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Gluten tag? Common restaurant practice transfers gluten to gluten-free pasta
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Gluten helps hold together and give shape to many food products derived from wheat, barley and rye. But the naturally occurring protein can also trigger an autoimmune response — celiac disease — that eats away at the lining of the small intestine in roughly 1% of people.
Pasta is among the gluten-containing foods for which gluten-free alternatives have been developed. The U.S. Food and Drug Administration allows packaged foods to be labeled as gluten-free if they contain less than 20 parts per million gluten. Yet in a recent study, consumers using handheld devices reported that 50% of supposedly gluten-free pastas being served in restaurants exceeded the 20 ppm threshold.
Melanie Downs, Jennifer Clarke, Steve Taylor and then-UCARE (now doctoral) student Nate Korth wondered whether the unexpected levels of gluten in “gluten-free” pasta might stem from the fact that restaurants commonly boil different types of pasta in shared water. So the Nebraska team ran an experiment to assess whether gluten from traditional pasta could infiltrate the gluten-free under that condition.
First, the researchers boiled three 52-gram, package-recommended servings of traditional penne pasta in the same water as a 52-gram serving of gluten-free penne, repeating the process with four more batches. Then they did it all again — only this time, each serving was restaurant-sized, weighing in at 140 grams.
While gluten levels in the gluten-free penne did rise slowly when boiling 52-gram servings over the course of five batches, those levels never exceeded 20 ppm. When boiling restaurant-sized servings, though, the gluten-free penne registered nearly 40 ppm after the fifth batch.
Replicating the experiment, and varying its conditions, could help better quantify the rate of gluten transfer among pastas, the researchers said. But given the initial findings, the team recommended that restaurants prepare gluten-free pastas separately from their traditional, gluten-containing counterparts.