Meat is defined as the dressed flesh, of certain animals, consumed as food. Most often this includes the skeletal muscles and associated fat and other tissues along with edible organs and offal. Meat and meat products have a great significance in human nutrition and thus for maintenance of consumer health. Meat is very rich source of proteins, containing all the essential amino acids Detection of species fraud in meat products is important for consumer protection and food industries. As meat and meat products represent an important and large component of human food, their quality is of concern to the consumers, the regulatory authorities, the processors and the retailers. The higher demand for meat and meat products accompanied by their escalating cost makes them prone to fraudulent adulteration, substitution and mislabelling. Adulteration literally means debasing something or rendering it impure by mixing it with some inferior or harmful substance. The determination of food authenticity and the detection of adulteration are major issues in the meat industry and are attracting increasing amount of attention. Identification of the species of origin in meat samples can be done using physical method, DNA based techniques and spectrophotometry method.

Fraudulent adulteration of costly meat with cheap meat is a common practice observed throughout the world. The ability to detect less desirable or objectionable species in meat products is important not only for economic, health, religious, and ethical reasons; but also, to ensure fair trade and compliance with legislation. Authenticity testing of the animal species present in food is important for economic, safety, legal, religious and health reasons (1-7). Product consumption containing non declared meat proteins can induce allergic reactions in predisposed individuals. Customers are gaining interest to know the origin of the foods because of quality related reasons, health and safety reasons and concerns about animal welfare. Due to some cost and religion concerns the meat producers have to comply with some rules issued by the legal institutions (8-15). Hence, it is an important task for food control laboratories to be able to carry out species differentiation of raw materials to be used for industrial food preparation and the detection of animal species in food products. 

Available methods used to identify different species are electrophoresis, liquid chromatography, dot blot hybridization, randomly amplified polymorphic DNA PCR, RFLP analysis, and species-specific PCR. However, molecular techniques are considered as reliable methods to identify meat types since there is a need to develop faster, cheaper and safe methods [16-22]. Besides histological tests, immunoassays or DNA analysis, spectroscopic techniques are gaining interest due to being low cost and easily applied. The power of the spectroscopy comes from giving chance to detect or quantify physical, chemical and biological attributes of the samples based on their spectral signature, and imaging transforms this information into chemical maps for spatial visualization. Thus, these methods can be used to determine what attributes, how much and where they are located in the sample [23-29]. DNA Based Methods to Identify the Meat Types,Today, many consumers are concerned about the meat they eat and accurate labelling is important to inform consumer choice. The choice one product over another can reflect aspects of lifestyle (e.g. vegetarianism and organic food), religion (e.g. absence of pork from some diets), diet and health concerns (e.g. absence of allergens) [30-36]. In addition, accurate labelling is important to support fair-trade. Additional descriptive label information can be added as a consequence of branding, product marketing purposes and regulations [37-43]. False or inadvertent mislabeling of meat products, which cannot be distinguished using conventional strategies is still predominant over the world. Some individuals may not like to consume the meat of equine and pork due to ethical, religious, or compassionate reasons. So, these clusters of consumers demand methods to detect types of meat (equine, pork, chicken, and mouse) in the food [44-50]. The Meat adulteration and quality assurance of meat and meat products are very important for human health protection. For detection of adulteration of meat and meat products by unauthorized plant food additives and low-priced, illegal, or decomposed animal tissues, lung, heart, connective tissue, smooth muscles, cartilage, and plant tissues [51-57]. Consumption of adulterated food contributes to numerous diseases in society, ranging from mild to life threatening. Therefore, detection of adulteration in food is essential to ensure the safety of the food we consume [58-64]. Meat species adulteration is a worldwide problem which violates food labeling laws. Thus, determination of the species of the meat components in meat products is an essential task in food hygiene, meat adulteration in ground and comminuted products has been a widespread problem in retail markets [65-71]. In the Egyptian markets, the addition of an undeclared meat species (such as chicken in beef products) and/ or unacceptable meat type (pork and donkey or the replacement of one valuable species by another inexpensive one are common examples of meat adulteration [72-78]. Away from price, religious customs are one of the distinguished subjects that should be considered. For example, it is forbidden for Muslims to consume the flesh of pork and its derivatives. Something else, some permitted meat is not alluring for Egyptian customers, as donkey and horse meat, that may be sold without any offered costs, and thus there's a critical chance of blending them in Egyptian nourishments [79-85]. The species of meat used in prepared, cooked, or compounded blends is not continually plausible to be distinguished by schedule examination. However, denaturation of meat proteins during heat treatment or any other technological processes and variation of protein compositions, even in the same species, reduce the chance of success for these methods. Besides, these strategies may be insufficient to segregate between species which are in near connection and are not reasonable for schedule utilize, as the confinement of species-specific proteins is troublesome and time-expending [86-92]. Adulteration of meat and its products is a dangerous and worldwide problem which violates food labeling laws so, must apply reliable and scientifically accepted tests for detecting that adulteration. Actually, applications of PCR technique were reliable, easier, faster and relatively stable for detection of meat adulteration compared with other trials [93-99].

