Video: Testing Foods for Gluten

Video: Testing Foods for Gluten

At Gluten Free Watchdog we are frequently asked about how foods are tested for gluten. In this video I explain the protocol we follow and how we decide what assay and extraction solution to use. Note: I have been asked to provide a transcript for all of the videos. These videos are “off the top of my head.” A transcript is not available for this video. Update: A wonderful subscriber to GFWD who happens to do transcription professionally volunteered to transcribe this video. Thank you to Corbin’s mom! For the time being the transcription is included in the comments section.


Share this post

Comments (7)

  • Bonnie Reply


    I find these videos very helpful; they are great to reference time and again. Thank you for making them.


    August 9, 2016 at 8:09 pm
    • Tricia Thompson Reply

      It is so good to hear that you find the videos helpful, Bonnie! I will continue making them as time allows.

      August 10, 2016 at 1:43 pm
  • Ann Reply

    I too find these videos extremely informative and enjoy them. You have mentioned the “low budget production” of them. I like them all the more for that aspect. It makes them feel more user friendly and like you are connecting with us on a more personal level.
    I am so happy we have you who understands all the intricacies of testing and makes sure everything gets done correctly.

    August 11, 2016 at 5:01 pm
  • Bonnie Reply


    I agree with Ann – on the low-budget production aspect. It is as if you have invited us to share a cup of tea around your kitchen table while informally sharing/teaching the “ins and outs” of the often complicated yet vital issues at hand. Thank you, once again.

    August 16, 2016 at 6:29 pm
  • Tricia Thompson Reply

    A wonderful GFWD subscriber (aka Corbin’s mom) volunteered to transcribe this video. Please know that I speak differently than I write (and I am resisting the urge to “rewrite” this transcript). Please use this transcript in conjunction with the video.

    Video transcript: Testing Foods for Gluten

    Hi, everyone. This is Tricia Thompson from GlutenFreeWatchdog.

    We get a lot of questions about testing so I thought it would be helpful for me to run you through the protocol that we follow at GlutenFree Watchdog when we receive a product request. Typically these requests come from subscribers. Products are purchased either at a store in Massachusetts, or they are ordered through Amazon, or Vitacost, or the manufacturer website. Once we have the product in hand, it takes up some space on a shelf in my office until we’re ready to ship it to the lab. Before shipping it to the lab, a lot of information is recorded from the product packaging. This includes the lot number, the ingredients list, whether or not there’s a contain statement for wheat, a may contain statement for wheat. What the gluten free labeling claim looks like. Is there a certification symbol for gluten.

    So once all of this information is gathered, the most important piece of it before we send it off to the lab is the ingredients list. The ingredients list is used to inform us of the test that we have to request from the lab. And so typically what we do, this is a submission form. This is the form for Bia Diagnostics, the lab that we use. And the specific tests and testing procedures are recorded on this form and it accompanies the product to the lab. So, this is a product that’s in the immediate que for testing. And if I look on the ingredients list, one of the things that I notice that it contains is cocoa. And I’ll explain why that’s important in just a minute. But keep that in mind, the cocoa. So the first decision we have to make is whether or not to test using the Sandwich R5 ELISA, which tests for intact gluten protein or the Competitive R5 ELISA, which tests for hydrolyzed gluten protein. Protein that’s been broken down, protein fragments.

    So once that decision is made and sometimes we do have to test with both the Sandwich and the Competitive R5 ELISAs. But once that decision is made, we have to decide on the extraction solution. Now the extraction solution that’s always used with the Sandwich R5 ELISA is called the cocktail extraction. But sometimes different materials – I don’t know if materials is the best word, but different substances are added to that cocktail extraction to help prevent either false positives or false negatives. So looking back at this product and the fact that it contains coca, this product – the cocoa in this product contains tannins. As a result, when the lab is extracting the gluten, they have to add a skim milk additive to that cocktail extraction solution to guard against a false positive or a false negative. Now, sometimes when we’re using the Competitive R5 ELISA, fish gelatin has to be added to the ethanol extraction purposes. To help guard against false positives and false negatives.

    And one of the more recent things that is being done when we test anything containing a bacteria or an enzyme in large quantities, like a probiotic or an enzyme supplement, those bacteria and enzymes must be neutralized before that product can be tested or again, we could get false positives or false negatives. There are other things that we consider, but that covers a lot of it. So the product is sent to the lab. The product is tested following whatever procedure we’ve determined. We get the results back and the process doesn’t really stop there. I mean the results are scrutinized for any red flags. Does anything not look right? Do we have one extraction that’s high and one extraction that’s low? And the other thing is that even though we only report out two extractions, actually four extractions are tested per sample. And this is because two of the extractions are done using another extraction solution that serves as a check to the cocktail extraction.

    So if we have four extractions and one tests high, even if it’s not the cocktail extraction, that raises a red flag sometimes that we need to look further at that product. Was that high result due to a hot spot? Was it a false positive? Does the sample need to be homogenized a bit more? And so typically what happens is that we will do additional testing on that product. In fact, that’s being done on the product that’s at the lab right now. So I hope this helps a little bit and it helps you understand how very complicated testing can be. It’s not an easy process.

    And if you have any questions, please feel free to send me an e-mail, post a comment and I will try to clarify. I do understand that testing is very, very complicated. Thank you so much.

    August 31, 2016 at 6:45 pm

Leave a Reply

Your email address will not be published. Required fields are marked *