Tea Samples Research Articles

Sensory Profiling of Indonesian White Tea Using Quantitative Descriptive Analysis

Silver needle is a common type of white tea in Indonesia. The silver needle is produced from unbloomed pekoe, is pointed, slightly hairy, and silver in color. Quantitative descriptive analysis is a sensory evaluation method that relies on trained panelists' abilities in the experiment. The purpose of this study is to create a sensory profile of white tea from Indonesia using the QDA method. Five tea samples registered to the Indonesian National Agency for Drug and Food Control (Brand Gamboeng, Ennie 1, and Cap Pucuk from the West Java, Teh Dandang from Central Java, and Brand Heizl from East Java) were evaluated by trained panelists with extensive experience who had passed selection and training processes. Water was used as the neutralizer and crackers as the carrier. Three grams of each sample were brewed at 98°C with 150 mL of water for 7 min. Each panelist described the attribute, determined the reference, and evaluated all samples on a 15-cm scale. The results of the focus group discussion has obtained 12 lexicon sensory attributes, namely: yellow-brown, burned aroma, floral aroma, dry aroma, woody aroma, green aroma, burned flavor, green flavor, fermented flavor, floral flavor, bitter taste, astringent aftertaste, and bitter aftertaste. The results also showed that the "Heizl" white tea had the following sensory characteristics: yellow-brown, burned aroma, burned flavor, fermented flavor, bitter taste, bitter aftertaste, and astringent aftertaste. Moreover, the "Dandang" white tea had the following attributes: dry aroma, floral aroma, woody aroma, green aroma, green flavor, and floral flavor.

Synthesis of ionically imprinted Poly(Alylthiourea) in the presence of 1-(2-Pyridylazo)-2-Napthol (PAN) for preconcentration in magnetic dispersive solid phase of nickel ions in water and food samples

In the present study, a magnetic ion-imprinted polymer based on n-allylthiourea in the presence of 1-(2-pyridylazo)-2-naphthol (MIIP-PAN) was synthesized, characterized, and applied in the preconcentration of nickel ions by dispersive magnetic solid phase extraction (DMSPE) with FAAS detection. For comparison, non-imprinted polymer (MNIP-PAN) and imprinted polymer without PAN were synthesized. The characterization of the polymers was performed by FT-IR, DRX, TEM, TGA, VSM, and BET. Selectivity studies were performed comparing the competitive adsorption of Ni2+ with other cations on MIIP-PAN and MNIP-PAN, achieving higher relative selectivity coefficients for MIIP-PAN than for MNIP-PAN and NIP. Under optimized conditions, the method provided a preconcentration factor of 76.70, detection limit of 0.25 µg/L and intra-day (2.06 – 2.33 %) and inter-day (1.82 – 4.90 %) precision. The developed method was applied to samples of water, teas, and chocolate powder, and its precision was evaluated through tests of recovery and analysis of certified materials.

Determination of C═C Positions of Unsaturated Fatty Acids in Foods via Ambient Reactive Desorption Ionization with Water Dimer Radical Cations.

The positions of C═C bonds in unsaturated fatty acids (FAs) are one of the main factors determining the quality of food flavor. Herein, we developed an approach for the determination of C═C bonds of FAs by online epoxidation reaction with water dimer radical cations. The limit of detection for octenoic acid isomers was ∼9 μg/L. The positions of C═C bonds in trans-2/3-hexenoic acid, trans-2/3-octenoic acid, oleic acid, linoleic acid, and linolenic acid in black tea or olive oil samples were directly determined by the established method. These results indicate that the established method allows the rapid determination of unsaturated FAs in black tea and olive oil. The advantages of this approach include the analysis speed (∼1 min per sample), simple device, and no need for complex pretreatment. This study not only provides a strategy for the determination of C═C positions but also offers new possibilities for applications in the field of food chemistry.

