Effect of Thermal Treatment on the Amplification and Quantification of Transgenic and Non-transgenic Soybean and Maize DNA

Abstract

Processing of raw plant materials causes occurrence of degraded DNA in foods. The effect of DNA degradation on amplification and quantification of transgenic and non-transgenic DNA in raw and experimentally thermally processed foods was studied. The degree of DNA degradation was checked by agarose gel electrophoresis and polymerase chain reaction (PCR). Cetyl trimethyl ammonium bromide method yielded DNA of a better quality, while Genespin and Wizard were less appropriate. Baking at 220°C considerably reduced the size of DNA fragments. In order to measure the length of amplifiable DNA, primers for soybean and maize genes were used. Small DNA fragments ranging from 100 to 200 bp were amplified in all samples. DNA fragments over 1 kbp were amplified only if heating at 220°C lasted less than 30 min. Baking of flour (220°C) reduced the size of extracted DNA fragments so that 1,100 bp amplicon was no longer amplifiable, while the amplicons of 913 and 1,100 bp were obtained from the baked bread. When PCR assays targeting maize high mobility group and zein genes were used under the same conditions, analogous results were achieved. Quantification of genetically modified organism content was not influenced by baking.

The Effect of Heat Processing on PCR Detection of Genetically Modified Soy in Bakery Products

“…Although the purity values of the extracts that we obtained were between 1.06 and 1.34, the detection of the lectin sequence in all the extracts proved that they contain amplifiable quality DNA. Similar to our results, the purity values of the DNA extracts that Bergerova et al (2010) obtained from baked soy flour samples were between 1.10 and 1.38.…”

“…The mean DNA concentration that we obtained with the Wizard ® Magnetic DNA Purification System for Food was 84.8-213 ng/µL (Table 1). These values were significantly higher from those reported by Bergerova et al (2010), who reported that the DNA concentration they could obtain with the same method was 20-70 ng/µL. This difference may be attributable to the higher sample portion that we used.…”

“…According to Pauli et al (2000), the DNA concentration in highly processed soy samples was higher. Bergerova et al (2010) also determined that the DNA concentration of soy flour boiled for 30 min was higher than that of samples boiled for 7 and 15 min. Their results also showed that the DNA concentration decreased in parallel with the boiling time.…”

“…Several different extraction methods have been recommended for different food matrixes so far (Peano et al, 2004;Taski-Ajdukovic et al, 2009;Tengel et al, 2001). However, various factors such as the matrix type and processing conditions influence the performance of the extraction methods (Bergerova, et al, 2010;Gryson, 2010;Peanoet al, 2004). At the beginning of this study, we used the cetyltrimethylammonium bromide (CTAB) method, which had been modified to start with 1 g of sample (Ozgen Arun et al, 2013).…”

“…The identification of novel DNA sequences or proteins is the main principle of such detection methods (Ahmed, 2002;Greiner and Konietzny, 2008;Lipp et al, 2000;Miraglia et al, 2004;Taski-Ajdukovic et al, 2009). However, because proteins are sensitive to most food processing factors, proteinbased methods do not serve as sensitive and reliable tests for processed products in many cases (Ahmed, 2002, Bergerova et al, 2010. Because DNA is more resistant than proteins to such processes, DNA-based methods are more widely used for this purpose (Greiner and Konietzny, 2008;Taski-Ajdukovic et al, 2009).…”