Geographical origin authentication of onions using stable isotope ratio and compositions of C, H, O, N, and S

Geographical differentiation between South Korean and Chinese onions using stable isotope ratios and mineral content analysis

Geographical origin authentication of onions has become significant owing to origin labelling fraud in South Korea. Various analytical techniques based on stable isotope ratios, organic and inorganic constituents, or their combinations, can distinguish agricultural products geographically. However, studies on the geographical classification of South Korean and Chinese onions using stable isotopes and minerals remain scarce. This study aimed to discriminate geographically between South Korean and Chinese onions using stable isotope ratios (δ13C, δ15N, and δ34S) and mineral contents (K, Ca, Mg, Na, P, Fe, Zn, Mn, Cu, and Sr) combined with multivariate statistical analysis. Fifty-eight onion samples cultivated in South Korea and China were collected in 2023. The two stable isotope ratios (δ15N and δ34S) and six minerals (K, Ca, Na, Fe, Zn, and Sr) significantly differed between these onions. These variables were applied in orthogonal partial least squares discriminant analysis to classify the onion samples regionally. The predictive ability and goodness-of-fit parameters (R2X and R2Y) were 0.671, 0.383, and 0.677, respectively. K, Sr, δ34S, and Na served as potential markers contributing to the classification. Therefore, stable isotopes and mineral elements may serve as effective indicators for the geographical discrimination of South Korean and Chinese onion samples using multivariate analyses.

Stable Isotope Ratio Analysis for the Geographic Origin Discrimination of Greek Beans "Gigantes-Elefantes" (Phaseolus coccineus L.)

Adulteration of high-value agricultural products is a critical issue worldwide for consumers and industries. Discrimination of the geographical origin can verify food authenticity by reducing risk and detecting adulteration. Between agricultural products, beans are a very important crop cultivated worldwide that provides food rich in iron and vitamins, especially for people in third-world countries. The aim of this study is the construction of a map of the locally characteristic isotopic fingerprint of giant beans, "Fasolia Gigantes-Elefantes PGI", a Protected Geographical Indication product cultivated in the region of Kastoria and Prespes, Western Macedonia, Greece, with the ultimate goal of the discrimination of beans from the two areas. In total, 160 samples were collected from different fields in the Prespes region and 120 samples from Kastoria during each cultivation period (2020-2021 and 2021-2022). The light element (C, N, and S) isotope ratios were measured using Isotope Ratio Mass Spectrometry (IRMS), and the results obtained were analyzed using chemometric techniques, including a one-way ANOVA and Binomial logistic regression. The mean values from the one-way ANOVA were δ15NAIR = 1.875‱, δ13CV-PDB = -25.483‱, and δ34SV-CDT = 4.779‱ for Kastoria and δ15NAIR = 1.654‱, δ13CV-PDB = -25.928‱, and δ34SV-CDT = -0.174‱ for Prespes, and showed that stable isotope ratios of C and S were statistically different for the areas studied while the Binomial logistic regression analysis that followed correctly classified more than 78% of the samples.

Trace the origin of yak meat in Xizang based on stable isotope combined with multivariate statistics

In this study, the feasibility of tracing the origin of yak meat in Xizang Autonomous Region based on stable isotope combined with multivariable statistics was researched. The δ13C, δ15N, δ2H and δ18O in yak meat were determined by stable isotope ratio mass spectrometry, and the data were analyzed by analysis of variance, fisher discriminant analysis (FDA), back propagation (BP) neural network and orthogonal partial least squares discrimination analysis (OPLS-DA). The results showed that the δ13C, δ15N, δ2H and δ18O had significant differences among different origins (P < 0.05). The overall original correct discrimination rate of fisher discriminant analysis was 89.7 %, and the correct discrimination rate of cross validation was 88.2 %. The correct classification rate of BP neural network based on training set was 93.38 %, and the correct classification rate of BP neural network based on test set was 89.83 %. The OPLS-DA model interpretation rate parameter R2Y was 0.67, the model prediction rate parameter Q2 was 0.409, which could distinguish yak meat from seven different producing areas in Xizang Autonomous Region. The results showed that the origin of yak meat in Xizang Autonomous Region can be traced based on stable isotope combined with multivariate statistics.

