Detection of adulterated murine components in meat products by TaqMan© real-time PCR

Simple and field-adapted species identification of biological specimens combining multiplex multienzyme isothermal rapid amplification, lateral flow dipsticks, and universal primers for initial rapid screening without standard PCR laboratory

Species identification of biological specimens can provide the valuable clues and accelerate the speed of prosecution material processing for forensic investigation, especially when the case scene is inaccessible and the physical evidence is cumbersome. Thus, establishing a rapid, simple, and field-adapted species identification method is crucial for forensic scientists, particularly as first-line technology at the crime scene for initial rapid screening. In this study, we established a new field-adapted species identification method by combining multiplex multienzyme isothermal rapid amplification (MIRA), lateral flow dipstick (LFD) system, and universal primers. Universal primers targeting COX I and COX II genes were used in multiplex MIRA-LFD system for seven species identification, and a dedicated MIRA-LFD system primer targeting CYT B gene was used to detect the human material. DNA extraction was performed by collecting DNA directly from the centrifuged supernatant. Our study found that the entire amplification process took only 15 min at 37 °C and the results of LFDs could be visually observed after 10 min. The detection sensitivity of human material could reach 10 pg, which is equivalent to the detection of single cell. Different common animal samples mixed at the ratio of 1 ng:1 ng, 10 ng:1 ng, and 1 ng:10 ng could be detected successfully. Furthermore, the damaged and degraded samples could also be detected. Therefore, the convenient, feasible, and rapid approach for species identification is suitable for popularization as first-line technology at the crime scene for initial rapid screening and provides a great convenient for forensic application.

Detection and Quantification of Adulterated Beef and Mutton Products by Multiplex Droplet Digital PCR

In order to seek high profit, businesses mix beef and mutton with cheap meat, such as duck, pork, and chicken. Five pairs of primers were designed for quintuple droplet digital PCR (qddPCR) of specific genomic regions from five selected species and specificity and amplification efficiency were determined. The mixed DNA template with an equal copy number was used for detecting the accuracy and limit of multiplex PCR. The results showed that the primers and probes of the five selected species had good specificity with the minimum number of detection copies: 0.15 copies/µL beef (Bos taurus), 0.28 copies/μL duck (Anas platyrhynchos), 0.37 copies/μL pork (Sus scrofa), 0.39 copies/μL chicken (Gallus gallus), and 0.41 copies/μL mutton (Ovis aries), respectively. The five sets of primers and probes could quickly judge whether the specified meat components existed in the food commodities.

Detection of Species Substitution in the Meat Value Chain by High-Resolution Melting Analysis of Mitochondrial PCR Products

Substituting high commercial-value meats with similar cheaper or undesirable species is a common form of food fraud that raises ethical, religious, and dietary concerns. Measures to monitor meat substitution are being put in place in many developed countries. However, information about similar efforts in sub-Saharan Africa is sparse. We used PCR coupled with high-resolution melting (PCR-HRM) analysis targeting three mitochondrial genes—cytochrome oxidase 1 (CO1), cytochrome b (cyt b), and 16S rRNA—to detect species substitution in meat sold to consumers in Nairobi, Kenya. Out of 107 meat samples representing seven livestock animals, 11 (10.3%) had been substituted, with the highest rate being observed in samples sold as goat. Our results indicate that PCR-HRM analysis is a cost- and time-effective technique that can be employed to detect species substitution. The combined use of the three mitochondrial markers produced PCR-HRM profiles that successfully allowed for the consistent distinction of species in the analysis of raw, cooked, dried, and rotten meat samples, as well as of meat admixtures. We propose that this approach has broad applications in the protection of consumers against food fraud in the meat industry in low- and middle-income countries such as Kenya, as well as in developed countries.

An effective analytical droplet digital PCR approach for identification and quantification of fur-bearing animal meat in raw and processed food

Available nuclear gene sequences for meat detection are still rare and little applicability in the investigation of new types of meat adulteration such as fox, mink and raccoon dog was performed. In the present work, we developed a reliable qualitative and quantitative detection method for fur-bearing animal meat based on droplet digital PCR (ddPCR). Three sets of primers and probes targeted nuclear genes for fox, mink and raccoon dog were designed for ddPCR system; In addition, turkey was selected as internal reference to transform the copy numbers to the fraction of target species. Results indicated that the dynamic ranges of three fur-bearing animals were all from 1% to 90%; the limit of detection (LOD) and limit of quantification (LOQ) for three fur-bearing animals were same, with LOD 0.1% (w/w) and LOQ 1% (w/w). Moreover, we confirmed that different additives had no effect on quantification accuracy in the ddPCR assay.

