Stable isotopes as a tool to differentiate eggs laid by caged, barn, free range, and organic hens

Application of multiple stable isotopes to aid identification of the origin of regional and organic animal products in Hesse, Germany

There is an increasing global demand for regional and organic produce. However, the growth of these markets depends on consumers' trust. Thus, novel methods must be developed to aid the verification of the origin of produce. We built on our previous study to identify the geographical origin and production method of animal-derived food products. Thirty-samples of eggs, 99 of milk, 34 of beef, and 62 of pork were collected from different regions in central Germany and analysed for their stable isotopic composition. The analysis followed a single-variate authentification approach using five isotope signatures, δ18O, δ2H, δ13C, δ15N, and δ34S. The best-performing indicators for verification of the geographical origin were δ15N and δ34S for beef; δ18O, δ2H, and δ13C for milk, and δ2H and δ13C for pork. These tracers indicated statistically significant differences among regions with the exception of pork; the results recorded for eggs were inconclusive. It was possible to distinguish between production methods by means of δ15N and δ34S (beef); all five tracers (eggs), and δ13C, δ15N, and δ34S (milk). This study demonstrated how the analysis of stable isotopes can be employed to determine the geographic region of origin and production method of animal-derived products in Germany.

Comparative Analysis of LC-ESI-IM-qToF-MS and FT-NIR Spectroscopy Approaches for the Authentication of Organic and Conventional Eggs

The importance of animal welfare and the organic production of chicken eggs has increased in the European Union in recent years. Legal regulation for organic husbandry makes the production of organic chicken eggs more expensive compared to conventional husbandry and thus increases the risk of food fraud. Therefore, the aim of this study was to develop a non-targeted lipidomic LC-ESI-IM-qToF-MS method based on 270 egg samples, which achieved a classification accuracy of 96.3%. Subsequently, surrogate minimal depth (SMD) was applied to select important variables identified as carotenoids and lipids based on their MS/MS spectra. The LC-MS results were compared with FT-NIR spectroscopy analysis as a low-resolution screening method and achieved 80.0% accuracy. Here, SMD selected parts of the spectrum which are associated with lipids and proteins. Furthermore, we used SMD for low-level data fusion to analyze relations between the variables of the LC-MS and the FT-NIR spectroscopy datasets. Thereby, lipid-associated bands of the FT-NIR spectrum were related to the identified lipids from the LC-MS analysis, demonstrating that FT-NIR spectroscopy partially provides similar information about the lipidome. In future applications, eggs can therefore be analyzed with FT-NIR spectroscopy to identify conspicuous samples that can subsequently be counter-tested by mass spectrometry.

Isotopic and Elemental Fingerprint of Edible Egg Parts-The Health Risk Assessment Based on Potentially Toxic Elements Content

The present study investigated the isotopic and elemental profile (by IRMS and ICP-MS) of edible egg parts (29 egg whites and 29 yolks) mainly collected from Romania. In order to differentiate the egg white and yolk coming from different hen rearing systems (backyard and barn), Partial Least Square-Discriminant Analysis (PLS-DA) models were developed. The models' accuracies for the discrimination according to the hen growing system were 96% for egg white and 100% for egg yolk samples, respectively. Elements that proved to have the highest discrimination power for both egg white and yolk were the following: δ¹³C, Li, B, Mg, K, Ca, Mn, Fe, Co, Zn, Rb, Sr, Mo, Ba, La, Ce, and Pb. Nevertheless, the important compositional differentiation, in terms of essential mineral content, between the edible egg parts (egg white and egg yolk) were also pointed out. The estimated daily intake (EDI), the target hazard quotient (THQ) for Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Cd, Pb, and As, as well as the hazard index (HI) were used to assess non-carcinogenic human health risks from egg consumption. The obtained results showed no noticeable health risks related to egg consumption for humans from the point of view of the potentially toxic metals.