Effects of geographical origin, vintage, and soil on stable isotopes and mineral elements in Ecolly grape berries for traceability

Stable isotopes and multi-element profiles of grapes and corresponding soils from different origins and vintages were determined by IRMS and ICP-MS, respectively. Stable isotope ratios and multi-element contents show significant differences among distinct regions and vintages. Grapes and soils were separated using δ2H and δ18O according to regions and vintages. PCA and CA results further verified that multi-element profiles were influenced by origins and vintages. In particular, δ2H, δ18O, and 21 elements in grapes were correlated with those in soil. Redundancy and Spearman analyses revealed that the BCF values were related to the longitude, latitude, altitude, precipitation, and average temperature. RF shows better performance than PLS-DA for discriminating grape origins and vintages. K, Tb, Cs, δ2H, and Co were important variables in discriminating grape origins. These findings confirm that isotopic and elemental profiles depend on the origin, vintage, and soil, establishing a promising method to discriminate grape origins and vintages.

Application of Stable Isotope Analysis for Detecting the Geographical Origin of the Greek Currants "Vostizza": A Preliminary Study

There is a plethora of food products with geographical indications registered in the European Union without any study about their discrimination from other similar products. This is also the case for Greek currants. This paper aims to analyze if stable isotope analysis of C, N, and S could discriminate the Greek currants "Vositzza", registered as a product of Protected Designation of Origin, from two other currants registered as products of Protected Geographical Indication coming from neighboring areas. The first results show that the stable isotope ratio of sulfur is not detectable due to the very low sulfur content in the samples, and the analysis should be based on the stable isotope ratios of carbon and nitrogen to discriminate these products. The mean value of δ¹⁵N (1.38‱) of PDO "Vostizza" currants is lower than that of currants grown outside the PDO zone (2.01‱), while the mean value of δ¹³C of PDO "Vostizza" currants is higher (-23.93‱) in comparison to that of currants grown outside the PDO zone (-24.83‱). Nevertheless, the results indicate that with only two isotopic ratios, discrimination could not be achieved, and further analysis is required.

Simultaneously Verifying the Original Region of Green and Roasted Coffee Beans by Stable Isotopes and Elements Combined with Random Forest

Simultaneously verifying the original region of green and roasted coffee beans is very important for protecting legal interests of the stakeholder according to the chemical analyzing method. 131 green coffee bean samples are collected from six different original regions and pretreated with three degrees (green, middle, and dark roasted); five stable isotope ratios (δ13C, δ14N, δ18O, δ2H, and δ32S) and twelve elemental contents (Al, Cr, Ni, Zn, Ba, Cu, Na, Mn, Fe, Ca, K, and Mg) of green, middle, and dark roasted coffee bean samples (131×3) were analyzed. Fractionation of stable isotopes and variation of elemental contents were evaluated, only isotope hydrogen (2H) significantly fractionated, and elemental concentrations increased with a certain rate during the roasting process. One-way analysis of variance (ANOVA) was used to compare the stable isotope ratios and elemental concentrations of all coffee bean samples from six different original regions. Random forest (RF) was employed to build a discriminating model for simultaneously verifying the original regions of green and roasted coffee bean samples; this model provided 100% accuracy. Inclusion of this mathematical model for simultaneously verifying the original region of green and roasted coffee beans had powerful distinguishing capability and which will not be influenced by fractionation of hydrogen (2H) and variation of element contents during the roasted process.

Relationship between the Grade and the Characteristic Flavor of PCT (Panyong Congou Black Tea)

Panyong Congou black tea (PCT) is one of the most representative and historically famous Congou black teas in China and has been gaining more and more attention for its beneficial health properties. Currently, four grades of PCT are available, based on the raw leaf materials and consumer palatability. The chemical profiles distinguishing different grades of PCT are yet to be defined, nor has the relationship with grade been evaluated. In the present study, chemometric analysis showed that epigallocatechin (EGC), catechin (C), polyphenols, gallic acid (GA), and free amino acids are grade related bio-markers of PCT. These compounds are associated with the sweet and mellow aftertaste of PCT. A total of 34 volatile components were identified, of which the three component types with the highest relative percentages were alcohols (51.34–52.51%), ketones (27.31–30.28%), and aldehydes (12.70–13.18%). Additionally, our results revealed that sweet floral and fruity aromas were positively correlated with six volatile organic compounds (VOCs), 1-pentanol, propyl hexanoate, linalool, cyclohexanone, hexanal, and 2,5-dimethylpyrazine. Clear discrimination was achieved using orthogonal projections to latent structures discriminant analysis (OPLS-DA). The findings provide vital information on the characteristic flavor of each grade of PCT.