Fraud in Animal Origin Food Products: Advances in Emerging Spectroscopic Detection Methods over the Past Five Years

Animal origin food products, including fish and seafood, meat and poultry, milk and dairy foods, and other related products play significant roles in human nutrition. However, fraud in this food sector frequently occurs, leading to negative economic impacts on consumers and potential risks to public health and the environment. Therefore, the development of analytical techniques that can rapidly detect fraud and verify the authenticity of such products is of paramount importance. Traditionally, a wide variety of targeted approaches, such as chemical, chromatographic, molecular, and protein-based techniques, among others, have been frequently used to identify animal species, production methods, provenance, and processing of food products. Although these conventional methods are accurate and reliable, they are destructive, time-consuming, and can only be employed at the laboratory scale. On the contrary, alternative methods based mainly on spectroscopy have emerged in recent years as invaluable tools to overcome most of the limitations associated with traditional measurements. The number of scientific studies reporting on various authenticity issues investigated by vibrational spectroscopy, nuclear magnetic resonance, and fluorescence spectroscopy has increased substantially over the past few years, indicating the tremendous potential of these techniques in the fight against food fraud. It is the aim of the present manuscript to review the state-of-the-art research advances since 2015 regarding the use of analytical methods applied to detect fraud in food products of animal origin, with particular attention paid to spectroscopic measurements coupled with chemometric analysis. The opportunities and challenges surrounding the use of spectroscopic techniques and possible future directions will also be discussed.

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.

Comparative review and the recent progress in detection technologies of meat product adulteration

Meat adulteration, mainly for the purpose of economic pursuit, is widespread and leads to serious public health risks, religious violations, and moral loss. Rapid, effective, accurate, and reliable detection technologies are keys to effectively supervising meat adulteration. Considering the importance and rapid advances in meat adulteration detection technologies, a comprehensive review to summarize the recent progress in this area and to suggest directions for future progress is beneficial. In this review, destructive meat adulteration technologies based on DNA, protein, and metabolite analyses and nondestructive technologies based on spectroscopy were comparatively analyzed. The advantages and disadvantages, application situations of these technologies were discussed. In the future, determining suitable indicators or markers is particularly important for destructive methods. To improve sensitivity and save time, new interdisciplinary technologies, such as biochips and biosensors, are promising for application in the future. For nondestructive techniques, convenient and effective chemometric models are crucial, and the development of portable devices based on these technologies for onsite monitoring is a future trend. Moreover, omics technologies, especially proteomics, are important methods in laboratory detection because they enable multispecies detection and unknown target screening by using mass spectrometry databases.

Development and validation of a rapid kit for authenticity of murine meat in meat products with a species-specific PCR assay

Adulteration of meat products with murine meat poses a huge threat to consumer health and leads to serious disruption in food markets. Species authentication of murine meat is still technically challenging. We, therefore, developed a species-specific PCR kit consisting of murine meat DNA extraction, PCR reaction and identifying systems. We designed novel universal primers targeting highly conserved region on mitochondrial cytochrome b gene (cyt b) from four murines (lab rats, lab mice, wild rat and wild mice), as well as specific primers for meat from four widely consumed animal species, cattle, sheep, duck and donkey. Simultaneously, pasmid inserted specific cyt b fragment was cloned and used as the internal positve control in the kit. The kit parameters of specificity, sensitivity, stability and validity were determined using mimic counterfeiting meatball. The specificity of the DNA detection kit was 100% in authentication of the four fraudulent meats of cattle, sheep, duck and donkey mixed murine meat. The minimum detection limit of the sample DNA was 0.1 μg. The kit, which had freeze-thawed up to 20 times and stored for 1 year, also was powerful in detecting an amount of 0.1 mg in artificial counterfeited cattle, sheep, duck and donkey meat products. The murine-species DNA detection kit proposed in this study has proved to be a simple, accurate and effective assay, and can be applied to the identification of murine meat traces in common edible meat, to ensure the realisable implementation of meat product market supervision.

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.

N-Glycan Profile as a Tool in Qualitative and Quantitative Analysis of Meat Adulteration

Adulteration of meat and meat products causes concerns to consumers. It is necessary to develop novel robust and sensitive methods that can authenticate the origin of meat by qualitative and quantitative means to minimize the drawbacks of the existing methods. This study has shown that the protein N-glycosylation profiles of different meats are species specific and thus can be used for meat authentication. Based on the N-glycan pattern, the investigated five meat species (beef, chicken, pork, duck, and mutton) can be distinguished by principal component analysis, and partial least square regression was performed to build a calibration and validation model for the prediction of adulteration ratio. Using this method, beef samples adulterated with a lower-value duck meat could be detected down to the addition ratio as low as 2.2%. The most distinguishing N-glycans from beef and duck were elucidated for the detailed structures.