The Occurrence of Lead in Animal Source Foods in Iran in the 2010s Decade: A Systematic Review

Lead is a toxic, non-biodegradable, and accumulative heavy metal released into the environment by natural and anthropogenic activities. Despite health concerns due to the consumption of lead-contaminated foods, no systematic and comprehensive review studies have been published about the lead occurrence in animal source foods in Iran. The present study aimed to review the papers investigating the Pb contamination in animal-based food groups (including meat, fish, milk and dairy products, egg and honey) in Iran. A comprehensive search was performed with selected keywords in databases of Scopus, Web of science, and Magiran to find articles that had been published from January 2010 to December 2019. Of 371 identified articles on Pb contaminations in foods, 60 articles were selected using PRISMA. The lead concentrations were higher than the maximum recommended limits in 3 of 9 studies on meat and meat products, 12 of 26 studies on fish and canned fish, and 5 of 18 studies on milk and dairy products. However, the Pb contamination observed in studies on honey and egg was not comparable due to the lack of national and international standards. These results represent the importance of environmental monitoring and assessment for reducing exposure of animals to Pb, resulting in an improvement of food safety.

Review: Quality and authentication of organic animal products in Europe

The 'organic' label guarantees a production process that avoids the use of synthetic fertilisers, pesticides and hormones and minimises the use of veterinary drugs; however, consumers are demanding guarantees regarding food quality. This article reviews the current state of knowledge on the quality of organic animal products, including the authentication of their organic origin. Quality has been considered as an integrative combination of six core attributes: commercial value, and nutritional, sensory, technological, convenience and safety attributes. The comparison of these attributes between organic and conventional animal products shows high heterogeneity due to variability in farming pratices in both organic and conventional systems. To overcome this, we pinpoint the farming practices underlying the differences observed. This enables light to be shed on the consequences of possible trajectories of organic farming, if specifications are relaxed or tightened up on commitments concerning farming practices that impact product quality. Two recent meta-analyses showed better nutritional attributes in organic milk and meat linked to their higher poly-unsaturated fatty acid (PUFA) content, particularly n-3 PUFAs. Regarding safety, we point to a lack of integrated studies quantifying the balance between positive and negative effects. Organic farming reduces the risk of drug residues and antibiotic resistance, but both outdoor rearing and a frequently longer rearing period increase the animals' exposition to environmental contaminants and the risk of their bioaccumulation in milk, eggs, meat and fish flesh. We highlight antagonisms between quality attributes for certain animal products (lamb, pork). In general, attributes are more variable for organic products, which can be explained by lower genetic selection (poultry), lower inputs and/or greater variability in farming conditions. However, the literature does not address the implications of this greater variability for the consumers' acceptability and the necessary adaptation of manufacturing processes. Further research is needed to document the impacts on human nutritional biomarkers and health. Methods used to authenticate organic origin are based on differences in animal diet composition between organic and conventional systems, but their reliability is hampered by the variability in farming practices.

High-resolution 1H NMR profiling of triacylglycerols as a tool for authentication of food from animal origin: Application to hen egg matrix

Metabolomics of complex biological matrices conducted by means of ¹H NMR leads to spectra suffering from severe signal overlapping. Previously, we have developed a high-resolution spectral treatment method to help solving this issue in ¹H NMR of triacylglycerols. In this work, we tested the potential of the developed method in the characterization and authentication of food products from animal origin using egg yolk as a model matrix. The approach consisted in a spectral deconvolution guided by the precision obtained on the deconvoluted peaks after reference lineshape adjustment of spectra. Thus, 135 peaks were quantitated and successfully used as biomarkers of origin, of hens breed, and of farming system. This required multivariate statistical analyses for classification. The same pool of variables allowed construction of multivariate quantitation models for individual fatty acids. Furthermore, minute amounts of conjugated fatty acids were quantitated and used as fingerprints of samples from backyard and free-range farming.

