Determination of the source of bioavailable Sr using ⁸⁷Sr/⁸⁶Sr tracers: a case study of hot pepper and rice

Strontium leaching from municipal waste subjected to incineration

The aim of the study was to determine the content and leachability of Sr in ashes obtained through combusting municipal waste in household furnaces. The waste had been collected as a mixed stream and as separate fractions (i.e. furniture, sponges, waste paper, PCV packaging, plastic-coated paper cartons, imitation leather, rubber, textiles and polystyrene). Using single-step chemical extractions, (HCl + HNO3, H2O, 0.01 M CaCl2, 0.1 M CH3COOH), we determined the total content of Sr (TC) and proportions of the following fractions: water-leachable, phytoavailable and easily soluble and bound to carbonates. We also analyzed the effect of reducing pH in the extraction solutions on St leachability from the study material. The study showed that Sr concentration in ash generated from the combustion of conventional fuels, alternative fuels and municipal waste ranged from 114 to 1006 mg/kg. The largest amounts of Sr were found in ash generated from the combustion of alternative fuels (coal pellets 488-1006 mg/kg), conventional fuels (hard coal 430-670 mg/kg) and mixed waste (237-825 mg/kg). The most mobile fraction of Sr (water-leachable) comprised from 1.3% to nearly 91% TC; the phytoavailable fraction and the ion-exchange and carbonate-bound fraction comprised 3-92% TC and 9-72% TC, respectively. We also found that the greatest pH reductions do not always entail the greatest amounts of extracted Sr. A much more significant factor in this respect is the mineral and chemical composition of primary materials, which can buffer changes in pH. The Risk Assessment Code (RAC) values pointed to a varied environmental risk and the highest RAC values (> 70) were found for coal pellets, wood pellets, straw, rubber and plastic containers for mixed oils.

Transfer of 137Cs and 90Sr from soil-to-potato: Interpretation of the association from global fallout in Aomori to accidental release in Fukushima and Chornobyl

Ceasium-137 and 90Sr are major artificial radionuclides that have been released into the environment. Soil-to-plant transfer of radionuclides is an important route to food contamination. The radionuclide activity concentrations in crops must be quantitatively predicted for estimating the internal radiation doses from food ingestion. In this study, soil and potato samples were collected from three study sites contaminated with different sources of 137Cs and 90Sr: Aomori Prefecture (global fallout) and two accidental release areas (Fukushima Prefecture and the Chornobyl exclusion zone). The 137Cs activity concentrations in the soil and potato samples widely ranged from 1.0 to 250,000 and from 0.048 to 200,000 Bq kg-1 dry weight, respectively. The soil-to-potato transfer factor of 137Cs also ranged widely (0.0015-1.1) and decreased with increasing concentration of exchangeable K. Meanwhile, the activity concentrations of 90Sr in the soil and potato samples were 0.50-64,000 and 0.027-18,000 Bq kg-1 dry weight respectively, and the soil-to-potato transfer factor of 90Sr was 0.023-0.74, decreasing with increasing concentration of exchangeable Ca. The specific activity ratios of 137Cs/Cs and 90Sr/Sr in the exchangeable fraction were similar to those in potatoes, with a factor of 3 in the ±95 % confidence intervals over six orders of magnitude and a factor of 2 in the ±95 % confidence intervals over five orders of magnitude, respectively. According to the data, the accuracy of predicting the activity concentrations of 137Cs and 90Sr in potatoes can be improved by applying the specific activity ratios of 137Cs/Cs and 90Sr/Sr in the exchangeable fraction. This approach accounts for variable factors such as the effects of K and Ca fertilization and soil characteristics. It also emphasizes the benefit of determining the stable Cs and Sr concentrations in potatoes and other crops prior to possible future contamination.

National-scale distribution of strontium isotope ratios in environmental samples from South Korea and its implications for provenance studies

