3. Results
3.1. Identification of meat species by multiplex PCR
The specificity of an establishedmultiplex PCRmethod to identify
pork, beef, chicken andmuttonwas 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.