Assessment of marine fish mislabeling in South Korea's markets by DNA barcoding

Mislabeled and ambiguous market names in invertebrate and finfish seafood conceal species of conservation concern in Calgary, Alberta, Canada

Background

The mislabeling of seafood, wherein a food product's marketed name does not match its contents, has the potential to mask species of conservation concern. Less discussed is the role of legally ambiguous market names, wherein a single name could be used to sell multiple species. Here we report the first study in Canada to examine mislabeling and ambiguous market names in both invertebrate (e.g., bivalve, cephalopod, shrimp) and finfish products.

Methods

A total of 109 invertebrate and 347 finfish products were sampled in Calgary between 2014 and 2020. Market names were documented from the label or equivalent and determined to be precise (the name could apply to only one species) or ambiguous (multiple species could be sold under that name). A region of the cytochrome c oxidase I gene was sequenced and compared to reference sequences from boldsystems.org. Samples were considered mislabeled if the species identified through DNA barcoding did not correspond to the market name, as determined through the Canadian Food Inspection Agency Fish List. Mislabeling was further differentiated between semantic mislabeling, wherein the market name was not found on the Fish List but the barcode identity was in line with what a consumer could reasonably have expected to have purchased; invalid market names, wherein the market name was so unusual that no legitimate inferences as to the product's identity could be made; and product substitution, wherein the DNA barcode identified the product as a species distinct from that associated with the market name. Invalid market names and product substitutions were used to provide conservative estimates of mislabeling. The global conservation status of the DNA-identified invertebrate or finfish was determined through the International Union for the Conservation of Nature Red List. A logistic regression was used to determine the relationship between precision and accuracy in predicting conservation status of the sampled species.

Results

There was no significant difference in mislabeling occurrence between invertebrates (33.9% total mislabeling occurrence, 20.2% product substitution) and finfish (32.3% total mislabeling occurrence, 21.3% product substitution/invalid market names). Product substitutions sometimes involved species of conservation concern, such as foods marketed as freshwater eel (Anguilla rostrata) that were determined through DNA barcoding to be European eel (Anguilla anguilla), or cuttlefish balls putatively identified as the Endangered threadfin porgy (Evynnis cardinalis). Product substitutions and ambiguous market names were significantly associated with the sale of species of conservation concern, but ambiguity was a more important predictor. Although preventing the mislabeling of seafoods can and must remain a priority in Canada, our work suggests that moving towards precise names for all seafood products will better support sustainable fisheries goals.

Development of sequential online extraction electrospray ionization mass spectrometry for accurate authentication of highly-similar Atractylodis Macrocephalae

The accurate and rapid authentication techniques and strategies for highly-similar foods are still lacking. Herein, a novel sequential online extraction electrospray ionization mass spectrometry (S-oEESI-MS) was developed to achieve spatio-temporally resolved ionization and comprehensive characterization of complex foods with multi-components (high, medium, and low polarity substances). Meanwhile, a characteristic marker screening method and an integrated research strategy based on MS fingerprinting, characteristic marker and chemometrics modeling were established, which are especially suitable for the accurate and rapid authentication of highly-similar foods that are difficult to be authenticated by traditional techniques (e.g., LC-MS). Thirty-two batches of highly-similar Atractylodis macrocephalae rhizome from four different origins were used as model samples. As a result, S-oEESI-MS enabled a more comprehensive MS characterization of substance profiles in complex plant samples in 1.0 min. Further, 22 characteristic markers of Atractylodis macrocephalae were ingeniously screened out and combined with multivariate statistical analysis model, the accurate authentication of highly-similar Atractylodis macrocephalae was realized. This study presents a comprehensive strategy for accurate authentication and origin analysis of highly-similar foods, which has potentially significant applications for ensuring food quality and safety.

Molecular Barcoding: A Tool to Guarantee Correct Seafood Labelling and Quality and Preserve the Conservation of Endangered Species

The recent increase in international fish trade leads to the need for improving the traceability of fishery products. In relation to this, consistent monitoring of the production chain focusing on technological developments, handling, processing and distribution via global networks is necessary. Molecular barcoding has therefore been suggested as the gold standard in seafood species traceability and labelling. This review describes the DNA barcoding methodology for preventing food fraud and adulteration in fish. In particular, attention has been focused on the application of molecular techniques to determine the identity and authenticity of fish products, to discriminate the presence of different species in processed seafood and to characterize raw materials undergoing food industry processes. In this regard, we herein present a large number of studies performed in different countries, showing the most reliable DNA barcodes for species identification based on both mitochondrial (COI, cytb, 16S rDNA and 12S rDNA) and nuclear genes. Results are discussed considering the advantages and disadvantages of the different techniques in relation to different scientific issues. Special regard has been dedicated to a dual approach referring to both the consumer's health and the conservation of threatened species, with a special focus on the feasibility of the different genetic and genomic approaches in relation to both scientific objectives and permissible costs to obtain reliable traceability.

