Article pp.311-325 du Vol.28 n°4-5 (2008)

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FOCUS : JSMTV

Authentication of meat products

E. Engel*, J. Ratel

RÉSUMÉ

La traçabilité analytique des produits carnés

Il existe une demande sociétale croissante de moyens permettant de garantir la qualité des produits carnés et leurs conditions d’élaboration. La traçabilité papier offre une première réponse mais reste falsifiable comme le montrent les crises récentes qui ont secoué la filière. Il est donc nécessaire de développer en com- plément des méthodes instrumentales permettant d’authentifier, à partir de l’analyse du produit fini, les informations clés véhiculées par la traçabilité papier.

L’objectif de cette revue bibliographique est de présenter les grands axes des recherches menées dans ce domaine. Les questions relatives à l’authentification de l’espèce animale d’origine, de la zone géographique de production ou de l’ali- mentation des animaux d’élevage sont plus particulièrement développées. Pour chacune de ces questions, la nature des bio-marqueurs les plus pertinents, les méthodes analytiques les plus performantes et les applications dans la littérature récente sont discutées.

Mots clés

Produits carnés, qualité des aliments, authentification, biomarqueurs, techniques analytiques.

SUMMARY

There is increasing society-wide demand for methods able to guarantee the quality of meat products and the meat production chain. Paper-based traceability offers an initial response but, as recent meat sector crises have shown, it is not fraud proof. It is therefore essential to develop additional instrument-based methods that use analyses run on the finished product to authenticate the key data channelled through the paper-based traceability system. This literature review aims to cover the main lines of research in this direction. Specific focus is given to the issues involved in authenticating the original livestock breed, geographic production zone and diet of the farmed animals. Each of these issues is discussed in terms of the most suitable biomarkers, the most advanced analytical methods and the very latest applications published in the literature.

Keywords

Meat products, food quality, authentication, biomarkers, analytical techniques.

INRA, UR 370 Qualité des Produits Animaux, 63122 Saint-Genès-Champanelle, France

* Correspondence: erwan.engel@clermont.inra.fr

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1 – A RESPONSE TO INCREASING SOCIETY-WIDE DEMAND FOR GUARANTEES ON FOOD QUALITY

There is rising consumer demand for guarantees on food quality and food safety, especially for meat products. Where meat products are concerned, this growing need is largely driven by widely-publicized food safety scares, and cases of inappro- priate risk management practices (Van Rijswijk et al., 2008). Consumers are aware that the quality of an animal product is largely determined by production conditions, and are pressing for guaranteed food production logs. EC regulation 178/2002 laying down regulatory requirements governing documented information traceability throughout the food production chain is a first step in this direction. However, docu- ments can be faked, making it essential to develop additional robust methods that use analyses run on the finished product to authenticate the key data channelled through the paper-based traceability system.

Meat products, which have been at the centre of a number of recent food scares, are now first in line for research, and priority should be given to addressing certain issues related to critical points in the production chain that have heavy repercussions on meat product quality. These priority issues are specific origin, geographical source, and the production procedures employed in rearing the source animals, especially diet. These critical points impact on the quality of meat products by altering their composition and/or structure. Robust analytical methods developed to characterise these variables will eventually make it possible to reliably authenticate the end-to-end history of the meat product.

This article reviews the main methods and systems implemented to authenticate the specific source of meat products, their geographic origin, and how they were produced, with special focus on the type of feed received by the animals being farmed.

2 – AUTHENTICATION OF SPECIFIC ORIGIN

The specific properties of meat products can be shaped by the animal’s genetic background. It is these characteristics that make it possible to distinguish animal breed or species, which is of paramount importance in the production specifications for many meat products. The majority of published research on this issue concerns the authentication of the animal species providing the raw material, whether sourced for human consumption or other non-food uses. The authentication of the animal species providing the raw material for meat-based foods has major importance as a food issue, especially in light of the potential financial losses if materials are fraudulently replaced or added, the specific medical requirements of certain people (with allergies, for example), or even for religious reasons.