Development of a fast real-time PCR assay based on TaqMan probe for identification of edible rice grasshopper (Oxya chinensis) in processed food products

Interest in using insects as an alternative source of food for humans is increasing. However, few analytical methods provide accurate information about the presence of insect species in processed foods. In this study, we developed a fast real-time PCR assay based on a TaqMan probe that can be performed within 40 min to detect edible rice grasshopper in commercial food products. A rice grasshopper-specific primer pair and probe targeting the cytochrome c oxidase subunit 1 (COI) gene were newly designed, having an amplicon size of 110 bp. The specificity of this primer pair and probe was verified using 19 insects and five crustaceans and no cross-reactivity was obtained against the non-target species. The absolute limit of detection (LOD) was 0.5 pg of rice grasshopper DNA, and as low as 0.1% of rice grasshopper was detected in raw, heat-treated, and autoclaved binary insect mixtures. To evaluate the effect of food matrix, binary mixtures containing rice grasshopper in wheat were used additionally, and at least 0.1% of target species was detected using this assay. The applicability of this assay was confirmed using nine commercial food samples labeled as containing rice grasshopper or locust. The fast real-time PCR developed in this study is a specific and sensitive method for identifying edible rice grasshopper in various food samples.

A Multiplex PCR Assay Mediated by Universal Primers for the Detection of Adulterated Meat in Mutton

This study aimed to establish a multiplex PCR detection system mediated by "universal primers," which would be able to determine whether mutton meat contained nonmutton ingredients from rats, foxes, and ducks. Based on the sequence variation of specific mitochondrial genes, nine different multiplex PCR primers were designed, and four kinds of meat products were rapidly identified by electrophoresis using an optimized multiplex PCR system based on the molecular weight differences of the amplified products. Multiplex PCR applications optimized for meat food source from food samples for testing was used to verify the accuracy of the identification method. The results showed that the primers in multiple PCR system mediated by universal primers could be used for the rapid identification of rat, fox, duck, and sheep meat in mutton products, and the detection sensitivity could reach 0.05 ng/μL. The identification of food samples validated the practical value of this method. Therefore, a multiplex PCR system mediated by universal primers was established, which can be used to quickly identify the origin of animal ingredients from rats, foxes, and ducks in mutton products.

Insight into Rapid DNA-Specific Identification of Animal Origin Based on FTIR Analysis: A Case Study

In this study, a methodology has been proposed to identify the origin of animal DNA, employing high throughput extension accessory Fourier transform infrared (HT-FTIR) spectroscopy coupled with chemometrics. Important discriminatory characteristics were identified in the FTIR spectral peaks of 51 standard DNA samples (25 from bovine and 26 from fish origins), including 1710, 1659, 1608, 1531, 1404, 1375, 1248, 1091, 1060, and 966 cm⁻¹. In particular, the bands at 1708 and 1668 cm⁻¹ were higher in fish DNA than in bovine DNA, while the reverse was true for the band at 1530 cm⁻¹ was shown the opposite result. It was also found that the PO₂⁻ V_as/V_s ratio (1238/1094 cm⁻¹) was significantly higher (p < 0.05) in bovine DNA than in fish DNA. These discriminatory characteristics were further revealed to be closely related to the base content and base sequences of different samples. Multivariate analyses, such as principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were conducted, and both the sensitivity and specificity values of PLS-DA model were one. This methodology has been further validated by 20 meat tissue samples (4 from bovine, 5 from ovine, 5 from porcine, and 6 from fish origins), and these were successfully differentiated. This case study demonstrated that FTIR spectroscopy coupled with PLS-DA discriminant model could provide a rapid, sensitive, and reliable approach for the identification of DNA of animal origin. This methodology could be widely applied in food, feed, forensic science, and archaeology studies.

Collaborative ring trial of two real-time PCR assays for the detection of porcine- and chicken-derived material in meat products

In this study, we describe an inter-laboratory collaborative ring trial validation of species-specific TaqMan real-time PCR assays for the detection of porcine- and chicken-derived materials in meat products. We comprehensively evaluated the performance of these assays in different environments and situations. This validation included the participation of thirteen laboratories across Europe and Asia. The results from the thirteen participating laboratories were analyzed to determine the specificity, accuracy, false positive rate, limit of detection (LOD), and probability of detection (POD) of the developed methods. These results indicated that the methods developed to detect porcine- and chicken-derived materials in meat products are robust and repeatable. The false positive and false negative rates were both 0%, and the LOD was determined to be five copies/reaction. The laboratory standard deviation (σ_L) was 0.30 for both detection methods, indicating that the developed methods are suitable for detection and identification of the porcine- and chicken-derived materials in meat products.

