Technologies in individual animal identification and meat products traceability

Abstract

An effective and trustworthy traceability system contributes to improving food quality and safety and responds to consumers’ demand for food provenance information. Safe meat and its products are crucial to consumers and society. Livestock feeding regime and geographical origin are closely related to the properties and the safety of animal origin food, but the information is often invisible to consumers, which makes is easier to use fraudulent practices throughout the whole supply chain. Technologies and their proper use in traceability systems are important for the safety of animal origin foods. An essential component in an integrated traceability chain includes individual animal identification and trace back of related meat products. In this review, we examine the technologies for individual animal identification, including the radio frequency identification system and DNA fingerprinting. For meat products, traceability technologies focus on the chemical components fingerprinting, including measurement of stable isotope ratios, mineral element tracing and organic component fingerprinting. Also, future trends in food traceability systems need to be improved to promote the establishment of more efficient and trustworthy traceability systems to ensure food safety and quality up to standard.

Keywords:

• Food safety
• food quality
• traceability technology
• individual animal identification
• meat products traceability

Introduction

In the last couple of decades, some astounding food safety events, such as bovine spongiform encephalopathy (BSE), foot-and-mouth disease and avian influenza [1–3], made consumers increasingly concerned about the safety of their food consumption. Meanwhile, food fraud is becoming a serious problem worldwide driven by global food trade and economic opportunity [4–8]. To ensure food quality and safety and to respond to consumers’ demand for information on food provenance, food traceability has received unprecedented attention in many countries [9,10]. European Union (EU) established regulations (1760/2000/EC, 1825/2000/EC) to enforce all Member States to identify food-producing animals, including flocks and individuals [11,12]. Traceability was also introduced in the United States through the Food and Drug Administration (FDA) [10,13,14]. Japan, Canada, Australia and other countries have built their meat traceability management systems in succession [15,16]. Food traceability management in China has also started up recently [17]. In 2011, China established a cloud computing center in Shanghai’s Jinshan district to ensure food traceability [18], which traces food or ingredients across the partially or entirely reconstructed supply chain, so that recalls can be issued when quality problems arise.

Food traceability is increasingly recognized as an essential tool to guarantee food safety and quality through the food supply chain [10,19]. One advantage of an effective traceability system is the precise recall and elimination of non-consumable food products and promotes the investigation of the causes of food safety issues [20–23]. Another advantage is that traceability is an effective method to protect famous brand products by providing a geographical indication or designations for product origin, promoting fair competition and protecting consumers’ rights [24,25].Traceability is considered key to re-establish consumer confidence in food consumption [26,27]. Furthermore, animal identification and traceability have become a non-tariff barrier during recent years as a major tool for international trade of food products. Countries that have well-developed traceability programs will enjoy competitive advantages in product exports over those without such systems [28].

The EU Regulation (EC) 178/2002 defined traceability as the ability to trace food, feed, animal and the related components throughout all stages of production and distribution [29,30]. The FDA defined traceability as the ability to record product origin and destination by paper or electronic means [31]. Although the definition of traceability differs between organizations, the main factors involve three elements: animal individual identification, screening and recording the main information, and the use of information to record each link in the activity traces from animals to meat products [32,33]. To be specific, one kind of unique identifier is attached to an individual animal at birth, and being continuously identifiable during their feed, slaughter, transport, packing, storing and sale via one or more traceability techniques [34]. Thus, an effective traceability system should trace and track the complete associated information from individual animals to their corresponding meat product throughout the food supply chain [35]. In recent years, traceability related technologies are being developed rapidly. The currently used and potential methods suitable for individual animal and meat product identification are summarized in this paper. In Individual animals identification, the methods suitable for individual animal identification based on radio frequency identification (RFID) and DNA fingerprinting are presented. In Meat products identification, the new techniques on chemical components fingerprinting technology for meat product identification, including stable isotope ratios fingerprinting, mineral element fingerprinting and organic component fingerprinting are discussed. In Conclusion, our suggestions to the field and the conclusions are presented.

