A Droplet Digital PCR Based Approach for Identification and Quantification of Porcine and Chicken Derivatives in Beef

Adulteration of high-value beef with lower-priced alternatives is a world-wide problem resulting in consumers' distrust and market chaos. Therefore, effective methods for the identification and quantification of adulterated beef products are urgently needed. In this study, we developed a reliable droplet digital PCR (ddPCR) method targeting the single-copy nuclear genes for qualitative and quantitative detection of the presence of porcine and chicken derivatives in beef. A fixed constant (transfer coefficient) was introduced to directly transform the ratio of DNA copy number to the mass proportion of targeted meats. Results revealed that the linearity range of quantification for pork and chicken were both from 1% (w/w) to 90% (w/w). The limit of detection (LOD) and limit of quantification (LOQ) of the developed ddPCR method were the same for pork and chicken in beef, with LOD 0.1% (w/w) and LOQ 1% (w/w). The accuracy and applicability of the method was tested and verified using mixed samples with the known proportions and commercially available beef products. We conclude that our developed ddPCR method was accurate and reliable in identifying and quantifying porcine and chicken derivatives in beef and therefore has great potential to be applied in routine analyses and quality control of beef products.