Detection and quantification of beef and pork materials in meat products by duplex droplet digital PCR

Meat products often consist of meat from multiple animal species, and inaccurate food product adulteration and mislabeling can negatively affect consumers. Therefore, a cost-effective and reliable method for identification and quantification of animal species in meat products is required. In this study, we developed a duplex droplet digital PCR (dddPCR) detection and quantification system to simultaneously identify and quantify the source of meat in samples containing a mixture of beef (Bos taurus) and pork (Sus scrofa) in a single digital PCR reaction tube. Mixed meat samples of known composition were used to test the accuracy and applicability of this method. The limit of detection (LOD) and the limit of quantification (LOQ) of this detection and quantification system were also identified. We conclude that our dddPCR detection and quantification system is suitable for quality control and routine analyses of meat products.

Interlaboratory validation of a real-time PCR detection method for bovine- and ovine-derived material

In this work we performed interlaboratory validation of a Taqman real-time PCR method for the identification of bovine and ovine material. The Bos taurus beta-actin gene (ACTB) and Ovis aries prolactin receptor gene (PRLR) were selected as the bovine and ovine species-specific amplifying target sequences, and primers and TaqMan probes were designed accordingly. The precision, efficiency, false positive rate, limit of detection (LOD_95%) and probability of detection (POD) were determined, and the results demonstrated that both bovine and ovine detection methods performed well. The high homogeneity of the results indicates that the detection methods are suitable for a wide range of applications, and the tools developed herein could be applied by official and third-party detection institution to maintain quality in the food and feedstuff industries.

Weigh Biomaterials by Quantifying Species-specific DNA with Real-time PCR

What's on the label is not what's in the bottle, from food products to herbal medicinal products (HMPs), economically-motivated biomaterials adulteration is a long-term problem affecting the food and drug industry. Accurate identification of the biomaterial ingredients in processed commodities is highly desirable. In this field, DNA-based techniques have proved to be powerful tools to overcome qualitative challenges. However, is it possible to quantify the weight of biological materials with PCR? Therefore, a basic scientific question needs to be answered: what's the relationship between DNA content and the mass of biological materials? Is DNA content directly proportional to the mass of biological materials as most of the researchers previously thought? In this study, we firstly found that there exists a linear relation between DNA contents and the weight of biomaterials indeed when the analytical practices are fully controlled. In this case, the mass of targeted biomaterials in the highly processed commercial products can also be calculated by quantifying the species-specific DNA through classic real-time PCR with a good reproducibility.

Lab-on-a-Chip-Based PCR-RFLP Assay for the Detection of Malayan Box Turtle (Cuora amboinensis) in the Food Chain and Traditional Chinese Medicines

The Malayan box turtle (Cuora amboinensis) (MBT) is a vulnerable and protected turtle species, but it is a lucrative item in the illegal wildlife trade because of its great appeal as an exotic food item and in traditional medicine. Although several polymerase chain reaction (PCR) assays to identify MBT by various routes have been documented, their applicability for forensic authentication remains inconclusive due to the long length of the amplicon targets, which are easily broken down by natural decomposition, environmental stresses or physiochemical treatments during food processing. To address this research gap, we developed, for the first time, a species-specific PCR-restriction fragment length polymorphism (RFLP) assay with a very short target length (120 bp) to detect MBT in the food chain; this authentication ensured better security and reliability through molecular fingerprints. The PCR-amplified product was digested with Bfa1 endonuclease, and distinctive restriction fingerprints (72, 43 and 5 bp) for MBT were found upon separation in a microfluidic chip-based automated electrophoresis system, which enhances the resolution of short oligos. The chances of any false negative identifications were eliminated through the use of a universal endogenous control for eukaryotes, and the limit of detection was 0.0001 ng DNA or 0.01% of the meat under admixed states. Finally, the optimized PCR-RFLP assay was validated for the screening of raw and processed commercial meatballs, burgers and frankfurters, which are very popular in most countries. The optimized PCR-RFLP assay was further used to screen MBT materials in 153 traditional Chinese medicines of 17 different brands and 62 of them were found MBT positive; wherein the ingredients were not declared in product labels. Overall, the novel assay demonstrated sufficient merit for use in any forensic and/or archaeological authentication of MBT, even under a state of decomposition.