Stable isotope ratios, major, trace and radioactive elements in emmental cheeses of different origins

Isolation of casein for stable isotope ratio analysis of butter, cheese, and milk powder

RATIONALE

Stable isotope ratio analysis (SIRA) is commonly used for the authentication of dairy commodities, providing evidence to support the geographical origin and production background of products. We set out to optimise methods for the isolation of a common constituent (casein) from three dairy commodities, which would permit easier inter- and intra-commodity comparisons following SIRA.

METHODS

Three published methods for isolation of protein (from cheese, milk, and butter) were adapted to yield protein (casein) fractions from commercial cheddar cheese, whole milk powder (WMP), and butter samples with a high degree of purity for subsequent SIRA. The casein fractions isolated underwent elemental analysis (H, C, and N), protein determination, and some also underwent SIRA of O and S. Two-way analysis of variance and Tukey post hoc comparisons tested differences between methods.

RESULTS

For each product, an optimised casein isolation method was chosen based on the C/N ratio and protein content. An optimum solvent lipid extraction (petroleum spirit-diethyl ether (2:1)) and casein precipitation method was chosen for cheddar cheese casein. A final solvent lipid extraction (heptane-isopropanol (3:2)) was necessary for WMP and butter casein extraction. δ¹³ C and δ² H values validated the methods' abilities to remove contaminating lipid and isolate pure casein.

CONCLUSIONS

Casein of high purity, for subsequent SIRA, can be isolated from cheddar cheese, WMP, and butter following modifications of previously published methods.

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), a Useful Tool in Authenticity of Agricultural Products' and Foods' Origin

Fraudulent practices are the first and foremost concern of food industry, with significant consequences in economy and human's health. The increasing demand for food has led to food fraud by replacing, mixing, blending, and mislabeling products attempting to increase the profits of producers and companies. Consequently, there was the rise of a multidisciplinary field which encompasses a large number of analytical techniques aiming to trace and authenticate the origins of agricultural products, food and beverages. Among the analytical strategies have been developed for the authentication of geographical origin of foodstuff, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) increasingly dominates the field as a robust, accurate, and highly sensitive technique for determining the inorganic elements in food substances. Inorganic elements are well known for evaluating the nutritional composition of food products while it has been shown that they are considered as possible tracers for authenticating the geographical origin. This is based on the fact that the inorganic component of identical food type originating from different territories varies due to the diversity of matrix composition. The present systematic literature review focusing on gathering the research has been done up-to-date on authenticating the geographical origin of agricultural products and foods by utilizing the ICP-MS technique. The first part of the article is a tutorial about food safety/control and the fundaments of ICP-MS technique, while in the second part the total research review is discussed.

The Provenance of Slovenian Milk Using 87Sr/86Sr Isotope Ratios

This work presents the first use of Sr isotope ratios for determining the provenance of bovine milk from different regions of Slovenia. The analytical protocol for the determination of ⁸⁷Sr/⁸⁶Sr isotope ratio was optimised and applied to authentic milk samples. Considerable variability of ⁸⁷Sr/⁸⁶Sr ratios found in Slovenian milk reflects the substantial heterogeneity of the geological background of its origin. The results, although promising, cannot discount possible inter-annual or annual variation of the Sr isotopic composition of milk. The ⁸⁷Sr/⁸⁶Sr ratios of groundwater and surface waters are in good correlation with milk, indicating that the Sr isotopic fingerprint in milk is reflective of cow drinking water. The ⁸⁷Sr/⁸⁶Sr ratio has the potential to distinguish between different milk production areas as long as these areas are characterised by geo-lithology. Discriminant analysis (DA) incorporating the elemental composition and stable isotopes of light elements showed that ⁸⁷Sr/⁸⁶Sr ratio together with δ¹³C_cas and δ¹⁵N_cas values have the main discrimination power to distinguish the Quaternary group (group 6) from the others. Group 1 (Cretaceous: Carbonate Rocks and Flysch) is associated with Br content, 1/Sr and δ¹⁸O_w values. The overall prediction ability was found to be 63.5%. Pairwise comparisons using OPLS-DA confirmed that diet and geologic parameters are important for the separation.

