Comments from Gluten Free Watchdog to FDA on the Proposed Rule to Establish Requirements for the Gluten-Free Labeling of Fermented or Hydrolyzed Foods

Comments from Gluten Free Watchdog to FDA on the Proposed Rule to Establish Requirements for the Gluten-Free Labeling of Fermented or Hydrolyzed Foods


Comments submitted by Tricia Thompson, MS, RD

Founder, Gluten Free Watchdog, LLC

In response to Docket Number FDA-2014-N-1021



This letter is also attached as a pdf document (attachment 1)

Dear FDA,

Thank you for your efforts on behalf of the gluten-free community to establish requirements for the gluten-free labeling of fermented or hydrolyzed foods. As you make decisions regarding the final rule, please consider the testing and ingredient information included in this response. Note that testing commissioned by Gluten Free Watchdog is done by Bia Diagnostics, an ISO 17025 certified lab.

It is agreed that the competitive R5 ELISA may be more of a qualitative test than a quantitative test (i.e., the assay detects gluten fragments but may not be able to accurately quantify these fragments into intact gluten protein). It is also understood that the potential inability of the assay to accurately quantify intact gluten may make it difficult for FDA to use the competitive assay to enforce compliance with the gluten-free labeling rule (i.e., the rule addresses intact gluten protein versus gluten protein fragments). However, FDA presumably would not want to dismiss out of hand test results from the competitive R5 ELISA indicating the presence of gluten peptides in foods labeled gluten-free.

Wheat Starch/Wheat Starch Hydrolysates

FDA considers wheat starch to be an ingredient “processed to remove gluten” and wheat starch is allowed in labeled gluten-free foods. FDA states in the proposed rule that “variations in the processing could result in different trace amounts of gluten remaining in the starch” and “the use of such ingredients must not result in the presence of 20 ppm or more gluten in the finished food.”

While wheat starch is not typically considered a “hydrolyzed” food or ingredient it nonetheless contains hydrolyzed wheat protein (see references 1 and 2 below). Wheat starch may be further hydrolyzed to make other ingredients commonly referred to as “wheat starch hydrolysates.” An example of a wheat starch hydrolysate is wheat starch-based dextrin.

Under the FDA’s gluten-free labeling rule, wheat starch hydrolysates are allowed ingredients in gluten-free foods as long as all criteria of the rule are met including that the final food product contains less than 20 ppm gluten. Dextrin (and other wheat starch hydrolysates) derived from the partial hydrolysis of wheat starch may be found in single ingredient foods labeled gluten-free and multi-ingredient foods labeled gluten-free. Based on the proposed rule, manufacturers who label such products gluten-free would have to demonstrate that the “non-hydrolyzed” raw ingredient (i.e., wheat starch) is gluten-free. However, testing wheat starch with the sandwich R5 ELISA alone may not be sufficient to determine the safety of wheat starch and wheat starch hydrolysates for the celiac disease community. Please consider the following information on wheat starch:

A recent study found wheat starch to contain from less than 5 parts per million of gluten to over 10,000 parts per million of gluten (1). “Gluten may be partially degraded during the manufacturing process of starch which could lead to a loss of the second epitope required for antibody recognition in the Sandwich assay” (see reference 1). As a result, R-biopharm (the manufacturer of both the sandwich and competitive R5 ELISAs) recommends using the competitive R5 ELISA to test starch (see reference 2).

Gluten Free Watchdog has tested wheat starch and foods containing wheat starch using both the sandwich and competitive R5 ELISAs. As expected, wheat starch not labeled gluten-free contains higher levels of gluten and gluten peptide fragments than wheat starch labeled gluten-free. Nonetheless, wheat starch labeled gluten-free contains small levels of both intact and hydrolyzed gluten (see attachment 2).

Given the above information, how does FDA recommend that manufacturers ensure that the wheat starch and wheat starch hydrolysates used in their products do not contain hydrolyzed gluten in amounts that may cause harm to individuals with celiac disease? At Gluten Free Watchdog, foods containing wheat starch and wheat starch hydrolysates are tested with both the sandwich and competitive R5 ELISAs. To do otherwise would be irresponsible.

Can FDA also comment on whether barley-derived enzymes (e.g., alpha and beta amylase from malt) used to breakdown starch such as rice starch into sugar may be used in foods labeled gluten-free?