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2.1 “Biomarkers” of specific origin

The first-stop components for certifying the specific origin of meat products are proteins and deoxyribonucleic acid (DNA), both of which are molecules present in virtually all biological tissue (Asensio et al., 2008).

Methods based on protein analysis include immunological methods (Ayaz et al., 2007; Macedo-Silva et al., 2000), electrophoresis methods (Vallejo-Cordoba et al., 2005; Bean & Lookhart, 2001) and chromatographic methods (Aristoy et al., 2004;

Schonherr, 2002). These techniques are generally quick and relatively inexpensive.

However, the type and configuration of “biomarker proteins” can vary depending on the tissue analysed and the meat processing procedures involved, especially ther- mal treatments which often have an impact on biomarker structure and stability (Saez et al., 2004).

Conversely, DNA does not change during the animal’s lifetime nor according to the tissue studied, and shows greater stability in response to the treatment used in meat product processing (Dalvit et al., 2007). Furthermore, methods based on DNA analysis also offer much broader potential due to their sensitivity and specificity (Mafra et al., 2008). Therefore, even though proteins remain widely used as biomarkers of the specific origin of meat products, DNA is still undisputedly the first-choice target for development programs focused on authenticating the specific origin of food materials.

2.2 Methods in molecular biology

DNA molecules are analysed through molecular biology techniques based on the extraction, amplification, detection and sometimes on the quantification of targeted or untargeted molecular regions. Amplification, which is a pivotal step in this analytical process, is often performed by a technique called “Polymerase Chain Reaction”

(PCR). PCR is an in vitro gene amplification technique that makes it possible to repli- cate several billions copies of a specific piece of target RNA or DNA sequence. PCR employs specific nucleotide primers capable of hybridizing a determined DNA region, and thus specifically amplifies the region recognized by the primers.

Two PCR amplification approaches are currently being used to authenticate the specific origin of a meat material. The first approach is based on the fact that certain regions of the animal genome are highly specific to the animal kingdom but vary greatly between species. Employing primers specific to these regions leads to the amplification of a pre-determined DNA region which can then be used to screen for the presence of a particular species of interest in a complex sample that also contains the DNA of other species. The second approach is based on the use of randomly-chosen nucleotide sequences as specific primers, which leads to the amplification of several untargeted DNA regions. The “fingerprints” created by these randomly amplified nucleotide sequences often turn out to be characteristic of a given species. PCR techniques have recently gained widespread popularity as a means of authenticating the source species of meat products (Pascoal et al., 2004;

Mafra et al., 2008).

2.3 Applications

Detecting added pork in beef meat. Labelling errors, whether fraudulent or acci- dental, are not just a fraud law problem but can also potentially lead to issues com- promising religious diet choices or consumer health, especially if unwanted germs or

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allergy outbreaks are introduced. This has prompted a large body of research aimed at detecting the presence of pork in meat products that are supposed to be pork- free. By running PCR amplification on a gene marker that is not in the bovine, ovine, chicken or human genomes, Montiel-Sosa et al. (2000) were able to develop a method for detecting pork meat in a range of fresh or processed meat products, to 5% sensitivity. Che Man et al. (2007) also identified a gene marker that could be used to screen various meat products for pork by-products, particularly for guaran- teeing the halal label. However, there are other cases where the food adulteration consists in increasing the proportion of pork meat in a meat product in order to cut product production costs, which makes it insufficient to simply screen for presence or absence of the target species. Quantitative PCR methods, including quantitative competitive PCR, densitometry and real-time PCR, have been developed for quanti- fying the presence of pork meat in raw, cooked or processed meat matrices (Rod- riguez et al., 2005).

