As part of the Labelfish Project’s work to broaden interest in, and deepen the knowledge of, stakeholders in seafood labelling, traceability and molecular techniques, please find below the third edition of a series of brief reviews of papers in the area. These papers are salient works in terms of their recency or their importance to the area of conservation genetics.
Lamendin, R., Miller, K. & Ward, R. D., 2014. Labelling accuracy in Tasmanian seafood: An investigation using DNA barcoding. Food Control doi: 10.1016/j.foodcont.2014.07.039
DNA barcoding is a tool which can be used to identify a fish species from fillets, fins, fragments, juveniles, larvae and eggs and can be used on raw, cooked and smoked specimens. DNA barcoding as a tool for detecting mislabelled seafood products has rarely been attempted in Australia and this study examines the incidences of mislabelling in Tasmania. Tasmania represents one of Australia’s most valuable fisheries and uses labelling which places a strong focus on the state’s “clean” and “green” credentials. The study sampled 51 seafood products which were fresh, uncooked and unprocessed. The CO1 gene was PCR amplified using primers FishF1 and FishR1. DNA sequences were identified using a BLAST search of GenBank and using the BOLD identification engine. Of the 51 products sampled, 38 produced sequences which were of sufficient quality for analysis. This shows a high failure rate which the authors suggest may be related to “transport, handling and storage, whereby fish may have suffered under a freeze/thaw process that resulted in the degradation of their muscle tissue DNA.”
The study found that none of the analysed samples were mislabelled or substituted, however some of the names used on the labels were considered “obsolete, too broad, or potentially misleading.” The Australian and New Zealand Food Standards Code (ANZFSC) details the required standards for food produced, sold or imported in Australia. The Australian Fish Names Standard (AFNS) is a suggested guidance document for the labelling of fish products, but because this document is not included in Commonwealth legislation, compliance cannot be enforced or monitored by the food enforcement state body. This may explain why a number of samples were labelled ambiguously since retailers who do not comply with the AFNS are not breaking the law.
Pramod G., Nakamura K., Pitcher T.J. & Delagran L., 2014. Estimates of illegal and unreported fish in seafood imports to the USA. Marine Policy 48: 102-113.
Recent estimates of illegal, unreported and unregulated (IUU) fishing have revealed IUU represented between 13 to 31% by weight of reported catches, and over 50 % in some regions. This study has been built to estimate the amount of illegal and unreported fish entering in the US market on the basis of more than 180 document sources and interviews. It looked only on edible seafood import (wild caught marine imports) for human consumption. The methodology was based on taking the top 3 products from the top 10 exporters to US (from 120 supplying nations). These ranges were combined to produce a trade-weighted average of IUU infection for each of the top 30 country/species products categories. The results of this study show that the catches represented 20–32% by weight of wild-caught seafood imported to the USA in 2011. These illegal imports are valued at between $1.3 and $2.1 billion, representing between 4% and 16% of the value of the global illegal fish catch, and revealing the unintentional role of the USA one of the largest seafood markets in the world, in funding the profits of illegal fishing. Supply chain case studies are presented for tuna, wild shrimp and Chinese re-processed Russian pollock, salmon and crab imported to the USA. Unlike European Union, which has begun to implement direct trade controls through traceability and certifications, the USA does not have yet a robust system to exclude illegal products from its market, except for particular species groups such as toothfish. Possible remedies from industry practices and government policies may include improved chain of custody and traceability controls and an amendment to the USA Lacey Act.
Herrero, B., Vieites, J. M. & Espiñeira, M., 2014. Development of an in-house fast real-time PCR method for detection of fish allergen in foods and comparison with a commercial kit. Food Chemistry 151: 415-420.
This study describes a real-time PCR method which can be used to detect fish allergen in all kind of products including processed products and which is also appropriate for the analysis of cross-contamination in production chains. The analysis is based on the detection of 18S rRNA gene sequences with a fish specific primers and probe set. It was tested with a lot of fish species and specificity was confirmed with DNA from different species of bivalves, cephalopods, crustaceans as well as meats, vegetables and spices. The minimum fish DNA which could be detected was 0.05 ng. In order to validate the method, fish was cooked in water and the water was used to spike different food matrices and processed products, which simulated canned and precooked food. Furthermore, the method was applied to samples from different points in the food production chain. When compared with a commercial real-time PCR system (SureFood Allergen Fish, R-Biopharm), this newly developed method was more sensitive and specific, cheaper and less time-consuming (about 43 min) than the commercial kit.
Dalmasso, A., Chiesa, F., Civera, T. & Bottero, M. T., 2013. A novel minisequencing test for species identification of salted and dried products derived from species belonging to Gadiformes. Food Control 34: 296-299.
This short communication shows the development of an assay for the identification of Gadus morhua, Gadus ogac, Molva molva and Brosme brosme based in the analysis of diagnostic sites by minisequencing in cytochrome b fragment.
The assay was tested in 52 raw samples, and 30 salted and dried products from retailers. The small size of the preliminary PCR fragment (188 bp) allowed its use in degraded products. This PCR product is used afterwards as a template in a minisequencing reaction: 4 primers adjacent to 4 diagnostic sites have been designed and added to this reaction were only ddNTP are present. As a result of this reaction, only the diagnostic ddNTP joins each primer. Primers lengths have been modified by adding a poly T tail in 5’, so the 4 types of fragments generated can be separated by capillary electrophoresis. As each ddNTP is labelled with a different fluorescent dye, discrimination of species is possible with a single reading of the specific pattern generated using the GeneScan software.
All results were confirmed by fragment sequencing. During the validation of the method, no cases of mislabelling were found. The method is precise and reliable and can be applied to processed food products. It should be tested for other species of Gadiformes that can be found in the market, and other types of processing.
Armani, A., Tinacci, L., Xiong, X., Castigliego, L., Gianfaldoni, D. & Guidi, A., 2015. Fish species identification in canned pet food by BLAST and Forensically Informative Nucleotide Sequencing (FINS) analysis of short fragments of the mitochondrial 16s ribosomal RNA gene (16S rRNA). Food Control 50: 821-830.
This study looked at 43 tins of fish-based cat food available on the Italian market. Due to the highly processed nature of tinned cat food, DNA is often degraded. Methods used for species authentication generally involve mitochondrial DNA (mtDNA) due to its high mutation rate, multi-copy rate and maternal inheritance. Primers currently available for amplification of mtDNA target ~700 bp. This means they are unsuitable for DNA which has been substantially degraded. The 16S rRNA gene has been used to identify fish belonging to a number of families and due to its high conservation rate, 16S rRNA has been used to design universal primers capable of amplifying different lengths of DNA fragments. For these reasons this was the method used in this study.
84% of the minnow sequences and 100% of the fillet sequences analysed were identified to species level. 100% of the 43 samples taken were found to be mislabelled. Mislabelling was more prevalent in relation to the whole minnow component of the cat food (100%) as opposed to the fillet component (40%). The labels claimed that all the minnow species present were whitebait (Bianchetto), a name which can only be used for the juvenile form of the sardine (S. pilchardus) and is typically used in high-price products. In the majority of cases the species present belonged to the genus Encrasicholina. The paper points out that the use of undeclared juvenile anchovies of Asian origin in the preparation of pet food could lead to sustainability issues for the fishing industry.