Duplex PCR approach for the detection and quantification of donkey, horse and mule in raw and heat-processed meat products

Rapid detection of duck ingredient in adulterated foods by isothermal recombinase polymerase amplification assays

Duck is often used in meat fraud as a substitute for more expensive meats. Rapid detection of duck ingredient in meat products is of great significance for combating meat fraud and safeguarding the interests of consumers. Therefore, we aim to develop duck-specific recombinase polymerase amplification (RPA)-based assays for the rapid detection of duck ingredient in animal-derived foods. Using Cytb gene as target, the real-time RPA and RPA combined with lateral flow strips (LFS RPA) were developed successfully for the rapid detection of ducks in 20 min at 39 °C and 40 °C, respectively. The assays did not show cross-reactions with 6 other livestock and poultry. The developed RPA assays could detect 10 pg duck genomic DNA per reaction and 0.1 % (w/w) duck ingredient in duck and mutton mixed powder within 30 min, including a rapid nucleic acid extraction. Furthermore, duck ingredient could be detected in 30 different actual foods including heat-processed meats and blood products. Therefore, duck-specific real-time RPA and LFS RPA assays were successfully developed with good specificity and sensitivity, which could enable rapid detection of duck ingredient in the field and provide technical support for combating the meat fraud.

Amplification Refractory Mutation System (ARMS)-PCR for Waxy Sorghum Authentication with Single-Nucleotide Resolution

Waxy sorghum has greater economic value than wild sorghum in relation to their use in food processing and the brewing industry. Thus, the authentication of the waxy sorghum species is an important issue. Herein, a rapid and sensitive Authentication Amplification Refractory Mutation System-PCR (aARMS-PCR) method was employed to identify sorghum species via its ability to resolve single-nucleotide in genes. As a proof of concept, we chose a species of waxy sorghum containing the wx^c mutation which is abundantly used in liquor brewing. The aARMS-PCR can distinguish non-wx^c sorghum from wx^c sorghum to guarantee identification of specific waxy sorghum species. It allowed to detect as low as 1% non-wx^c sorghum in sorghum mixtures, which ar one of the most sensitive tools for food authentication. Due to its ability for resolving genes with single-nucleotide resolution and high sensitivity, aARMS-PCR may have wider applicability in monitoring food adulteration, offering a rapid food authenticity verification in the control of adulteration.

CRISPR-Cas12-Based Rapid Authentication of Halal Food

The halal food market is globally growing along with the increased risk of adulteration. We proposed an amplification-free and mix-to-read CRISPR-Cas12-based nucleic acid analytical strategy allowing rapid identification and analysis of pork components, thus enriching the toolbox for ensuring halal food authenticity. We designed and optimized guide RNA (gRNA) targeting the pork cytochrome b (Cyt b) gene. gRNA allowed specific identification of the target Cyt b gene from pork components followed by activation of Cas12 protein to abundantly cleave single-stranded DNA probes with terminally labeled fluorophore and quencher groups, thus turning on fluorescence. The presence of the pork Cyt b gene thus can be mix-and-read- and only-one-step-detected, which may indicate the risk of halal food adulteration. The method allowed specific discrimination of pork meat from beef, mutton, and chicken and yielded a detection limit of 2.7 ng/μL of total DNA from pork meat. The reliability of the method was tested using the following processed meat products: halal foods beef luncheon meat and spiced beef and non-halal foods sausage and dried pork slices. The CRISPR-Cas12-based nucleic acid test strategy is promising for rapid food authentication.

Detection of meat from horse, donkey and their hybrids (mule/hinny) by duplex real-time fluorescent PCR

Meat adulteration is currently a common practice worldwide. In China, adulteration of donkey meat products with the similar species (horse and mule/hinny) meat and mislabeling are becoming widespread concerns. In this study, a sensitive and species-specific duplex real-time PCR assay based on the simultaneous amplification of fragments of the creatine kinase muscle gene family, was developed and optimized for the identification of horse, donkey and mule /hinny species in raw and heat-processed meat products. Duplex real-time PCR results showed different fluorescence amplification curves for horse and donkey. Both kinds of fluorescence amplification curves appeared simultaneously for mule/hinny. The limit of detection (LOD) of the method was up to 0.01 ng /μL. The method and strategy developed in this study could be applied to detect the presence of adulterants from horse and mule /hinny meat in raw donkey meat and meat products.

Single tube multiplex PCR assay for the identification of banned meat species

Food adulteration has a direct impact on public health, religious faith, fair-trades, and wildlife. In the present study, a reliable and sensitive assay has been developed for verifying meat adulteration in food chain. The multiplex PCR system was optimised for identification of chicken, cow/buffalo, sheep/goat, horse/donkey, pork, and dog DNAs in a single reaction mixture simultaneously. The primers were designed using 12 S rRNA gene sequences with fragment size in the range of 113 bp to 800 bp, which can be easily visualised on agarose gel electrophoresis making the technique economical. After validation of accuracy, specificity, and sensitivity, commercially available meat products (n = 190) were screened, comprising both raw and cooked meat samples. The results demonstrated a high rate of adulteration (54.5%) in meat products. The technique developed here can be easily used for screening of different meat products for export and import purposes as well as for food inspection and livestock diagnostic laboratories.

