Gluten-free and wheat-based crackers hung out together: Will the Nima Sensor pick up any cross-contact?
One of Gluten Free Watchdog’s criticisms of the Nima Sensor is that it is unlikely to pick up uneven cross contact in a food sample that has not been homogenized—ground up in a blender for example—prior to testing. To help address this issue the Nima Now team suggests using, “the teeth on the bottom of the capsule cap to dab food from different areas of your plate.” Let’s see how well that works…
A labeled gluten-free mini rice cake and a wheat-based cracker were put into a baggie. The crackers were left together for about one month. This wasn’t intentional. It just took some time to get around to testing.
Prior to the first test, the crackers were removed from the bag. A pea sized amount of the rice cake was place into the Nima Capsule. The capsule cap teeth were moved around the rice cake to hopefully pick up any wheat-based crumbs. The test result was a smiley face meaning no detectable gluten found. The capsule was removed from the sensor to check the test strip. The strip result was negative for detectable gluten. In other words, both the sensor reading and the test strip reading matched.
For the second test, a piece of the wheat cracker was smushed into crumbs between two fingers and mashed into the rice cake. A pea-size amount of the rice cake was placed into the test capsule. The capsule cap teeth were moved around the rice cake to hopefully pick up any wheat-based crumbs that had been mashed into it. The test result was a smiley face.
But was the result really no detectable gluten found? The capsule was removed from the sensor to check the test strip. The strip indicated that gluten was in the sample (light red bottom line). In other words, the sensor reading and the test strip reading did not match.
The sensor returned two smiley face results suggesting that no detectable gluten was found in the sample. But the actual test strips told a different story. Recommendation—if you test foods with a Nima Sensor, remove the capsule from the sensor immediately after getting a sensor result and check the test strip. Putting aside the issue of false positives, if you see three lines, meaning a test line is present, this indicates there is gluten in the sample regardless of whether the sensor reading is a smiley face. Addendum 4/7/26: The Nima Now website states that the sensor reading should be relied upon over a reading of the LFD test strip by the naked eye, even stating that, ‘What looks like a faint pink line to the eye may still correspond to a “No Gluten Found” result.” However, as we stated in our J AOAC Int. article, “… in the manufacturer validation of the sensor, it appears that visual readings of the test strips were used to validate the sensor readings (i.e., smile, gluten found).” See validation report.
Note: We have only one Nima testing capsule remaining. We do not anticipate purchasing more capsules for testing unless additional issues are brought to our attention.
Comments (3)
Thank you!
Tricia, thank you for your scientific mind and some creativity in devising this “test”. In the case with the 1st test, if I suspect or know that a gluten containing product has cozied up to a GF product, that’s enough for me to leave it alone, REGARDLESS of what the Nima Sensor indicates. The results of the 2nd test just re-confirm my belief that the lateral flow devices are: 1. not reliable, 2 not consistent, and 3. not accurate. The risk is way too high compared to my own investigative and communication skills. It amuses me to imagine dabbing the teeth of the capsule around my dinnerplacte at a restaurant or other social event in hopes of picking up random gluten to test. It’s not practical and it’s not realistic.
I want to thank the scientists, engineers and inventors of the Nima Sensor and similar devices for their efforts in bringing to market a gluten testing device for the individual consumer. Unfortunately, it is not an option for me.
Thanks for commenting, Bonnie. I know you know this, but just to be perfectly clear, the two crackers were placed together for experimental purposes only. Taking a random sample of rice cake and using the capsule cap teeth to dab around the rice cake clearly didn’t work to pick up cross contact. The smiley face result should not be interpreted to mean it is safe to eat a gluten-free product that has been touching a gluten-containing product.
Lateral flow devices when developed by labs and used by industry have their place in the food testing world (lateral flow devices from R-Biopharm for example). Here is the link to a brochure for the RidaQuick Gluten LFD https://food.r-biopharm.com/r-biomedia/ral7073-rq-gluten-quant-2p/. Notice how it reads, “1 gram homogenized sample.” This is the first issue the developers of the consumer LFDs must come to grips with–if a tiny sample is tested from a larger non-homongenized sample (i.e., a sample that has not been mixed, ground, etc. to evenly distribute any gluten present in the sample), the result tells you next to nothing about the gluten content of the food or meal. Unfortunately, this issue is generally ignored by those in the consumer LFD space.