  1. Proceedings of the 27thMeeting Working Group on Prolamin Analysis and Toxicity. Analytical Research Reports. Katharina Konitzer, Herbert Wieser, Peter Koehler. German Research Centre for Food Chemistry, Leibniz Institute, Freising, Germany. Quantitation of gluten in wheat starch by gel permeation chromatography with fluorescence detection Available at:
  2. R-biopharm. Ridascreen Gliadin Competitive. Available at:

Other ingredients that may contain “hidden” hydrolyzed gluten (not a complete list)

Spent brewer’s yeast/yeast extract/autolyzed yeast extract: The term “brewer’s yeast” refers to both the “live yeast” used to make beer and the “spent yeast” that is a by-product of the beer brewing process—in other words, what is left of the yeast once it has been used to make beer (see references 3 and 4). Brewer’s yeast also may be grown on sugar beets. When brewer’s yeast is used in food as a flavoring agent, it is typically “spent yeast” and as a result may be contaminated with small amounts of gluten-containing grain and malt (see references 3 and 4). The ingredients “yeast extract” and “autolyzed yeast extract” also may be made from spent yeast and may be contaminated with malt. If the ingredients brewer’s yeast, yeast extract, or autolyzed yeast extract are spent yeast, gluten contamination may be in the form of hydrolyzed gluten (see reference 4).

Test results for a yeast extract spread (the source of yeast extract in this spread is spent yeast arising as a by-product of beer making (testing commissioned by me and conducted at FARRP):

Sandwich R5 ELISA
Extraction One: 28 ppm gluten
Extraction Two: 31 ppm gluten

Lower limit of quantification for this assay is 5 ppm gluten

Competitive R5 ELISA*
Extraction One: 3,700 ppm gluten peptide
Extraction Two: 3,400 ppm gluten peptide

Lower limit of quantification for this assay is 1,250 ppm gluten peptide

*At the time this testing was conducted results of the competitive R5 ELISA were reported as gluten peptides.

Unfortunately, the source of yeast is not included in the ingredients list in the US. While it is hoped that manufacturers of gluten-free food would not use spent yeast-derived ingredients in their products, they may not know the source of yeast extract.

Can FDA please comment on whether yeast ingredients potentially contaminated with malt are allowed in labeled gluten-free foods? If they are, how is FDA proposing that manufacturers test yeast ingredients to ensure that no hydrolyzed gluten fragments remain in the yeast? At Gluten Free Watchdog, foods containing brewer’s yeast and yeast extract are tested with both the sandwich and competitive R5 ELISAs. To do otherwise would be irresponsible.

Can FDA also please clarify the Agency’s position on the use of malt and malt extract in foods labeled gluten-free? Both of these ingredients contain hydrolyzed gluten protein. FDA has advised me via email correspondence that FDA considers malt extract an “ingredient not processed to remove gluten.” The Agency has also stated during a webinar to the Medical Nutrition Practice Group of the Academy of Nutrition and Dietetics on March 12, 2014 that,

 “Malt is a product of barley germinated under controlled conditions. Malt syrup and malt extract are interchangeable terms for a viscous concentrate of water extract of germinated barley with or without the preservative. Malt syrup is usually a brown and viscous liquid containing varying amounts of amylolytic enzymes with plant constituents. So if malt syrup or malt extract are further processed in some way to remove proteins we believe that would change its nature to such an extent and alter the characteristics of the ingredient so that they would no longer bear the same common or usual name. Malt extract and malt syrup are ingredients derived from gluten containing grains and containing gluten therefore we would consider them as ingredients not processed to remove gluten and they would not be permitted in foods bearing the claim gluten-free.”

Nonetheless, there continue to be products sold in the US, especially products imported from Europe that are labeled gluten-free yet contain barley malt or barley malt extract.


  1. Manley CH, Choudhury BH, Mazeiko P. Thermal process flavorings. In: Ashurst PR, ed. Food Flavorings. 3rd ed. Gaithersburg, MD: Aspen Publishers; 1999:283-325.
  2. Thompson T. Additional information: Update on the gluten-free status of yeast extract. Gluten Free Watchdog Website. July 29, 2014.