Protecting labelled products. It may also be necessary to authenticate specific origin in order to protect labelled products, which often have greater market value than more conventional products. Various studies have used the amplification of

“species-specific” DNA regions to distinguish the farm animal species most widely used for food, such as beef, pork, lamb, chicken and turkey (Dooley et al., 2004;

Lahiff et al., 2001; Laube et al., 2007). There have also been numerous studies designed to authenticate the main species of game, which gives meat products a characteristic taste, texture, and low fat and low cholesterol content (Colombo et al., 2004; Pfeiffer et al., 2004; WOLF et al., 1999, Fajardo et al., 2006), but also to screen for the absence of hormones or veterinary drugs (La Neve et al., 2008). “Species- specific” PCR fingerprints generated through random amplified polymorphic DNA- PCR and arbitrarily primed PCR have also been trialled for distinguishing between the main animal species used in common meat products (Saez et al., 2004). Much of the research designed to check that a meat product matches to the original source breed is based on studying the genes coding for coat colour, which given the human-led genetic selection on European cattle is the main trait for differentiating between breeds (Maudet & Taberlet, 2002). Cattle pigmentation is determined by the distribution of the pigments eumelanin and pheomelanin, which are responsible for brown and black or red and yellow pigmentation, respectively. One of the main targets for identifying meat source breed is the gene encoding the protein receptor binding for the hormone regulating the synthesis of the two melanins, i.e. tyrosinase.

This gene is vulnerable to numerous mutations in cattle populations, and several alleles of the gene have already been identified in different cattle breeds (Klungland et al., 1995; Rouzaud et al., 2000; Maudet & Taberlet, 2002; Graphodatskaya et al., 2002). This has prompted a flurry of research into markers of dairy cattle coat colour as a means of authenticating specific dairy products, but these same markers could also be useful for authenticating the source breeds of specific beef cuts (Maudet &

Taberlet, 2002; Crepaldi et al., 2003). For example, the markers of coat colour in pigs have been paired with other characteristic polymorphic markers to discriminate certain Spanish hams labelled as being sourced exclusively from “pure Iberian” pigs, whereas other Spanish hams are allowed to contain up to 50% Duroc-breed pigs (Fernandez et al., 2004).

Detecting the presence of animal tissue that carries consumer health risks. The bovine spongiform encephalopathy (BSE) crisis and the emergence of a new variant Creutzfeldt-Jakob disease (vCJD), have focussed attention on the use of animal- based meat and bone meal, and particularly central nervous system (CNS) tissue, as ruminant feed. As a consumer protection measure, the EU has legislated against the use of certain ruminant tissues in the food chain (EC Regulation No. 999/2001). The composition of gelatin from animal sources has since been tightly monitored, and

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PCR-based methods have been able to detect beef gelatin in pork gelatin and fish gelatin at concentrations ranging from 0.1 to 0.001% (Tasara et al., 2005). Using PCR identification of “species-specific” DNA regions, Dalmasso et al. (2004) were able to authenticate most of the animal sources used in the rendering industry in animal feed, including meat and bone meal, at a 0.002% limit of detection. Quantita- tive PCR could prove an efficient method for pinpointing whether the presence of ruminant source that is not indicated on the label is actually due to a fraudulent act or accidental contamination. For example, Abdulmawjood et al. (2005) have developed a quantitative PCR method to specifically quantify the presence of cattle tissue considered a consumer risk in meat and meat products. Figure 1 reports one of the results of this work, showing the efficient detection of 0.01% ruminant CNS tissue in meat products (Abdulmawjood et al., 2005).

3 – AUTHENTICATION OF GEOGRAPHIC ORIGIN

The main research stands in this discipline deal with the geographic origin of raw meat material, and thus the authentication of the zone where the livestock was farmed. In economic terms, authenticating the geographic origin of meat products is a leading research priority, given that geographic origin features as one of the core demands in the specifications for the majority of labelled foods. The authentication of geographic origin is also a major issue in terms of food safety. In response to the human vCJD following the BSE crisis, the European Commission established a far- reaching program of legislation governing the labelling of beef products. The intro- duction of pan-European compulsory beef labelling rules from 1^st September 2000 onwards (Council Regulation [EC] No 2772/1999) is designed to provide consumers with correct, complete and transparent information to enable them to make an informed choice on the type and origin of beef they purchase. There is therefore a need to develop on-farm analytical traceability methods.

