New Russian technique uncovers meat contamination

More than 90 per cent of meat samples tested in Russia’s capital contain DNA from other species not listed on the label, including traces of human and rat, a study has revealed.

The small investigation, published in the journal Meat Science, designed a technique to identify ten meat species and tested it on 53 meat samples from supermarkets in Moscow and the Moscow Region.

The samples – which included salamis, sausages, cutlets, canned meat and frozen ready-to-cook food – tested for five commonly consumed and five commonly banned meat species, including beef, lamb, pork, chicken, turkey, cat, dog, rat, mouse and human.

According to the results analysing the technique’s performance, 49 out of the 53 samples contained meat species not listed on the label, with the most frequent adulteration being the substitution of quite pricey meat (such as beef and turkey) by chicken, which suggests economically motivated adulteration, the researchers from the Russian Academy of Sciences concluded.

A couple of samples were also found to contain trace amounts of sheep DNA, which had not been listed on the label, while DNA from rats and humans were found in two samples, in cutlets and sausages, respectively.

The researchers noted that the presence of sheep was likely to be through contamination during manufacturing or sale, while “the gross non-compliance of sanitary rules in food manufacturing and/or processing could be the only explanation for human and rat Polymerase Chain Reaction (PCR) fragments detected in samples Nos. 22 and 40”.

The research was borne out of the “serious problem” of meat adulteration, and especially the emerging Russian meat market, with the researchers noting that “a sensitive and reliable technique for meat species identification by regulatory authorities is required to prevent food fraud incidents”.

The researchers aimed to develop and assess a usable technique to identify adulteration. They decided on multiplex PCR to simultaneously detect more than one species in the meat samples.

Specifically, they designed novel primers that amplified the mitochondrial ATPase subunit 8 gene sequence regions of different lengths of the ten species tested for. The assay was validated for its specificity, sensitivity, reproducibility, and robustness.

The assay was further validated in experiments with deliberate adulteration of the samples. “The PCR amplification results for these mixes showed the assay to be capable of reliably detecting 0.1–0.2% contaminants in a mixture of various meat species, thus confirming the feasibility of the developed assay for the analysis of a voluntary adulteration and/or accidental contamination."

“The developed multiplex PCR assay proved to be specific, sensitive down to 30 pg DNA per reaction, reproducible and economical,” the researchers concluded, although they added that a more representative investigation should be undertaken to assess the extent of adulteration in retailed meat products.

The researchers, however, believed that based on the validated accuracy, specificity, sensitivity and applicability in assaying food samples, the technique was “robust and simple”, that it could be used with a variety of raw meats and processed food samples, and that it “can be easily implemented in a routine laboratory analysis without specific sophisticated equipment”.