A duplex polymerase chain reaction for the quantitative detection of cows’ milk in goats’ milk cheese

Double-Tube Multiplex TaqMan Real-Time PCR for the Detection of Eight Animal-Derived Dairy Ingredients

Milk and dairy products represent important sources of nutrition in our daily lives. The identification of species within dairy products holds importance for monitoring food adulteration and ensuring traceability. This study presented a method that integrated double-tube and duplex real-time polymerase chain reaction (PCR) with multiplex TaqMan probes to enable the high-throughput detection of animal-derived ingredients in milk and dairy products. The detection system utilized one pair of universal primers, two pairs of specific primers, and eight animal-derived specific probes for cow, buffalo, goat, sheep, camel, yak, horse, and donkey. These components were optimized within a double-tube and four-probe PCR multiplex system. The developed double-tube detection system could simultaneously identify the above eight targets with a detection limit of 10-0.1 pg/μL. Validation using simulated adulterated milk samples demonstrated a detection limit of 0.1%. The primary advantage of this method lies in the simplification of the multiplex quantitative real-time PCR (qPCR) system through the use of universal primers. This method provides an efficient approach for detecting ingredients in dairy products, providing powerful technical support for market supervision.

Assessment of cheese frauds, and relevant detection methods: A systematic review

Dairy products are widely consumed in the world due to their nutritional and functional characteristics. This group of food products are consumed by all age groups due to their health-giving properties. One of these products is cheese which has a high price compared to other dairy products. Because of this, it can be prone to fraud all over the world. Fraud in food products threatens the world's food safety and can cause serious damage to human health. There are many concerns among food authorities in the world about the fraud of food products. FDA, WHO, and the European Commission provide different legislations and definitions for fraud. The purpose of this review is to identify the most susceptible cheese type for fraud and effective methods for evaluating fraud in all types of cheeses. For this, we examined the Web of Science, Scopus, PubMed, and ScienceDirect databases. Mozzarella cheese had the largest share among all cheeses in terms of adulteration due to its many uses. Also, the methods used to evaluate different types of cheese frauds were PCR, Spectrometry, stable isotope, image analysis, electrophoretic, ELISA, sensors, sensory analysis, near-infrared and NMR. The methods that were most used in detecting fraud were PCR and spectrometry methods. Also, the least used method was sensory evaluation.

DNA-based qualitative and quantitative identification of bovine whey powder in goat dairy products

As one of the main ingredients in some milk powders, whey powder is sometimes added to pure goat milk products, which causes health risks, economic fraud, and unfair competition of food industries. This study is the first to explore qualitative and quantitative methods to identify adulteration of bovine whey powder in goat dairy products based on DNA. We extracted DNA from whey powder using a modified DNA extraction method; this exhibited good quality and integrity, with purity of 1.53 to 1.75 and concentration of 122 to 179 ng/μL. Conventional PCR and real-time PCR were compared for qualitative detection of bovine whey powder; real-time PCR demonstrated sensitivity of 0.01 ng/μL, which was higher than the 0.05 ng/μL detected by the conventional PCR method. Furthermore, real-time PCR was conducted for DNA quantitative detection, with good linearity (R² = 0.9858) obtained for bovine whey powder contents from 0.1% to 30%. Relative error decreased with increase of the mixing proportion of whey powder; the coefficient of variation above 0.1% of the mixing ratio was close to or less than 5%; and the relative standard deviation of repeatability results was less than 5%. Considering the economic costs of testing, conventional PCR could be performed first, and samples with obvious intentional adulteration detected can be further accurately quantified by real-time PCR. Overall, this research provides a realistic and effective method for qualitative and quantitative identification of bovine whey powder in goat dairy products, thus laying a good foundation for verification of goat dairy product label claims and industrial control.

Animal Species Authentication in Dairy Products

Milk is one of the most important nutritious foods, widely consumed worldwide, either in its natural form or via dairy products. Currently, several economic, health and ethical issues emphasize the need for a more frequent and rigorous quality control of dairy products and the importance of detecting adulterations in these products. For this reason, several conventional and advanced techniques have been proposed, aiming at detecting and quantifying eventual adulterations, preferentially in a rapid, cost-effective, easy to implement, sensitive and specific way. They have relied mostly on electrophoretic, chromatographic and immunoenzymatic techniques. More recently, mass spectrometry, spectroscopic methods (near infrared (NIR), mid infrared (MIR), nuclear magnetic resonance (NMR) and front face fluorescence coupled to chemometrics), DNA analysis (real-time PCR, high-resolution melting analysis, next generation sequencing and droplet digital PCR) and biosensors have been advanced as innovative tools for dairy product authentication. Milk substitution from high-valued species with lower-cost bovine milk is one of the most frequent adulteration practices. Therefore, this review intends to describe the most relevant developments regarding the current and advanced analytical methodologies applied to species authentication of milk and dairy products.