Figure 1

Authentication of the specific origin of meat products using the PCR technique borrowed from molecular biology. Detection of the presence of residual levels of ruminant central nervous system tissues in meat products. Results testing positive, i.e. detection of target

messenger RNA of the glial fibrillary acid protein following analysis of CNS tissue from cattle (column 1), sheep (column 2) and goat (column 3), but result testing negative

for pig CNS tissue (column 4). Columns 5, 6 and M show control samples and markers.

Source: Abdulmawjood et al. (2005).

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3.1 “Biomarkers” of geographic origin

Certain components entering into the composition of meat products are particularly unambiguous indicators of geographical source (Franke et al., 2005; Luykx &

Van Ruth, 2008). This list includes stable isotopes of elements like hydrogen, oxygen, carbon, nitrogen, sulphur or strontium (Kelly et al., 2005). It also includes other trace components, such as minerals, fatty acids and volatile compounds (Franke et al., 2005), as well as microorganisms (Peres et al., 2007), whose presence and con- centrations depend on the natural environment of the production site. Although there are other potentially efficient methods, measuring isotope ratios is undisputedly the first-choice method for identifying the geographical source of a meat product.

Each environment contains different forms of the atoms, and the isotopes are used to discriminate between environments by a specific number of neutrons. The distribution profile between stable isotope forms traditionally expressed as the relative abundance of two isotopes can be influenced by local environment-related factors. The atoms involved, which principally include hydrogen, oxygen, carbon, nitrogen, sulphur or strontium, can be used to characterize the geographic origin of meat products (Kelly et al., 2005). The ²H/¹H and¹⁸O/¹⁶O ratios reveal the latitude and altitude at which the animal was farmed. ⁸⁷Sr/⁸⁶Sr ratio translates the age and composition of the subsoil bedrock. ¹³C/¹²C ratio is modulated by the type of photosyn- thesis employed by the plants the animal has fed on, while ¹⁵N/¹⁴N ratio gives information on the use of nitrogen fertilizer and ³⁴S/³²S ratio on the use of ammonium sulphate fertilizer.

3.2 Isotope detection methods

Stable isotope ratios are usually measured using a specialization of mass spectrometry called isotope ratio mass spectrometry (IRMS). IRMS is able to differentiate compounds with the same chemical structure but a different relative content of stable isotopes. Boner & Förstel (2004) demonstrated that using this technique makes it possible to determine the stable isotope ratios of carbon (¹³C/¹²C), nitrogen (¹⁵N/¹⁴N), oxygen (¹⁸O/¹⁶O), hydrogen (²H/¹H) and sulphur (³⁴S/³²S). This is achieved by heating the product to a high temperature to transform all its component compounds into gases, generally by combustion or pyrolysis, that are then purified by gas-phase chromatography before being injected into a magnetic sector mass spectrometer.

NMR with compound-specific isotopic enrichment cascades can also be used to assess ²H/¹H ratios (Renou et al., 2004). Rather than working on the full product, this method can be applied to target components extracted from the product before- hand, including water, lipid fractions or even molecules pre-extracted from the meat matrix and separated by gas-phase chromatography.

The heavy isotope ratios of strontium (⁸⁶Sr/⁸⁷Sr) are detected using inductively coupled plasma-mass spectrometry. This “plasma torch” technique consists in ion- izing the sample by injecting it into a high-temperature argon plasma and using mass spectrometry to selectively count the ions of the target element.

The element isotope ratio of a given sample (R_sample) is conventionally compared relative to the standard value measured on a reference product (R_ref), and expressed as an index δ_0/00= (R_sample/R_ref-1)*1000, reported in per mil units.

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At the present time, research is mainly directed at unprocessed meat products.