Achieving Food Authenticity and Traceability Using an Analytical Method Focusing on Stable Isotope Analysis

High-value agricultural products are characterized by the geographical conditions of the production areas such as climatic and soil conditions. These products are protected by the geographical indication (GI) protection system, which has been introduced in more than 100 countries. Because GI products are expensive in the market, products are often mislabeled as GI. Thus, there is an urgent need for the development of analytical methods that enable the tracing of geographical origins of food materials. Stable isotope analysis is used to trace the geographical origin of food materials. In this study, we review the applications for tracing the geographical origin of agricultural products (especially rice, beef, and honey) focusing on an analytical method for analyzing stable isotopes (δD, δ¹³C, δ¹⁵N, δ¹⁸O, and δ³⁴S).

Geographical verification of Slovenian milk using stable isotope ratio, multi-element and multivariate modelling approaches

This work examines the use of stable isotopes and elemental composition for determining geographical origin and authenticity of cow milk from four geographical regions of Slovenian. Samples (277) were collected during summer and winter (2012-2014). It was possible to discriminate milk samples according to the year, season and production region using discriminant analysis (DA). The overall temporal prediction variability was 84.6% and 56.4% for regional differences. It was also possible to discriminate milk from three geographic regions, although Alpine samples overlap with Dinaric and Pannonian ones. Prediction ability was the highest for the Pannonian (82.1%) and lowest (26.9%) for the Alpine region. Pairwise comparison using OPLS-DA also displaying good regional predictability (≥0.77) with δ¹³C_cas values and Br content carrying the most variance. A model based on DD-SIMCA was also developed and applied to the control of Slovenian milk. The results revealed the mislabeling of three Slovenian milk products.

Feasibility of Casein to Record Stable Isotopic Variation of Cow Milk in New Zealand

Dairy products occupy a special place among foods in contributing to a major part of our nutritional requirements, while also being prone to fraud. Hence, the verification of the authenticity of dairy products is of prime importance. Multiple stable isotopic studies have been undertaken that demonstrate the efficacy of this approach for the authentication of foodstuffs. However, the authentication of dairy products for geographic origin has been a challenge due to the complex interactions of geological and climatic drivers. This study applies stable isotope measurements of d2H, d18O, d13C and d15N values from casein to investigate the inherent geo-climatic variation across dairy farms from the South and North Islands of New Zealand. The stable isotopic ratios were measured for casein samples which had been separated from freeze-dried whole milk samples. As uniform feeding and fertilizer practices were applied throughout the sampling period, the subtropical (North Island) and temperate (South Island) climates were reflected in the variation of d13C and d15N. However, highly correlated d2H and d18O (r = 0.62, p = 6.64 × 10-10, a = 0.05) values did not differentiate climatic variation between Islands, but rather topographical locations. The highlight was the strong influence of d15N towards explaining climatic variability, which could be important for further discussion.

A review of the newly identified impurity profiles in methamphetamine seizures

Forensic intelligence of synthetic illicit drugs suffers a problem of continuous introduction of new synthetic methods, modification of the existing routes of manufacture, and adulterations practiced by criminal networks. Impurity profiling has been indispensable in methamphetamine intelligence based on precursors, synthetic routes, and chemical modifications during trafficking. Law enforcement authorities maintain the credibility and integrity of intelligence information through constant monitoring of the chemical signatures in the illicit drug market.

Changes in the synthetic pattern result in new impurity profiles that are important in keeping valuable intelligence information on clandestine laboratories, new synthetic routes, trafficking patterns, and geographical sources of illicit Methamphetamine.