Real Time-PCR coupled with melt curve analysis for detecting the authenticity of camel milk

The study evaluated the use of Real Time-Polymerase Chain Reaction (RT- PCR) to detect the adulteration of camel milk with goat, cow milk. DNA was isolated from camel milk, camel milk powder, camel milk soap, cow milk, and goat milk using DNA extraction kit. RT- PCR amplified a single piece of DNA into millions of copies. The camel specific primers were designed using the primer- 3 online software and quantification of the isolated DNA was carried out by RT- PCR system through DNA standard curves and cycle threshold (Ct) values. The detection limit of DNA template was in the range of 0.001-0.002%. The reaction mixture (20μL) contained 10 μL SYBR Green master mix, 0.3 μL of 10 μM of each primer and 5 μL DNA. Thermal cycling consisted of an initial denaturation at 95 °C for 1 min, followed by 40 cycles for 15 s at 95 °C and 60 °C for 30 s. The primer pairs used were confirmed for their PCR efficiency, and specific products were evaluated by melt curve analysis. Results indicated positive amplification for the camel milk, camel milk powder, and camel milk soap but negative amplification for cow and goat milk. In conclusion, the RT- PCR based identification is a low cost and appropriate method for camel milk and its products. Although, the yield of DNA from camel milk soap after isolation is low but the isolated DNA segment was easily identified.

Authenticity assessment of dairy products by capillary electrophoresis

Milk and derivatives are a very important part in the diet of the world population. Products from goat, buffalo, and sheep species have a greater economic value than the cow ones, therefore, authenticity frauds by improperly adding cow's milk occur frequently: dairy products are among the seven more attractive foods for adulteration. Milk from each of the above-cited animal species has its own definite profile of whey proteins (variants of α-lactalbumin and β-lactoglobulin) and its definite profile of caseins (variants of α_S1 -, α_S2 -, β-, and κ-casein). Such proteins can be usefully exploited as markers of authenticity by using capillary electrophoresis which is the technique of choice for the analysis of proteins. Due to the multiple adjustable parameters that are unknown to other analytical techniques, capillary electrophoresis is able to detect frauds in milk mixtures and cheese with little use of solvents, fast analysis time, and ease of operation. This makes it attractive and competitive for routine checks that are very important to fight the adulteration market. Advantages and limitations are discussed.

Short communication: Detection of undeclared presence of bovine milk in buffalo yogurt

The authenticity of buffalo (Bubalus bubalis) dairy products is a focal issue, considering the increasing demand for buffalo milk products. Therefore, the aim of this study was to investigate the undeclared presence of bovine (Bos taurus) milk in buffalo yogurt, to understand which risk factors might make the product vulnerable to fraud. Real-time PCR assay showed the undeclared presence of bovine DNA in addition to buffalo DNA in 18 of 72 samples. Given the widespread lack of data on the presence of undeclared milk species in buffalo dairy products, the study provides a significant insight into the incidence of fraud in the buffalo dairy field. The data from this study could help improve the analysis of food safety risks along the buffalo milk supply chain and in the dairy processing industry, perceived as being highly vulnerable to food fraud, and prioritize target areas for food policy making to steer and enforce European food fraud regulations.

Identification and Detection of Bioactive Peptides in Milk and Dairy Products: Remarks about Agro-Foods

Food-based components represent major sources of functional bioactive compounds. Milk is a rich source of multiple bioactive peptides that not only help to fulfill consumers 'nutritional requirements but also play a significant role in preventing several health disorders. Understanding the chemical composition of milk and its products is critical for producing consistent and high-quality dairy products and functional dairy ingredients. Over the last two decades, peptides have gained significant attention by scientific evidence for its beneficial health impacts besides their established nutrient value. Increasing awareness of essential milk proteins has facilitated the development of novel milk protein products that are progressively required for nutritional benefits. The need to better understand the beneficial effects of milk-protein derived peptides has, therefore, led to the development of analytical approaches for the isolation, separation and identification of bioactive peptides in complex dairy products. Continuous emphasis is on the biological function and nutritional characteristics of milk constituents using several powerful techniques, namely omics, model cell lines, gut microbiome analysis and imaging techniques. This review briefly describes the state-of-the-art approach of peptidomics and lipidomics profiling approaches for the identification and detection of milk-derived bioactive peptides while taking into account recent progress in their analysis and emphasizing the difficulty of analysis of these functional and endogenous peptides.