Development and comparison of parallel reaction monitoring and data-independent acquisition methods for quantitative analysis of hydrophilic compounds in white tea

In the present work, parallel reaction monitoring (PRM) and data-independent acquisition (DIA) methods were developed for the accurate quantitation of amino acids, alkaloids nucleosides and nucleotides in tea. The quality peaks were significantly enhanced by optimizing the LC elution procedure, HCD voltage, MS resolution, and scanning event. Both methods were validated with good liner linearity (0.004–200 μg/mL), LODs (0.001–0.309 μg/mL for PRM and 0.001–0.564 μg/mL for DIA). Applied to white tea sample, the contents of these hydrophilic compounds were range from 34,655.39 to 70,586.14 mg/kg, and caffeine (32,529.02 mg/kg) and theanine (5483.46 mg/kg) were determined as the most abundant ones. Based on the quantitation data set, the white tea samples from Puer, Lincang and Xishuangbanna were clearly discriminated using multivariate data analysis. The results of the present works show that PRM and DIA have great potential in quantitative analysis of multiple hydrophilic compounds in food samples.

Promoting a circular economy by developing new gastronomic products from brassica non‐edible leaves

SummaryThis study aims to apply circular economy principles by reintroducing discarded Brassica leaves into the value chain as innovative products. Non‐edible leaves of three Brassica varieties were used to develop kombucha, a fermented beverage with health benefits. The fermentation time (9 days), temperature (25 °C), starter culture, and container shape (2 L round‐shape glass jar) influenced the beverage's physicochemical properties, including pH, vitamin content, polyphenols, and sugar levels. Different Brassica varieties showed various effects on antioxidant capacity and polyphenol content during fermentation, with potential implications for microbial engagement. Sensory analysis revealed differences in appearance, colour, aroma, and taste between black tea and Brassica samples, which are due to glucosinolates and volatile compounds, thus providing opportunities for improving consumer acceptability through flavour masking. Overall, this work showcases the potential of using non‐edible Brassica by‐products and highlights the potential of fermented beverages like kombucha to address food waste and promote value addition from otherwise discarded plant parts.

Contents of ɑ-dicarbonyl compounds in commercial black tea and affected by the processing

The species and contents of ɑ-dicarbonyls in commercial black tea were examined, along with the effects of the manufacturing process and drying temperature on the formation of ɑ-dicarbonyls. Ten ɑ-dicarbonyls were quantified in commercial and in-process black tea samples by using UPLC-MS/MS and their derived quinoxalines. The ɑ-dicarbonyls content in commercial black tea decreased significantly (p < 0.05) in the following order: 3-deoxyglucosone > glucosone > 3-deoxypentosone = threosone > galactosone ≥ methylglyoxal = glyoxal ≥ 3-deoxygalactosone = 3-deoxythreosone = diacetyl. Except for 3-deoxyglucosone and 3-deoxygalactosone, a further eight ɑ-dicarbonyls were identified in all manufacturing steps of black tea. Except for the drying step, the rolling and fermenting played important roles in the formation of ɑ-dicarbonyls. The total contents of ɑ-dicarbonyls in black tea infusion ranged from 16.48 to 75.32 μg/g based on our detected ten ɑ-dicarbonyls.

Assessment and health risk of fluoride from Northeast Indian tea (Camellia sinensis L.): Fixing up the maximum residue level of fluoride in tea

The tea plant is considered a strong fluoride (F-) hyperaccumulator plant. We have proposed the Maximum Residue Limit (MRL) of F- in tea based on 321 tea samples collected from 8 tea-growing regions of Northeast India. Total F- as well as water-soluble F- content was analysed through the ion selective electrode with the recovery percentage of 100–108 to ascertain the risk associated with F- towards human health. It has been observed that total F- contents (mg kg−1) in Cachar, Darjeeling, Dooars, North Bank, South Bank, Terai, Tripura, and Upper Assam ranged from 42.5 to 111.5, 16.0 to 168.0, 48.0 to 291.0, 36.5 to 314.0, 60.0 to 154.0, 26.5 to 233.5, 26 to 118 and 44 to 244, respectively. The F- content in tea infusion varied between 1.08 mg L−1 and 2.43 mg L−1 across all eight regions with a mean of 1.90 mg L−1. The average transfer of F- from made tea (processed young shoot of tea plants comprising a bud and 2 to 3 leaves) to tea infusion was 100.46%. Fluoride content in infusion was decreased with the increment of infusion number but increased gradually with continuous infusion time. The non-carcinogenic health risk was assessed. Calculated Hazard Quotient values were far below 1. The calculated and rounded MRL (300 mg kg−1) was recommended for F- in tea in India.