Application and Preparation Progress of Stable Isotope Reference Materials in Traceability of Agricultural Products

In the field of food traceability analysis, stable isotope ratio analysis is a relatively new technology. The measurement and calibration of isotope data depends on stable isotope reference materials. The isotope reference materials commonly used are chemical matrix. These reference materials are inappropriate-especially for food matrix origin analysis. This review focuses on the research progress on stable isotope reference materials by (1) classification of stable isotope reference materials, (2) application of stable isotope reference materials, and (3) research progress of preparation of stable isotope reference materials. Selecting appropriate isotope reference materials will help improve the effectiveness of stable isotope ratio analysis in food traceability. By cooperation with different laboratories, high-quality isotope reference materials can be prepared to add new food matrix types to provide more choices for users.

Authentication of organic pork and identification of geographical origins of pork in four regions of China by combined analysis of stable isotopes and multi-elements

The purpose of this study was to verify that the organic status of pork purchased in the markets from four different regions of China can be authenticated by the combined analysis of stable isotopes and multiple elements. Four stable isotope ratios (δ¹³C, δ¹⁵N, δ²H and δ¹⁸O) and the concentrations of seven elements (K, Na, Mg, Ca, Fe, Cu and Se) were determined in organic and conventional pork samples from four locations of China. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to analyze stable isotope ratios and multi-element concentrations in pork. Based on the limited database of analytical values, the methodology would be potentially able to confirm whether a sample of pork came from the region and organic status it claimed. These results provide a possibility for authenticity of organic agricultural products from a large scope such as a province even a country.

Assessing the authenticity of animal rennet using δ15N analysis of chymosin

Chymosin is a protease that curdles the milk casein. Animal rennet was the first discovered source of chymosin and its use is mandatory for the production of PDO cheeses such as Parmigiano Reggiano and Grana Padano. Of the alternatives, fermentation-produced chymosin is the most competitive because it functions in a similar way, but is much cheaper. Analytical tools are necessary in order to distinguish the 2 types of chymosin and verify the compulsory use of animal rennet in the production of PDO cheeses. In this work, a method to analyse ¹⁵N/¹⁴N in chymosin after extraction was developed. The δ¹⁵N values of animal rennet range from 5.7‰ to 8‰, whereas the δ¹⁵N values of fermentation-produced chymosin are significantly lower, ranging from -5.3‰ to 2.2‰. A threshold value of 5.7‰ was defined for authentic animal rennet. Addition of fermentation-produced chymosin to animal rennet, or its complete substitution, can be therefore detected.

NMR-based differentiation of conventionally from organically produced chicken eggs in Germany

Both the German and European organic food markets are growing fast, and there is also a rising demand for organic chicken eggs. Consumers are willing to pay higher prices for organic eggs produced in an animal-appropriate environment considering animal welfare. Strict labelling requirements do not prevent chicken eggs from being a subject of food fraud. Conventionally produced (barn/free-range) eggs can easily be mislabeled as organic eggs. Especially because the demand for organically produced chicken eggs is likely to exceed supply in the future, mislabeling appears to be a realistic scenario. Therefore, there is a need for analytical methods that are suitable to classify eggs as being either conventionally or organically produced. Nuclear magnetic resonance (NMR) spectroscopy in combination with multivariate data analysis is a suitable tool to screen eggs according to the different systems of husbandry. Sample preparation is based on a fat extraction method, which was optimised for application to freeze-dried egg yolk. Samples were analysed using typical q-NMR parameters. A nontargeted approach was used for the analysis of the ¹ H NMR data. Principal component analysis (PCA) was applied followed by a linear discriminant analysis (PCA-LDA) and Monte Carlo cross-validation. In total, 344 chicken eggs (214 barn/free-range eggs and 130 eggs from organic farms), most of them originating from Germany, were used to build and validate the prediction model. The results showed that the prediction model allowed for the correct classification of about 93% of the organic eggs.