Assessment of the Authenticity of Whisky Samples Based on the Multi-Elemental and Multivariate Analysis

Two hundred and five samples of whisky, including 170 authentic and 35 fake products, were analyzed in terms of their elemental profiles in order to distinguish them according to the parameter of their authenticity. The study of 31 elements (Ag, Al, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Sb, Sn, Sr, Te, Tl, U, V, Ca, Fe, K, Mg, P, S, Ti and Zn) was performed using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Cold Vapor-Atomic Absorption (CVAAS) techniques. Additionally, the pH values of all samples were determined by pH-meter, and their isotopic ratios of ⁸⁸Sr/⁸⁶Sr, ⁸⁴Sr/⁸⁶Sr, ⁸⁷Sr/⁸⁶Sr and ⁶³Cu/⁶⁵Cu were assessed, based on the number of counts by ICP-MS. As a result of conducted research, elements, such as Mn, K, P and S, were identified as markers of whisky adulteration related to the age of alcohol. The concentrations of manganese, potassium and phosphorus were significantly lower in the fake samples (which were not aged, or the aging period was much shorter than legally required), compared to the original samples (in all cases subjected to the aging process). The observed differences were related to the migration of these elements from wooden barrels to the alcohol contained in them. On the other hand, the sulfur concentration in the processed samples was much higher in the counterfeit samples than in the authentic ones. The total sulfur content, such as that of alkyl sulfides, decreases in alcohol with aging in the barrels. Furthermore, counterfeit samples can be of variable origin and composition, so they cannot be characterized as one group with identical or comparable features. Repeatedly, the element of randomness dominates in the production of these kinds of alcohols. However, as indicated in this work, the extensive elemental analysis supported by statistical tools can be helpful, especially in the context of detecting age-related adulteration of whisky. The results presented in this paper are the final part of a comprehensive study on the influence of selected factors on the elemental composition of whisky.

Spatial variability of water quality and sedimentary organic matter during winter season in coastal aquaculture zone of Korea

We investigated the composition, source, and reactivity of sedimentary organic matter (OM) present in aquaculture systems along the Korean coast. A multi-isotopic approach was applied to 216 surface sediments from five sections: western (W)-1, W-2, southern (S)-1, S-2, and eastern (E)-1 sections. The ¹⁵N-enriched total nitrogen signatures in the surface sediments of the W-1 section may indicate that a substantial fraction of sedimentary OM has anthropogenic origins exported through the Han River. Simultaneously, the deposition of allochthonous OM is predominant in the S sections (Jinhae and Masan Bays). The ³⁴S-depleted patterns at the S-2 section may indicate that sulfate reduction occurring at the sedimentary boundary contributes to active OM decomposition, depending on the increased sedimentation of the aquaculture-derived OM. Our results highlight that isotopic-based source tracking near aquaculture systems provide important information for identifying anthropogenic contamination in coastal marine sediments and for improving environmental management.

Geographical origin traceability of Sengcu rice using elemental markers and multivariate analysis

Multi-element analysis combined with chemometric method has been used to investigate the distinguish between Sengcu rice and other types of rice origins in Vietnam. In Sengcu rice, As, Ba Sr, Pb, Ca, Se were confirmed as the key elements for geographical traceability among three fields of Lao Cai, whereas Al, Ca, Fe, Mg, Ag, As were major factors to distinguish between Sengcu and other types of rice. Based on linear discriminant analysis and partial least squares-discriminant analysis model, overall correct identification rates distinguishing between Sengcu and other types of rice were approximately 100% in both training and validation test. Moreover, to distinguish geographical origin of Sengcu rice samples, these rates vary from 80% to 99%. These results suggest the presence of food adulteration illustrated in the latter.