Description of tea quality using deep learning and multi-sensor feature fusion

To address the problem of the lack of rapid discrimination technology for comprehensive evaluation of product quality and grade in the field of tea quality control, this study uses near-infrared spectroscopy, electronic eye, electronic tongue, and electronic nose technology to sense the external and internal quality sensing characteristics of tea leaves, and realizes comprehensive evaluation of four quality factors such as "color, aroma, taste and shape" of tea leaves through cross-sensor multimodal quality characteristics data fusion. For the first time, a comprehensive method for assessing the grade quality of tea based on deep learning algorithms combining cross-sensor multimodal fusion features such as color, texture, shape, optical, electronic tongue, and electronic nose is established. The results showed that the constructed deep convolutional neural network (CNN) classification model had a misclassification rate of only 0.86% in the prediction set, which was better than the modeling results based on traditional classification methods. This study reveals that the CNN algorithm can effectively evaluate the quality grade of tea samples and realize the digital evaluation of multiple evaluation factors of tea sensory quality.

A target-triggered ultra-sensitive aptasensor for simultaneous detection of Cd2+ and Hg2+ using MWCNTs-Au NPs modified electrode

A sensitive electrochemical assay for simultaneously detecting cadmium ion (Cd2+) and mercury ion (Hg2+) with the aptamer as recognition unit was established, in which methylene blue (MB) and target-triggered in-situ generated Ag nanoclusters (Ag NCs) were identified as signal reporters. Multi-walled carbon nanotubes and gold nanoparticles composites were prepared with polyethyleneimine to amplify electrical signals of screen-printed electrodes. Due to the particular base sequences, MB labeled Cd2+ aptamer paired with ssDNA through T-Hg-T structure with Hg2+. Notably, the C-rich structure in ssDNA acted as a template for the generation of Ag NCs, which could induce differential pulse voltammetry signals corresponding to Hg2+ concentrations. This electrochemical aptasensor exhibited detection limits of 94.01 pg/mL and 15.74 pg/mL for Cd2+ and Hg2+, respectively. The developed aptasensor allowed for practical application to tea and vegetable samples with satisfactory accuracy. This work possesses potential in developing biosensing technologies for simultaneous determination of multiple heavy metals.

Effects of yellowing and drying treatment temperatures on the taste of autumn green tea

This study aimed to reduce the bitterness and astringency properties of autumn green tea using different yellowing and drying treatments. The results showed that as the yellowing temperature increased, the contents of tea polyphenols, gallated catechins, flavonol glycosides, and bitter amino acids decreased, while the content of soluble sugar and flavonols increased. The tea sample (YEL35 °C) subjected to yellowing treatment at 35 °C exhibited weak bitterness and astringency intensities and a relatively low content of flavonol glycosides. As the drying temperature increased, the content of gallated catechins decreased. In addition, the tea sample (DRY75 °C) subjected to drying treatment at 75 °C exhibited weak bitterness and astringency intensities, the highest contents of umami amino acids and Thea, and a relatively low content of gallated catechins. Multivariate statistical analysis revealed that vitexin-2-O-rhamnoside, pferol-3-O-rutinoside, myricetin-3-O-galactoside, and quercetin-3-O-glucoside played an important role in the astringency property of the tea. In addition, Asn, Thr, Pro, and Met were positively correlated with umami. Hence, the quality of autumn green tea was improved under optimal yellowing and drying temperatures of 35 and 75 °C, respectively.

