Abstract
The extraction of DNA is a critical step for species identification by PCR analysis in processed food and feed products. In this study, eight DNA extraction procedures were compared—DNeasy Blood and Tissue Kit, DNeasy mericon Food Kit, chemagic DNA Tissue 10 Kit, Food DNA Isolation Kit, UltraPrep Genomic DNA Food Mini Prep Kit, High Pure PCR Template Preparation Kit, phenol—chloroform extraction, and NucleoSpin Food—Using self-prepared samples from both raw and heat-processed and/or mechanically treated muscles and different types of meat products and pet food (pork, beef, and chicken). The yield, purity, and suitability of DNA for PCR amplification was evaluated. Additionally, comparisons between the effectiveness of various extraction methods were made with regard to price, and labor- and time-intensiveness. It was found that the DNeasy mericon Food Kit was the optimal choice for the extraction of DNA from raw muscle, heat-treated muscle, and homemade meat products from multiple and single species.
Highlights
Authenticity of species origin in food and feed products is important for law enforcement and for the protection of consumer health, as well as for economic and religious reasons
The highest DNA concentrations were observed when using extraction method G. These results could be misleading due to the particular procedure used for DNA extraction, which might have resulted in the presence of chemical reagents in the purified DNA samples because of a less thorough purification step. Such residual chemical contaminants could have caused an increase in absorbance of the DNA solution
at 260 nm (A260) absorbance measurements are sensitive to free nucleotides, ssDNAs and ssRNAs, as well as to some other organic contaminants such as chloroform and phenol [26], which can interfere with spectrophotometric analysis and may result in overestimation of the DNA yield
Summary
Authenticity of species origin in food and feed products is important for law enforcement and for the protection of consumer health, as well as for economic and religious reasons. Total accuracy is not always guaranteed by labeling. For the identification of species in processed food products, an analytical approach must be used. Most analyses target proteins or DNA molecules which are extracted from tissues [1]. As the heating or canning process (121 ◦ C, 15 min, 200 hPa) causes protein denaturation [2], DNA is a more suitable molecular marker for species authentication. DNA is degraded into small fragments during the thermal process, but these are still detectable [3]
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