This review presents a critical analysis of the methamphetamine impurity profiles and more specifically, profiling based on impurity profiles from Leuckart, Reductive amination, Moscow, Emde, Nagai, Birch, Moscow route; a recent nitrostyrene route and stable isotope signatures. It also highlights the discrimination of ephedrine from pseudoephedrine sources and the emerging methamphetamine profiling based on stable isotopes.

Greek Graviera Cheese Assessment through Elemental Metabolomics-Implications for Authentication, Safety and Nutrition

This study presents the comprehensive elemental profile of Greek Graviera (Gruyère) cheeses. In total, 105 samples from nine different geographic regions produced from sheep, goat and cow milk and their mixtures were assessed. Elemental signatures of 61 elements were investigated for determination of geographic origin and milk type. Regional and milk type classification through Linear Discriminant Analysis was successful for almost all cases, while a less optimistic cross validation exercise presented lower classification rates. That points to further research using a much larger sample set, increasing confidence for cheese authentication utilizing also bioinformatics tools under development. This is the first study reporting signatures of 61 elements in dairy products including all sixteen rare earth elements and all seven precious metals. Safety and quality were assessed regarding toxic and nutritive elements. According to both EU and USA regulations and directives, Graviera is a nutritional source for trace and macro elements with low levels of toxic elements.

Validation of methods for H, C, N and S stable isotopes and elemental analysis of cheese: results of an international collaborative study

RATIONALE

PDO cheeses, such as Parmigiano Reggiano and Grana Padano, which cost more than double generic similar cheeses, must be protected against mislabelling. The aim of this study was to validate the methods for the isotopic and elemental analysis of cheese, in order to support official recognition of their use in authenticity assessment.

METHODS

An international collaborative study based on blind duplicates of seven hard cheeses was performed according to the IUPAC protocol and ISO Standards 5725/2004 and 13528/2005. The H, C, N and S stable isotope ratios of defatted cheese determined using Isotope Ratio Mass Spectrometry (IRMS) and the content of Li, Na, Mn, Fe, Cu, Se, Rb, Sr, Mo, Ba, Re, Bi, U in cheese after acid microwave digestion using Inductively Coupled Plasma Mass Spectrometry or Optical Emission Spectrometry (ICP-MS or -OES) were measured in 13 different laboratories.

RESULTS

The average standard deviations of repeatability (sr) and reproducibility (sR) were 0.1 and 0.2 ‰ for δ(13)C values, 0.1 and 0.3 ‰ for δ(15)N values, 2 and 3 ‰ for δ(2)H values, and 0.4 and 0.6 ‰ for δ(34)S values, thus comparable with results of official methods and the literature for other food matrices. For elemental data, the average RSDr and RSDR values ranged between 2 and 11% and between 9 and 28%, respectively, consistent with methods reported by the FDA and in the literature for cheese.

CONCLUSIONS

The validation data obtained here can be submitted to the standardisation agencies to obtain official recognition for the methods, which is fundamental when they are used in commercial disputes and legal debates.

The utilization of stable isotope analysis for the estimation of the geographic origins of unidentified cadavers

The number of unidentified cadavers is increasing worldwide and the effective methods which reveal their geographic origin are not well known. This study reports on the utilization of δ(18)O, δ(13)C, δ(2)H and δ(15)N ratios gained through stable isotope analysis of urine samples collected from eight locations: Chiba, Japan; Fuzhou, China; and Denpasar, Indonesia in our pilot study with data from healthy volunteers from five further locations from healthy volunteers: Melbourne and Perth, Australia; Qingdao, China; Turku, Finland and Oklahoma, USA. This study posits that the utilization of δ(18)O and δ(2)H is more feasible than δ(13)C and δ(15)N stable isotope ratios in differentiating or estimating the origin of human samples. Secondly, this study demonstrated that the δ(18)O and δ(2)H stable isotope ratios of urine samples from eight locations differed significantly.

