LAUSR

Abstract A duplex droplet digital PCR (ddPCR) is described for the detection and quantification of contaminations by common wheat (Triticum aestivum) in food products made from spelt (Triticum spelta). A single nucleotide polymorphism (SNP) in the locus Q, as well as a short sequence of the γ-gliadin gene of the wheat genome are exploited for the development of our duplex ddPCR method. Minimal variations of DNA sequences causing different probe hydrolysis efficiencies during PCR amplification can be detected and evaluated in ddPCR. By utilizing the SNP in the locus Q, all 84 tested spelt cultivars could unambiguously discriminated from common wheat cultivars. Discrimination using the γ-gliadin gene sequence could be achieved for 10 of 84 spelt cultivars. Additionally, we could show that impurities caused by common wheat can also be detected in einkorn wheat (T. monococcum) and in emmer (T. dicoccon). For the quantification of contaminations by common wheat in food products from spelt, we prepared flours, vegetarian burger patties and bread based on defined proportions of spelt and common wheat. These materials were tested in three different laboratories using in-house DNA extraction methods and a predefined ddPCR protocol. The results indicated precise quantification of common wheat in spelt and a low relative measurement uncertainty of the ddPCR method without the further use of reference material for calibration.