Determining the optimal method for DNA isolation from fruit jams

Abstract

DNA extraction is a crucial step in PCR analysis especially when analysing food samples that can be degraded and can potentially contain PCR-inhibiting substances. In this study, we compared the suitability of three DNA extraction methods – two kits: DNeasy^® Plant Mini Kit and NucleoSpin^® Food, and the CTAB method – for DNA extraction from commercial fruit jams. Fourteen jams with different contents of fruit, sugar and other additives were extracted in triplicate using the above-mentioned methods directly and after a washing step. The concentration and optical density were analysed using UV spectrophotometry and the amplifiability of the obtained DNA was evaluated using a PCR assay targeting a sequence coding for chloroplast tRNA-Leu. Samples isolated using the NucleoSpin^® Food kit contained non-amplifiable DNA in eight cases, and samples isolated using the CTAB method could not be quantified. The DNeasy^® Plant Mini Kit thus proved to be the most suitable method, since well-amplifiable DNA was obtained for all the analysed samples.