Quantitative determination of mutton adulteration with single-copy nuclear genes by real-time PCR

Mitochondrial genes were generally adopted for PCR-based meat adulteration authentication due to their excellent specificity to species and numerous copies in one cell. However, the number of mitochondrial gene copies varies according to cells and tissues, which leads to quantification errors for meat adulteration. To address this problem, single-copy nuclear genes were selected to develop a quantitative method for identifying mutton adulteration in this study. Both single-copy genes specific to sheep species and single-copy reference genes show good linearity between Ct values and series diluted DNA concentrations, with the correlation coefficients of 0.9999 and 0.9993, respectively. Meanwhile, a constant (correction factor) was introduced to transform DNA concentrations into mutton proportions in adulterated meat. With this method, simulated mutton-pork, mutton-chicken and mutton-duck adulteration samples could be accurately quantified with the recovery rates of 89.56%, 107.13% and 95.20%, respectively.