Comparative assessment of essential and heavy metals in fruits from different geographical origins

The aim of this investigation was to estimate and compare essential and heavy metals contents in 98 commercially available fresh fruits from different geographic regions using multivariate techniques. The concentrations of 12 elements (calcium, magnesium, potassium, sodium, phophorus, cobalt (Co), manganese, iron, chromium (Cr), nickel (Ni), zinc and copper) were determined using flame atomic absorption spectrometry with deuterium-background correction. Phosphorus was determined in the form of phosphomolybdate by a spectrophotometric method. Reliability of the procedure was checked by analysis of the certified reference materials tea (NCS DC 73351), cabbage (IAEA-359) and spinach leaves (NIST-1570). Recoveries of the elements analysed varied between 85.5 and 103%, and precisions for the reference materials were 0.13-6.08%. Based on recommended dietary allowance and adequate intake estimated for essential elements, it was concluded that accessory fruits such as pineapples, raspberries and strawberries supply organism with the highest amounts of bioelements. Although accessory fruits were also found to be the greatest source of Ni among all the analysed fruits, in all the fruits Ni was more abundant than Cr and Co. Significant correlation coefficients (p < 0.001, p < 0.01 and p < 0.05) were found between concentrations of some metals in fresh fruits. Application of ANOVA Kruskal-Wallis test and multivariate techniques such as factor analysis and cluster analysis enabled us to differentiate particular botanical families and types of fruits.

Tracing the geographic origin of beef in China on the basis of the combination of stable isotopes and multielement analysis

The potential for classifying beef samples on the basis of their geographical origin was investigated by stable isotope and multielement analysis using samples from various provinces in China. C and N isotope composition and the concentrations of 23 elements of the defatted beef samples were determined. It was shown that as compared to the Tibet beef fed predominantly on C3 pasture, maize-fed beef produced in Shandong and Heilongjiang province gave rise to a significant difference in (13)C content. Significant differences were also observed in 18 elements among the defatted beef samples. Stable isotope data and multielement concentrations determined in the beef were subjected to multivariate analysis, including principal component analysis (PCA) and discriminant analysis (DA). Eight key variables were identified as providing maximum discrimination among samples. DA gave an overall correct classification rate of 100% and a cross-validation rate of 100%. This research has proved that the geographical origin of beef in China can be identified by a combination of stable isotopes and multielement analysis.

How much do soil and water contribute to the composition of meat? A case study: meat from three areas of Argentina

The main goal of this study was to propose a reliable method to verify the geographical origin of meat, establishing the influence of soil and water on its isotopic and elemental composition. Thus, beef meat, soil, and water samples were collected from three major cattle-producing regions of Argentina (Buenos Aires, Córdoba, and Entre Ríos). Multielemental composition was determined on these three matrices by inductively coupled plasma mass spectrometry (ICP-MS), δ(13)C and δ(15)N by isotope-ratio mass spectrometry (IRMS), and the (87)Sr/(86)Sr ratio by thermal ionization mass spectrometry (TIMS). Soil and drinking water samples could be characterized and clearly differentiated by combining the isotopic ratios and elements, demonstrating differences in geology and climatic conditions of three regions. Similarly, meat originating at each sampling area was characterized and differentiated using only five key variables (Rb, Ca/Sr, δ(13)C, δ(15)N, and (87)Sr/(86)Sr). Generalized procrustes analysis (GPA), using the three studied matrices (soil, water, and meat) shows consensus between them and clear differences between studied areas. Furthermore, canonical correlation analysis (CCA) demonstrates significant correlation between the chemical-isotopic profile of meat with those corresponding to both soil and water (r(2) = 0.93, p < 0.001; and r(2) = 0.83, p < 0.001, respectively). So far, there are clear coincidences between the meat fingerprint and those from soil/water where cattle grew, presenting a good method to establish beef provenance. To the authors' knowledge this is the first report linking the influence of soil and water all together on the composition of beef, presenting the basis for the authentication of Argentinean beef, which could be extended to meat from different provenances.

