemia (iron deficiency), bone loss (calcium deficiency), and growth retardation in children, along with nausea, abdominal cramping, and diarrhea.
Gluten is a complex mixture of different individual proteins and includes two major fractions—prolamins (also referred to as gliadins) and glutelins. Individuals affected by celiac disease must strictly avoid gluten-containing foods to prevent serious adverse health outcomes, making establishment of regulatory criteria for the use of gluten-free claims critical to their ability to make safe food choices.
For many years, food manufacturers catering to celiac consumers had been labeling products as gluten free, but there was no established regulatory definition in the U.S. prior to 2013. The development of the current regulatory structure started with the Food Allergen Labeling and Consumer Protection Act of 2004, which required the Secretary of Health and Human Services to issue regulations to define and permit use of the term “gluten-free” for food labels. The final rule for gluten-free labeling of foods under FDA jurisdiction was published in August 2013, with a compliance date of August 5, 2014.
Gluten-Free Regulatory Definition
The gluten-free labeling regulation finalized by FDA and incorporated as 21 CFR 101.91 defines gluten-containing grains as wheat (any species belonging to the genus Triticum), rye (any species belonging to the genus Secale), barley (any species belonging to the genus Hordeum), or any of their crossbred hybrids (e.g., triticale). As illustrated in Table 1, this definition can encompass many different individual species, particularly when it comes to wheat. The rule also defines gluten as “the proteins that naturally occur in gluten-containing grains that may cause adverse health effects in persons with celiac disease (e.g., prolamins and glutelins).”
With respect to the definition of gluten-free, the rule stipulates that a product bearing a gluten-free label may not contain any of the following:
- An ingredient that is a gluten-containing grain;
- An ingredient that is derived from a gluten-containing grain and that has not been processed to remove gluten; or
- An ingredient that is derived from a gluten-containing grain and that has been processed to remove gluten, if the use of that ingredient results in the presence of 20 ppm or more gluten in the food.
Foods that inherently do not contain gluten may be labeled as gluten free if the presence of any unavoidable gluten is less than 20 ppm gluten.
Failure to meet these requirements for a product labeled as gluten free would result in a misbranded product. In addition, the terms “no gluten,” “free of gluten,” and “without gluten” must meet the same requirements as products labeled “gluten free.”
When compliance with the gluten-free rule is based on analysis, FDA indicated it would use a “scientifically valid method that can reliably detect and quantify the presence of 20 ppm gluten in a variety of food matrices, including both raw and cooked or baked products.” The reliance on analytical methods for evaluating compliance with the regulation plays a key role in the agency’s perspectives on fermented and hydrolyzed foods.
Methods for Gluten Quantification
Several methods have been developed for the detection and quantification of gluten in food matrices, including a few that have been validated as AOAC Official Methods of Analysis. These methods are generally sandwich enzyme-linked immunosorbent assays (ELISAs) that employ different types of gluten-specific antibodies. Sandwich ELISAs can provide sensitive, reproducible, and accurate quantification of intact gluten, but they require multiple intact binding sites to be present on the target protein molecule (see Figure 1). When gluten proteins undergo partial hydrolysis during fermentation, one or more of the required binding sites may be disrupted, affecting detection.
Competitive ELISA methods, on the other hand, only require one binding site for protein detection. While competitive ELISAs are more appropriate for detection of partially hydrolyzed gluten proteins, accurate quantification remains a challenge. Different fermentation processes and conditions may result in different levels of hydrolysis and different cleavage sites yielding multiple peptides of varying length and immunogenicity. These differences in hydrolysis make it difficult to develop a single ELISA calibrant that will be applicable for accurate quantification of gluten in a diverse range of fermented and hydrolyzed products.
In the preamble to the final rule for gluten-free labeling, FDA indicated that they were unaware of any currently available methods that could reliably detect and quantify the presence of 20 ppm intact gluten in fermented or hydrolyzed foods. They therefore indicated their intent to issue a separate rule for how they would verify the compliance of fermented and hydrolyzed foods.
Gluten-Free Labeling of Fermented or Hydrolyzed Foods
In the final rule, FDA outlined compliance requirements for situations in which a scientifically valid method is not available to quantify gluten because the food is fermented or hydrolyzed or contains ingredients that are fermented or hydrolyzed. For fermented and hydrolyzed foods, manufacturers must make and keep records adequately demonstrating that all three of the following are met:
- The food meets the definition of gluten free prior to fermentation or hydrolysis;
- The potential for gluten cross-contact occurring after fermentation or hydrolysis has been adequately evaluated; and
- If risks of gluten cross-contact are identified, the manufacturer has implemented sufficient controls to prevent cross-contact during production.
For foods that contain fermented or hydrolyzed ingredients, manufacturers must maintain records demonstrating that the ingredients meet the requirements for gluten-free fermented or hydrolyzed foods.
The particular types of documentation necessary for demonstrating that a food meets the definition of gluten free prior to fermentation should be assessed by the manufacturer. While the rule does not mandate analysis or specific documents, the preamble to the proposed rule does indicate that ingredients are likely to be at different levels of risk for gluten cross-contact and therefore may require different forms of documentation. For example, ingredients derived from commodities such as legumes, grains, or seeds that are susceptible to cross-contact with gluten-containing grains may require different types of documentation than foods that are inherently gluten free and have a low-risk of gluten cross-contact (e.g., fluid milk). In general, examples of documentation include certificates of analysis, analytical test results, and verification of supplier cross-contact management.