Individual animals identification

RFID tag

Radio frequency identification (RFID) is a contactless technology for transferring data to identify objects, animals or people using wireless electromagnetic fields [28,36,37]. It is widely used for traceability, logistics and industrial access control, as well as for domestic applications, including ticketing, payment, passports and car keys [36]. It has been successfully implemented in real-time monitoring and decision support systems of perishable products [37–39]. There are three components in this system: a tag containing specific information that is attached to the traced objector subject, the corresponding information reader and the supporting and processing database. The tag can be stuck, attached or implanted on the target depending on the final applications. In animal identification, there are several types of RFID tags. The most common are the button ear tags, which are safer, easy to use, ideal for injection, and show a high retention rate [40]. In recent years, researchers have combined the RFID system with some other technologies to build a traceability system. For example, Li [41] used RFIDs to trace, track and monitor cattle individuals and built up an end-to-end tracking system embedded with a pre-warning function for cattle breeding and chilled-fresh beef production based on networking and database technologies. Feng et al. [38] developed and evaluated a cattle/beef traceability system that integrated RFID technology to acquire real-time, accurate and high-efficiency data of acquisition and transmission across the cattle/beef supply chain using a personal digital assistant (PDA) and barcode printer. To measure the traceability of meat products throughout the supply chain, Zhong et al. [42] developed a comprehensive traceability system combining RFID, quick response (QR) code and near field communication (NFC) technologies. The system divided the supply chain into animal breeding, processing and circulation stages and realized whole-course supervision of meat product supply chain seamlessly [42]. To ensure the safety of Halal food, Mohammed et al. [43] proposed an RFID-based monitoring system, which was coupled with a multi-target model to track the Halal meat supply chains (HMSCs). The second-generation RFID technique was employed in the system to store information including, both each livestock’s unique identification code and its health status. In the transportation stage, a GPRS system was used for tracking locations of the lorry sporadically, providing an estimated arrival time to retailers [43]. Moreover, other studies presented similar reports in beef traceability [44–47].

RFID technique is convenient for the identification of individual animals and the traceability of their related products, but there were some barriers in practice. First, the injectable transponders are easily lost during the animal’s life, the loss rate of about 2% [48]. Furthermore, once an animal is slaughtered, morphological traits are lost and the RFID tag is separated from the carcass, which may result in information loss, interruption or confusion in the following supply chain, making the traceability unreliable. Therefore, some independent or auxiliary methods are required for the identification and monitoring of product origin. In addition, the application of the RFID system should be based on the various types of farms, the number of animals and animal breeds, in order to prevent the mutual influence of individual’s information to the largest extent [47,49].