The question of authenticating geographic origin is a completely different issue for products from ruminants like goats, sheep and cattle, which can be strongly tied to the home soil due to local diet composition, and for products from monogastric animals like pigs and poultry, whose diet is essentially off-ground and relatively stand- ardized across countries and regions. This probably explains why the majority of research into isotope signature-based authentication of geographic origin is focused mainly on ruminant meat products.

Approaches based on measuring a single tracer have generally proven unable to categorically discriminate between products sourced from geographically disperse countries. Hegerding et al. (2002) showed that the δ¹⁸Ο_‰ratio of beef meat was unable to differentiate samples sourced from Germany or Argentina from samples sourced from the UK. Similarly, Franke et al. (2008) showed that simply measuring δ¹⁸Ο_‰ on chicken breast could not discriminate French-raised chickens from Brazilian-raised chickens.

In response to this first set of studies, several teams sought to capitalize on the informational complementarity between isotopic ratios through multi-tracer diagnostics solutions. Boner & Förstel (2004) managed to differentiate beef samples sourced from Germany, Argentina and Chile by measuring δ²Η_‰, δ¹⁸Ο_‰, δ¹³C_‰,δ¹⁴N_‰,δ³⁴S_‰. More recently, Nakashita et al. (2008) showed that δ¹³C_‰ measurements could be combined with δ¹⁸Ο_‰ measurements to discriminate between Japanese, Australian and American-sourced beef samples (figure 2).

However, the multi-tracer isotope-based approach still does not give a generic response to the question of authenticating geographic origin. As underlined by Kelly et al. (2005), seasonal and annual variations in δ¹⁸Ο_‰and δ²Η_‰ ratios together with other fluctuations in cattle diet sources or fodder production driven by economic, zootechnical or climatic factors can all significantly effect the performance of these diagnostics solutions. These arguments become stronger with increasingly similar climates and farming practices in the geographical zones compared.

Heaton et al. (2008) attempted to improve the robustness of these discrimina- tory methods by coupling isotopic and elemental tracers. However, the best discrimination between South American, European and Australian beef, which was obtained with a linear model built from 6 variables (δ¹³C_‰,Sr, Fe, δ²Η_‰, Rb and Se), was still unable to correctly classify the samples. It is probably by continuing in this direction and studying the informational complementarity between different types of geographic origin-targeted tracers (isotopes, trace elements, volatile compounds, microbial ecology-related data, etc.) that it will eventually become possible to give a categorical response on the geographical source of meat products.

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4 – AUTHENTICATION OF THE CONDITION OF PRODUCTION AND PROCESSING

The conditions governing livestock production and the technological processing of their raw meat material are a determinant factor of meat product quality, making them a key target for continued research in the field of product authentication.

In terms of processing modes, most scientific literature leans towards the “fresh vs. frozen” issue, due to its food safety repercussions and the incidence of fraud.

Since a recent review (Ballin & Lametsch, 2008) has already dealt with this issue in detail, we will reorient our analysis towards the authentication of different livestock farming systems, where the key indicator is the type of diet given to the livestock due to the fact that diet influences the core quality factors of the meat end-product, i.e. its nutritional properties, its taste and texture, food safety, and the brand image.

From a nutritional standpoint, it is the animal diet that modulates the fatty acid, antioxidant and mineral contents of the end-product (Scollan et al., 2006; Biesalski 2005; Valsta et al., 2005; Williamson et al., 2005). On a taste and texture level, meat colour, flavour, tenderness and juiciness are all affected by the diet given to the animals. Food-safety-wise, environmental pollutants or certain harmful microorganisms can more or less targetedly contaminate components of the animal diet and then be transferred through to the end-product, where they can potentially represent a human health risk. Finally, farming systems allowing ruminants to feed on pasture have a very positive brand image, as pasture-feeding is associated with good animal welfare, ties to home soil, and the natural, ethically-sound dimension attached to the food products produced. The development of analytical methods for authenticating the diet of farmed animals therefore represents a major challenge for product authentication research.