Successful application and accurate interpretation of strontium (Sr) isotope ratios (⁸⁷Sr/⁸⁶Sr) requires underlying information about the large-scale variabilities in their signatures from a variety of environmental samples, which can be correlated with the Sr isotopic signatures of underlying local geology. In this national-scale study, we analyzed ⁸⁷Sr/⁸⁶Sr in soil, plants, stream water, and Chinese mystery snail (Cipangopaludina chinensis) shells collected from South Korea to evaluate large-scale spatial variabilities, interpret relationships among isotopic signatures of various sample types, and generate spatial distribution isoscapes reflecting the heterogeneity of isotopic signatures across South Korea. Non-parametric comparisons among environmental samples showed non-significant differences in their isotopic ratios. The ⁸⁷Sr/⁸⁶Sr of plant and soil samples were strongly correlated (R²_adj = 0.93), suggesting that both reflect national-scale lithological properties. Similarly, the ⁸⁷Sr/⁸⁶Sr of shells showed strong correlations with the ⁸⁷Sr/⁸⁶Sr of both plant and soil samples (R²_adj = 0.90). The ⁸⁷Sr/⁸⁶Sr signatures of environmental samples in this study aligned with expected Sr isotopic values and generally reflected local geology. Spatial distribution maps of samples showed similar ⁸⁷Sr/⁸⁶Sr spatial patterns, with high radiogenic values from granitic and granitic gneiss rocks systems and low radiogenic values from volcanic and sedimentary rock systems. Stream water samples showed significant correlations with soil and plant isotopic ratios, but with a low coefficient of determination (R²_adj = 0.68). The deviations were much larger for samples with ⁸⁷Sr/⁸⁶Sr > 0.720. Further study is needed to improve the accuracy of baseline determination and interpretation of stream water isotopic variations.

A bioavailable strontium (87Sr/86Sr) isoscape for Aotearoa New Zealand: Implications for food forensics and biosecurity

As people, animals and materials are transported across increasingly large distances in a globalized world, threats to our biosecurity and food security are rising. Aotearoa New Zealand is an island nation with many endemic species, a strong local agricultural industry, and a need to protect these from pest threats, as well as the economy from fraudulent commodities. Mitigation of such threats is much more effective if their origins and pathways for entry are understood. We propose that this may be addressed in Aotearoa using strontium isotope analysis of both pests and products. Bioavailable radiogenic isotopes of strontium are ubiquitous markers of provenance that are increasingly used to trace the origin of animals and plants as well as products, but currently a baseline map across Aotearoa is lacking, preventing use of this technique. Here, we have improved an existing methodology to develop a regional bioavailable strontium isoscape using the best available geospatial datasets for Aotearoa. The isoscape explains 53% of the variation (R² = 0.53 and RMSE = 0.00098) across the region, for which the primary drivers are the underlying geology, soil pH, and aerosol deposition (dust and sea salt). We tested the potential of this model to determine the origin of cow milk produced across Aotearoa. Predictions for cow milk (n = 33) highlighted all potential origin locations that share similar ⁸⁷Sr/⁸⁶Sr values, with the closest predictions averaging 7.05 km away from their true place of origin. These results demonstrate that this bioavailable strontium isoscape is effective for tracing locally produced agricultural products in Aotearoa. Accordingly, it could be used to certify the origin of Aotearoa’s products, while also helping to determine if new pest detections were of locally breeding populations or not, or to raise awareness of imported illegal agricultural products.

Strontium Isotope Systematics of Tenerife Wines (Canary Islands): Tracing Provenance in Ocean Island Terroir

The production of fraudulent goods remains widespread and economically damaging. The high value of the wine industry makes it particularly vulnerable, and a number of geochemical methods have been developed to ensure traceability and identification of origin. Here, strontium (Sr) isotope data on wines from five defined regions in Tenerife (Canary Islands, Spain) show that the young volcanic geology imparts a clearly identifiable low 87Sr/86Sr signature (<0.7072). These values discriminate Tenerife wines from mainland Spanish and continental European produce, as these are much more radiogenic in general. However, unlike continental wine regions, wines from Tenerife show small but ubiquitous enrichments in 87Sr/86Sr above what is expected in the soils. Bentonite addition has not affected the 87Sr/86Sr signatures, with white wines at lower Sr concentrations than red wines in all regions. A number of natural contributions to the terroir are evaluated in relation to Tenerife’s unique combination of geology and geography. Atmospheric precipitation (rainfall) is likely a dominant influence on Sr isotope systematics in northern Denominación de Origen regions, and evaporation may play a role in buffering signatures in southern regions. Other natural additions of 87Sr are not precluded at a local scale, given the large range in climatic conditions of island terroir and known input of mineral dust from Africa. Despite natural explanations affecting the overall small shift observed, there are clear outliers with considerably higher 87Sr/86Sr and Sr concentration. This confirms the utility of Sr isotope systematics for oceanic-island viticulture and demonstrates the use of young volcanic soils for tracing natural inputs that may be masked in other regions.