DNA fingerprinting

DNA fingerprinting technology is developed based on the particular DNA sequences or DNA molecular markers that present an innate characteristic of an individual or breed of animals, which provides the accurate and sensitive information regardless of morphological condition, thus avoiding the need of distinguishable morphological features for differentiation of animals [50,51]. Due to the unique and non-modifiable features and the difficult-to-lose advantage, some kinds of DNA markers are a powerful supplement to the electronic ear tagging system [52]. So far, simple sequence repeats (SSR) and single nucleotide polymorphisms (SNP) are the main DNA marker types used [53]. An SSR with numerous alleles has a higher mean polymorphic information content, which is beneficial to distinguish individuals with a smaller number of markers. Most SNPs only have two alleles, the polymorphisms are relatively lower, but the genotyping of SNP is relatively simple and low cost, which makes it the preferred marker in many situations [54]. Traceability studies based on SSR and SNP markers have been extensively conducted in recent years. Dalvit et al. [55] tested a set of 12 SSR markers for assessment of a genetic traceability system of six cattle breeds of Italy when genotyping five most polymorphic loci and found out that the probability of finding two identical animals was five in one million. Zhao et al. [56] used 16 SSRs to conduct individual identification and meat traceability for six common breeds of beef cattle in China. The results showed that when a combination of six highly polymorphic loci are used, the match probability value is about seven in one million. In the process of individual identification, different SSR markers usually exhibit different polymorphisms in the same population, while the identical markers may also show different polymorphisms in the different genetic background population. Under this circumstance, the selection of polymorphic markers is very important in the genetic traceability practices [56]. Thus, the SNP marker shows great potential in individual identification and meat traceability practice. Cheong et al. [57] used 90 SNP loci to differentiate 1602 cattle individuals from native Korean breed Hanwoo and other breeds such as Holstein. The results showed that the accuracy was 100% [57]. Zhao et al. [58] selected 36 SNPs with minor allele frequencies, more than 30% from the 59 SNP markers belonging to 29 autosomes of the bovine genome. Using the SNPs panel, the probability that one individual is incorrectly assigned ranges from 1.12 out of 10 (×15) to 3.38 out of 10 (×12), depending on the different breeds. At the same time, the selected twelve most polymorphic SNPs were successfully used for meat traceability of Halal beef through meat and reserved blood sample comparison, which had the potential to further guarantee the safety of Halal beef in the Chinese market [58]. Wu et al. [59] employed seven polymorphic SNPs to verify the origins of lamb in Northwest and East of China, and the results showed that the probability for two random individuals to have the same genotype was only 0.185% [59]. Besides individual identification, SSR and SNP markers can also be used for breed information confirmation. Rogberg-Muñoz et al. [60] utilized 22 SSRs to discriminate the Chinese yellow cattle breed from seven foreign breeds. The result showed that all foreign breeds could be differentiated from the Chinese yellow cattle, although some individuals of Chinese yellow cattle were wrongly allocated as Limousin or Holstein, which may have been the result of the introduction of these breeds into China in recent years [60]. Mateuset al. [61] employed SSRs to determine the cattle breeds origin of beef products present in the Portuguese market with the Protected Designation of Origin (PDO) mark. When the population origin information was unknown, the matching probability of 90 representative samples with their correct populations was 96%; when the population origin information was known, the probability reached 98% [61]. Dimauro et al. [62] used 110 SNPs and 108 SNPs with high PIC values to successfully differentiate 21 sheep populations in five different geographic areas. With advancements in DNA-related detection technologies, the use of DNA fingerprinting for individual identification and breed differentiation will have more extensive applications.

DNA traceability technology is the most reliable genetic marking technique followed by morphological labeling, cytological labeling and biochemical marking [63,64]. DNA polymorphisms directly reflect differences in the genetic makeup of the individual. Each animal possesses the unique DNA code, which is permanent and remains intact throughout life [23,65]. In addition, DNA fingerprinting does not need any external product labeling system. DNA can be taken at any point in the production chain, and it can be matched with the history of the animal, thus providing the information for the individual traceability [66]. However, one limitation of DNA fingerprinting is that it is a multi-step process that requires DNA extraction, designing specific amplification primers, PCR amplification and identification of the corresponding PCR fragment, which need high technical requirements [67]. Meanwhile, some factors may also affect the accuracy and reproducibility of DNA fingerprint authentication like DNA degradation and PCR inhibitors [51]. Furthermore, due to genetic differences between populations, the same DNA marker has varied polymorphism, raising the need to screen more specific genetic markers [56]. Finally, the cost of the DNA fingerprinting technique is higher, which is one of the reasons for limiting its application in a wide range. If the above limitations could be addressed, the promotion and application of DNA fingerprinting technique will become imminent. Table 1 summarises the technologies used for individual animal identification and breed information confirmation.

Table 1. Summary of the recent literature on the use of RFID tag, DNA fingerprinting for individual animal identification and breed information confirmation.

Technology	Purpose	Reference
RFID, networking and database technologies	Monitor cattle individual and built up an end-to-end tracking system	[41]
RFID, PDA and barcode printer	Acquire real-time, accurate and high efficiency data of acquisition and transmission across the cattle/beef supply chain	[38]
RFID, QR code, and NFC technologies	Develope a comprehensive traceability system to realise a whole-course supervision of meat product supply chain	[42]
RFID and GPRS system	Ensure the safety of Halal food	[43]
SSR markers	Assess a genetic traceability system in six cattle breeds of Italy	[55]
SSR markers	Conduct individual identification and meat traceability for six common breeds of beef cattle in China	[56]
SNP markers	Differentiate cattle individuals including Korean native breed Hanwoo and other breeds	[57]
SNP markers	Identify cattle individuals and for meat traceability of Halal beef	[58]
SNP markers	Verify the origins of lamb in Northwest and East of China	[59]
SSR markers	Discriminate Chinese yellow cattle beef breed from seven foreign breeds	[60]
SSR markers	Determine the origin of beef products among cattle breeds present in the Portuguese market with the Protected Denomination of Origin	[61]
SNP markers	Differentiate 21 sheep populations in five different geographic areas	[62]