Health Risk Assessment for Human Exposure to Trace Metals and Arsenic via Consumption of Hen Egg Collected from Largest Poultry Industry in Iran

The relative contribution of foodstuffs to intake of heavy metal is still equivocal, and thus, available data are rare. Here, the concentration of ten heavy metals and arsenic were measured in the content of hen egg from five strains of commercial laying hens to evaluate contamination level and potential health risk among local and international consumers in Iran. The estimated daily intake (EDI) of all heavy metals was significantly lower than the provisional tolerable daily intake (PTDI) and respective tolerable daily intake (TDI). The non-carcinogenic and carcinogenic risk values for eating eggs were in the safe range for all consumers, indicating that the no health risk for consumers due to the daily intake of either arsenic or heavy metals. Therefore, intake of heavy metal exposure through the consumption of commercial egg product in Iran is completely safe for both national and international consumers.

Diversity of management strategies in Mesoamerican turkeys: archaeological, isotopic and genetic evidence

The turkey (Meleagris gallopavo) represents one of the few domestic animals of the New World. While current research points to distinct domestication centres in the Southwest USA and Mesoamerica, several questions regarding the number of progenitor populations, and the timing and intensity of turkey husbandry remain unanswered. This study applied ancient mitochondrial DNA and stable isotope (δ¹³C, δ¹⁵N) analysis to 55 archaeological turkey remains from Mexico to investigate pre-contact turkey exploitation in Mesoamerica. Three different (sub)species of turkeys were identified in the archaeological record (M. g. mexicana, M. g. gallopavo and M. ocellata), indicating the exploitation of diverse local populations, as well as the trade of captively reared birds into the Maya area. No evidence of shared maternal haplotypes was observed between Mesoamerica and the Southwest USA, in contrast with archaeological evidence for trade of other domestic products. Isotopic analysis indicates a range of feeding behaviours in ancient Mesoamerican turkeys, including wild foraging, human provisioning and mixed feeding ecologies. This variability in turkey diet decreases through time, with archaeological, genetic and isotopic evidence all pointing to the intensification of domestic turkey management and husbandry, culminating in the Postclassic period.

Stable carbon and nitrogen isotopes as a potential tool to differentiate pork from organic and conventional systems

BACKGROUND

Isotopic discrimination, dietary composition and feeding regime determine the carbon and nitrogen stable isotope ratios of animals. Accordingly, measurement of the stable isotope ratios of carbon and nitrogen can be a potential method to identify patterns of pork production.

RESULTS

In the current study, we investigated the carbon and nitrogen isotopic ratio in pork from organic and conventional systems. The average carbon and nitrogen isotope ratios for various organic tissues, including hair, blood and defatted meat, were higher than those of conventionally raised ones. The discriminant analysis results based on the combination of carbon and nitrogen isotopic ratios in defatted meat reached a 100% correct classification. Furthermore, the variation in carbon and nitrogen stable isotope ratios of retail organic and conventional pork has been studied over 1 year. The results suggested that organic pork had a higher δ(13) C value than that of the conventional pork in all but three fortnights. Grouping of the δ(15) N data showed that the δ(15) N value in organic pork was higher than that of the conventional one throughout the whole year.

CONCLUSION

The method established in the present study provides a potential detection that can be highly valuable to prevent fraudulent labelling of organic pork. © 2015 Society of Chemical Industry.

