A DNA-based approach to discriminate between quince and apple in quince jams

Authentication of food products is of primary importance for consumers and industries. They expect that product labeling represents its true identity. However, in many cases, either accidental or fraudulent substitution occurs. Molecular biology based methodologies are acquiring great interest for their applicability to track a given item at any stage along the food supply chain. PCR analysis allows the identification of DNA traces that may remain in a given food matrix from the principal component and/or from contaminants. This work describes a novel experimental protocol to extract, amplify and identify apple DNA from commercially available quince jams. Aiming to extract DNA from this complex matrix, a DNA extraction method was developed, based in reagents such as CTAB and PTB, that minimize the amount of contaminants co-precipitating with DNA and thus reducing PCR inhibition. In order to identify apple DNA in quince jam, two molecular methods based on the amplification by PCR and RFLP analysis of the highly conserved chloroplast gene maturase-k (matk), were developed. The results obtained show the presence of two distinct species Cydonia oblonga (quince) and Malus sp. (apple) in all commercial quince jams analyzed. This study represents an advance in DNA methodologies for the detection of fraud and/or contaminants in this complex food matrix.