Meat products identification

Stable isotope ratios fingerprinting

In recent years, many research papers focus on the use of stable isotope ratios of H, C, N, O, S and Sr for the verification of the geographical origin and mis-labeled meat products [68]. Due to the difference in mass number, isotopic molecules are slightly different in their physical and chemical properties, under the effect from the climate, altitude, latitude, metabolic processes of living system and other factors, the isotope abundance (δ) changes, which provides the fingerprint information for the identification of the geographic origin of products [69,70]. Initially, stable isotope ratio analysis traced meat geographic origin by using single element isotope composition, such as ¹⁸O. Currently multiple-element isotope compositions (¹³C, ¹⁵N, ¹⁸O, ²H, ³⁴S) are employed, making the method more powerful [68]. The ¹³C/¹²C isotope ratio reflects the ratio of C₃ to C₄ plants in feed, and the ²H/¹H ratio is associated with water intake. Thus, by using δ¹³C and δ²H as indicators, beef from the USA, Mexico, Australia, New Zealand and Korea could be well distinguished [71]. Bong et al. [72] used the oxygen and carbon isotopes to analyze the production areas of local and imported beef in Korea. The results showed that the ¹³C/¹²C isotope ratio successfully differentiated local beef products from the beef products imported from the US, New Zealand and other countries, whereas the ¹⁸O/¹⁶O ratio effectively identified Australian beef [72]. The combination of stable isotopes ¹³C, ¹⁵N and ¹⁸O was used to verify the geographical origin of beef in China, and the study showed that the defatted beef from different origins had different carbon and oxygen isotopes compositions. At the same time, the values of δ¹⁸O in crude fat were also different, which was associated with the values of δ¹⁸O in drinking water from the origin areas [73]. Therefore, stable isotopes ratio analysis could not only differentiate beef from different geographic areas but also could be used to identify the main components in the feed of cattle with the help of the value of δ¹³C in the feed. Lv et al. [74] investigated the geographical origin of Chinese beef using the stable isotopes δ¹³C, δ¹⁵N, δ²H and δ¹⁸O. They collected beef samples from Shandong, Inner Mongolia and Shanxi in China. The results indicated that the δ¹³C, δ¹⁵N, δ²H and δ¹⁸O values in beef were different among the production areas [74].

There are also some barriers in the traceability and authenticity of food of animal origin by isotope fingerprinting. Among the stable isotope ratios used for meat traceability, carbon isotopes are directly related to feed ingredients dependent on different photosynthetic pathways, namely C₃ or C₄ plants [75]. Therefore, changes in feed or mixed feed use may conceal the geographic origin information of meat products, which results in the inaccurate recognition of the geographical origin. Moreover, the δ¹⁵N in meat products is affected by both environmental factors and the type of fertilizer used for the growing of plant fed, either of which will make the results unreliable. The hydrogen and oxygen isotopes are inevitably affected by precipitation, climate and the terrain; therefore, these factors affect the differentiation of products from distinct geographical origins with similar environmental conditions [76]. The factors influencing sulfur isotopes in meat are more complex, and the related change does not follow a predictable pattern. In addition, the sample preparation and analysis equipment are expensive, leading to a relatively higher cost for its application [77,78].

