One Decision: A Limit of Gluten Detection

This is part of a series of blog posts on decisions we’ve made in the course of business, to provide some insight into our business and product development process. Posts are not chronological. This post examines how we determined our level of gluten detection.

a gluten-free hamburger about to be tested for gluten

Once Nima is in the hands of consumers next year, everyone will be eager to see a smiley face looking back at them after testing their food for gluten. But what does the smile emoticon actually mean?

We spent a year developing our own custom antibody for gluten. The detection is based on a type of assay called an immunoassay. These assays take advantage of protein antibodies, which are able to specifically recognize a single target of interest – in our case, gluten. A small amount of gluten will trigger the antibody to bind to the gluten molecule which we can detect and display with the device – the smile or frown emoticon you see. A frown for detected gluten, a smile for “gluten-free.”

As we worked toward our detection efforts for gluten, we had to decide how sensitive our test would be and what would appear as a negative result.

Nima’s Level of Detection

We are aiming to detect gluten at 20 ppm, meaning if the display shows a negative result for gluten, the sample has less than 20 ppm of gluten.

Why 20 ppm?

There are a few considerations we had to make when choosing a limit of detection. First, we noted that while individuals have sensitivities and/or reactions to different levels of gluten, there is currently no way to determine a gluten tolerance level on an individual basis (lest you make yourself sick to find out).

As a result of this range of consumer reaction levels, consumers have looked to various regulatory agencies to define what gluten-free means. This way, food manufacturers and preparers can be held to specific standards. However, countries differ on what defines a food as gluten-free, and some people react to levels below these guidelines.

In August 2013, the U.S. FDA issued a gluten-free labeling rule specifying that a food can only be labeled as “gluten-free” if it contains less than 20 ppm of gluten. The U.K. has the same rule, while Australia and New Zealand have less than 5 ppm as their standard for gluten-free.

Since we’re launching Nima in the U.S. first, the U.S. FDA ruling of less than 20 ppm is the best guideline that we currently have for labeling which foods are gluten-free.


PPM is an abbreviation for “parts per million.” This measurement is the mass of a chemical or contaminate per unit volume of water. One ppm is equivalent to the absolute fractional amount multiplied by one million. A better way to think of ppm is to visualize putting four drops of ink in a 55-gallon barrel of water and mixing it thoroughly. This procedure would produce an ink concentration of 1 ppm. Here is a video that helps give other examples of ppm concentrations.

Say you have a piece of gluten-free bread that has been cut with a knife that was also used to cut whole-wheat bread. If you test the part of the bread that the knife touched, the ppm of gluten will be high because that whole piece is covered in gluten. However, if you take the whole piece of bread and test it for gluten, the gluten from the knife is dispersed throughout the whole sample and may come out as less than 20 ppm, which is gluten-free by FDA standards. Will the whole piece of bread cause a reaction for someone with celiac disease or a gluten allergy? The piece that touched the knife is not gluten-free, but technically the whole piece of bread is.

From our own restaurant food testing, we have seen results come back both ways – either a sample has higher ppm of gluten and the entire dish is considered gluten-free, or a sample is gluten-free and the entire dish comes back with a higher ppm of gluten, meaning the plate was elsewhere contaminated.

Therefore, it’s important to understand that Nima will tests just one sample from your dish. The risk of cross-contamination remains for any food you did not sample, and folks with allergies, celiac disease or other sensitivities should always proceed with caution even if a test comes back negative for gluten. Each person is different.

Other Allergens

Limits of detection will get trickier as we expand to other allergens for Nima. One challenge of peanuts, milk, shellfish, soy and others is that regulatory agencies have not defined any thresholds for allergen levels that are sufficient to cause an adverse reaction in the allergic population. Without a better understanding of such a threshold, it’s difficult to choose a limit of detection for our assay. We are consulting with regulatory agencies to better understand the problem and to propose a reasonable limit of detection that would cover a majority of cases. For example, if 99 percent of the peanut allergic population is responding to a certain peanut level, we should try to meet or exceed this level of detection in our test.

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