Traceability along the production chain of Italian tomato products on the basis of stable isotopes and mineral composition

The paper shows the variability of stable isotope ratios and mineral composition in tomato and derivatives along the production chain (juice, passata and paste) in order to evaluate the possibility of tracing their geographical origin. The ratios (13)C/(12)C, (15)N/(14)N, (18)O/(16)O, D/H, (34)S/(32)S and the content of Li, Be, B, Na, Mg, Al, P, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Mo, Ag, Cd, Sn, Sb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Tm, Yb, Ir, Tl, Pb, U and of nitrates, chlorides, sulphates and phosphates were measured by Isotope Ratio Mass Spectrometry, Inductively Coupled Plasma Mass Spectrometry and Ion Chromatography, respectively. The tomato products were from three Italian regions - Piedmont, Emilia Romagna, and Apulia. By applying linear discriminant analysis on 17 of these parameters (Gd, La, Tl, Eu, Cs, Ni, Cr, Co, δ(34)S, δ(15)N, Cd, K, Mg, δ(13)C, Mo, Rb and U) excellent discrimination among products from the three regions was achieved. Irrespective of the processing technology, over 95% of the samples were correctly reclassified in cross-validation into the production site. The use of these parameters will allow the development of analytical control procedures that can be used to check the geographical provenance of Italian tomatoes and products derived from them.

Relevance of isotopic and molecular biomarkers for the authentication of milk according to production zone and type of feeding of the cow

The first objective of the present paper was to assess the potential of both isotopic ( (18)O/ (16)O in milk water) and molecular biomarkers (terpenes, fatty acids, carotenoids, and vitamins) and milk color to discriminate the production zone (lowland or upland areas) from which 49 tanker bulk milks were collected over one year from a total of 204 farms. The milk water (18)O enrichment was higher in lowland (<500 m altitude) than in upland (>700 m altitude), but the delta (18)O values failed to discriminate systematically the production zone at the scale of the year because of its high variability related to the sampling period. In contrast with vitamins A and E, carotenoids, and milk color measurements, terpenes and fatty acids were confirmed to be relevant tracers of the production zone. The milk compounds with the strongest discriminative potential were fatty acids, which were determined by high-resolution gas chromatography. The calculation of fatty acid ratios, which permits the limitation of using fatty acid relative quantity expressed in percentage of total fatty acids to be overcome, was shown to be particularly relevant in discriminating upland from lowland milk ratios. The selection of two pairs of ratios, namely, iso-C17:0/C18:3 n-3 and iso-C15:0/iso-C14:0, enabled the authentication of 100% of the highland versus lowland milks whatever the season. The second objective was to evaluate the relevance of fatty acid composition to discriminate milks according to the proportion of corn silage in the diets of dairy cows. The selection of two fatty acids ratios, namely, trans11 cis15-C18:2/trans11-C18:1 and cis9-C16:1/iso-C16:0, enabled the correct classification of 100% of the milk samples according to the proportion of corn silage in the basic fodder rations (<25% vs >30%). The relationship between the milk production zone and the type of forage fed to the cows is discussed.

Genetic traceability of livestock products: A review

Traceability is the ability to maintain the identification of animal, or animal products, all along the production chain. It represents an essential tool to safeguard public and animal health and to valorize typical production systems. European food legislation is particularly strict and traceability systems, based on product labeling, have become mandatory in all European countries. However, the implementation of this system does not ensure consumers against fraud. Paper documents can be counterfeit so researchers have focused on the study of genetic traceability systems based on products identification through DNA analysis. In fact DNA is inalterable, detectable in every cell, resistant to heat treatments, and allows for individual, breed or species identification. Even if results are promising, these techniques are too expensive to be converted in routine tests but they could be a trusted tool for verification of suspected fraud. The present review proposes a synthesis of the major advances made in individual, breed, and species genetic identification in the last years, focusing on advantages and disadvantages and on their real future applications for animal productions.