DNA-based methodologies have become a powerful tool for food analysis, the detection of potential adulteration, and as a deterrent to economically motivated adulteration.
Traditionally, most methods usually target either a single or a small number of ingredients, and were based on polymerase chain reaction (PCR) amplification. This kind of targeting requires prior knowledge about which organism to search for and can be restricted by the narrow range of commercially available test kits. The results obtained by direct PCR detection produce presence/absence results for the targeted species, but no additional information is obtained—such as whether any other species is present in the sample.
At the end of an NGS analysis, millions of individual sequences are obtained, making it possible to identify species in complex foods containing multiple ingredients. This is because each ingredient will produce a single and unique DNA sequence. Following comparison with databases (containing several thousands of species) NGS generates a complete list of all the species present in a sample, including each species’ scientific name.
Currently, NGS is the only test method that ensures the correct identification of species in complex foods, due to the untargeted nature of the method. As a result, this method is increasingly popular and is being applied routinely in food authenticity analysis.
NGS techniques can also overcome the issue of DNA fragmentation caused during the manufacture of highly processed food products. Fragmented DNA caused by many manufacturing processes, like the high temperatures and/or pressures used for sterilisation, damage DNA and produce very short DNA fragments.
An NGS approach, optimised to work with those short fragments, avoids false negative results. Although the DNA sequences must still be informative enough to discriminate among closely related species. The DNA sequence analysis takes advantage of the uniqueness of DNA sequences for each organism. Each different species has its own DNA sequence that can be used as a unique identifier, and is commonly designated as a ‘DNA barcode’.
It is easy to see why NGS is becoming increasingly useful and powerful. It offers a way to check the robustness of controls for a large number of steps in a process, or to reduce the risk of undiscovered fraud when the number and variability of suppliers impacts the supply chain.