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What's the deal with Oats?

by Erika Macchione on April 21, 2023

Oats are considered a high-risk grain, because of repeated opportunity for exposure to gluten containing grains: wheat, barley, rye, and their hybrid forms. Those with celiac disease (CD) are recommended consumed only either purity protocol and/or certified gluten free oats. Within the CD population, there is a small percentage of people who experience symptoms, after consuming purity protocoled and/or certified gluten free oats, and are advised to avoid all oats, regardless of gluten free claims.

 The issue with commodity oats, for those with CD, is that the challenges of consistently producing gluten free products, that contain <20ppm of gluten, are many, beginning in the fields and continuing through to final packaging. As a result, oat producers, millers, and manufactures have developed various good manufacturing practices (GMPs) to help ensure that oats and oat-based products can contain <20ppm of gluten and are safe for those with CD to consume. Despite these measures, commodity oats, and their gluten free status, remain controversial.

Optically and Mechanically Sorted Processes:

Conventionally grown commodity oats are exposed to gluten containing grains anywhere between the growing fields to manufacturing of the final product; this includes seed selection, crop rotation practices, harvesting equipment, transportation, sorting, milling, and final product manufacturing. To increase the yield of gluten free oats, from these commodity oat supplies, mechanical sorting technology was developed to rid the oats of not only errant gluten containing grains, but foreign objects, like small stones, and undesirable and/or diseased grains. Mechanical sorting began by separating grains by size and weight, but more recently optical sorting technology can now allow for more exact sorting, by color and texture, in addition to weight and size, which has increased yield of usable oats.

Mechanical and optical sorting, to remove errant gluten containing grains, occurs after the oats have been harvested and is part of the general sorting, decontamination, and sanitation processes. Some manufactures note that their first opportunity to test for gluten occurs after this initial sorting and “cleaning.” If the lot of oats test >20ppm of gluten, some manufactures will allocate these oats to non-gluten free products and if they do fall <20ppm of gluten, they are deemed acceptable to be transported, in gluten free containers, to be milled in a gluten free milling facility, possibly tested again, and, finally, to the manufacturing facility, which provides a final opportunity to test the final product prior to being distributed to the consumer.

When and where testing for levels of gluten occurs is determined by the manufacturer. When a product is labeled gluten free, the manufacturer, when audited by the FDA, must demonstrate that all ingredients, production practices, and packaging ensure that the final product contains <20ppm of gluten. The GMPs for each product is determined by the manufacturer, with the FDA performing most audits when complaints have been filed by consumers.

Purity Protocol Oats:

Oats that have been grown and processed via purity protocol standards and methods, have, inherently less chance of coming into contact with gluten containing grains, but exposure to errant gluten containing grain cannot be prevented 100% of the time. While there are no legal or official standards for a purity protocol oats, in 2017 the Gluten Intolerance Group (GiG) published a paper which provides a framework for oat processors, farmers, millers, manufactures to help ensure that the final oat-based product is <20ppm of gluten, and in the case of some third-party certified gluten free products, <10ppm and <5ppm of gluten. Currently there are four oat processors, in North America, that follow the purity protocol standards. While seemingly strict and potentially restrictive for all involved, it was noted in the guideline’s discussion that the following measures are not dissimilar to existing practices that are followed by those who are producing non-genetically modified crops. The following procedures, which must be documented and recorded, are the current practices for growers and downstream manufactures of purity protocol oats (Allred, L.K., et al. 2017):

  • Seed Purity – all seeds used must not contain gluten containing seeds or come from a previous crop that contained gluten containing crops.
  • Crop Rotations – The first year of growing gluten free oats can only occur after at least three years since a gluten containing grain was grown and harvested. Growers may only use non-gluten containing grains during rotation.
  • Isolation Strips – In the case of neighboring growing areas that grow gluten containing grains, there is a minimum isolation strip, 6 feet wide, between the gluten free growing area and the gluten containing area.
  • Field Inspection – third party inspectors are to inspect the fields, during growing season, for possible sources of cross-contact with gluten.
  • Traceability – the growers need to have gluten free oat growing areas identified, along with all equipment used for those oats (harvesting, cleaning, transport, storage, and distribution).
  • Equipment Cleaning – When dedicated gluten free equipment is not used, validated cleaning methods of trucks, cutters, harvesters, augurs, and conveyors, must be used, prior to handling gluten free oats, and documented, including previous use of equipment.
  • Harvest Samples – this includes visual inspection of harvested oats, also known as seed count. It is recommended that this occurs by third party laboratory.
  • Storage – harvested oats need to be stored in dedicated gluten free containers.
  • Cleaned Samples – prior to delivery, growers perform a final inspection of the gluten free oats.

Either the grower or the purchaser of the gluten free purity protocol oats, must document the above steps and maintain the documented inspection records.

Food manufactures, including millers, processors, and packagers must adhere to the following steps, utilizing dedicated gluten free (DGF) equipment and procedures, to maintain the status of purity protocol oats:

  • DGF receiving systems.
  • DGF storage systems for holding, prior to and in-process, GF oats.
  • DGF cleaning systems for cleaning the grain, and possible portable grain cleaning equipment.
  • DGF milling equipment.
  • Appropriate air cleaning and dust removal procedures and equipment with air filter changing and/or cleaning schedules.
  • DGF pneumatic equipment/aspirators.
  • Dedicated extrusion equipment and/or written procedures, used for purging of processing equipment, with purging material volume documented and tested to not contain gluten, prior to processing gluten free oats.
  • DGF baggers and fillers.
  • DGF pre- and postprocess containers.
  • DGF transportation methods and/or procedure that document cleaning and inspection of transportation containers used to deliver product to facilities or customers.
  • Other oat sorting methods may not be used in lieu of the above practices, but additional sorting processes may be used in addition to the above-mentioned practices.
  • Prior to distribution, the final product must test <20ppm of gluten as required by international guidelines set by the Codex Alimentarius, and/or the maximum ppm limit set by country in which the product will be sold.
  • To receive the certified gluten free mark from the Gluten Free Certification Organization (GFCO), the final product must test <10ppm of gluten.


Allred, L.K., Kupper, C., Iverson, G., Perry, T.B., Smith, S. and Stephen, R. (2017), Definition of the “Purity Protocol” for Producing Gluten-Free Oats. CCHEM, 94: 377-379. https://doi.org/10.1094/CCHEM-01-17-0017-VO