Most Common Types of Food Adulteration, biological Adulteration, Substituting one type of meat with another, such as mixing beef with horse or dog meat. Selling meat from sick or dead animals instead of fresh, healthy meat. Mixing meat with non-meat components such as fat or ground animal skin [114-120]. Chemical Adulteration, adding unauthorized preservatives like formalin or nitrites to extend shelf life. Injecting meat with water, salt, or phosphates to increase weight and enhance appearance. Adulteration with adding preservatives like boric acid, sulphur salts and others with the aim of delaying or concealing the spoilage of meat and giving the meat colour Bright and appears fresh. Using artificial dyes to make the meat appear fresher [121-127]. physical adulteration, adding water or ice to increase its weight. using fillers as starch or flour to increase volume. adding non-meat tissues like bones, cartilages or connective tissue. adding foreign materials like metal,glass or plastic. using texturized protein like plant proteins increase volume and reduce costs [128-134].

Methods for the identification of meats, Anatomical, Colour, texture, odour, structure of bones, flesh and fat. Physical, Refractive index of fat, iodine value. Chemical, Glycogen content, lenolenic acid content.  Biochemical: Iso-electric focusing (IEF), SDS-PAGE technique. Immunological: Agar gel precipitation test (AGPT), Counterimmuno electrophoresis (CIEP), Agarose gel electrophoresis (AGE), Enzyme linked immunosorbant assay (ELISA), Peroxidase anti-peroxidase technique (PAP), Radioimmuno assay (RIA), Starch agarose electrophoresis. Novel methods: DNA analysis, DNA based techniques such as polymerase chain reaction (PCR) and gene probes [135-141]. Anatomical methods, Species of meat can be differentiated on the basis on anatomicalpeculiarities,Colour, texture and odour of flesh, Buffalo meat is darker and coarse when compared to cattle meat. Chevon has typical goaty odour especially in males. Osseous tissue like bones or cartilage, Bones or cartilages when present along with the meat can be used for species differentiation based on the anatomical pecularities of the specific bones. Poultry meat can be identified from other species owing to smaller and soft nature of the bones. Colour, consistency and distribution of fat, Cattle fat is yellowish in colour while buffalo fat is creamy white. Fat in pigs is present subcutaneously and in abundant quantity but is not intermixed with flesh, whereas cattle/buffalo fat is uniformly distributed with muscle tissues termed as marbling. Physical methods- Meat speciation, based on certain physical parameters is sometimes followed in absence of specific anatomical differences. In physical techniques, general appearance for detection of different meat species is taken into consideration. It is a combined perception of colour, texture, odour and presence of other body parts along with meat. One of the most important sensory qualities tested in meat is the appearance Texture and freshness, colour, Taste, smell, flavour, and juiciness.  It gives the primary idea about the meat species on the basis of quality characterstics of meat and fat. Each type of meat has a special colour as Cows meat is bright red and yellow fat, Buffalo’s meat is dark red and the fat is white, Goats and sheep meat hair tends to stick to it, Donkeys meat is dark red to dark bluish brown, bad smell, its fibres are prominent, a little fat with a copper colour and a greasy consistency. Physical methods of adulteration detection including microscopic and macroscopic visual structural assessments, as well as analysis of physical parameters such as morphological characteristics, structure, solubility, and bulk density, have been designed but these methods do not guarantee qualitative adulterant detection.  Visual structural analysis by macroscopic and microscopic methods is very valuable for identifying microbes as harmful types, especially fungi. Adulteration can be detected by sampling a small amount on a glass plate and visually examining impurities because clean foods do not contain such impurities [142-148]. The differentiation between lambs and goats’ meat through carcass identification, selling female meat as male meat, also by sewing, selling fatal meat as veal meat, one of the types of veal or beef meat or young buffalo, which feed only on milk; As the average age to obtain veal meat, The flesh of the foetus is saturated with water, pale in colour, and contains a high percentage of glycogen. Selling the meat of lean animals after slaughtering them without medical