Discriminant Analysis of the Geographical Origin of Asian Red Pepper Powders Using Second-Derivative FT-IR Spectroscopy

This study aimed to discriminate between the geographical origins of Asian red pepper powders distributed in Korea using Fourier-transform infrared (FT-IR) spectroscopy coupled with multivariate statistical analyses. Second-derivative spectral data were obtained from a total of 105 red pepper powder samples, 86 of which were used for statistical analysis, and the remaining 19 were used for blind testing. A one-way analysis of variance (ANOVA) test confirmed that eight peak variables exhibited significant origin-dependent differences, and the canonical discriminant functions derived from these variables were used to correctly classify all the red pepper powder samples based on their origins. The applicability of the canonical discriminant functions was examined by performing a blind test wherein the origins of 19 new red pepper powder samples were correctly classified. For simplicity, the four most significant variables were selected as discriminant indicator variables, and the applicable range for each indicator variable was set for each geographical origin. By applying the indicator variable ranges, the origins of the red pepper powders of all the statistical and blind samples were correctly identified. The study findings indicate the feasibility of using FT-IR spectroscopy in combination with multivariate analysis for identifying the geographical origins of red pepper powders.

Effects of Filter-Membrane Materials on Concentrations of Trace Elements in Acidic Solutions

Filtration is commonly used to separate liquids from solid materials before the determination of trace element concentrations in aqueous solutions. Therefore, it is important to determine how much elemental content is extracted from the filter itself or lost via absorption into the filter. In this study, we investigated three types of disposable syringe filters (polyvinylidene difluoride, PVDF; polytetrafluoroethylene, PTFE; PTFE with glass microfiber prefiltration media, GD/X) and their acid-cleaned versions using ammonium nitrate (NH4NO3) and acetic acid (HOAc) solutions. The concentrations of most trace elements (Li, Al, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Cs, Ba, Pb, and U) were higher in filtrates that had passed through acid-cleaned filters than those that had passed through uncleaned filters. In filtrates from PVDF and PTFE filters, many trace elements were below the detection limit. However, regardless of the filter type and acid cleaning, Li, Cu, Zn, Mo, and Ba concentrations in filtrates of NH4NO3 solutions, and Al, Cr, Mn, Cu, Zn, and Ba concentrations in filtrates of HOAc solutions were much higher than those of other trace elements. These differences were particularly noticeable in filtrates from GD/X filters containing glass microfiber layers. These data indicate that certain trace elements can be released from membrane materials by reacting with acid in the filtered solution. Furthermore, the amounts of each trace element were associated with the membrane type. These findings suggest that filter type should be carefully selected to obtain the required accuracy, in consideration of the target elements and whether an acid-cleaned filter is needed.

87 Sr/86 Sr isotope ratios in rocks determined using inductively coupled plasma tandem mass spectrometry in O2 mode without prior Sr purification

RATIONALE

An inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) instrument can be developed to determine ⁸⁷ Sr/⁸⁶ Sr ratios with an external precision better than 0.05% relative standard deviation (RSD) in "mass shift" mode without prior Sr purification. Previous studies suggested using CH₃ F, N₂ O, and SF₆ as reaction gases for this method because a better reaction rate can be achieved with Sr⁺ than with O₂ in the reaction cell. However, these gases are not commonly used in general chemistry laboratories, and processes using these gases are difficult to implement quickly due to regulations. We aim to develop a rapid method that can be applied to many samples for the accurate determination of ⁸⁷ Sr/⁸⁶ Sr isotope ratios with precision below 0.1% RSD (or approximately to the fourth decimal place).

METHODS

We evaluated the accuracy and precision of ⁸⁷ Sr/⁸⁶ Sr ratios in certified reference materials and different rock types determined using ICP-MS/MS with O₂ as the reaction gas in comparison with those determined using the multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) method.

RESULTS

This study showed that by using the ICP-MS/MS method, the ⁸⁷ Sr/⁸⁶ Sr ratios of BCR-2 and BHVO-2 do not vary significantly with and without prior Sr purification; when the Sr concentration of the measured solution is within the range of 60-350 ng/mL, there is no significant effect on the measured ⁸⁷ Sr/⁸⁶ Sr ratios. The results also showed that the ⁸⁷ Sr/⁸⁶ Sr ratios of 23 different rock types measured by ICP-MS/MS and MC-ICP-MS methods agree very well.

CONCLUSIONS

The precision of the ⁸⁷ Sr/⁸⁶ Sr ratio measured using ICP-MS/MS varies between 0.0001 and 0.0019 (2SD). This precision is less than that of the MC-ICP-MS method but is sufficient for certain applications, such as identifying ⁸⁷ Sr/⁸⁶ Sr ratios in different rock types. These results suggest that the developed ICP-MS/MS method has the potential for future studies involving the identification of Sr sources.

