Identification of fish species of sushi products in Hong Kong

Decoding Seafood: Multi-Marker Metabarcoding for Authenticating Processed Seafood

Given the recognized nutritional value of fish and shifting consumer lifestyles, processed seafood has become increasingly prevalent, comprising a significant portion of global food production. Although current European Union labeling regulations do not require species declaration for these products, food business operators often voluntarily provide this information on ingredient lists. Next Generation Sequencing (NGS) approaches are currently the most effective methods for verifying the accuracy of species declarations on processed seafood labels. This study examined the species composition of 20 processed seafood products, each labeled as containing a single species, using two DNA metabarcoding markers targeting the mitochondrial cytochrome c oxidase I (COI) and 16S rRNA genes. The combined use of these markers revealed that the majority of the products contained multiple species. Furthermore, two products were found to be mislabeled, as the declared species were not detected. These findings underscore that NGS is a robust technique that could be adopted to support routine food industry activities and official control programs, thereby enhancing the 'From Boat to Plate' strategy and combating fraudulent practices in the complex fisheries supply chain.

Development of rapid and cost-effective multiplex PCR assays to differentiate catfish of the genus Brachyplatystoma (Pimelodidae-Siluriformes) sold in Brazil

The catfishes Brachyplatystoma filamentosum (Kumakuma), Brachyplatystoma vaillantii (Laulao catfish), and Brachyplatystoma rousseauxii (gilded catfish) are important fishery resources in Brazil, where they are sold both fresh and in the form of fillets or steaks. These species have morphological similarities, thus, they can be easily misidentified or substituted, especially after processed. Therefore, accurate, sensitive, and reliable methods are needed for the identification of these species to avoid commercial fraud. In the present study, we develop two multiplex PCR assays for the identification of the three catfish species. Each multiplex protocol combined three species-specific forward primers and a universal reverse primer to produce banding patterns able to discriminate the target species unequivocally. The length of the cytochrome C oxidase subunit I (COI) fragments was approximately 254 bp for B. rousseauxii, 405 bp for B. vaillantii, and 466 bp for B. filamentosum, while the control region (CR) assay produced fragments of approximately 290 bp for B. filamentosum, 451 bp for B. vaillantii, and 580 bp for B. rousseauxii. The protocols were sensitive enough to detect the target species at a DNA concentration of 1 ng/µL, with the exception of the CR of B. vaillantii, in which the fragment was only detectable at 10 ng/µL. Therefore, the multiplex assays developed in the present study were sensitive, accurate, efficient, rapid, and cost-effective for the unequivocal identification of the target species of Brachyplatystoma. They can be utilized by fish processing industries to certify their products, or by government agencies to authenticate products and prevent fraudulent commercial substitutions.

DNA Barcode Identification of Fish Products from Guiyang Markets in Southwestern People's Republic of China

ABSTRACT

Global fish consumption is increasing in tandem with population growth, resulting in the dilemma of overfishing. Overfished high-value fish are often replaced with other fish in markets. Therefore, the accurate identification of fish products in the market is important. In this study, full-DNA and mini-DNA barcoding were used to detect fish product fraud in Guiyang, Guizhou Province, People's Republic of China. The molecular results revealed that 39 (20.42%) of the 191 samples were inconsistent with the labels. The percentages of mislabeling of fresh, frozen, cooked, and canned fish products were 11.70, 20.00, 34.09, and 50.00%, respectively. The average Kimura two-parameter distances of mini-DNA barcoding within species and within genera were 0.56 and 6.42%, respectively, and those of full-DNA barcoding were 0.53 and 7.25%, respectively. Commercial fraud was evident in this study; most high-priced fish were replaced with low-priced fish with similar features. Our findings indicate that DNA barcoding is an effective tool for identifying fish products and could be used to enhance transparency and fair trade in domestic fisheries.

HIGHLIGHTS

Geographic Pattern of Sushi Product Misdescription in Italy-A Crosstalk between Citizen Science and DNA Barcoding

The food safety of sushi and the health of consumers are currently of high concern for food safety agencies across the world due to the globally widespread consumption of these products. The microbiological and toxicological risks derived from the consumption of raw fish and seafood have been highlighted worldwide, while the practice of species substitution in sushi products has attracted the interest of researchers more than food safety agencies. In this study, samples of sushi were processed for species authentication using the Cytochrome Oxidase I (COI) gene as a DNA barcode. The approach of Citizen Science was used to obtain the sushi samples by involving people from eighteen different Italian cities (Northern, Central and Southern Italy). The results indicate that a considerable rate of species substitution exists with a percentage of misdescription ranging from 31.8% in Northern Italy to 40% in Central Italy. The species most affected by replacement was Thunnus thynnus followed by the flying fish roe substituted by eggs of Mallotus villosus. These results indicate that a standardization of fish market names should be realized at the international level and that the indication of the scientific names of species should be mandatory for all products of the seafood supply chain.

Identification and Authentication of Commercial Mi-iuy Croaker (Miichthys miiuy) Products by Two PCR-Based Methods

ABSTRACT

Mi-iuy croaker (Miichthys miiuy) is one of the most important ingredients of Korean cuisine and, thus, has a high economic value. However, the similar morphological traits among croaker fish belonging to family Sciaenidae are often exploited for seafood fraud. In this study, an M. miiuy-specific primer set was designed and further improved by the development of a rapid and cost-effective duplex PCR method. The specificity of M. miiuy-specific duplex PCR was tested using 22 seafood species, and no cross-reactivity was observed. The sensitivity of the PCR assay was found to be 0.1 ng/μL. For the first time, labeling compliance of 43 commercial mi-iuy croaker products was verified using both full DNA barcoding and M. miiuy-specific duplex PCR methods. For species identification, BOLDSYSTEMS and GenBank database were screened with the consensus sequences of each PCR product as a query. This identification result was further confirmed using the M. miiuy-specific duplex PCR method. The findings of this study revealed that principal species substituted were law croaker (Pseudotolithus senegallus, n = 4), bigeye croaker (Micropogonias megalops, n = 3), whitemouth croaker (Micropogonias furnieri, n = 1), and tigertoothed croaker (Otolithes ruber, n = 1). A significant percentage (21%) of mislabeling was present in commercial mi-iuy products sold on the South Korean market.

HIGHLIGHTS

Differentiation of Hedyotis diffusa and Common Adulterants Based on Chloroplast Genome Sequencing and DNA Barcoding Markers

Chinese herbal tea, also known as Liang Cha or cooling beverage, is popular in South China. It is regarded as a quick-fix remedy to relieve minor health problems. Hedyotis diffusa Willd. (colloquially Baihuasheshecao) is a common ingredient of cooling beverages. H. diffusa is also used to treat cancer and bacterial infections. Owing to the high demand for H. diffusa, two common adulterants, Hedyotis brachypoda (DC.) Sivar and Biju (colloquially Nidingjingcao) and Hedyotis corymbosa (L.) Lam. (colloquially Shuixiancao), are commonly encountered in the market. Owing to the close similarity of their morphological characteristics, it is difficult to differentiate them. Here, we sequenced the complete chloroplast genomes of the three species of Hedyotis using next-generation sequencing (NGS). By comparing the complete chloroplast genomes, we found that they are closely related in the subfamily Rubioideae. We also discovered that there are significant differences in the number and repeating motifs of microsatellites and complex repeats and revealed three divergent hotspots, rps16-trnQ intergenic spacer, ndhD and ycf1. By using these species-specific sequences, we propose new DNA barcoding markers for the authentication of H. diffusa and its two common adulterants.