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Duplex digital droplet PCR for the determination of apricot kernels in marzipan


Marzipan is a mixture of almonds, sugar, and water. Almonds can be replaced by apricot kernels, which results in a similar product called persipan. Depending on the prices of almonds, profit can be maximized using apricot kernels instead of almonds. If not specified on the product, this kind of substitution is illegal and is prosecuted by official food control authorities. Likewise, also commercial buyers would like to know which product they bought. Real-time PCR systems for the determination of apricot DNA are already available, however, real-time PCR requires the use of external standards, which have a direct impact on the accuracy of the measurement. Currently, such standards are not available. In contrast to real-time PCR, digital PCR does not require external standards and exhibits a smaller measurement uncertainty as shown in recent publications. Therefore, we developed a duplex droplet digital PCR system to measure the proportion of apricot in marzipan without the use of external standards. We present validation data and results of an international proficiency test, underlining the applicability of this system.

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We thank all the participants of the proficiency test for their participation: Official Food Control Authority of the Kanton Zürich, Zürich Switzerland, State Institute of Chemical and Veterinarian Analysis Freiburg Br, Germany, impetus bioscience, Fischkai 1, 27572 Bremerhaven, Germany, Service de la consommation et des affaires vétérinaires 5, Rue Jehanne-de-Hochberg, 2000 Neuchâtel, Switzerland, Stilla Technologies, Villejuif BioPark, 1 Mail du Professeur Georges Mathé, 94800 Villejuif, France; Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, Molekularbiologie (LH), Veterinärstr. 2, 85764 Oberschleißheim, Germany

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Correspondence to René Köppel.

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Köppel, R., Ledermann, R., van Velsen, F. et al. Duplex digital droplet PCR for the determination of apricot kernels in marzipan. Eur Food Res Technol 246, 965–970 (2020).

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