Authentication of caprine milk and cheese by commercial qPCR assay

The objective of the study was to investigate potential adulteration of commercial caprine milks and cheeses with bovine milk using commercial qPCR assay. The assay comprised of bovine-, ovine- and caprine-specific primers and TaqMan probe and mammalian internal control. Specificity, sensitivity, linearity, reproducibility and efficiency of the bovine assay were tested as well. Specificity was verified by running reaction on the DNA of other milk-producing species (caprine and ovine) and made-up bovine-caprine (v/v) milk mixes. In both experiments, a bovine DNA fragment was amplified whereas no amplification was obtained from the other species. Sensitivity, linearity, reproducibility and efficiency were tested on 10-fold dilution series of 10 ng bovine DNA. The assay has shown good linearity (R2 = 0.983) within whole range, with efficiency of 86% and excellent reproducibility (SD around the CT for the technical replicates <0.5). The sensitivity was adequate, as calculated LOD and LOQ were 1.44 pg and 2.94 pg of bovine DNA, respectively. Finally, the assay was used to authenticate 5 caprine milk samples and 5 caprine cheese samples, purchased from local supermarkets. Totally, 1 milk sample has shown the fluorescence signal, which exceeded baseline in cycle 39.01 ±0.69. However, the signal was above LOD and LOQ suggesting that there could not be unambiguously declared any adulteration with bovine milk. Amplification of bovine-specific DNA was not observed in the other samples indicating products were not adulterated. The commercial qPCR assay has proved that real-time PCR assays, as well as DNA-based techniques in a general, are the excellent and reliable tools for fighting with frauds in the food industry and protecting the public health. 

Forensic genetics and genomics: Much more than just a human affair

While traditional forensic genetics has been oriented towards using human DNA in criminal investigation and civil court cases, it currently presents a much wider application range, including not only legal situations sensu stricto but also and, increasingly often, to preemptively avoid judicial processes. Despite some difficulties, current forensic genetics is progressively incorporating the analysis of nonhuman genetic material to a greater extent. The analysis of this material-including other animal species, plants, or microorganisms-is now broadly used, providing ancillary evidence in criminalistics in cases such as animal attacks, trafficking of species, bioterrorism and biocrimes, and identification of fraudulent food composition, among many others. Here, we explore how nonhuman forensic genetics is being revolutionized by the increasing variety of genetic markers, the establishment of faster, less error-burdened and cheaper sequencing technologies, and the emergence and improvement of models, methods, and bioinformatics facilities.

Methodologies for the Characterization of the Quality of Dairy Products

The growing interest of consumers in food quality and safety issues has contributed to the increasing demand for sensitive and rapid analytical technologies. Physicochemical, textural, sensory, etc., methods have been used to evaluate the quality and authenticity of milk and dairy products. Despite the importance of these standard methods, they are expensive and time consuming. Recently, spectroscopic methods have shown great potential due to speed of analysis, minimal sample preparation, high repeatability, low cost, and, most of all, the fact that these techniques are noninvasive and nondestructive and, therefore, could be applied to any on-line monitoring system. This chapter gave examples of the application of the most commonly traditional methods for the determination of the quality of milk and dairy products. A special focus is devoted to the use of infrared and fluorescence spectroscopies for the evaluation of the quality of dairy products.

Validation of a fast real-time PCR method to detect fraud and mislabeling in milk and dairy products

Fast real-time PCR TaqMan assays were developed and validated for species identification in dairy products. Based on the amplification of 12S rRNA and cytB partial genes of mitochondrial DNA, the methods were demonstrated to be sensitive, fast, and species-specific for Bos taurus, Ovis aries, Bubalus bubalis, and Capra hircus. The limit of detection calculated was lower than 1%, and the efficiency was reported to be higher than 96% in every assay. An internal amplification control was used to detect possible false negatives. The method was validated by means of laboratory-prepared samples mixing different species. Moreover, 18 commercial dairy samples were analyzed by both real-time PCR and isoelectric focusing, the official European Union reference method. The 4 TaqMan assays were confirmed to be a useful tool for milk and dairy product authentication.

