Monitoring the authenticity of pu'er tea via chemometric analysis of multielements and stable isotopes

Discriminating the adulteration of varieties and misrepresentation of vintages of Pu'er tea based on Fourier transform near infrared diffuse reflectance spectroscopy

In the Pu'er tea market, the ubiquity of blending different varieties and the fraudulent representation of vintage years present a persistent challenge. Traditional sensory evaluation and experience are often inadequate for discerning the true variety and vintage of tea, highlighting the need for more sophisticated analytical methods to ensure authenticity and quality. Fourier transform near infrared diffuse reflectance spectroscopy combined with radial basis function neural network (RBFNN) was applied for determination of the varieties and vintages of Pu'er tea. For vintage identification, the accuracy, precision, recall, and F1-score of the RBFNN model for the prediction set were 99.2%, 98.2%, 98.0%, and 98.0%, respectively. For identification of varieties adulteration, the corresponding parameters were 98.9%, 97.2%, 96.7%, and 96.6%, respectively. These results illustrated the feasibility to identify the adulteration of varieties and misrepresentation of vintages of Pu'er tea with near infrared spectra and RBFNN model, proving an efficient alternative for Pu'er tea quality inspection, and offering a robust method for combating the pervasive issues within the market.

Improving the geographical traceability of tea in China based on stable isotope ratios

The potential of improving the classification of tea samples from different regions was studied by using stable isotope ratios analysis. The stable isotope ratios of 44 elements in tea samples were determined (p < 0.05).The results showed that 34 stable isotopes ratios were statistically significant, and tea in the four regions had their own characteristic variables. PCA, HCA, PLS-DA, BP-ANN and LDA were used to analyze the stable isotope ratio data in tea. Six key variables were identified to provide the greatest difference between the samples. The overall correct classification rate, cross validation rate and blind validation rate given by LDA are all 100%, and the result is the best. This study has proved that the stable isotope ratio analysis method could improve the geographical origin traceability of Chinese tea.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05970-w.

Development of sequential online extraction electrospray ionization mass spectrometry for accurate authentication of highly-similar Atractylodis Macrocephalae

The accurate and rapid authentication techniques and strategies for highly-similar foods are still lacking. Herein, a novel sequential online extraction electrospray ionization mass spectrometry (S-oEESI-MS) was developed to achieve spatio-temporally resolved ionization and comprehensive characterization of complex foods with multi-components (high, medium, and low polarity substances). Meanwhile, a characteristic marker screening method and an integrated research strategy based on MS fingerprinting, characteristic marker and chemometrics modeling were established, which are especially suitable for the accurate and rapid authentication of highly-similar foods that are difficult to be authenticated by traditional techniques (e.g., LC-MS). Thirty-two batches of highly-similar Atractylodis macrocephalae rhizome from four different origins were used as model samples. As a result, S-oEESI-MS enabled a more comprehensive MS characterization of substance profiles in complex plant samples in 1.0 min. Further, 22 characteristic markers of Atractylodis macrocephalae were ingeniously screened out and combined with multivariate statistical analysis model, the accurate authentication of highly-similar Atractylodis macrocephalae was realized. This study presents a comprehensive strategy for accurate authentication and origin analysis of highly-similar foods, which has potentially significant applications for ensuring food quality and safety.

Stable isotope signatures of deuterium, oxygen 18, and carbon 13 (δ2H, δ 18O, δ 13C) in imported apples available in the markets of Vietnam

This study examines whether fresh apples from the United States, New Zealand, and China sold in the markets of Vietnam can be distinguished based on the stable isotopic signatures of their water and carbon (δ²H, δ¹⁸O, and δ¹³C). The δ²H and δ¹⁸O in apples from the United States were found to average - 100.1 ‰ and - 10.5 ‰ vs VSMOW, respectively, lighter than those from New Zealand and China. In apples from China, the δ¹³C_VBDP averaged - 25.8 ‰, which is more enriched than apples from the United States and New Zealand. A clear distinction was shown in the δ²H, δ¹⁸O, and δ¹³C values in apple samples from the three regions based on the statistical treatment at a 95 % confidence level and p < 0.05. This method is reliable enough to control the import and export of agricultural products.

