Abstract
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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References
Glössel K (2004) Unterscheidung von Marzipan und Persipan mittels Polymerasekettenreaktion. Technische Universität Graz, Graz
Weber W, Hauser W (2007) Bestimmung von Aprikosenkernbestandteilen in Marzipan und Maripanvorstufen mittels Realtime-(Sonden)-PCR; Deutsche-Lebensmittelrundschau 103. Heft 9:416–419
Brüning P (2012) Dissertation universität Hamburg: DNA-Analytische Methoden zur Reinheitskontrolle von Marzipan, 1st edn. Verlag, Hut
Haase I, Brüning P, Matissek R, Fischer M (2013) Real-time PCR assays for the quantitation of rDNA from apricot and other plant species in marzipan. J Agric Food Chem 61(14):3414–3418
Schelm S, Haase I, Fischer Ch, Fischer M (2017) Development of a multiplex real-time PCR for determination of apricot in Marzipan using the plexor system. J Agric Food Chem 65(2):516–522
Van Gansbeke B, Bény G, De Loose M (2018) Taverniers I (2018) A TaqMan real-time PCR assay for apricot (Prunus armeniaca) as an authenticity test for detection of traces of persipan in marzipan. Food Anal Methods 11:62–68
Köppel R, Ganeshan A, Weber S, Pietsch K, Graf C, Hochegger R, Griffiths K, Burkhardt S (2018) Duplex digital PCR for the determination of meat proportions of sausages containing meat from chicken, turkey, horse, cow, pig and sheep. Eur Food Res Technol 245:853–562. https://doi.org/10.1007/s00217-018-3220-3
Morisset D, Stebih D, Milavec M, Gruden K, Zel J (2013) Quantitative analysis of food and feed samples with droplet digital PCR. PLoS ONE 8(5):e62583
Floren C, Wiedemann I, Brenig B, Schütz E, Beck J (2015) Species identification and quantification in meat and meat products using droplet digital PCR (Dpcr). Food Chem 15(173):1054–1058
Köppel RM, Dvorak V, Zimmerli F, Breitenmoser A, Eugster A, Waiblinger HU (2010) Two tetraplex real-time PCR for the detection and quantification of DNA from eight allergens in food. Eur Food Res Technol 230:367–374
Acknowledgements
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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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). https://doi.org/10.1007/s00217-020-03463-6
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DOI: https://doi.org/10.1007/s00217-020-03463-6