Verification of Egg Farming Systems from The Netherlands and New Zealand Using Stable Isotopes

Stable isotopes were used to develop authentication criteria of eggs laid under cage, barn, free range, and organic farming regimens from The Netherlands and New Zealand. A training set of commercial poultry feeds and egg albumen from 49 poultry farms across The Netherlands was used to determine the isotopic variability of organic and conventional feeds and to assess trophic effects of these corresponding feeds and barn, free range, and organic farming regimens on corresponding egg albumen. A further 52 brands of New Zealand eggs were sampled from supermarket shelves in 2008 (18), 2010 (30), and 2014 (4) to characterize and monitor changes in caged, barn, free range, and organic egg farming regimens. Stable carbon (δ(13)C) and nitrogen (δ(15)N) isotopes of 49 commercial poultry feeds and their corresponding egg albumens reveals that Dutch poultry are fed exclusively on a plant-based feed and that it is possible to discriminate between conventional and organic egg farming regimens in The Netherlands. Similarly, it is possible to discriminate between New Zealand organic and conventional egg farming regimens, although in the initial screening in 2008, results showed that some organic eggs had isotope values similar to those of conventional eggs, suggesting hens were not exclusively receiving an organic diet. Dutch and New Zealand egg regimens were shown to have a low isotopic correlation between both countries, because of different poultry feed compositions. In New Zealand, both conventional and organic egg whites have higher δ(15)N values than corresponding Dutch egg whites, due to the use of fishmeal or meat and bone meal (MBM), which is banned in European countries. This study suggests that stable isotopes (specifically nitrogen) show particular promise as a screening and authentication tool for organically farmed eggs. Criteria to assess truthfulness in labeling of organic eggs were developed, and we propose that Dutch organic egg whites should have a minimum δ(15)N value of 4.8‰ to account for an organic plant derived diet. Monitoring of New Zealand egg isotopes over the past 7 years suggests that organic eggs should have a minimum δ(15)N value of 6.0‰, and eggs falling below this value should be investigated further by certification authorities.

Identification, classification, and growth of moa chicks (Aves: Dinornithiformes) from the genus Euryapteryx

Background

The analysis of growth in extinct organisms is difficult. The general lack of skeletal material from a range of developmental states precludes determination of growth characteristics. For New Zealand's extinct moa we have available to us a selection of rare femora at different developmental stages that have allowed a preliminary determination of the early growth of this giant flightless bird. We use a combination of femora morphometrics, ancient DNA, and isotope analysis to provide information on the identification, classification, and growth of extinct moa from the genus Euryapteryx.

Results

Using ancient DNA, we identify a number of moa chick bones for the species Euryapteryx curtus, Dinornis novaezealandiae, and Anomalopteryx didiformis, and the first chick bone for Pachyornis geranoides. Isotope analysis shows that ∂¹⁵N levels vary between the two known size classes of Euryapteryx, with the larger size class having reduced levels of ∂¹⁵N. A growth series for femora of the two size classes of Euryapteryx shows that early femora growth characteristics for both classes are almost identical. Morphometric, isotopic, and radiographic analysis of the smallest Euryapteryx bones suggests that one of these femora is from a freshly hatched moa at a very early stage of development.

Conclusion

Using morphometric, isotopic, and ancient DNA analyses have allowed the determination of a number of characteristics of rare moa chick femora. For Euryapteryx the analyses suggest that the smaller sized class II Euryapteryx is identical in size and growth to the extant Darwin's rhea.

Investigating C-4 sugar contamination of manuka honey and other New Zealand honey varieties using carbon isotopes

Carbon isotopes (δ(13)C honey and δ(13)C protein) and apparent C-4 sugar contents of 1023 New Zealand honeys from 15 different floral types were analyzed to investigate which New Zealand honey is prone to failing the AOAC 998.12 C-4 sugar test and evaluate the occurrence of false-positive results. Of the 333 honey samples that exceeded the 7% C-4 sugar threshold, 324 samples of these were New Zealand manuka honey (Leptospermum scoparium, 97.2% of all fails found in the study). Three monofloral honeys (ling, kamahi, and tawari) had nine samples (2.8% of all fails found in the study) with apparent C-4 sugars exceeding 7%. All other floral types analyzed did not display C-4 sugar fails. False-positive results were found to occur for higher activity New Zealand manuka honey with a methylglyoxal content >250 mg/kg or a nonperoxide activity >10+, and for some ling, kamahi and tawari honeys. Recommendations for future interpretation of the AOAC 998.12 C-4 sugar method are proposed.