Extract of roasted barley/extract of roasted rye: Gluten Free Watchdog has contacted FDA regarding an instant herbal beverage product. This product contains as ingredients “extracts of roasted barley, rye” and is labeled gluten-free.

As I wrote in an email to FDA on November 13, 2014 concerning test results for this product, “The lot tested in January had results of 114 ppm gluten using the competitive R5 ELISA and less than 5 ppm gluten using the sandwich R5 ELISA. The results from the lot tested November 10th are 30 and 47 ppm gluten using the competitive and less than 5 ppm gluten using the sandwich.”

FDA responded, “We will review your information and follow up as warranted.”

Based on manufacturer website information, this product remains on the market and continues to be labeled gluten-free.

Regarding the ingredients in this product (e.g., “extracts of roasted barley, rye”), FDA responded to the original email dated January 10, 2014, “As far as the product, “manufacturer name redacted”, we do not have enough information to be able to decide if the product meets the requirements of the Gluten-free labeling regulations or not.  We would need more details as far as the processing steps and we are also not sure what extracts are being referred to in the description.”

Can FDA comment on how the Agency plans to address ingredients included in labeled gluten-free foods that:

  1. Are not defined in either the Code of Federal Regulations or the Compliance Policy Guide, AND
  2. Contain hydrolyzed gluten based on testing via the competitive R5 ELISA? 

Enzymes: Some products such as non-prescription digestive enzymes and probiotics may contain enzymes grown on wheat substrates. Some of these products are labeled gluten-free. According to Deerland Enzymes (see reference 5), “Enzymes for use in dietary supplements is a growing industry. Supplemental enzymes assist in the digestion of dietary sugars, fats and proteins. The enzymes are typically produced from either fermented bacteria or mold, and plant extraction. Fermentation requires the organism to grow using protein sources such as milk, soy and wheat as “food”. Bacteria and mold utilize the proteins in their environment by secreting enzymes to break down this food so that they can grow. Enzymes are specific to the substances they break down. For instance, the most potent enzymes that are manufactured to break down gluten usually contain wheat in the fermentation media.”

Putting aside problems associated with testing enzymes for gluten using the R5 ELISA (the enzymes must first be deactivated to prevent false positives) (see references 5, 6), testing enzymes for hydrolyzed gluten requires use of a competitive versus a sandwich ELISA.

Can FDA please comment on whether wheat and barley-based growth media can be used to “grow” the bacteria that secrete the enzymes used in labeled gluten-free digestive enzymes, probiotics, and similar products? If yes, how is FDA proposing that manufacturers test these enzymes to ensure that no hydrolyzed gluten fragments remain?

Can FDA also comment on whether other ingredients produced from fermented bacteria or mold (e.g., Xanthomonas campestris—used to make xanthan gum, Penicillium roqueforti—used to make blue cheese, etc.) grown on wheat or barley-based growth media are allowed in labeled gluten-free foods? If yes, how is FDA proposing that manufacturers test these bacterial/mold ingredients to ensure that no hydrolyzed gluten fragments remain?


  1. Deerland Enzymes. The use and limitations of the Competitive ELISA to detect proteins used in protease enzyme fermentation applications.
  2. Gluten Free Watchdog. Gluten Content of Gluten Digestive Enzyme Supplements: A Very Brief Summary.

On behalf of the Gluten Free Watchdog community, thank you for considering these comments and questions.


Tricia Thompson, MS, RD

Founder, Gluten Free Watchdog, LLC





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Comments (2)

  • Shirley @ gluten free easily (gfe) Reply

    Thank you so much for submitting these comprehensive comments/questions on behalf of all us in the gluten-free community, Tricia. I hate to think where we’d be without your extensive knowledge and daily, relentless support.


    January 12, 2016 at 12:01 am
  • Tricia Thompson Reply

    You are most welcome, Shirley. I am going to be issuing a call to action regarding malt and malt extract and the need for the community to stress to FDA through written comments on this proposed rule that while the Agency thinks the issue of malt is clear (i.e., it can not be used in foods labeled gluten-free) it is not at all clear to manufacturers. To prevent this same problem from happening again and again the Agency (IMO) must address malt specifically either in the final rule or in a Q&A.

    January 12, 2016 at 2:24 pm

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