treatment, Inflating the carcass to make the consumer think that it is full of meat, sell pastrami before it dries, the moisture content must not exceed @, Selling cat meat as rabbit meat. Injecting chicken meat with water with syringes to increase weight and freeze it, imported canned meat made from unhealthy meat as madness Cows, spoiled meat, containing entrails, heads, or appendages, Meat not fit for human consumption, Forgery of the declaration label on packages by changing the country of origin [149-155]. The Pre-cooking tests of meat, Heating the knife and then cutting the meat produce bad smell it is invalid, to find out the meat of dead animals the meat is very tough, and we put a piece of meat in water, if it is contaminated with blood indicate it is from dead animal. The tests while cooking of meat, when donkey meat is immersed in water, yellow oily spots appear. The texture of boiled meat is rough plus a sweet taste. Measurement of refractive index of fat, Fat is liquefied and refractive index of oil is measured by refractometer. R.I. values of some animals are: horse 53.5, cattle not above 40 and pig not above 51.9. Estimation of iodine value- This test measures the amount of iodine absorbed by unsaturated fatty acids present in the fat and varies in different animals. Iodine value of fat in loin is 71 to 86, in cattle 38 to 46, in sheep 35 to 46 and in pig it is 50 to 70. Chemical methods, Chemical methods are used to detect the presence or absence of a particular chemical constituent and/or its quantity in meat. The tests, however, have not gained popularity since the chemicals are not species specific and cannot differentiate between the chemical agents with similar reactivity. Besides, the methods are time consuming and exhaustive (156-161).  Some of the chemical methods used are Glycogen content, Horse flesh has higher glycogen content than other animals, but when horse is exhausted and glycogen is depleted, it may lead to misinterpret of the results. Lenolenic acid, Horse fat contains about 1-2% lenolenic acid, in other animals it is not present in proportions higher than 0.1%.  make moisture analysis to detect added water or ice make, Protein analysis to detect added fillers or non- meat tissues. Measure decomposition of meat components by microbes, autolysis enzymes, or because of chemical reactions such as fat rancidity, Chemical compounds, Total reduced volatiles, Estimation of the indole number, Determination of ammonia and Fat rancidity test. The Ehrlich test of meat, add formalin to a piece of meat after one day if it appears, a distinctive smell like that of a roasted goose. The meat is donkey meat. Biochemical methods, Electrophoresis of meat/ organ extract or any other biological material results in separation of various proteins when migrate on the suitable medium under the influence of an electrical field. These separated protein fractions are species specific and thus help in identifying origin of biological materials [160-166]. Iso-electric focusing (IEF), Proteins are low or high molecular weight compounds either acidic or alkaline in reaction and negatively charged substances. Besides, they have a specific pH at which their overall electric charge becomes zero and they get precipitated. This precipitation point is termed as iso-electric point (PI). A suitable pH gradient is formed on the polyacrylamide or agarose gel with the help of amphoteric buffers (ampholytes) having specific pH range such as 3-9, 5-8 etc. When muscleproteins migrate on polyacrylamide or agarose gel having ampholyte bed under strong electric field, they precipitate at respective PI points forming a precipitation band on the gel. The precipitation band/bands of proteins are detected by staining and/or by densitometric scanning. The number of bands, their distribution pattern and isoelectric (PI) point at which they are precipitated are very specific to a species of animal which helps in identifying the species origin of meat even in mixtures. This technique can be used for identification of species of animal using many biological materials like blood, serum, milk, meat, organs, serum etc. The results specific, reliable and can be reproduced [153-159]. SDS-PAGE technique, the overall charge on the proteins becomes zero when treated with detergents like sodium dodecyl sulphate (SDS) due to denaturation. While migrating on suitable medium like polyacrylamide gel (PAGE), agarose gel etc. having a corresponding pore size such proteins precipitate on the basis of the molecular weights forming the characteristic bands. Staining and densitometric