DNA Barcoding as a screening tool in the labelling analysis of Caviar Products Sold on Chinese e-commerce market

Caviar is a valuable seafood delicacy consisting of salt-cured roe of sturgeon and paddlefish species included among CITES endangered species and extensively farmed internationally. To cope with both overexploitation and counterfeits due to substitute and mimicking products, CITES implemented a labelling system bearing the mandatory information for caviar traceability and identification [1]. Counterfeits triggered the development of DNA based authentication techniques and DNA barcoding, among the approaches, represents an effective screening method in fraud monitoring [2,3]. Thus, the present study was set to verify the labelling compliance of the available products on the Chinese e-commerce platforms, potentially exposed to counterfeiting, to the requirements of the Chinese labelling standard (GB7718-2011) in force for pre-packaged food and CITES requirements [1]. In the study, a DNA barcoding approach targeting COI and cytb genes was applied as screening method [3] to highlight the occurrence of counterfeit phenomena and to verify labelling information validity. Forty caviar products were collected from one major e-commerce platform and the labelled information were checked against both national and international requirements. The final COI or cytb barcodes were queried against BOLD and NCBI reference databases and final identity values >98% or 99-100% were respectively applied to designate potential species identification [4,5]. DNA barcoding outcomes were compared to the labels analysis results to assess the occurrence of substitution and mislabelling incidents. All products were found fully compliant to GB7718-2011 standard and were verified belonging to Chinese producing plants. Conversely, CITES requirements were never satisfied and no references to either the production method (wild catch or aquaculture) or the origin of the roes processed for caviar production was reported. Nevertheless, the 32.5% of the products presented an explicit reference to the roe sturgeon species or hybrid. No counterfeits emerged by Barcoding analysis and all the products were confirmed belonging to sturgeon. Despite Barcoding ascertained limits in Acipenser sp. species discrimination and in commercial hybrids identification (2, 3), 42.5% of the products were finally found not matching the product expected identity according to the label information. The need to promote the application of CITES labeling system on the Chinese market clearly emerged by the study to protect both consumer interests and products sustainability. Noteworthy, the effective role of DNA barcoding as screening tool to monitor labelling validity.