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Authentic food is generally defined as reliable and trustworthy. The majority of foodstuffs are generally of animal origin; therefore species identification is currently an issue of major concern due to the consumers' increasing attention to food quality matters. Genetically modified organisms (GMOs) and genetically modified food (GM foods) have also become subjects of considerable public debate. The consumers' lack of confidence, in particular towards food of animal origin, is due to several reasons including both food safety and socio-economic changes. The promotion of health nowadays, requires the development of an environment to help people make healthy choices. The labels are used for providing necessary information to the consumers and also for promoting the products. Nutrition labelling regarding the content of a food product is one example of this approach. Nutrition labelling has been created by guidance and legislation, for consumers' assistance (Cowburn, 2004). There are several ways in which food can be mislabelled. The substitution of one of the components by a cheaper one, its adulteration with a neutral ingredient (e.g. water) as well as overdeclaring a quantitative ingredient declaration and the non-declaration of processes (e.g. freezing) are some misdescribed results (Woolfe, 2004).
Legislative authority establishes that meat products must be accurately labelled regarding species content. The European Union (EU) has always paid great attention to food safety because it is very important for the European economy. Commission Directive 2001/101/EC amended the Food Labelling Directive (2000/13/EC), and developed a European generic definition of meat for the purposes of labelling, presentation and advertising of foodstuffs. The definition puts meat ingredient declarations in meat products on the same basis throughout the European Union, providing consumers with consistent and more transparent information. It also contributes to the smooth function of the common market by removing impediments equal condition and competition (Blanchfield, 2005).
Bovine Spongiform Encephalopathy (BSE) is certainly concerned as one of the most serious food safety problems of the past years, contributing towards a drastic reduction of beef consumption in all European countries. BSE was then followed by the dioxin crisis and the avian influenza in the poultry industry (Asensio, 2008). Nowadays, people are more aware than years ago of ecological and environmental matters, and the demand for organic food products has increased, although the market's globalisation makes it difficult to check on processing methods. All these reasons have contributed to develop an authentication system for meat products. Authenticity is the answer to the consumers' demand of transparency and it is becoming synonymous with safe and high quality control. Authorities and scientists are looking into reliable and convenient authentication methods to prevent fraud. Several identification methods have been studied analysing different compartments of the animal species cells.
Quantitative and qualitative methods for animal species identification
Reliable and sensitive analytical tools are required for detection and identification of animal food ingredients. All methods employed for the determination of animal species, are based on the biochemistry of the animals' cell compartments in one form or another. Therefore, qualitative and quantitative biochemical traits set all individuals apart from one another. For animal species only, the detection is based on protein- and DNA-based methods. Before the development of the DNA-based methods, some discriminative ingredients (e.g. histidine dipeptides or fatty acids), were used to differentiate between domestic animal species. Isoelectric focusing (IEF) and Liquid Chromatography (LC) used to be the commonly used methods for species identification. IEF is based on the properties of the protein using a pH gradient and is successful for frozen or raw, unheated meat and fish products. Adulteration test on meat products is quite difficult, especially on heat processed or spiced products since heat treatment results in denaturised or degraded muscle proteins. Therefore, antibodies which retain their antigenicity after high temperature process must be prepared to heat stable soluble proteins. Enzyme Linked Immunosorbent Assay (ELISA) enables the detection and quantification of heat treated proteins in meat products. One major disadvantage of immunoassays is the non-availability of antibodies of many species or cross-reactions of the antibodies with related organisms. Furthermore, the presence of proteins is always a function of age, maturity and type of tissue in which they are expressed. For the identification of meat species, is largely growing and genetic analysis has been proposed for future implementation due to its precision, durability and ability to overcome limits of heat processing and canning. For the above reasons, protein-based methods are being replaced more and more by methods based on nucleic acids. DNA hybridisation and Polymerase Chain Reaction coupled with Restriction Length Polymorphism (PCR-RFLP) sequencing are routinely used nowadays to identify animal species in food products, although some of these techniques cannot distinguish between closely related species at chemical level. Additionally quantitative PCR methods have shown the ability to identify the origin of cooked mammalian cooked products.
Raw and cooked meat proteins
The extraction of serum albumin proteins from raw meat samples compared to muscle related glycoproteins which are species specific regarding cooked or lightly processed meat containing food products. Gelatine is produced by partial hydrolysis of collagen mainly from bones and skin, so should not be present in vegetarian foodstuffs.
Recent consumer concern relating to a variety of issues, such as BSE and genetically modified products has resulted in increased awareness regarding the composition of meat meals. Methods for identification of raw and cooked meat based on ELISA have been established. Detection of species adulteration in cooked meats appears to be more complicated than in raw meats because heat induces the denaturation of myoglobin and most other immunogenic proteins. A variety of DNA-based methods are potentially available in meat and meat products authentication. Genetic methods require expertise and are usually expensive for every day use in food control laboratories.