Results
3.1. Identification of meat species by multiplex PCR
The specificity of an established multiplex PCR method to identify pork, beef, chicken and mutton was verified. Fig.1was the nucleotide sequences of the primer targeting regions on cytochrome b gene. As
shown in Fig. 2A, the various combinations of target meat species could be simultaneously detected without cross-reaction with donkey, horse, fish and soybean. The bands of amplified fragments were at the expected size. The LOD for each species was 0.1 ng (Fig. 2B). Then, a test panel including 255 processed food sampleswas submitted to identify the target meat species. In half-cooked meats, cooked meats and further processed foods, undeclared meat species were found in 13.3%, 17.6% and 19.4% of cases, respectively (Table 1). These undeclared species were all pork or chicken substituting beef or mutton. For instance, nearly half of the mutton shashliks were produced by chicken or pork, and some ready-to-eat beef products were actually pork treated with essence. However, in the furtherprocessed food, 25.0% of the samples, including 21 dried meat flosses, 4 dried meat slices and 2 beef sausages, could not been
identified using this multiplex PCR method.