scanning of such bands provides an indication about the species of animal as the banding patterns of tissues from different animals vary. Identification of species is based on the molecular weight of proteins and not on the basis of their PI points as in IEF. Isoelectric focussing and SDS-PAGE technique enable differentiation of raw and partially heated (cooked) meats. Besides, it has been reported that the results vary from laboratory to laboratory, and person to person. In boiled or cooked meats, the bands produced are diffused, non-reproducible and difficult to decifer. As such the technique is not of much use in differentiation of cooked/processed meats [107-113]. Immunological/serological methods, on introduction in body, foreign proteins (antigen) stimulate the host immune system to generate antibodies which can be demonstrated in its serum. In vitro combination of the antigen and antibody results in a variety of reactions such as flocculation, precipitation, agglutination, cytolysis and neutralisation. The response is very specific to the antigen or antibody types involved as the reactions occur only between homologous antigen and antibody. The principle is employed for species identification of variety of biological materials such as milk, meat, organs, semen etc. In meat speciation, raw meat extract is commonly used as antigen for antibody formation in a suitable animal like rabbit or sheep. Though the antibodies can be used for species identification of raw meats, their greatest drawback is the occurrence of cross reactions with similar proteins which makes differentiation of phylogenetically related species (e.g. sheep and goat) difficult. Also, cooked meat is not identifiable. However, these limitations have been managed with the development of antibodies to heat stable antigens from adrenal glands.  Use of adrenal glands for antibody production has been advocated as they have two antigenic fractions, one adrenal specific and another present in other organs, blood and skeletal muscles. This widely distributed antigen is found to be species specific. Because of their resistance to boiling temperature and ethanol perceptibility, these are widely known as BE antigens, wherein B stands for resistance to boiling temperature and E for ethanol perceptibility the antisera can be developed either in rabbits or sheep, and cross-reacting antibodies can be removed by immunoadsorption to make them species specific. These mono specific antisera are useful for identification of tissues, organs, biological fluids (urine, milk, semen, etc.), semi cooked and cooked meats, and processed meat products employing various immunological techniques [133-139]. Novel methods, Chromatography based, Chromatography is a sensitive technique used to separate, identify, and purify small molecules in a mixture, such as fatty acids, carbohydrates, and amino acids, for qualitative and quantitative analyses. Chromatographic methods are the most common priority for assessing the authenticity of most foods. This is partly because techniques such as chromatography can be used both to detect adulterants and as a motive to determine authenticity. Modern analytical methods like high-performance liquid chromatography, gas chromatography–mass spectrometry, etc. can accurately identify the types and concentrations of different types of food degrading agents. gas chromatography is often used for the separation of different types of unseparated products, for adulteration detection, and for the authentication and identification of organic substances. Chromatography combined with mass spectroscopy (MS) and Fourier transform infrared spectroscopy (FTIR) has been widely used for the detection of harmful materials in food [122-128]. Spectroscopy based, Defined spectroscopy as the study of the absorption, transmission, and emission of light and other radiations of matter and their dependence on the wavelength of the radiation. Spectroscopic techniques like near-infrared (NIR), mid-infrared (MIR), and Raman spectroscopy have been widely and successfully used as sensitive and fast analytical techniques for detecting food adulteration. These techniques have the advantage of being nondestructive and having a relatively low analysis cost. The Fourier transform infrared (FTIR) based on mid-infrared (MIR) spectroscopy is one of the most commonly used spectroscopic technique for food fraud currently used by both industry and government laboratories. Infrared Spectroscopy (FT-IR) have been taken into consideration due to the need for new and rapid analytical methods in the field of food