NSF’s technique was developed to work with old, degraded DNA pieces, or very small fragments of DNA. The method uses targeted DNA primers to definitively identify species through a polymerase chain reaction, or PCR, technique that amplifies DNA segments of interest, or those segments that uniquely identify a species. Primers are like a probe that is made specifically to target a particular species to allow replication of DNA. To develop primers capable of identifying species in processed and degraded products, NSF scientists reverse engineered these primers from known DNA sequences of the target species.
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Creating primers requires advanced knowledge of the biology, evolutionary history, and DNA of the target and closely related species. NSF developed specific primers using a proprietary database of thousands of validated DNA reference sequences obtained from museum specimens through partnerships with academic institutions and botanical gardens. NSF sequenced the source DNA of these specimens and determined which regions of the genome (genes) are unique identifiers for each of the target species of interest. Next, NSF designed primer sets to amplify the specific gene region of interest to use in NGS.
Identification for Seafood
DNA barcode methods are appropriate for testing and identifying seafood and meat because a single gene region can be used to differentiate and ID a wide range of different animal species. The U.S. FDA has validated a single gene region or barcode, and created specific guidelines for the DNA barcode testing of seafood. Plant species, on the other hand, have more than one gene region critical for identification, and due to hybridization, one plant genus can contain thousands of species, whereas most animal (mammal and fish) genera contain only a few species in comparison.
Unlike DNA barcoding, however, NSF’s NGS can use the single gene region and sequence it many thousands of times from a single sample. Therefore, instead of identifying a single species in a material—which would be appropriate for a whole fish fillet—NGS can identify all elements of processed or ground products (like crab cake or fishmeal), including fillers (such as soy protein, rice flower, and maltodextrin), binder starches, contaminants, undeclared additives, and any other animal species.
DNA Testing in Quality Control
Integrating DNA testing as a standard of quality control can help food companies create a “first line of defense” against adulteration and fraud. Testing all or sample lots of incoming raw materials ensures they are the correct species and free from harmful adulterants, and can also help companies verify suppliers.
The cost of DNA testing is comparable to other analytical testing methods, but is more accurate at detecting adulteration. DNA tests identify over 25 percent of routine samples as adulterated or substituted, most commonly by unexpected species and by closely related species not detected by other testing methods.
Additionally, DNA testing assures that finished products are “pure” by screening for the presence of labeled ingredients and the absence of allergens, fillers, and GMOs. The best way to ensure products are pure is to test raw ingredients, but knowing what is on the shelf is also important.
Dr. Reynaud is global director of scientific innovation for NSF International and co-founder of NSF AuthenTechnologies. She is a botanical taxonomist and geneticist with over 15 years of DNA testing experience. Reach her at firstname.lastname@example.org.