How much gluten gets into gluten-free food in the home kitchen?

Researchers have tested the levels of gluten cross-contact caused by sharing kitchen equipment when preparing gluten free food. The details of their study have been published in an Open Access paper.

Three scenarios were tested in a simulated home kitchen environment. Gluten-free pasta was cooked in water that had previously been used to cook standard pasta; gluten-free bread was cooked in a toaster that had been used to toast wheat bread; and gluten-free cupcakes were cut using a knife that had been used to cut gluten-containing cupcakes.

The impact of several variables relating to rinsing and washing of utensils were also tested.

The gluten-free pasta cooked in gluten-containing cooking water had the highest level of gluten in it, but the researchers found that rinsing the cooked pasta under running water largely removed this. It should be noted that, while the gluten levels were reduced to below 20ppm, there is currently no clear consensus on the safe amount of daily gluten intake for those with coeliac disease.

Using a shared toaster resulted in minimal transfer of gluten to gluten-free bread (~5-8ppm), even when there was visible accumulation of gluten-containing crumbs in the toaster pans.

Sharing a knife to cut both gluten containing and gluten-free cupcakes also resulted in gluten transfer but in the majority of samples this was below 20ppm. Two gluten-free samples (out of a total of 30) had more than 20ppm gluten after being cut with the used knife. When the knife was either rinsed or washed with soap and water between uses, no gluten transfer occurred.

The authors hope their study will help to put the risk of gluten cross-contact into perspective for those who live with or care for people with coeliac disease. Acknowledging the poor quality of life for many with this condition, this small-scale study provides early indication that good kitchen practices and normal washing can largely preserve the integrity of gluten-free food prepared at home.

Reference: Weisbrod et al. 2019. Gastroenterology. DOI: 10.1053/j.gastro.2019.09.007. This paper is available with Open Access.