adulteration. These methods are generally based on transmittance or reflectance readings, and they require none or very little sample pre-treatment. Infrared (IR) spectroscopy as a well-accepted analytical technique because it is environment-friendly and does not need complicated sample preparation procedure. The power of the spectroscopy comes from giving chance to detect or quantify physical, chemical and biological attributes of the samples based on their spectral signature, and imaging transforms this information into chemical maps for spatial visualization. Thus, these methods can be used to determine what attributes, how much and where they are located in the sample [66-72]. Molecular technique, Nowadays, DNA is preferred for species identification due to its great constancy, compared to proteins. Applications of polymerase chain reaction (PCR) have been augmented because of their easiness, speed, and specificity. Multiplex PCR is an effective technique that can instantaneously amplify the template mix, diminish the recognition charge, and eliminate the failure of single PCR of detecting only one meat species at a time. Moreover, it investigated the application of a novel multiplex PCR (M-PCR) as a sensitive and specific method to detect adulteration in meat products sold in different supermarkets in Cairo, Egypt with equine, pig, chicken, and mouse meat.The PCR was applied to identify six meat (cattle, pig, chicken, sheep, goat and horse) as raw materials for products. By mixing seven primers in appropriate ratios, species-specific DNA fragments could be identified by only one multiplex PCR. Application of PCR for identification of cyt b genes for differentiation of meats of different animal species was performed essentially by using primers. It was noticed that the sensitivity and accuracy of PCR in detection of species of meat and its adulteration greatly overcome potency of AGID test as PCR depends on the detection of the specific DNA molecules which is a relatively stable allowing analysis of processed and heat-treated food products. Failure of AGID to detect species adulteration may be attributed to addition of spices, salts and another ingredient. Species identification in heat processed products is hindered by progressive denaturation of the protein markers, leading to loss of solubility and antigenicity. The information suggests that PCRRFLP are useful tools for detecting food adulteration, depending on the processed food chosen, and will help to protect consumers’ rights by enabling the enforcement of labelling regulations in a country, so we recommend continuous screening of meat products for adulteration in local markets and restaurants should be applied under veterinary authority. Similar issue should be done for imported meat and meat products. Education of consumers is the keystone of the effective control of meat adulteration. Then consumers should purchase their requirement of meat and meat products from known trusted shops and restaurants. DNA analysis is now a famous approach for meat species identification. Nowadays, DNA is preferred for species identification due to its great constancy, compared to proteins. Applications of polymerase chain reaction (PCR) have been augmented because of their easiness, speed, and specificity. Multiplex PCR is an effective technique that can instantaneously amplify the template mix, diminish the recognition charge, and eliminate the failure of single PCR of detecting only one meat species at a time. DNA based techniques such as gene probes and polymerase chain reaction (PCR) can be used for speciation of meat. Complimentary DNA or RNA strands can be used for the detection of DNA or RNA of suspected species by nucleic acid hybridization technique. A specific nucleic acid sequence can be exponentially amplified in vitro in PCR resulting in large quantity of DNA sequence. Selected primers are used for amplification of searched genetic material and the amplicones can be detected by gel electrophoresis or detection methods antibody. Identification of the species of origin in meat samples can be done using physical method, DNA based techniques and spectrophotometry method. Current available methods used to identify different species are electrophoresis, liquid chromatography, dot blot hybridization, randomly amplified polymorphic DNA PCR, RFLP analysis, and species-specific PCR. However, molecular techniques are considered as reliable methods to identify meat types since there is a need to develop faster, cheaper and safe methods. Besides histological tests, immunoassays or DNA analysis, spectroscopic