Assessment of goat milk adulteration with a label-free monolithically integrated optoelectronic biosensor

The label-free detection of bovine milk in goat milk through a miniaturized optical biosensor is presented. The biosensor consists of ten planar silicon nitride waveguide Broad-Band Mach-Zehnder interferometers (BB-MZIs) monolithically integrated and self-aligned with their respective silicon LEDs on the same Si chip. The BB-MZIs were transformed to biosensing transducers by functionalizing their sensing arm with bovine k-casein. Measurements were performed by continuously recording the transmission spectra of each interferometer through an external spectrometer. The amount of bovine milk in goat milk was determined through a competitive immunoassay by passing over the sensor mixtures of anti-k-casein antibodies with the calibrators or the samples. The output spectra of each BB-MZI recorded during the reaction were subjected to Discrete Fourier Transform in order to convert the observed spectral shifts to phase shifts in the wavenumber domain. The method had a detection limit of 0.04 % (v/v) bovine milk in goat milk, dynamic range 0.1-1.0 % (v/v), recoveries 93-110 %, and intra- and inter-assay coefficients of variation less than 12 and 15 %, respectively. The proposed biosensor compared well in terms of analytical performance with a competitive ELISA developed using the same monoclonal antibodies. Nevertheless, the duration of the biosensor assay was 10 min whereas the ELISA required 2 h. Thus, the fast and sensitive determinations along with the small size of the sensor make it ideal for incorporation into portable devices for assessment of goat or ewe's milk adulteration with bovine milk at the point-of-need.

A duplex polymerase chain reaction assay for the identification of goat cashmere and sheep wool

In this article attempts were made to establish one-step duplex PCR assay for the identification of goat cashmere and sheep wool. Primers were selected from published papers or designed in the well-conserved region of mitochondrial D-loop genes after alignment of the available sequences in the GenBank database. A fragment of 294 bp from cashmere goat was amplified and three PCR fragments including a bright main band of approximately 404 bp in length were obtained from sheep. The duplex PCR was found to be effective in detecting mixed samples precisely when sheep wool was mixed to goat cashmere with the relative proportion of over 9.09%. The duplex PCR could be considered as a simple and promising method in identification of goat cashmere and sheep wool.

New method for the simultaneous identification of cow, sheep, goat, and water buffalo in dairy products by analysis of short species-specific mitochondrial DNA targets

A novel method is presented here as an analytical tool for food control and authentication of dairy products manufactured from the milk of cow, sheep, goat, and buffalo. The method is based on multiplex polymerase chain reaction (PCR) of species-specific mitochondrial DNA (mtDNA) targets followed by fragment size analysis by capillary electrophoresis. The method includes (a) simultaneous detection of four species, (b) internal control for DNA extraction and PCR, (c) mtDNA as a target for PCR, (d) amplicons of <200 bp, and (e) flexibility in the electrophoresis and fragment size detection method. Species identification proved to be straightforward, efficient, sensitive, and robust. The method is sensitive to an at least 1% (v/v) relative proportion of milk in binary mixtures. A survey of commercial products showed that 12.5% failed to conform to the description of the contents, by either the introduction or absence of listed species, thus demonstrating the relevance of this type of testing.

Identification of hare meat by a species-specific marker of mitochondrial origin

Meat species identification in food has gained increasing interest in recent years due to public health, economic and legal concerns. Following the consumer trend towards high quality products, game meat has earned much attention. The aim of the present work was to develop a DNA-based technique able to identify hare meat. Mitochondrial cytochrome b gene was used to design species-specific primers for hare detection. The new primers proved to be highly specific to Lepus species, allowing the detection of 0.01% of hare meat in pork meat by polymerase chain reaction (PCR). A real-time PCR assay with the new intercalating EvaGreen dye was further proposed as a specific and fast tool for hare identification with increased sensitivity (1pg) compared to end-point PCR (10pg). It can be concluded that the proposed new primers can be used by both species-specific end-point PCR or real-time PCR to accurately authenticate hare meat.