DNA barcoding coupled with high-resolution melting analysis for nut species and walnut milk beverage authentication.

BACKGROUND: Walnut (Juglans regia L.) is one of the most widely cultivated nuts. Walnut milk beverage is very popular in China due to its nutritional value. However, adulterated walnut milk ingredients have been detected in the Chinese market. Peanut and soybean are sold at much lower prices than walnut and are reported to be commonly used for adulteration in the industrial chain of walnut milk production. The purpose of this study is therefore to develop an accurate and efficient method for detecting the authenticity of the raw materials used in walnut milk beverage. RESULTS: DNA barcoding and high-resolution melting (HRM) analyses were used to identify common adulterated raw ingredients such as peanut and soybean in commercial walnut milk beverage samples. The chloroplast psbA-trnH gene was used for sequencing, and HRM analysis was performed. We also prepared experimental mixtures, in the laboratory, with different quantities of walnut, peanut, and soybean. High-resolution melting analysis of the experimental mixtures clearly distinguished all of them. The results revealed that most of the walnut milk beverage samples fell in the same cluster of walnut species. Several samples fell in the peanut cluster, confirming that they were adulterated products. CONCLUSION: The results revealed that HRM analysis based on the psbA-trnH barcode sequence can be used to identify raw ingredients in walnut milk beverages. © 2020 Society of Chemical Industry.

Advances in DNA Barcoding of Toxic Marine Organisms.

There are more than 200,000 marine species worldwide. These include many important economic species, such as large yellow croaker, ribbonfish, tuna, and salmon, but also many potentially toxic species, such as blue-green algae, diatoms, cnidarians, ctenophores, Nassarius spp., and pufferfish. However, some edible and toxic species may look similar, and the correct identification of marine species is thus a major issue. The failure of traditional classification methods in certain species has promoted the use of DNA barcoding, which uses short, standard DNA fragments to assist with species identification. In this review, we summarize recent advances in DNA barcoding of toxic marine species such as jellyfish and pufferfish, using genes including cytochrome oxidase I gene (COI), cytochrome b gene (cytb), 16S rDNA, internal transcribed spacer (ITS), and Ribulose-1,5-bisphosphate carboxylase oxygenase gene (rbcL). We also discuss the application of this technique for improving the identification of marine species. The use of DNA barcoding can benefit the studies of biological diversity, biogeography, food safety, and the detection of both invasive and new species. However, the technique has limitations, particularly for the analysis of complex objects and the selection of standard DNA barcodes. The development of high-throughput methods may offer solutions to some of these issues.