Detection of Salmonidae ingredient using mini-DNA barcoding in conjunction with a rapid visual inspection method

Using species outside Salmonidae to prepare salmon products has been widely revealed as a new type of fraud in China and other countries with less stringent labeling stipulations, highlighting the necessity to establish proper methods for rapid screening of Salmonidae ingredient. The present work selected mitochondrial Cytb gene as the target, and developed a novel mini-DNA barcoding assay to identify the salmonids ingredient in processed fish products. Results showed that the novel method is highly specific for salmonids detection and only the seven common salmonids species were successfully amplified. With the inclusion of HRM analysis, we can make an accurate differentiation of Salar salar, Oncorhynchus mykiss, and the other wild-caught Oncorhynchus species, which are deep in the scandal of species mislabeling. Moreover, a closed-tube visual detection can also be achieved by the preaddition of HNB (hydroxyl naphthol blue) and SYTO 9 in the reaction mixture, allowing an easy and rapid way to distinguish positive from negative. Finally, the novel assay was successfully applied on commercial products and the absence of salmonids ingredient indicated mislabeling with 4 commercial products. Overall, mini-DNA barcoding is a robust tool for fish species identification and the novel method is effective in screening Salmonidae ingredient.

Automated summary

Using species outside Salmonidae for salmon products is a new type of fraud found in China and other countries with lenient labeling regulations. This study developed a mini-DNA barcoding assay to detect Salmonidae ingredient in processed fish products using the mitochondrial Cytb gene. The assay showed high specificity and successfully identified the seven common salmonid species. It also allowed accurate differentiation of species like Salar salar and Oncorhynchus mykiss, which are often mislabeled. The method is effective in screening Salmonidae ingredient in commercial products.