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PCR Amplification of Wheat Sequences from DNA Extracted During Milling and Baking

¹USDA-ARS Grain Marketing and Production Research Center, 1515 College Avenue, Manhattan, KS. E-mail: mtilley@gmprc.ksu.edu Mention of firm names or trade products does not constitute endorsement by the U.S. Department of Agriculture over others not mentioned. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.

DNA-based analyses are highly sensitive and specific. Because processing steps can have profound effects on the proteins and DNA present in foods, this project examined the effects of breadmaking on wheat DNA size and polymerase chain reaction (PCR)-based detection of sequences. DNA was extracted from wheat kernels, milling fractions, and flour, and from samples taken at various steps during and after the baking process. Kernels contained primarily high molecular weight DNA (>12,000 base pairs [bp]), whereas flour DNA exhibited a broad range of molecular weights from >12,000 bp to <300 bp. A marked reduction in DNA yield and size occurred after the first 5 min of baking. PCR successfully amplified products of both high and low copy number genes, even from DNA extracted from bread loaves five days after baking. However, successful amplification required that the maximum product size be no more than the average molecular weight of the DNA recovered from the source. The data also demonstrate that PCR can be used to detect the presence of yeast (Saccharomyces cerevisiae), a minor ingredient.