Mineral element fingerprinting

Mineral elements, including essential and non-essential elements for humans and animals, have been proven to be an effective way to determine the geographic origin of foods. The mineral elements composition of plants and animals is related to their growth environment, including soil, water intake and locally grown feeds [79]. Thus, the mineral element fingerprint is also a good indicator for the characterisation of the geographical origin of food products [76]. Moreover, mineral element fingerprinting technique is a rapid analysis and possesses higher sensitivity and low detection limit [80]. So far, there are various research papers on discriminating the origins of beef, lamb and other meat products. The element signature, including the type and concentration of mineral mixtures, is different depending on the geographical origin of meat. For example, Franke et al. [81] drawn the fingerprints of dried beef from different countries with B, Ca, Cd, Cu, Dy, Eu, Ga, Li, Ni, Pd, Rb, Sr, Te, Tl, Tm, V, Yb and Zn, among of which ¹⁰B, ¹¹¹Cd, ¹⁶¹Dy, ¹⁵¹Eu, ⁶⁹Ga, ⁷Li, ⁶⁰Ni, ¹⁰⁴Pd, ⁸⁵Rb, ¹²⁸Te, ²⁰³Tl, ¹⁶⁹Tm, ⁵¹V, ¹⁷¹Yb and ⁶⁸Zn were significantly different in raw meat between countries. Also, characteristic natural elements and the element profiles of meat products were significantly different in different countries after processing. Processing generally increases the element concentrations compared to raw material. To authenticate mutton samples from five major mutton-producing regions (three pastoral regions and two agricultural regions) in China, Sun et al. [82] tested 25 element contents in 99 mutton samples, and the results showed that 21of them (Be, Na, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Sb, Ba, Tl, Pb, Th and U) in defatted mutton showed significant differences (p < 0.05). The multivariate statistical analysis gave an overall correct classification rate of 93.9% and a cross-validation rate of 88.9%. Furthermore, the accuracy for the identification of the agricultural regions and pastoral regions was 100% [82]. For the geographical origin traceability, the combination of a multi-element analysis and stable isotope ratio analysis was an effective analytical strategy. Carbon and nitrogen isotopes composition and the concentrations of 18 elements were investigated to classify beef samples from various provinces in China by Zhao et al. [83]. The discriminant analysis gave an overall correct classification rate of 100% and a cross-validation rate of 100% [83].

As the above researches demonstrate, the mineral element fingerprinting is a promising approach in meat traceability throughout the food supply chain. However, there are still some limitations to this method. First, the screening of the most typical mineral elements to ensure these elements could truly respond to the animal growth environment, including soil, feed, drinking water and air [83,84]. Second, because animal tissues have different capabilities of elements accumulation, the appropriate selection of experimental materials is crucial [80]. Additionally, different cooking methods, animal breed and age might also influence the element composition of meat [82,85]. All of the above factors should be fully considered to offset these limitations and ensure the optimised elements have wide applicability and stability for the authentication of the geographical origin.

Organic component fingerprinting

In recent years, an increasing number of researchers in China and other countries carried out studies on the fingerprint analysis technique based on organic components. The selected organic component compositions differ in the authentication of the geographical origin of plants and animals [86]. For animal meat samples, the organic components primarily include protein, fat, fatty acids, vitamins, carbohydrates and aromatic components. The content and proportion of these organic components vary under different feeding regimes, especially with organic and conventional farming, soil, climate and seasonal change; thus, the organic component fingerprinting is a promising method to distinguish the source of origin. To differentiate mutton samples from four England regions, the fat content and fatty acid composition were analyzed by Fisher et al. [87]. Results suggest that the content of n-3 and n-6 polyunsaturated fatty acids were different which could be used to distinguish the place of origin [87]. Likewise, based on the analysis of fatty acid composition and content, Chinese researchers gathered beef samples from four areas in China, and the results indicated that there were significant differences in the muscle fatty acid composition between regions [88]. For geographical traceability, the organic component fingerprinting has been widely used in plant-sourced food, such as Kiwi Fruit [85], fresh oranges [89], white truffle [90] and tomato [91]. In the future, the organic component fingerprinting will have a broader range of applications.

Organic component analysis as a useful tool for tracing the geographical origin and authenticating the provenance of meat products still have some shortcomings. On the one hand, the contents of the organic components are affected by environmental factors, including soil, rainfall and temperature [92]. On the other hand, feed management, animal breed, age, product processing methods and other factors should also be considered [86,93]. Relevant literature for the geographical origin of meat product traceability is summarised in Table 2.

Table 2. Summary of the recent literature on the use of stable isotope ratios fingerprint, mineral element fingerprint and organic component fingerprint for meat product traceability.

