Application of DNA barcoding and metabarcoding for species identification in salmon products.

Mislabelling is a significant manifestation of food fraud. Traditional Sanger sequencing technology is the gold standard for seafood species identification. However, this method is not suitable for analysing processed samples that may contain more than one species. This study tested the feasibility of next-generation sequencing in identifying mixed salmon products. Salmon samples containing up to eight species were amplified using 16S rRNA mini-barcode primers, and sequenced on an Illumina HiSeq2500 platform. All species were accurately identified, and mixtures as low as 1% (w/w) could be detected. Furthermore, this study conducted a market survey of 32 products labelled as salmon. For pure and mixed fish products, Sanger and next-generation sequencing techniques were respectively used for species identification, and for NGS results, we also used real-time PCR method to cross-validate the mixed products to further verify the accuracy of the DNA metabarcoding technology established in this study. DNA barcoding and metabarcoding of commercial salmon food products revealed the presence of mislabelling in 16 of 32 (50%) samples. The developed DNA barcoding and metabarcoding methods are useful for the identification of salmon species in food and can be used for quality control of various types of salmon products.

DNA barcoding and mini-barcoding in authenticating processed animal-derived food: A case study involving the Chinese market.

This study used DNA barcoding and DNA mini-barcoding to test a variety of animal-derived food products sold in the Chinese market for potential mislabeling. Samples (52) including meat, poultry, and fish purchased from retail and online sources were examined. Regions of cytochrome C oxidase I (COI) gene (~650 bp) and 16S rRNA (~220 bp) were used as full- and mini-barcode markers, respectively. Approximately 94% (49 of 52) of the samples generated barcode sequences. The failure rate for full COI full-barcodes was 44%, but we obtained the 16S rRNA mini-barcode from 87% of the COI-failed cases. Overall, the survey revealed that 23% (12 of 52) of animal-derived products were mislabeled and, in most cases, contain undeclared species. Thus, regulatory measures and continuous monitoring for mislabeling of animal-derived products should be conducted.

[Effect of High Hydrostatic Pressure Combined with Temperature on the Antigenicity and Conformation of Tropomyosin Purified from Shrimp].

Foodborne shrimp allergy events have occurred in recent years. To illustrate the mechanism of high hydrostatic pressure technology to change the allergenicity of shrimp, the major allergen tropomyosin was separated and purified from Litopenaeus vannamei, and indentified with matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). The effect of temperature factor under high hydrostatic pressure was measured with indirect ELISA method, CD and fluorescence spectrum. The results showed that the antigenicity of TM protein had an increase after being heated at 35 or 45 ℃ when treated at 300 MPa for 15 minutes, while the antigenicity decreased at 55, 65, and 75 ℃. With the increase of heat temperature, the secondary structure of TM also changed. The mutual transformation happened between the alpha-helix and beta-sheet, beta-turn, and the random coil. The tertiary structure of TM was observed dynamic changes from the extended state to the folded state, and then re-extended state to re-folded state. These results suggested that high hydrostatic pressure combined with temperature could influence the antigenicity of TM by the change of conformation which would be useful as theoretical guidance on developing new methods or technologies for producing hypoallergenic shrimp products.