What the FDA has to say about gluten-free labeling of foods containing bacteria, enzymes, & yeast grown on gluten-containing mediaTricia Thompson
This post is part of a series covering the FDA’s Final Rule on Gluten-Free Labeling of Fermented or Hydrolyzed Foods. The information on growth media in the Federal Register document is located in multiple sections and is not 100% clear. This post may be updated as FDA provides additional clarification.
Manufacturers, if you are labeling a food gluten-free that contains microbes or enzymes, please make sure that the growth media used in their development did not contain any gluten source material.
- Various microbes (e.g., bacteria, yeast) and enzymes produced by microbes used in food may be grown on growth media (the food source for the microbes) that includes gluten-containing grain, such as wheat or barley.
- These microbes in turn, may be used in foods and ingredients during the fermentation process.
- During production of the microbes and enzymes, any gluten in the growth media may become fragmented.
- Gluten fragments from the growth media may be carried over with microbes into an ingredient or food product.
If bacteria, yeast, or enzymes are grown on media containing wheat barley, or rye, can they be used as ingredients in foods labeled gluten-free? The answer from FDA appears to be NO—not at this time.
What foods and ingredients are potentially impacted by this clarification from FDA depending upon the growth media used?
- Supplements containing probiotics
- Supplements containing enzymes
- Foods and ingredients that contain or are made using bacteria
- Foods and ingredients that contain or are made using enzymes
- Foods and ingredients that contain or are made using yeast
Real world evidence that use of gluten-free source material is important
Gluten Free Watchdog tested a popular probiotic through Bia Diagnostics, LLC on three separate occasions. While the bacterial strain remained the same in all lots, the growth media was different—spent brewer’s yeast or molasses. The probiotic containing the bacterial strain grown on spent brewer’s yeast (and likely contaminated with barley malt) tested at > 283.5 ppm of gluten. The same probiotic containing the same bacterial strain but this time grown on molasses tested at < 10 ppm of gluten on two separate occasions.
For more information please see Gluten-Free Labeling: Are Growth Media Containing Wheat, Barley, and Rye Falling through the Cracks? Tricia Thompson, Melinda Dennis, Luke Emerson. J Acad Nutr Dietet. 2018;118:2025-2028. Epub 2017 Sep 1. https://www.glutenfreewatchdog.org/news/wp-content/uploads/2020/08/JANDProbioticsInPress.pdf
Please also see: Fermentation Growth Media for Yeast and Concerns about Residual Gluten https://www.glutenfreewatchdog.org/news/fermentation-growth-media-for-yeast-and-concerns-about-residual-gluten/
GFWD interpretation of what the FDA has to say about growth media in the Q&A comment section of the final rule
- If wheat, barley, or rye is used as a food source for a microbe, consumers are justified in their concerns that gluten could be present in the microbe ingredient due to the lingering presence of growth media.
- If bacteria grown on media that contain wheat, barley, or rye is used to produce enzymes, gluten may be present in an enzyme ingredient due to the lingering presence of growth media.
- If gluten is present in the growth media it may have been broken down into protein fragments.
- FDA does not know at this time if gluten fragments produced during fermentation of growth media are capable of causing an immune response in people with celiac disease.
- FDA also does not know if it is possible to accurately test for the presence of any residual gluten in bacteria, yeast, or enzymes produced on growth media containing a gluten source.
- Manufacturers should use microbial starting materials (e.g., bacteria, yeast) that are gluten-free.
- One way to guarantee that bacteria and yeast are gluten-free is to use a growth media that does NOT include wheat, barley, or rye.
If you have any questions, please leave a comment. Your comments will help inform updates to this post. Thank you.