The final rule for fermented and hydrolyzed foods also contains separate information about gluten-free claims on distilled foods, such as distilled vinegars. Unlike fermentation, which FDA does not consider to be a process that can be validated as removing gluten, distillation is a process that physically separates gluten proteins and peptides from other components based on clearly defined properties. When conducted following good manufacturing practices, distillation will separate volatile compounds (e.g., alcohols) from nonvolatile compounds, including any proteins and protein fragments. As a result, for distilled foods, FDA will use methods capable of detecting the presence of proteins and protein fragments in foods to evaluate compliance with the gluten-free requirements.
In response to comments to the proposed rule, the final rule preamble specifically indicates that FDA declines to exempt enzymes from the requirements that apply to fermented and hydrolyzed foods. When enzymes are produced in a system with gluten-containing nutrient media, FDA expressed concerns about how much carryover of gluten into the finished enzyme product would occur. Given that microbial fermentation processes used to produce the enzymes may also partially hydrolyze any gluten protein present, FDA points to the analytical challenges involved in verifying the subsequent removal of gluten residues from the enzyme product that will result in a final gluten concentration below 20 ppm intact gluten.
Soy sauce is a commonly used fermented or hydrolyzed food ingredient that may be derived from gluten-containing grains. Traditional soy sauce is commonly produced from a fungal fermentation of soybeans and wheat. As these types of soy sauce do not meet the gluten-free definition prior to fermentation, they are not allowed to be labeled as gluten free. Certain styles of traditionally fermented soy sauce, including some types of tamari, do not include any wheat in the formulation. If the ingredients used to make tamari meet the gluten-free definition prior to fermentation, then the resulting product could be labeled as gluten free. Lastly, some types of soy sauce do not rely on fermentation but rather use a combination of acid-hydrolyzed soybeans and other ingredients to formulate the product. If all the ingredients meet the gluten-free definition prior to hydrolysis and production, the soy sauce may be labeled as gluten free.
Malt, Malt Extract, and Malt Syrup
Malt is defined in 21 CFR 184.1445 as the “product of barley (Hordeum vulgare L.) germinated under controlled conditions.” Malt extract and malt syrup are terms both referring to viscous concentrated water extracts obtained from barley malt. FDA has indicated that because malt, malt extract, and malt syrup are derived from a gluten-containing grain and have not been processed to remove gluten, they may not be used as ingredients in foods labeled as gluten free.
Gluten-Free Beer, Wine, and Spirits
In the U.S., beer (malt beverages), wine, and spirits primarily fall under the regulatory authority of the Alcohol and Tobacco Tax and Trade Bureau (TTB). Beers not meeting the definition of a malt beverage, however, are regulated by FDA. Beers regulated by FDA would include those that are not made from both malted barley and hops—for example, beers using substitutes for malted barley such as sorghum, millet, or rice. Often, these beers have been formulated with gluten-free claims in mind, as they are not made from gluten-containing grains. Despite differences in regulatory jurisdiction, FDA and TTB both recognize the same definition of gluten free for fermented and hydrolyzed beverages. For beer or wine to be labeled as gluten free, the ingredients or mash used to make the beer must meet the definition of gluten free prior to fermentation, and controls must be in place to prevent gluten cross-contact after fermentation.
The TTB does, however, allow alternative statements on products fermented from gluten-containing grains (TTB Ruling 2020-2). In certain instances, manufacturers can include the claim that the products are “[Processed or Treated or Crafted] to remove gluten.” If this claim is used, there are additional requirements that must be met:
- The label must also include the following statement: “Product fermented from grains containing gluten and [processed or treated or crafted] to remove gluten. The gluten content of this product cannot be verified, and this product may contain gluten”;
- The manufacturer must submit a detailed description of the method used to remove gluten and must be prepared to substantiate claims about gluten reduction upon request;
- Gluten cross-contact must be controlled after treatment to reduce gluten;
- No labeling statements are allowed with respect to specific gluten concentrations.
TTB requires pre-authorization of all product labels, and allowable label claims meeting these criteria would be evaluated during that process. For FDA-regulated beers, the final rule indicates that beers not meeting the definition of gluten free are not precluded from using the types of alternative statements recognized by TTB, but the claims must be truthful and not misleading. That being said, FDA does not consider fermentation or hydrolysis itself a process that can be verified as reducing the gluten content of beers made from
TTB has also indicated that distilled spirits would be allowed to bear a gluten-free claim, and these products would need to comply with the same requirements as distilled products regulated by FDA. Specifically, manufacturers of distilled spirits made from gluten-containing grains must follow good manufacturing practices to prevent introduction of any gluten-containing material into the distillate and must implement controls to prevent gluten cross-contact after distillation. Manufacturers must also be prepared to provide verification of the absence of protein from the distillate and the absence of gluten from any ingredients added after distillation.
Impacts and Future Directions
Given the wide range and diversity of fermented foods and ingredients, the final rule has the potential to impact many products that had previously been labeled as gluten free. Even if the product is inherently gluten free, manufacturers must develop and maintain the required documentation for compliance with the rule.
While FDA has left the door open to enforcing compliance through use of novel gluten quantification methods developed in the future, there are many challenges associated with such an undertaking. Development and validation of a single method capable of quantifying intact gluten equivalents across the wide diversity of relevant fermented and hydrolyzed foods would require substantial time, effort, and resources.
The authors are with the Food Allergy Research and Resource Program in the Department of Food Science and Technology at the University of Nebraska-Lincoln. Reach Dr. Downs at [email protected] and Dr. Taylor at [email protected].