Rape, sunflower and forest honeys for long-term environmental monitoring: Presence of indicator elements and non-photosynthetic carbon in old Hungarian samples

In this paper, we present the time-dependent elemental composition and AMS radiocarbon dating results of 36 rape, sunflower and forest honey samples, collected between 1985 and 2018 in geographically close locations. Based on the elemental information, we conclude that bee products regardless the type provide useful environmental information of the previous decades, such as the decreasing trend of airborne Pb emission can be traced. However, radiocarbon results agree less with the atmospheric bomb peak. Random offsets were observed in the specific radiocarbon activity of the honey samples indicating that rape, sunflower and forest honey samples are not as reliable materials for radiocarbon dating as acacia honeys. The radiocarbon results show that the rape, sunflower and forest honey samples can contain non-photosynthetic carbon, presumably derived from the soil. Thus, the complex application of honey samples for environmental reconstruction requires the species-separated investigation of bee products to reveal their adaptability for assessment approaches.

Improved accuracy of geographical origin identification of shiitake grown in sawdust medium: A compound-specific isotope model-based pilot study

In countries like South Korea and the USA, origin labeling of shiitake grown using imported Chinese-inoculated medium is an issue. Therefore, we evaluated the use of compound-specific isotope analysis (CSIA) for the accurate identification of the geographical origin of shiitake (Korean, Chinese-inoculated medium, and Chinese); Chinese-inoculated medium shiitake were cultivated in Korea using inoculated sawdust medium from China. The CSIA-discriminant model showed an overall accuracy of 100% in the geographical classification of the original set and 96.4% for the cross-validated set. Glutamate and aspartate δ¹⁵N values were the most important variables for differentiating shiitake based on their origins. Compared to that observed upon using the bulk stable isotope analysis, the CSIA model was associated with significantly improved predictability of origin identification. Our findings elucidate the importance of isotope signatures in developing a reliable origin labeling method for shiitake cultured on the sawdust medium for the global market.

Dietary homogenization and spatial distributions of carbon, nitrogen, and sulfur isotope ratios in human hair in South Korea

Dietary homogenization has progressed worldwide due to westernization and the globalization of food production systems. We investigated dietary heterogeneity in South Korea by examining the spatial distribution of carbon (C), nitrogen (N), and sulfur (S) isotope ratios using 264 human hair samples. Overall, variation in isotope values was small, indicating low dietary heterogeneity. We detected differences in δ13C, δ15N, and δ34S values between administrative provinces and metropolitan cities; inter-regional differences were typically < 1 ‰. Values of δ34S were significantly lower in hair samples from inland regions relative to those from coastal locations, and a similar pattern was observed in δ15N values. Understanding geographic variation in δ34S and δ15N values in human hair is useful for provenancing humans in South Korea.

Efficacy of using stable isotopes coupled with chemometrics to differentiate the production method and geographical origin of farmed salmonids

The δ²H and δ¹⁸O of 105 salmonids cultured in freshwater and seawater and from different regions were combined with linear discriminant analysis (LDA), k-nearest neighbor (KNN), and random forest (RF) to create discrimination models. To assess the stability of the discrimination models, seasonal variation in δ²H and δ¹⁸O in salmonids cultured in different systems was studied. δ²H and δ¹⁸O were significantly different between salmonids cultured in freshwater and seawater and from different geographical origins. δ²H and δ¹⁸O of salmonids cultured in an open system were vulnerable to seasonal effects. The KNN model had 100% accuracy for identifying the production methods of salmonids and was less affected by seasonal variation. The RF model had the highest accuracy for identifying the geographical origins of salmonids with an accuracy of over 80%. Thus, δ²H and δ¹⁸O were more effective for identifying the production methods of salmonids than their geographical origins.