Sr isotope discrimination of multi species aquaculture productions at a worldwide scale and contribution of the water reservoir in Sr plant input

Aquatic plants commonly used in landscaping or as ornaments are subject to a growing worldwide market that is source of trade between countries which can induce the transfer of unwanted invasive alien plant species. To protect national biodiversity and economy, authorities promote the use of local markets without however providing the method to do so. This study deals with the feasibility of using Sr stable isotopes for discriminating the origin of aquatic plants at a worldwide scale. More than 15 aquatic plant species were collected from main producers in four countries (China, Hungary, Germany, France). Each plant was analysed for its ⁸⁷Sr/⁸⁶Sr ratio and the results are compared within samples from each producer and between countries. For a given produce, significant ⁸⁷Sr/⁸⁶Sr can be measured as a function of the plant species. However, at the scale of Europe, plants from different producers are almost isotopically identical with ⁸⁷Sr/⁸⁶Sr ratios of 0.71228 ± 218.10^-5, 0.71116 ± 178.10^-5 and 0.71066 ± 156.10^-5 for France, Hungary and Germany, respectively. These values are clearly distinguishable from those measured in Chinese aquatic plants, which yield a mean ⁸⁷Sr/⁸⁶Sr ratio of 0.70591 ± 168.10^-5. This Sr isotopic discrimination between European and Chinese aquatic plants is explained by the specific agricultural and hydrogeological environments of the producing countries. Indeed, the cycle of Sr in aquatic plants is studied here for the first time. Natural and anthropic materials of French origin were collected and characterized in terms of ⁸⁷Sr/⁸⁶Sr. Mixing models reveal that irrigation water is the main source of Sr for plants (35-85%). Clays from the substrate (4-38%) and fertilizers (5-19%) can also contribute, in proportions depending on the plant species. This model accounts for the small variations in ⁸⁷Sr/⁸⁶Sr ratios of species from the same producer and allows a discrimination between producers using different agricultural practices.

Intra- and Intertree Variability of the 87Sr/86Sr Ratio in Apple Orchards and Its Correlation with the Soil 87Sr/86Sr Ratio

The ⁸⁷Sr/⁸⁶Sr ratio of horticultural products mostly derives from that of the bioavailable Sr fraction of the soil where they grow and, therefore, varies according to the local geolithological features. This study investigated the intra- and intertree variability of the ⁸⁷Sr/⁸⁶Sr ratio in two apple orchards in South Tyrol and its relation with the soil ⁸⁷Sr/⁸⁶Sr ratio. In both orchards, a moderate homogeneity of the ⁸⁷Sr/⁸⁶Sr ratio was observed among subsamples of the same tree part (shoot axes, leaves, apple peels, and pulps). Moreover, the ⁸⁷Sr/⁸⁶Sr ratio homogeneity among tree parts was high intratree and low intertree. The variability of the ⁸⁷Sr/⁸⁶Sr ratio within the tree and within the orchard is explained in light of the ⁸⁷Sr/⁸⁶Sr ratios of the soil. This ⁸⁷Sr/⁸⁶Sr variability within orchards does not preclude its use as a geographical tracer; however, this aspect should be evaluated to correctly design a sampling campaign or to generalize the results.

Geographical origin discrimination of pepper (Capsicum annuum L.) based on multi-elemental concentrations combined with chemometrics

The concentrations of twenty-four elements in twenty-five peppers from three cultivated regions in Guizhou Province (China) were analyzed. The chemometric data processing, including one-way analysis of variance, principal component analysis, linear discriminant analysis (LDA), and orthogonal partial least squares discriminant analysis (OPLS-DA) were executed to differentiate the peppers. Consequently, the contents of 16 elements (Arsenic, Ba, Cu, Co, Cr, Ni, Pb, Sn, Sb, Mo, Sr, Y, Zn, Ca, P, and Fe) were significantly different among the three regions (p < 0.05). The correct discrimination rates of 25 peppers were 92.0% for LDA and 96.0% for OPLS-DA. The variable importance in the projection (VIP) values were ranged from 1.063 to 1.262 for seven elements (Tin, Fe, Zn, Y, Cr, Sr, and Mo) indicating that they played an important role for the geographical origin traceability of pepper. To sum up, multi-element concentrations together with chemometric data-processing can be promising for the geographical origin differentiation of pepper.