A case study on DNA barcoding for pet food mislabeling in South Korea

Due to the close relationship between pets and humans, pet owners are highly invested in proper diets for their pets. Even though pet food mislabeling is concerning, there are few studies on this topic. This study investigated pet food mislabeling in South Korea’s market based on DNA barcoding. In total, 10 pet food products were purchased, and 200 sequences of the partial Cytochrome c oxidase subunit 1 (COI) gene were generated from clones of the samples. The obtained sequences were compared to available public databases to identify species present in the ingredients. The data analyses showed that the labeled species were consistent with species detected by COI sequences in 6 of the products. However, the expected species were not detected in 4 products, revealing possible mislabeling in these samples. Our findings indicated that DNA barcoding might represent a promising tool to detect pet food mislabeling.

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

Molecular tools for assuring human health and environment-friendly frozen shellfish products in the United Arab Emirates markets

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Frozen UAE shellfish samples were identified using 16S rDNA barcoding.

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Significant substitutions were identified for calamari by peanut worm, cattle, and rat.

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Although labelled as UAE in origin most shrimps were non-native species.

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Analyzed shellfish barcodes showed most species belong to low diversity populations.

Shellfish consumption in the United Arab Emirates (UAE) exceeds local supply and frozen fish and seafood products are imported to fill the gap. To determine the species in frozen shellfish brands on the UAE markets, 95 frozen samples were subjected to PCR amplification and sequencing of the hypervariable region of the 16S rDNA. This identified 11 different shrimp species and two squid species in the frozen shellfish packs. About 40% of calamari brands contained peanut worm, cattle, and rat 16S rDNA. Also, most shellfish species analyzed had low nucleotide diversity, including two shrimp species (Litopenaeus vannamei and Metapenopsis barbata), which had very limited genetic diversity, low raggedness, and an absence of population expansion. Species misnaming, substitution, overexploitation, origin misreporting, and low genetic diversity were found across frozen UAE shellfish samples analyzed, suggesting inspection and monitoring of frozen seafood sold in UAE markets would be appropriate.

Fraud in highly appreciated fish detected from DNA in Europe may undermine the Development Goal of sustainable fishing in Africa

Despite high effort for food traceability to ensure safe and sustainable consumption, mislabeling persists on seafood markets. Determining what drives deliberate fraud is necessary to improve food authenticity and sustainability. In this study, the relationship between consumer's appreciation and fraudulent mislabeling was assessed through a combination of a survey on consumer's preferences (N = 1608) and molecular tools applied to fish samples commercialized by European companies. We analyzed 401 samples of fish highly consumed in Europe and worldwide (i.e. tuna, hake, anchovy, and blue whiting) through PCR-amplification and sequencing of a suite of DNA markers. Results revealed low mislabeling rate (1.9%), with a higher mislabeling risk in non-recognizable products and significant mediation of fish price between consumer´s appreciation and mislabeling risk of a species. Furthermore, the use of endangered species (e.g. Thunnus thynnus), tuna juveniles for anchovy, and still not regulated Merluccius polli hake as substitutes, points towards illegal, unreported and/or unregulated fishing from African waters. These findings reveal a worrying intentional fraud that hampers the goal of sustainable seafood production and consumption, and suggest to prioritize control efforts on highly appreciated species.

Re-visiting the occurrence of mislabeling in frozen "pescada-branca" (Cynoscion leiarchus and Plagioscion squamosissimus - Sciaenidae) sold in Brazil using DNA barcoding and octaplex PCR assay

In Brazil, Cynoscion leiarchus and Plagioscion squamosissimus are the species allowed to be labeled as "pescada-branca". These species have high economic value, especially when sold in the form of fillets. Therefore, when morphological traits are removed, fish are highly prone to be substituted, which has been reported for species of the family Sciaenidae sold in Brazil, including "pescada-branca". We have sequenced 618 bp of the COI of 143 samples to re-evaluate the occurrence of substitutions in frozen "pescada-branca" marketed in Brazil. We observed more than 73% of mislabeling, with only 26.57% being P. squamosissimus, and none, C. leiarchus. In general, the substitutes were closely related Sciaenidae, but cheaper species, which indicates commercial fraud. Based on these results we used 1.2 kb of COI to develop an octaplex PCR assay that unequivocally identified the target species and six substitute species through the banding pattern. Specific reverse primers combined with a universal forward primer were used in the protocol and identified the species C. leiarchus (~290 bp), N. microps (~340 bp), M. ancylodon (~470 bp), C. acoupa (~540 bp), C. microlepidotus (~850 bp), P. auratus (~950 bp), C. virescens (~1050 bp), and P. squamosissimus (~1140 bp). The DNA barcoding and the multiplex PCR were accurate and specific to authenticate processed products labeled as "pescada-branca". The multiplex assay constitutes a cost-effective alternative for the authentication of these products and other sciaenids. Additionally, we suggest that the multiplex assay can be adopted by both companies and regulatory agencies to prevent commercial fraud in the marketing of processed fishery products in Brazil and other countries where these products are commercialized.