Investigation of chlorinated phenols sorption mechanisms on different layers of the Danube alluvial sediment

The characteristics of the Danube river alluvial sediment are of great importance in assessing the risk for transport of pollutants to drinking water sources. Characterization of the sediment column layers has shown that the alluvial sediment, sampled near the city of Novi Sad, is a mesoporous sandy material with certain differences in the properties of individual layers. In order to investigate the sorption mechanisms of four chlorinated phenols (CPs) on the alluvial deposit, static sorption experiments were performed at pH 4, 7 and 10. The results of sorption experiments, confirmed by principal components analysis sugest different mechanisms govern the sorption process at different pH conditions. This can be attributed to the molecular characteristics of CPs, geosorbent properties and to variations in the surface charge of the sorbent at different pH conditions.

Honey as an indicator of long-term environmental changes: MP-AES analysis coupled with 14C-based age determination of Hungarian honey samples

Several studies show that the elemental content of honey entirely depends on the botanical and geographical origin, but the information is incomplete regarding its time-dependent composition changes. Twenty-six acacia and three honey samples with unknown botanical origin were collected between 1958 and 2018 and analysed for elemental composition by Microwave Plasma Atomic Emission Spectrometry (MP-AES). The elemental analysis was coupled with independent dating method by Accelerator Mass Spectrometry (AMS) to confirm the calendar age of the honey samples and test the possibility of radiocarbon based dating of bee products, which has not been applied before. According to the analytical measurements and statistical analysis, we can conclude that the elemental composition shows change with time in the acacia honey during the last five decades. We have proven that honey preserves carbon isotopic and elemental information of its production time and thus can be applied as an environmental indicator (e.g. trace urban pollutants, precipitation, local industrial or agricultural emission) in reconstruction studies by analysing the non-degradable mineral content. Our results further show that acacia honey is a suitable material for radiocarbon dating, proved by the results compared to the atmospheric radiocarbon bomb-peak. The new approach presented for investigation of honey by radiocarbon-based age determination coupled with elemental analysis can be used in biological, dietary, archaeological or other multidisciplinary studies as well. Some samples show slightly depleted radiocarbon content. This could be an indication of local fossil CO₂ emission. Based on these depleted ¹⁴C results, honey could be used for atmospheric monitoring of fossil CO₂ urban or industrial hot-spots.

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.

Geographical Origin Authentication of Agri-Food Products: Α Review

This study is a systematic literature review of geographical origin authentication by elemental analytical techniques. Authentication and certification of geographic origin of agri-food products is a useful tool toward the protection of the quality for products. The aim of this work was to map the current state of research in the area of agricultural products and food, identifying emerging fields to the geographical origin of products. The article is divided in three parts. The first part of the article deals with the analytical techniques applied in the food authentication. Special mention is made to elemental analysis and multiple isotope ratio. The second section focuses on statistically published data concerning published research for geographical origin authentication for the period 2015-2019. Specific results are presented inter alia: number of articles according to the type of product, articles according to the type of the analytical techniques, and others. The third part contains characteristic results from articles that were published in the period 2015-2019, on certification of geographical origin on specific agricultural products.

Linking growing conditions to stable isotope ratios and elemental compositions of Costa Rican bananas (Musa spp.)

Traceability of agricultural produce is getting increasingly important for numerous reasons including marketing, certification, and food safety. Globally, banana (Musa spp.) with its high nutritional value and easy accessibility, is a popular fruit among consumers. Bananas are produced throughout the (sub-)tropics under a wide range of environmental conditions. Environmental conditions could influence the composition of bananas. Understanding the effect of these conditions on fruit composition provides a way of increasing the fruit's traceability and linking it to its origin - a crucial aspect for the increasing global supply chain. In this study, we examined the influence of growing conditions on the isotopic and elemental composition of bananas produced in 15 Costa Rican farms. A total of 88 bananas (peel and pulp) were collected from the farms and analysed for isotopic signatures (δ¹³C, δ¹⁵N, and δ¹⁸O) and elemental compositions. The growing conditions were characterized in terms of climate, topography and soil conditions. The isotopic ratios differed significantly between groups of farms. The δ¹³C and δ¹⁵N values were mainly influenced by soil types, while rainfall and temperatures related more to the δ¹⁸O values. The elemental compositions of the bananas were primarily influenced by the local rainfall and soil types, while the geographical origin could be distinguished using principal component analysis. The overall results link the growing conditions to the isotopic and elemental compositions of bananas, thereby also providing a way to trace its origin.

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.