Innovative isotopic method to evaluate bioaccumulation of As and MTEs in Vitis vinifera

The transfer of metal and metalloid trace elements (MTEs) from contaminated soil to grapevines is a major issue for grape consumption and for the associated health risks. Based on an isotopic approach, we shed light on the concept of MTE bioavailability. The bioavailable fractions are identified by using the Sr-isotope ratio as a proxy for MTEs. This allows us to differentiate three soil reservoirs: the 'current available fraction' in soil water, the 'reserve available fraction' stored in mineral phases of the soil fractions, and the 'non-available fraction'. The reserve available fraction, representing 10 to 60% of bulk soil depending on the MTE, includes the exchangeable, carbonates, humic substance and oxides fractions. The ⁸⁷Sr/⁸⁶Sr isotopic signatures of grape berries and vine leaves show an additional source of MTEs, which is imported by foliar uptake and can contribute up to 10% of the MTEs in leaves. In addition, root-uptake and translocation rates show high accumulation rates of Co, Sn and Cu, and low ones for As, Sb, Zn and Cd. A daily intake between 1 and 3 kg of (dry grapes) would reach the benchmark dose level for a 0.5% (BMDL_0.5). While such a daily intake of grapes is unreasonable, consumption of other local vegetables and fruit would contribute to the daily intake. Hence, a chronic arsenic exposure is of great concern for human health in mining areas. We outline the importance of geochemical tracers, such as Sr isotopes, when determining the transfer and translocation of MTEs in plants. Our method presents a high-precision evaluation of the bioavailability and bioaccumulation of MTEs, and a better understanding of these processes in plants, thus leading to a better assessment of the environmental risk on human health.

Modelling strontium isotopes in past biospheres - Assessment of bioavailable 87Sr/86Sr ratios in local archaeological vertebrates based on environmental signatures

⁸⁷Sr/⁸⁶Sr isotopic ratios in skeletal remains of archaeological vertebrates are used for provenance analysis since long. However, the definition of the past bioavailable isotopic ratio at the site of recovery is not known beforehand and geological maps can provide no more than gross expectations. Therefore, the assessment of the "local Sr isotopic signature" is still of crucial importance. In this study, we present a tool for the prediction of such local isotopic signatures by creating a concentration weighted mixing model that links lithospheric, biospheric, and atmospheric strontium per site. The major strontium sources and their input into an animal's body were assessed by choosing elemental strontium and its isotopic signature in groundwater, soil, vegetation, and precipitation as components for the mixing model, augmented by literature values. The model was applied to 24 sites located in the alpine transect of the Inn-Eisack-Adige-Brenner passage across the European Alps, a passage used since the Mesolithic. Predicted local bioavailable ⁸⁷Sr/⁸⁶Sr ratios were compared with measured values from locally excavated archaeozoological bone samples from three taxa of large and mainly residential vertebrates (cattle, pig, red deer) to verify the models' accuracy. With regard to the fact that the environmental samples predict the past local bioavailable ⁸⁷Sr/⁸⁶Sr at a specific site while the vertebrates had different and species-specific home ranges, thereby integrating strontium from a region of primarily unknown size, the model is capable of assigning reasonable expectation values. For 11 sites, up to 100% of the vertebrate isotopic signatures were correctly predicted. Mismatches at the remaining sites are explainable by special environmental factors, and also the fact that some import of animals can never be excluded beforehand. Suggestions for site-specific adjustments of the model are made.

Plant Sr Isotope Ratios As Affected by the Sr Isotope Ratio of the Soil and of the External Sr Inputs

The ⁸⁷Sr/⁸⁶Sr ratio of a produce is generally linked with the soil geological features of the growing areas. This study aimed at assessing to which extent the addition of external Sr by agricultural practices, like irrigation and mineral nutrient supply, influences this relationship. In a first experiment, oat plants in two soils reflected the ⁸⁷Sr/⁸⁶Sr of the soil. However, this link was significantly altered at increasing levels of external Sr soil supplies. In a second experiment, apple trees transplanted in pots modified their original ⁸⁷Sr/⁸⁶Sr, which became progressively closer to the soil Sr isotope ratio. The addition of tap water and fertilizers, with different Sr isotopic signatures, slightly affected plant ⁸⁷Sr/⁸⁶Sr. Results confirm the potential of the ⁸⁷Sr/⁸⁶Sr ratio as a geographical tracer of agricultural commodities, but whenever the range of ⁸⁷Sr/⁸⁶Sr variability among soils from different geographical areas is narrow, the influence of external Sr-sources may smooth over these diversities.

