DETECTION OF WHEAT CONTAMINATION IN OATS BY POLYMERASE-CHAIN-REACTION(PCR) AND ENZYME-LINKED-IMMUNOSORBENT-ASSAY (ELISA)

It is well established that the consumption of wheat prolamins causes the characteristic symptoms of coeliac disease (CD) in subjects who ar e predisposed to it. There is currently much discussion about the role of oats in the pathogenesis of CD. Evidently, it is important that oa ts used for clinical studies are not contaminated with wheat. In this study, 38 oat samples were investigated by polymerase chain reaction ( PCR) and enzyme-linked immunosorbent assay (ELISA): 30 samples consist ed of flakes or grains and 8 probes were industrially processed oat di ets. Wheat prolamin (gliadin) detection by ELISA showed that 16 of the se samples contained less than the detection limit of 0.2 mg gliadin/1 00 g dry weight; 21 samples contained less than 2.8 mg gliadin/100 g d ry weight and 1 sample reached 38 mg gliadin/100 g dry weight, clearly exceeding the allowed Swiss limit of 10 mg gliadin/100 g dry weight f or gluten-free products. Spiking experiments showed that the wheat PCR system is about ten times more sensitive than the ELISA system, provi ded that the isolated DNA is fully amplifiable. Thus, wheat DNA could be detected by the wheat PCR system in ten samples with gliadin conten ts below the detection limit of the ELISA system used. Applying a euka ryote-specific 18S-PCR system the presence of amplifiable DNA was veri fied. Only two of eight samples of industrially processed oat products contained amplifiable DNA, the other six samples had no detectable DN A left. One sample was wheat-PCR positive. However, all eight samples contained detectable amounts of gliadin in the ELISA.