Recent advances in plant biotechnology have established transgenic wheat lines, which are almost ready to be cultivated for commercial production in the field. Wheat flours are used as ingredients in many food products. Here, in order to detect genetically modified wheat in processed foods, the yield and fragmentation of genomic DNA prepared from processed foods were investigated. Qualitative PCR using primer sets that gave 96-755 bp PCR products at ca. 100 bp intervals showed that in fermenting processes by yeast and baking processes for breads and buns, including steaming and frying, DNA fragmentation of less than 430 bp did not occur. Amplicons longer than 755 bp were found in all noodles, but roasting and retort processes to produce stews caused severe degradation of genomic DNA leading to fragmentation and reduced yields. A Japanese traditional sweet, kuzumochi, which is processed by Lactobacillus fermentation with kneaded flours for a year, gave amplicons shorter than 323 bp. These results indicated that PCR detection methods for transgenes in wheat processed foods should be established using primer pairs that target DNA sequences shorter than 200 bp.
