Identifying Exogenous DNA in Liquid Foods by Gold Nanoparticles: Potential Applications in Traceability

Quality control of food products requires the development of powerful analytical tools and regulations to avoid fraud to consumers and ineffective product recalls. DNA barcoding represents a potential strategy for application in food traceability, which involves the use of exogeneous short DNA oligonucleotides (DNA markers) for tracing the origin of food, such as suppliers, producers, attributes, and points of distribution. However, it is generally considered that exogeneous DNA molecules are strongly shielded by complicated interactions with intrinsic ingredients and easily degraded in complex food systems. This consideration leads to the lack of analytical methods to readily identify DNA markers in food, thereby preventing one from exploiting the barcoding capability of DNA markers in food. In this work, we explored the applicability of DNA markers coupled with rapid DNA detection by gold nanoparticles to traceability of various liquid foods, including wines, condiments, and soft drinks. Our results revealed that the gold nanoparticles afford colorimetric identification of DNA markers in liquors, condiments, and milk with a quick (≤5 min) "yes" or "no" readout depending on the solution color. Importantly, the DNA markers stored in these liquid foods remain chemically stable and bioactive in hybridization within months, thereby allowing for barcoding liquid foods with considerably long shelf lives. Given the nutritional value of nucleic acids and the direct DNA identification avoiding complicated isolation and analysis, the present work could provide a practical approach to food traceability.