Figure 2

Authentication of geographical origin of meat using Isotope Ratio Mass Spectrometry:

differentiation of beef products from Australia, Japan, and USA based on stable carbon, nitrogen, and oxygen isotope analysis. Distribution of carbon and oxygen stable isotopic compositions (a) and carbon and nitrogen stable isotopic compositions

(b) of beef defatted dry matter.

Source: Nakashita et al. (2008).

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4.1 “Biomarkers” of farmed-animal feed

There are two components of a meat product that are capable of revealing the type of diet given to farmed animals.

The first possibility is molecular or elemental components in the feed consumed by the animal that are able to more or less resist degradation during ingestion or digestion. Examples include stable isotopes (as discussed in the section on authenticating geographic origin), carotenoids, polyphenols and terpenes. However, the fact that they are extremely specific to plant diversity (polyphenols, terpenes), easily flawable by supplementation (carotenoids) or sensitive to numerous other farm factors (isotopes in general) means that these tracers alone cannot really be viably deployed to authenticate animal diet.

The second possibility also involves metabolites produced by the animal and whose concentrations vary according to type of feed. The main examples are fatty acids, hydrocarbons, ketones, aldehydes, lactones, sulphur compounds. This compound group includes a very broad range of “volatile” molecules with an atomic mass of less than 300 Daltons and whose composition is extremely sensitive to animal farming conditions. These tiny molecules are the end-products of the metabolism in animal tissues or fluids, making them the best-choice control sources. Recent research has confirmed their position as gold-standard “biomarkers” for authenticating the type of diet given to farmed animals (Vasta & Priolo, 2006).

4.2 Methods analysing volatile diet tracers

The technique best-geared to assaying volatile or low-molecular-weight compounds in meat products is gas chromatography-mass spectrometry (GC-MS).

Once the volatile compounds have been extracted from the meat products and made into a concentrate, they are separated by gas-phase chromatography (GC).

GC consists in separating the molecules according to atomic mass and polarity by running them via a carrier gas through a chromatographic column – a fused-silica capillary tube whose inner walls are coated in a stationary phase. The retention time, i.e. the length of time required for a given compound to travel through the column, gives a first clue to the compound’s identity.

Once separated, the volatile components are identified and quantified by mass spectrometry (MS). Mass spectrometry is able to identify and quantify each component. The chemical compound is impacted by high-power electron beam until it fragments into ions, and the abundances of each ion present are measured after a separation step. The component is identified by analysing the relative abundance of the different ions, called a “mass spectrum”, which gives a characteristic profile for each component. The component is quantified by measuring the absolute abundance of the signal of one or more of the ions. Recent advances in GC-MS are set to make it the gold standard in the search for biomarkers of quality. The key emerging technology is two-dimensional gas chromatography coupled with mass spectrometry (GC/GC-MS), which can identify an array of volatile components that were unde- tectable via traditional GC-MS techniques (Tranchida et al., 2004; Ratel & Engel, 2009). Figure 3 shows the chromatogram obtained following GC/GC-MS analysis of the volatile fraction of adipose tissue from lambs.

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The majority of studies performed in this field have addressed the ruminant diet issue. Given that this is probably the point that the quality sector has work on the most, research in this field has focused on discriminating pasture-based and concentrate-based diets (Vasta & Priolo, 2006).

Recent breakthroughs in the analysis of volatile compounds in body fluids and tissues have made it possible to identify a large number of tracers that act as signa- tures distinguishing pastured-based or concentrate-based diet in ruminants fed exclusively on either feed. Since these volatile compounds are generally lipophilic, it is adipose tissue that has proven the main target for screening (Engel & Ratel, 2007).