Geographic authentication of Asian rice (Oryza sativa L.) using multi-elemental and stable isotopic data combined with multivariate analysis

Rice (Oryza sativa L.) is the world's third largest food crop after wheat and corn. Geographic authentication of rice has recently emerged asan important issue for enhancing human health via food safety and quality assurance. Here, we aimed to discriminate rice of six Asian countries through geographic authentication using combinations of elemental/isotopic composition analysis and chemometric techniques. Principal components analysis could distinguish samples cultivated from most countries, except for those cultivated in the Philippines and Japan. Furthermore, orthogonal projection to latent structure-discriminant analysis provided clear discrimination between rice cultivated in Korea and other countries. The major common variables responsible for differentiation in these models were δ³⁴S, Mn, and Mg. Our findings contribute to understanding the variations of elemental and isotopic compositions in rice depending on geographic origins, and offer valuable insight into the control of fraudulent labeling regarding the geographic origins of rice traded among Asian countries.

The determination and application of (87) Sr/(86) Sr ratio in verifying geographical origin of wheat

As ⁸⁷ Sr/⁸⁶ Sr ratio plays a significant role in authenticating the geographical origin of foodstuff, it is important to identify where the ⁸⁷ Sr/⁸⁶ Sr signature in food comes from, and the methods of ⁸⁷ Sr/⁸⁶ Sr ratio analysis in food and environmental samples. Wheat with three genotypes, soil and groundwater samples were collected from three regions of China during harvest time of 2014. The ⁸⁷ Sr/⁸⁶ Sr ratios in the samples were determined by thermal ionization mass spectrometer in order to investigate the possible source of ⁸⁷ Sr/⁸⁶ Sr in wheat, and the concentrations of Rb and Sr in wheat and soils were also detected by inductively coupled plasma mass spectrometry and combined with ⁸⁷ Sr/⁸⁶ Sr ratio in order to trace the geographical origin of wheat. The ⁸⁷ Sr/⁸⁶ Sr ratio, the contents Rb and Sr, and Rb/Sr ratio of wheat and soil samples showed significant differences among three regions. The ⁸⁷ Sr/⁸⁶ Sr ratios and the concentrations of Rb and Sr in soils were higher than those in corresponding wheat. The ⁸⁷ Sr/⁸⁶ Sr ratio in wheat was identical to that corresponding soil NH₄ NO₃ extracts (labile fraction of soil) and groundwater. Wheat uptake more Rb than Sr. 3D distribution of ⁸⁷ Sr/⁸⁶ Sr, Rb and Sr could identify wheat samples from different regions clearly. The ⁸⁷ Sr/⁸⁶ Sr ratio of wheat reflects the ⁸⁷ Sr/⁸⁶ Sr ratio of the associated environment including soil and groundwater. It is expected that the use the parameters of ⁸⁷ Sr/⁸⁶ Sr ratio, the contents of Rb and Sr will allow to trace geographical origin of wheat. Copyright © 2017 John Wiley & Sons, Ltd.

Authenticity of rice (Oryza sativa L.) geographical origin based on analysis of C, N, O and S stable isotope ratios: a preliminary case report in Korea, China and Philippine

BACKGROUND

Although rice (Oryza sativa L.) is the third largest food crop, relatively fewer studies have been reported on rice geographical origin based on light element isotope ratios in comparison with other foods such as wine, beef, juice, oil and milk. Therefore this study tries to discriminate the geographical origin of the same rice cultivars grown in different Asian countries using the analysis of C, N, O and S stable isotope ratios and chemometrics.

RESULTS

The δ(15) NAIR , δ(18) OVSMOW and δ(34) SVCDT values of brown rice were more markedly influenced by geographical origin than was the δ(13) CVPDB value. In particular, the combination of δ(18) OVSMOW and δ(34) SVCDT more efficiently discriminated rice geographical origin than did the remaining combinations. Principal component analysis (PCA) revealed a clear discrimination between different rice geographical origins but not between rice genotypes. In particular, the first components of PCA discriminated rice cultivated in the Philippines from rice cultivated in China and Korea.

CONCLUSION

The present findings suggest that analysis of the light element isotope composition combined with chemometrics can be potentially applicable to discriminate rice geographical origin and also may provide a valuable insight into the control of improper or fraudulent labeling regarding the geographical origin of rice worldwide. © 2015 Society of Chemical Industry.