Analytical authentication of organic products: an overview of markers

Consumers' interest in organic foods is increasing and so is the need for robust analytical tools for their authentication. This review focuses on the most promising biomarkers/analytical approaches that are available for the authentication of organic produce. Food products have been subdivided into two groups: foods of plant origin (crops) and foods of animal origin (meat, milk and dairy products, eggs and fish). For each food category the most suitable biomarkers are presented and their potential for authentication is discussed. In the light of current knowledge, it is unlikely that the authentication of organic food products can be attained by the measurement of a single marker. Analytical approaches based on the measurement of multiple markers and/or complex chemical or physical profiles/fingerprints supported by multivariate statistical analysis seem considerably more promising in this respect. For the development of robust classification models, well-designed experimental studies must be performed that rely on data sets that are both well balanced and of sufficient size to ensure that all relevant sources of variation for the target biomarkers are included in the reference database.

Tracing the source of cooking oils with an integrated approach of using stable carbon isotope and fatty acid abundance

We report a new approach to identify swill-cooked oils that are recycled from tainted food and livestock waste from commercial vegetable and animal oils by means of carbon isotope values and relative abundance of fatty acids. We test this method using 40 cooking oil samples of different types with known sources. We found significant differences in both total organic carbon isotope as well as compound-specific isotope values and fatty acid C(14)/C(18) ratios between commercial vegetable oils refined from C(3) plants (from -35.7 to -27.0‰ and from 0 to 0.15) and animal oils (from -28.3 to -14.3‰ and from 0.1 to 0.6). Tested swill-cooked oils, which were generally refined by mixing with animal waste illegally, fall into a narrow δ(13)C/fatty acid ratio distribution: from -25.9 to -24.1‰ and from 0.1 to 0.2. Our data demonstrate that the index of a cross-plotting between fatty acid δ(13)C values and C(14)/C(18) ratios can be used to distinguish clean commercial cooking oils from illegal swill-cooked oils.

Isotopic analysis of eggs: evaluating sample collection and preparation

Egg traceability/authenticity is a worldwide concern. Stable isotope techniques have been suggested as a tool to address this issue. To further validate the use of these techniques, a research project was undertaken to evaluate what effect sample collection and preparation have on the measured isotopic composition of egg components. The timing of egg collection, the timing of egg preparation after collection, and the use of pasteurisation were investigated. The C, N, O, and S isotopic compositions of egg components from 7 different production systems were measured. Two sets of eggs were collected (4 months apart). It was found that the 'isotopic fingerprint' of a particular production system was maintained over time, and that it may be possible to trace liquid egg products based on isotopic data from fresh eggs. The findings from this study support the integration of stable isotope techniques in egg traceability/authenticity systems.

Avian embryonic development does not change the stable isotope composition of the calcite eggshell

The avian embryo resorbs most of the calcium for bone formation from the calcite eggshell but the exact mechanisms of the resorption are unknown. The present study tested whether this process results in variable fractionation of the oxygen and carbon isotopes in shell calcium carbonate, which could provide a detailed insight into the temporal and spatial use of the eggshell by the developing embryo. Despite the uncertainty regarding changes in stable isotope composition of the eggshell across developmental stages or regions of the shell, eggshells are a popular resource for the analysis of historic and extant trophic relationships. To clarify how the stable isotope composition varies with embryonic development, the δ(13)C and δ(18)O content of the carbonate fraction in shells of black-headed gull (Larus ridibundus) eggs were sampled at four different stages of embryonic development and at five eggshell regions. No consistent relationship between the stable isotope composition of the eggshell and embryonic development, shell region or maculation was observed, although shell thickness decreased with development in all shell regions. By contrast, individual eggs differed significantly in isotope composition. These results establish that eggshells can be used to investigate a species' carbon and oxygen sources, regardless of the egg's developmental stage.