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.

DNA-based techniques for seafood species authentication

Global trade of seafood has increased in the last decade, leading to significant concerns associated with seafood fraud. Seafood fraud involves the intentional misrepresentation of fish or shellfish for the purpose of economic gain and includes acts such as species substitution, illegal transshipment, overtreatment/short weighting, and mislabeling country of origin or production method. These fraudulent acts have had economic, environmental, and public health consequences on a global level. DNA-based techniques for seafood authentication are utilized by regulatory agencies and can be employed as part of a food fraud risk mitigation plan. This chapter will focus specifically on the use of DNA-based methods for the detection of seafood species substitution. Various methods have been developed for DNA-based species identification of seafood, including polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), species-specific PCR, real-time PCR, Sanger sequencing, microarrays, and high-resolution melting (HRM). Emerging techniques for seafood authentication include droplet digital PCR, isothermal amplification, PCR-enzyme-linked immunosorbent assay (ELISA), and high-throughput or next-generation sequencing. Some of these DNA-based methods target specific species, such as real-time PCR and droplet digital PCR, while other methods allow for simultaneous differentiation of a wide range of fish species, including Sanger sequencing and high-throughput sequencing. This chapter will begin with an introduction on seafood fraud and species substitution, followed by an analysis of the main DNA-based authentication methods and emerging techniques for species identification.

Comparative Evaluation of Web Page and Label Presentation for Imported Seafood Products Sold on Chinese E-Commerce Platform and Molecular Identification Using DNA Barcoding

ABSTRACT

With the expansion of e-commerce, an increasing number of Chinese consumers are turning to online markets to purchase foreign seafood. When buying seafood online, customers cannot physically evaluate the product, and the market Web page instead of the seafood label conveys all of the product information. However, specific regulations concerning the information presented on the Web page have not been created, which may foster seafood fraud and misdescription. Because mislabeling of seafood has become a widely reported issue in the Chinese offline market, the online scenario must be investigated comprehensively. This study focused on various seafood products that originated from 20 countries and were sold by one of the largest e-commerce companies in China. For each country, only the product with the greatest overall monthly transaction volume was selected, and 5 samples were purchased per product for a total of 100 samples. The Web page description (including the heading of the Web page and the description of the commodity) and the label of the received products were compared to evaluate the description consistency. DNA barcoding technology was used for seafood species identification, and the scientific names retrieved from the sequence analysis after consulting the Barcode of Life Data systems and GenBank were compared with the expected species, genus, and family to determine the description authenticity. Only 25% of the samples had consistent descriptions on the Web page and on the label of the received product. Most of the inconsistency originated from the geographical origin, and only four products (G10, G50, G19, and G69) had inconsistent species, genus, and family descriptions. Molecular analysis revealed that in 65% of samples the species was correctly described. The online seafood market presents challenges regarding seafood fraud and opportunities for seafood species substitution.

HIGHLIGHTS

Swordfish or Shark Slice? A Rapid Response by COIBar-RFLP

Market transparency is in strong demand by consumers, and the authentication of species is an important step for seafood traceability. In this study, a simple molecular strategy, COIBar–RFLP (cytochrome oxidase I barcode–restriction fragment length polymorphism), is proposed to unveil commercial fraud based on the practice of species substitution in the swordfish trade. In particular, COI barcoding allowed the identification of the species Prionace glauca, Mustelus mustelus, and Oxynotus centrina in slices labeled as Xiphias gladius. Furthermore, the enzymatic digestion of COI amplicons using the MboI restriction endonuclease allowed the simultaneous discrimination of the four species. Interestingly, an intraspecific differential MboI pattern was obtained for the swordfish samples. This pattern was useful to differentiate the two different clades revealed in this species by phylogenetic analyses using several molecular markers. These results indicate the need to strengthen regulations and define molecular tools for combating the occurrence of fraud along the seafood supply chain and show that COIBar–RFLP could become a standardized molecular tool to assess seafood authenticity.