Technology	Parameters measured	Purpose	Reference
Stable isotope analysis	^13C/^12C, ^2H/^1H	Distinguish beef from the USA, Mexico, Australia, New Zealand and Korea	[71]
Stable isotope analysis	^13C/^12C, ^18O/^16O	Analyze the production areas from local and imported beef in Korea	[72]
Stable isotope analysis	^13C/^12C, ^15N/^14N,^18O/^16O	Verify the geographical origins of beef in China	[73]
Stable isotope analysis	^13C/^12C, ^15N/^14N,^2H/^1H, ^18O/^16O	Investigate the geographical origin of Chinese beef	[74]
Mineral element analysis	B, Ca, Cd, Cu, Dy, Eu, Ga, Li, Ni, Pd, Rb, Sr, Te, Tl, Tm, V, Yb and Zn	Differentiate dried beef from different countries	[81]
Mineral element analysis	Be, Na, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Ag, Sb, Ba, Tl, Pb, Th and U	Authenticate the mutton samples from five major mutton-producing regions in China	[82]
Stable isotope and mineral element analysis	^13C/^12C, ^15N/^14N, Na, Mg, K, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Se, Rb, Sr, Zr, Mo and Ba	Classify beef samples from various provinces in China	[83]
Organic component analysis	n-3 and n-6 polyunsaturated fatty acids	Differentiate the mutton from four regions in England	[87]
Organic component analysis	fatty acid	Differentiate the beef samples from four areas in China	[88]

Conclusions

After decades of study, traceability techniques have made significant progress and exerted important functions in meat traceability in practices. However, each type of technique has some limitations to overcome to further their application. RFID tags are useful in the identification of individual animals in farms, which is essential for the traceability system. However, under some circumstances RFID tags can be uncertain or need high accuracy, and thus, some other traceability techniques should be considered. DNA fingerprinting has the highest accuracy, but the complexity of the application and high cost may limit its promotion in the short term. The stable isotope ratios fingerprinting, mineral element fingerprinting and organic component fingerprinting are widely used for meat product traceability. There are still some shortages for each method, and if the three methods can be combined in some cases, the accuracy will be significantly improved. Technology itself does not ensure food safety, but the appropriate application and proper supervision can provide quality assurances throughout the supply chains to consumers, and at the same time, reduce the risks of foodborne diseases.

Nowadays, traceability is increasingly recognized as one of the critical tools for reducing and managing risk and is given continuously new functions. With the development of global food trade and modern logistics in industry, traceability is expected to provide not only the origin of the products but also the parameters of logistics throughout the food supply chain, which is beneficial to know the quality of the product comprehensively. So there are several aspects needed to be improved in the future. First, it is necessary to integrate more than one traceability technology in the trace system. Using only one type of technique is insufficient to ensure traceability accuracy throughout the supply chain, as each type of traceability technique has its unique advantages as well as intrinsic defects. If two or more techniques are combined in actual applications, their advantages can be exploited while their disadvantages could be avoided, ensuring the seamless integration of multiple techniques, which will exert great effects on food safety guarantee. Second, every participant in the food supply chain needs to perform their duty well. There are many participants in the traceability system, including the farmer, processors, wholesalers and retailers, and each of them plays a vital role in the program of food production and guarantees the hygiene and safety of food. If any link in the production supply chain goes wrong, the reliability of the information in the whole chain will break down. So each participant should be clear of their roles in the traceability system. Third, an interconnection platform of food traceability information is needed to be established for providing information to consumers, producers and regulators at any moment, in any case. The above considerations benefit the whole supply chain to be transparent and help to avoid intentional or unintentional food fraud to truly realise the food safety from farm to table. Although the possibility of the perfect traceability system seems to be still a bit far in time, the public and some organisations should do their best to improve the quality parameters of animal products to make the food quality and safety.

Acknowledgement

We are obliged to people who offered help in the in the process of the article completion.

Disclosure statement

No potential conflict of interests was reported by the authors.

Additional information

Funding

This work was supported by Beijing Natural Science Foundation (6194038), China Postdoctoral Science Foundation (2019M650554), and the Project of Key Laboratory of Agrifood Safety and Quality, Ministry of Agriculture of China (2018-KF-05).