Indeed, a recent study has demonstrated that running parallel analyses in several different adipose tissues makes the diet authentication tests more robust (Sivadier et al., 2008). Vasta et al. (2007) also demonstrated the feasibility of using volatile compound analysis to authenticate exclusive diets in lamb meat. Whatever tissue is studied, the tracers identified all belong to different chemical families (fatty acids, alkanes, alcohols, aldehydes, ketones, lactones, terpenes) and all carry complemen- tary information on animal diet regimen.

This initial research confirming the ability of volatile compounds to differentiate contrasting dietary regimens has prompted a handful of recent studies to investigate the possibilities for authenticating diets closer to real farm conditions. Many real- world farms run diet-switching, where zootechnical factors often dictate alternating periods of exclusively pasture or concentrate-based diet: it is common farm practice to finish pasture-fed animals on concentrates in order to achieve carcass fattening targets, but some farms may attempt to mimic an exclusively pasture-based system by fraudulently finishing stall-reared lambs on pasture. Recent research has been able to characterize the appearance and disappearance rates of volatile tracers of pasture-feeding in the adipose tissues of either pasture-fed lambs finished for different-length periods on a concentrate diet (Sivadier et al., 2009) or lambs finished on pasture following different-length periods of a concentrate-based diet (Sivadier et al., 2010). This information was integrated into chemometrics run on appropriate

Figure 3

2D chromatogram obtained from the analysis of lamb adipose tissue by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC/GC-TOFMS).

The second chromatographic dimension is able to highlight tracer compounds that could not be separated through the first chromatographic dimension.

Source: Ratel & Engel (2009).

First chromatographic dimension

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data to successfully discriminate between the 4 different finishing periods studied, and under both types of diet-switching system. For example, exploratory data analysis (figure 4) already discriminates between four degrees of grass finishing.

With the focus turned to diagnostic tests run on meat samples, there are changes in muscle tissue composition caused by the various processing steps once the sample is taken, which adds a further source of bias. By tracking the patterns of grass-diet tracers in muscle tissue during ageing, Lehallier et al. (2008) demonstrated that signature compounds of pasture feeding can be identified whatever the meat processing stage.

5 – CONCLUSION

This increase in literature on food authentication probably reflects a growing interest generated by these analytical breakthroughs in the ability to provide objective guarantees of transparency in food production practices but also legitimize and safeguard dis- tinctive signs of food quality in an increasingly segmented marketplace. There is expected to be significant spin-off, not just for customer-perceived trustworthiness of meat-product quality and safety claims, but also for animal producers and institutions, who will be given fully objective methods for vindicating the quality of their products.

Although this review covers the main analytical challenges currently facing the scientific community, research teams will quickly need to rise to new challenges involved in

Figure 4

Authentication of meat farming systems by gas chromatography-mass spectrometry:

discrimination between lambs whose diets have been switched during farming by probing the composition of the volatile fraction of their adipose tissue. First principal component analysis performed on dietary regimen markers identified in two types of adipose tissue (caudal subcutaneous and perirenal fat): clear discrimination between the 4 groups of lambs raised either exclusively on concentrate ( ), or raised on a concentrate diet

and “finished” on pasture for 17 days ( ), 51 days ( ) or 85 days ( ).

Source: Sivadier et al. (2009).

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authenticating meat products farmed according to “sustainable” practices (organically- farmed) or the authentication of meat products farmed from non-cloned animals.

The current focus for research is on developing robust and fraudproof methods that can be used for regulatory purposes. Undoubtedly the most promising solution is to use sensitive and resolutive methods to identify well-targeted and incontroverti- ble biomarkers of the issues addressed in this literature review. For industry sectors and institutions, the challenge is to update the regulations so they can quickly incor- porate these methodological advances in order to provide consumers with guarantees on the quality of meat products, and possibly also their unique selling points.

ACKNOWLEDGEMENTS

This work was supported by European Commission project Chain, Contract No.:

FP6 - 518451. Chain (2006) Developing a stakeholders guide on the vulnerability of food and feed chains to dangerous agents and substances. Available at http://

www.sigmachain.eu.

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