Development of a Real-Time PCR Assay for the Detection of Donkey (Equus asinus) Meat in Meat Mixtures Treated under Different Processing Conditions

In this study, a donkey-specific primer pair and probe were designed from mitochondrial cytochrome b gene for the detection of raw donkey meat and different processed meat mixtures. The PCR product size for donkey DNA was 99 bp, and primer specificity was verified using 20 animal species. The limit of detection (LOD) was examined by serially diluting donkey DNA. Using real-time PCR, 0.001 ng of donkey DNA could be detected. In addition, binary meat mixtures with various percentages of donkey meat (0.001%, 0.01%, 0.1%, 1%, 10%, and 100%) in beef were analyzed to determine the sensitivity of this real-time PCR assay. At least 0.001% of donkey meat was detected in raw, boiled, roasted, dried, grinded, fried, and autoclaved meat mixtures. The developed real-time PCR method showed sufficient specificity and sensitivity in identification of donkey meat and could be a useful tool for the identification of donkey meat in processed products.

Mass ratio quantitative detection for kidney bean in lotus seed paste using duplex droplet digital PCR and chip digital PCR

Two "mass ratio-DNA copy concentration ratio" formulas were established respectively on droplet digital PCR (ddPCR) and chip-based digital PCR (cdPCR) to determine the mass ratio of kidney bean, a common alternative plant-derived ingredient in lotus seed paste. The limit of detection for DNA copy concentration of kidney bean and lotus seed was 6 copies/μL. Quantitative detection range was set from 5 to 80%, and the limit of quantification for mass ratio of kidney bean in lotus seed paste was defined as 5%. Results of 6 simulated samples and 16 prepackaged pastes in this work offer compelling evidence that an innovative scheme for quantitative detection of kidney bean in lotus seed paste was available, and provide technical support for the identification of suspicious ingredients from fraudulent substitution or adventitious contamination. Graphical abstract Two "mass ratio-DNA copy concentration ratio" formulas were established respectively on droplet digital PCR (ddPCR) and chip digital PCR (cdPCR) to determine the mass ratio of kidney bean in adulterated lotus seed paste. It was the first time to quantify adulterate food by directly converting DNA copy concentration ratio obtained from digital PCR to mass ratio, which could provide strong technical support for quantitative detection of adulterated food.

Identification of donkey meat in foods using species-specific PCR combined with lateral flow immunoassay

Food authenticity is a global issue and has raised increasing concerns in the past decades. DNA-based methods are more favourable than the conventional protein-based techniques and have been applied to species identification and meat fraud detection. To effectively identify donkey meat for meat product authentication, a highly specific and robust method that coupled polymerase chain reaction (PCR) with lateral flow immunoassay (LFI) was developed. Donkey-specific PCR primers were designed by targeting at the mitochondrial D-loop gene and the specificity was verified in silico and in vitro against 22 species involved in meat authentication. A limit of detection of 0.0013 ng μL^-1 DNA extract was achieved and as low as 0.001% w/w (raw) and 0.01% w/w (cooked) donkey meat in beef were successfully detected using the developed PCR-LFI. LFI strip-based visualization of PCR products allowed for a 10-fold higher sensitivity than conventional gel electrophoresis and significantly reduced the analysis time for the post-PCR analysis. This PCR-LFI is highly suitable for rapid identification of donkey or incorporating into multiplex screening protocol for other meat authentication in the laboratories of both regulatory agencies and commercial services.

Specific PCR method for detection of species origin in biochemical drugs via primers for the ATPase 8 gene by electrophoresis

A PCR method is described to identify the species origin of various animal and human tissue-derived biochemical drugs. Four commercialized drugs, including spermary tablets, compound embryonic bovine liver extract tablets, spleen aminopeptide solution, and placenta polypeptide injection, were used as a proof-of-principle in this study. Primers were designed to amplify conservative regions of mitochondrial cytochrome b and ATPase 8 genes from beef, pork, lamb and human DNA, respectively. The specificity of primers for ATPase 8 gene is found to be higher than those for cytochrome b under the given experimental conditions. The amplicon sizes of ATPase 8 were 212, 271, 293 and 405 bp for pork, beef, lamb and human tissue, respectively. The minimum detectable concentration of DNA sample for species identification is 0.05-0.5 pg·μL^-1. The species origin can be distinguished by this method in extremely low concentrations of template DNAs extracted. Conceivably, this PCR method for meat authentication may be extended to quality control of other biochemical drugs and raw materials. Graphical abstract A specific PCR method was developed for the detection of species origin in biochemical drugs via species-specific primers targeting mitochondrial ATPase 8 genes. The PCR products were separated by gel electrophoresis and species origins were indicated by comparison to references.

A simple and sensitive two-tube multiplex PCR assay for simultaneous detection of ten meat species

A sensitive and reliable technique for meat species identification is required to prevent food adulteration, particularly in meat production. This work developed an optimized multiplex PCR assay for simultaneous identification of five commonly consumed and five commonly banned meat species in meat products. We designed primers that specifically amplified mitochondrial ATPase subunit 8 gene regions of different lengths of bovine, ovine, swine, chicken, turkey, cat, dog, mouse and human DNAs. The developed multiplex PCR assay proved to be specific, sensitive down to 30pg DNA per reaction, reproducible and economical. It could be used with a variety of raw meats and processed food samples and is easily applicable in a routine laboratory analysis without specific sophisticated equipment.