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 specific DNA barcodes based on chloroplast genes for species identification of Theaceae plants

More than 600 species in over 40 genera have been identified in family Theaceae worldwide. The accurate identification of Theaceae plants can ensure the market economic order, and it plays a vital role in achieving the sustainable utilization of germplasm resources. DNA barcoding, one of the most potential species identification technologies at present, has advanced in the rapid, accurate and repetitive discrimination of species. In this study, matK + ndhF + ycf1 was observed as the optimal combined candidate gene sequence of DNA barcodes by analyzing genetic information of four single chloroplast DNA sequences, including matK, rbcL, ndhF and ycf1, as well as six combined gene sequences. Subsequently, the experiments were performed on phylogenetic analysis based on genetic distance to study the phylogenetic relationship of Theaceae plants and evaluate the species identification accuracy of matK + ndhF + ycf1. Lastly, the species-specific DNA barcodes were designed by searching the variable sites (one type of single nucleotide polymorphism sites) for the accurate identification of Camellia amplexicaulis, Franklinia alatamaha, Gordonia brandegeei and Stewartia micrantha. The previous methods of screening and testing candidate gene sequences were optimized, and innovation was made in the above methods. The process of making visual DNA barcodes was standardized. Besides, DNA barcoding technology increased the accuracy of species identification and DNA barcoding was analyzed in accordance with the theories of population genetics (e.g., neutral theory of molecular evolution). The results of the study will lay a basis for the identification and protection of Theaceae species and germplasm resources.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-022-01175-7.

Rapid identification of the green tea geographical origin and processing month based on near-infrared hyperspectral imaging combined with chemometrics

The geographical origin and processing month of green tea greatly affect its economic value and consumer acceptance. This study investigated the feasibility of combining near-infrared hyperspectral imaging (NIR-HSI) with chemometrics for the identification of green tea. Tea samples produced in three regions of Chongqing (southeastern Chongqing, northeastern Chongqing, and western Chongqing) for four months (from May to August 2020) were collected. Principal component analysis (PCA) was used to reduce data dimensionality and visualize the clustering of samples in different categories. Linear partial least squares-discriminant analysis (PLS-DA) and nonlinear support vector machine (SVM) algorithms were used to develop discriminant models. The PCA-SVM models based on the first four and first five principal components (PCs) achieved the best accuracies of 97.5% and 95% in the prediction set for geographical origin and processing month of green tea, respectively. This study demonstrated the feasibility of HSI in the identification of green tea species, providing a rapid and nondestructive method for the evaluation and control of green tea quality.

The Role of Soil Mineral Multi-elements in Improving the Geographical Origin Discrimination of Tea (Camellia sinensis)

The combination of mineral multi-elements with chemometrics can effectively trace the geographical origin of tea (Camellia sinensis). However, the role of soil mineral multi-elements in discriminating the origin of tea was unknown. This study aimed to further validate whether the geographical origin of tea can be authenticated based on mineral multi-elements, the concentrations of which in tea leaves were significantly correlated with those in soil. Eighty-seven tea leaves samples and paired soils from Meitan and Fenggang (MTFG), Anshun, and Leishan in China were sampled, and 24 mineral elements were measured. The data were processed using one-way analysis of variance (ANOVA), Pearson correlation analysis, principal component analysis (PCA), and stepwise linear discriminant analysis (SLDA). Results indicated that tea and soil samples from different origins differed significantly (p < 0.05) in terms of most mineral multi-elemental concentrations. Conversely, the intra-regional differences of different cultivars of the same origin were relatively minor. Seventeen mineral elements in tea leaves were significantly correlated with those in soils. The SLDA model, based on the 17 aforementioned elements, produced a 98.85% accurate classification rate. In addition, the origin was also identified satisfactorily with 94.25% accuracy when considering the cultivar effect. In conclusion, the tea plant cultivars unaffected the accuracy of the discrimination rate. The geographical origin of tea could be authenticated based on the mineral multi-elements with significant correlation between tea leaves and soils. Soil mineral multi-elements played an important role in identifying the geographical origin of tea.