The number of products marketed as gluten-free is increasing worldwide, but even with the establishment of regulations allowing such labeling; it is possible that foods labeled as gluten-free may be contaminated during processing by equipment previously used for gluten-containing foods.
Because of the high prevalence of wheat in the food supply, even products that are formulated or processed to not contain it may still contain enough trace amounts of gluten to produce symptoms in gluten-sensitive individuals. Consequently, reliable gluten testing is required for the detection of gluten in food.
Gluten (from Latin gluten, “glue”) is a protein composite found in foods processed from wheat and related grain species, including barley and rye.
Gluten is a mixture of gliadin and gluten proteins naturally present in wheat, rye, barley, and related grains, including those wheat varieties known by such names as durum (semolina), spelled, einkorn, emmer, Khorasan (Kamut), club wheat, triticale, and farro.
It is most commonly present in products made from wheat flour and in certain other food products in which it is used as an ingredient, providing elasticity in baked goods, for example, as well as texture, moisture retention, and flavor. Gluten may also be found in some cosmetics, hair products, and other dermatological preparations.
Worldwide, gluten is a source of protein, both in foods prepared directly from sources containing it and as an additive to foods otherwise low in protein
Celiac disease also referred to as celiac sprue, is a genetic disease that is said to affect about 1% of the people in North America and Europe. The immune system of people with the disease responds to the consumption of gluten by damaging the lining of the small intestine, thus interfering with the absorption of nutrients. The intestinal damage can cause weight loss, bloating and sometimes diarrhea. Eventually, your brain, nervous system, bones, liver and other organs can be deprived of vital nourishment. In children, malabsorption can affect growth and development. The intestinal irritation can cause stomach pain, especially after eating. The disease has no cure but can be managed by avoiding gluten in the diet.
Methods for Gluten Testing
The majority of tests for gluten in food products are enzyme-linked immunosorbent assays (ELISAs). Microwell versions of ELISAs provide quantitative results. Lateral-flow devices generally provide qualitative results, indicating the presence of gluten above a threshold level, but in some instances can also provide semi-quantitative results. Other types of tests include polymerase chain reaction (PCR), which detects DNA rather than protein.
ELISAs are far more specific than the other methods for gluten testing, according to Steve Taylor, Professor in the Dept. of Food Science & Technology at the University of Nebraska-Lincoln, and Director of the Food Allergy Research & Resource Program (www.farrp.org) at the university. Other sources as ATP testing are good for general cleanliness but are not as sensitive as ELISA.
The most common form of ELISA for gluten detection is the sandwich format in which the antigen (gluten proteins in this case) binds to anti-gluten antibodies that are affixed to a surface, generally a microwell plate. Then a second gluten-specific antibody—this one linked to an enzyme—is applied over the surface and also binds to any gluten that is now affixed to the surface. Finally, a substance is added that the enzyme can convert into a detectable signal, such as a color change.
Lateral flow tests for gluten testing, also known as immunochromatographic assays, are usually available in dipstick format, in which the test sample flows along a solid substrate by capillary action, the sample is applied to the strip, it mixes with a colored reagent and moves with the substrate into specific zones on the strip that contain the specific antibodies. When liquid from a sample or wet equipment surface passes over this zone, the gluten will bind to the antibody. Color also forms a line in this zone on the strip. A control zone is also usually included that will form a color that merely indicates that the strip has worked correctly. Thus, a negative test is the formation of one line while a positive test is the formation of two lines.
Regulatory Requirements for Gluten Testing
U.S. Food and Drug Administration (FDA) Center for Food Safety and Applied Nutrition (CFSAN), doing a lot of research on testing for gluten. The legal definition of the phrase “gluten-free” varies from country to country.
In the United States, the FDA considers foods containing less than or equal to 20 ppm to be gluten-free, but there is no regulation or law in the U.S. for labeling foods as ‘gluten-free’ because the U.S. Food and Drug Administration has classified gluten as GRAS (Generally Recognized As Safe).
But in several countries (especially Australia and the European Union ) new product labeling standards are enforcing the labeling of gluten-containing ingredients
The official limits described in the Codex Draft are 20 ppm for foodstuffs that are considered naturally gluten-free and 200 ppm for foodstuffs rendered gluten-free.
AOAC International has approved the method “Gliadin as a Measure of Gluten in Foods” as Official Method 991.19. This method of ELISA uses the R5 monoclonal antibody, which binds to gliadin/gluten and similar prolamins from related grains. AOAC’s Research Institute, which provides an independent evaluation of test kits, has certified R-Biopharm’s RidaScreen® Gliadin method as a Performance Tested Method. The test uses the R5 monoclonal antibody, which is recommended by the Codex Alimentarius and considered food product which contains less than 20ppm can be labeled as “gluten-free”. Food products labeled as “very low gluten” can have a gluten content above 20 and up to 100ppm.
Arbro is well versed with the molecular techniques and expertise is involved in the routine testing of Gluten in raw and processed food samples through ELISA. Contact us today for you Gluten testing needs.