techniques are gaining interest due to being low cost and easily applied [38-44]. DNA Based Methods to Identify the Meat Types Meat and meat products are very susceptible to spoilage and also expensive as compared to other food types. Among the techniques used for species identification, PCR is a DNA based technique allowing the detection of very low amounts of nucleic acid probes and the determination of their sequence via the amplification of DNA or RNA individual strains. This method has some advantages such as high sensitivity and rapid performance with high sample numbers. DNA-based techniques frequently used for meat species identification include DNA barcoding, DNA hybridization, and sequence analysis and PCR-based techniques include randomly amplified polymorphic DNA (PCR-RAPD), restriction fragment length polymorphism (PCR-RFLP), PCR with species-specific primers, real-time PCR and PCR-nucleotide sequencing. Among DNAbased methods, polymerase chain reaction (PCR) is the most welldeveloped molecular technique up to now and provides a simple, rapid, highly sensitive and specific tool for detecting constituents of animal origin in foods. A primary aspect of successfully detecting a species by PCR is to choose adequate genetic markers to develop the assay. Both nuclear and mitochondrial genes have been targeted for the identification of meet fraud. In addition, the use of PCR in food analysis has provided various analytical methods for rapid detection and identification at species and intra-species levels; however, DNA-based methods still face some important limitations, especially for quantitative measurements of food composition. To keep things simple, the molecular methods for identifying meat species and meat products are divided into three categories: PCR, DNA barcoding, and DNA hybridization [99-105]. Species-specific PCR for meat species identification, A PCR assay is used to validate the meat types and to check crosscontamination against the product and ingredient classification, using mitochondrial species-specific markers. At present, the PCR technique using species-specific primers is one of the genetic methods that allow novel identification of different meat species, both raw meats and meats subjected to thermal treatments. This technique is a precise, sensitive, cheap, and less time-consuming method that helps the novel identification of many mammalian and bird species in meat and meat products as compared to other PCR-based assays. DNA Barcoding, puts forward the use of a sequence from a single genomic region (defined as barcode), as the base of a recognition system capable to identify all animal species. This biomolecular methodology consists in the identification of the belonging species through the sequencing of a fragment of mitochondrial genes, its alignment and comparison with the information available on the databases. RAPD (Random Amplified Polymorphic DNA) is a very fast, easy to perform, and does not require expensive equipment method. In this method, PCR allow the examination of genomic variation without prior knowledge of DNA sequences. PCR can be used to identify the meat species and produce good fingerprints from processed products in which DNA has been only slightly degraded, such as smoked or salted products. RAPD is a modified PCR technique in which DNA fragments are generated in a very short period of time which can be visualized in a gel electrophoresis. In this technique DNA extraction is the first step, then it is amplified with specific primer. It is followed by denaturation of strand at 94°C for 1min, the primer annealing at 47°C for 1min. Then extension of primer is done at 72°C for 1min. Electrophoresis (10µL portion of amplification) is carried out at at 100V in a 3% agarose gel [100-106].

The adulteration of meat and meat products, it has a harmful effect on health, Hides the smell of rotting meat, it hides the true colour of raw meat, adding nicotinic acid compounds (one of the elements of a group) Vitamin B garage) or sodium nicotinate to meat Preserved to maintaining the desired red colour of meat for the consumer. Eating a large amount of these compounds leads to symptoms that appear Pathology in humans as flushing of the face and neck with itching, nausea, Sweating and abdominal cramping. Selling meat from animals infected with diseases This is done by slaughtering sick animals outside approved state slaughterhouses indicates It is recommended to avoid buying meat without seals and Selling goat meat as lamb by sewing a lamb into the back of the goat.

The author declares no conflicts of interest.