ISBN 978-3-8439-0485-8

978-3-8439-0485-8, Reihe Lebensmittelchemie

Philipp Brüning
DNA-analytische Methoden zur Reinheitskontrolle von Marzipan

206 Seiten, Dissertation Universität Hamburg (2012), Softcover, A5

Zusammenfassung / Abstract

According to German food guidelines for the production of marzipan almonds are only allowed as oilseed ingredient. In many companies of the sector “Raw Pastes” cross contamination of marzipan products with “Persipan” (from apricot kernels) may occur if both products are produced. Adulterations of marzipan with other plant derived products are also known. Almond and apricot plants are closely related and therefore classical analytical methods for the identification often fail.

The objective of the dissertation was the development of DNA-analytical methods for the purity assessment of marzipan, its intermediate products and raw materials. The specific detection of apricot, bean, cashew, chickpea, lupine, pea, peach, pistachio and soy was required.

The detection of possible contaminations by PCR requires the extraction of DNA with high purity and in a sufficient quantity. Different methods from literature were screened and the extraction methods were optimised for the matrix of marzipan. The DNA extracts achieved from four different methods were characterised according to yield, purity and amplifiability. Finally a protocol was presented that guarantees high amounts and certain amplification for further purity assessment of marzipan through PCR. This method is based on a cell lysis using CTAB and DNA isolation through precipitation with isopropanol and a binding step with Silica Spin Columns.

PCR methods with species specific primer pairs were developed fulfilling the requirements of the task to control the purity of marzipan products. They are highly specific for the detection of apricot, bean, cashew, chickpea, lupine, pea, peach, pistachio and soy. For qualitative detections conventional simplex and duplex PCR methods were optimized. Additionally the real-time PCR methods based on a SYBR Green I detection can be used to quantify possible cross contaminations. To allocate the applicability to real matrices spiked raw pastes were tested. Around 0.1 % could be measured as the lowest spiked concentrations. The estimation of DNA admixtures and spiked samples showed that the matrix influences the efficiency of PCR and subsequently the final quantification results. Best results were achieved using DNA admixtures or known reference material as standards and through calculation of the total amounts with a relative quantification method.