Identification of four squid species by quantitative real-time polymerase chain reaction

Development of a multiplex PCR assay for the simultaneous detection of big blue octopus (Octopus cyanea), giant Pacific octopus (Enteroctopus dofleini), and common octopus (Octopus vulgaris)

Since octopuses are similar in appearance and can be processed into various forms, seafood fraud has been reported. In this study, we developed the PCR assay to simultaneously detect three octopuses (big blue octopus, giant Pacific octopus, and common octopus). Specific primer sets were designed based on COI gene. We observed that the specific PCR amplicon sizes were 84 bp for big blue octopus, 117 bp for giant Pacific octopus, and 166 bp for common octopus, respectively. This assay was then used to test for specificity and did not show cross-reactivity with 15 cephalopods families. The limit of detection of the multiplex PCR assay was 0.1 pg. Subsequently, 30 commercial food products were then monitored to evaluate the applicability of this assay. All products were specifically amplified, and three octopus species of interest were distinguished. Therefore, this assay can be used as an octopus authentication tool in the seafood industry.

Evaluation of High Resolution Melting (HRM) Analysis for Meat Species Identification of Raw and Cooked Meat

The current study aimed to examine a real-time PCR assay with high-resolution melting (HRM) analysis for the species identification of minced meat samples. Meat samples from several animal species were purchased and minced separately or as a mixture of two species. DNA was extracted from all meat samples and subjected to real-time PCR assay by amplifying species-specific mitochondrial cytochrome b regions. Regarding the meat mixtures, two separate melting curves with specific melt peak temperatures (Tm) were detected. Additionally, DNA from each species was quantified, based on the calibration curves. The results showed that a real-time PCR assay with HRM analysis is suitable for the species identification of meat products, and could be used for the detection of meat frauds.

A Real-Time PCR Method for the Authentication of Common Cuttlefish (Sepia officinalis) in Food Products

Cephalopods are very relevant food resources. The common cuttlefish (Sepia officinalis) is highly appreciated by consumers and there is a lack of rapid methods for its authentication in food products. We introduce a new minor groove binding (MGB) TaqMan real-time PCR (Polymerase Chain Reaction) method for the authentication of S. officinalis in food products to amplify a 122 base pairs (bp) fragment of the mitochondrial COI (Cytochrome Oxidase I) region. Reference and commercial samples of S. officinalis showed a threshold cycle (Ct) mean of 14.40, while the rest of the species examined did not amplify, or showed a significantly different Ct (p < 0.001). The calculated efficiency of the system was 101%, and the minimum DNA quantity detected was 10⁻⁴ ng. No cross-reactivity was detected with any other species, thus, the designed method differentiates S. officinalis from other species of the genus Sepia and other cephalopod species and works for fresh, frozen, grilled, cooked and canned samples of Sepia spp. The method has proved to be reliable and rapid, and it may prove to be a useful tool for the control of fraud in cuttlefish products.

Direct loop-mediated isothermal amplification assay for on-site detection of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a major human pathogen that may produce a variety of toxins and cause staphylococcal food poisoning. In the present study, a direct loop-mediated isothermal amplification (LAMP) assay was developed and validated to detect S. aureus in food samples. Without prior cultural enrichment and DNA extraction steps, bacterial DNA was released by heating at 100°C for 5 min and directly subjected to LAMP assay. Using a set of LAMP primers recognizing six distinct regions of nuc gene, the developed direct LAMP assay was highly specific, and the analytical sensitivity was determined to be 7.6 × 10² CFU/mL. Moreover, with the pre-mixed LAMP reagents stored at –20°C, the entire assay should be finished within 40 min. These features greatly simplified the operating procedure and made the direct LAMP a powerful tool for rapid and on-site detection of S. aureus in food samples.