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The canning process has a degrading effect on DNA, making the species verification of canned tuna more challenging than for raw fish.

In this paper (open access) the authors optimised and compared three PCR approaches: real-time PCR (RT-PCR), mitochondrial control region (CR) mini-barcode, and multiplex PCR.  They tested 24 samples labelled as either albacore, yellowfin, skipjack or light tuna.

They reported RT-PCR as having the highest identification rate (100%), followed by CR mini-barcoding (33%) and multiplex PCR (29%). They consider that the success of RT-PCR may have been due to the short (<100 bp) DNA fragments targeted. In comparison, multiplex PCR and CR mini-barcoding targeted slightly longer fragments of 127–270 and∼236 base pairs, respectively. Regarding species identification, CR mini-barcoding and multiplex PCR confirmed the presence of albacoreor yellowfin tuna in several samples; however, both methods struggled with the identification of skipjack tuna.

CR mini-barcoding enabled sequencing-based detection of a range of species in the products. The authors conclude that a combination of real-time PCR and CR mini-barcoding is the optimum approach for rapid screening of target species along with sequencing-based confirmation.

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There is a growing market for the use of insect protein in feed.  The cricket species Gryllus assimilis. is approved in the EU for feeding farmed animals whilst the closely-related G. locorojo is only permitted for pets. The two are difficult to distinguish analytically in a highly processed product.

This paper (purchase required) reports a method developed on the basis of the cytochrome oxidase I gene, (COI), which was sequenced with thoroughly characterised G. locorojo and G. assimilis samples. The method is highly sensitive, detecting 0.8 pg G. locorojo-DNA or 0.1% G. locorojo incurred in feed, respectively. Authentic G. assimilis specimens were used to ensure that the G. locorojo method (Gloco-PCR) discriminates this closely related sister taxon, with a comfortable Ct-difference of 10-15. For cross analysis of true G. assimilis, similar primers with another probe were employed (Gassim-PCR) and the annealing temperature was increased from 60 °C to 62 °C.

Under these conditions, authentic G. assimilis crickets were detectable with Ct-values around 20, while G. locorojo samples showed a low detection at cycles around Ct 35. An investigation of ten ‘G. assimilis’ samples collected from Germany and four other European countries revealed that all of them were of the G. locorojo type.

The authors conclude that this small preliminary survey proves the usefulness of the method and supports the assumption that many G. assimilis crickets marketed in the EU indeed belong to the species G. locorojo. Consequently, European legislation, currently based on a white list of allowed insect species, is critically questioned.

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DNA analysis is rarely used for the verification of edible oil species, because of the low amount of intact DNA in the refined oil and the genetic similarities between different oil varieties.  In this study (open access pre-print, not yet peer-reviewed) the authors compared different DNA extraction kits and PCR protocols and new genetic markers to try and resolve the issue.  They reported that DNA extraction kits such as NucleoSpin Food, DNeasy mericon Food, and Olive Oil DNA Isolation as well as modified CTAB method were found to be able to isolate amplifiable genomic DNA from highly processed oils. Novel uniplex, double, and nested PCR systems targeting the sunflower-specific helianthinin gene were developed for efficient identification of sunflower. New sunflower DNA markers were revealed by uniplex PCRs.

They concluded that a combination of modified CTAB and nested PCR gave the best performance, and was demonstrated as a reliable, rapid, and cost-effective technology for detecting traces of sunflower in highly processed oil, including refined and used cooking oil.

In this study (purchase required), 14 widely commercialized GM soybean events, including GTS40-3-2, MON89788, CV127, A2704-12, A5547-127, 305423, 356043, MON87701, MON87705, MON87708, MON87769, SYHT0H2, FG72, and DAS-444Ø6-6 were utilised as targets for event-specific identification. A high-throughput detection method was established by integrating a single universal primer multiplex PCR (SUP-M-PCR) with capillary electrophoresis  The authors report that this method enables the identification of 14 soybean events in a single PCR reaction, addressing the limitations of conventional multiplex PCR such as self-inhibition and amplification variations between different primers. Furthermore, it significantly enhances the sensitivity and accuracy of previous multiple detection methods, achieving a detection sensitivity of 0.05% (w/w). They conclude that this approach improves detection efficiency and holds promising potential for the identification and detection of the 14 targeted GM soybean events and their derivatives.

Photo by Meredith Petrick on Unsplash