Rapid detection of ash content in black tea using a homemade miniature near-infrared spectroscopy

Ash is a testing index with both health inspection value and quality decision value, and it is an essential detection item in the import and export trade of tea. To realize the rapid and effective quantitative analysis of ash content in tea, this study proposed the use of a homemade miniature near-infrared (NIR) spectroscopy combined with multivariate analysis for the rapid detection of ash content in black tea. First, NIR data of black tea samples from different countries were acquired and optimized by the spectral preprocessing method. Then, the optimized pre-processed spectral data were used as features, and four feature wavelength selection algorithms, such as competitive adaptive reweighted sampling, iteratively retaining informative variables (IRIV), variable combination population analysis (VCPA)-IRIV, and interval variable iterative space shrinkage approach (IVISSA), were utilized to optimize the feature spectra. Finally, the support vector machine regression (SVR) algorithm was employed to construct the quantitative models of ash content in black tea by combining the optimal wavelengths obtained from the four feature selection methods mentioned above. The experimental results showed that the IVISSA-SVR model had the best performance, with correlation coefficient (Rp), root mean square errors of prediction (RMSEP), and relative prediction deviation (RPD) of 0.9546, 0.0192, and 5.59 for the prediction set, respectively. The results demonstrate that a miniature NIR sensing system combined with chemometrics as an effective analytical tool can realize the rapid detection of ash content in black tea.

Determination of copper in rose tea samples using flame atomic absorption spectrometry after emulsification liquid–liquid microextraction

Rose tea infusion has gained popularity worldwide due to its health benefits. However, it is known that tea plants can be contaminated with heavy metals including copper. Hence, an accurate and applicable analytical method namely emulsification liquid–liquid microextraction based deep eutectic solvent – flame atomic absorption spectrometry (ELLME-DES-FAAS) was proposed to determine copper at trace levels in rose tea samples. Under the optimum experimental conditions, analytical figures of merit for the developed method were examined, and dynamic range, limit of detection (LOD) and limit of quantification (LOQ) were found to be 5.07–246.61 µg/kg (mass-based) with 0.9992 coefficient of determination, 2.50 µg/kg and 8.32 µg/kg, respectively. A matrix matching calibration strategy was employed to boost recovery results, and the acceptable recovery results were recorded between 95.9 % and 118.4 %. According to recovery results, the developed analytical method can be safely employed to determine the concentration of copper in rose tea samples accurately.

Estimation of Shelf Life of Pegagan Tea (Centella asiatica (L) Urban) using Accelerated Shelf Life Testing (ASLT) Method with Arrhenius Model

This research aimed to evaluate the shelf life of pegagan (Centella asiatica (L) Urban) tea using the Accelerated Shelf Life Testing (ASLT) method by applying the Arrhenius Model since its widely known for its various health benefits, including its ability to enhance cognitive function and exhibit antioxidant effects. The ASLT method was employed to accelerate the chemical and physical changes in the product, thereby enabling a shorter estimation of shelf life compared to conventional methods. In this research, samples of pegagan tea were packaged in paper sacks, aluminum foil, and vacuum-sealed plastic and stored at temperatures of 15, 30, and 45 °C for 28 days, with observations conducted every 7 days. The Arrhenius Model was utilized to predict the rate of chemical reactions in the product, taking into account the temperature's influence on these changes. The data were analyzed using Analysis of Variance (ANOVA) at a 5% confidence level. If the ANOVA results showed significant differences, Duncan Multiple Range Test (DMRT) was further conducted. The results of the observations indicated that storage temperature and packaging type significantly influenced the yield value and pH value, but had no significant effect on the moisture content of pegagan tea. The estimated shelf life of pegagan tea for 28 days using paper sack packaging at temperatures of 15, 30, and 45 °C was 173, 616, and 195 days, respectively. For aluminum foil packaging, the estimated shelf life was 189, 661, and 205 days at the same temperatures. As for vacuum-sealed plastic packaging, the estimated shelf life was 551, 192, and 597 days at the respective temperatures. The findings of this research are expected to provide valuable information for manufacturers and consumers regarding the shelf life of pegagan Tea. Additionally, the research aims to offer a scientific basis for appropriate packaging and storage practices to better maintain the product's quality.

Fe3O4-SiO2-MIL-53 (Fe) nanocomposite for magnetic dispersive micro-solid phase extraction of cadmium (II) at trace levels prior to HR-CS-FAAS detection.

A magnetic metal-organic framework Fe3O4-SiO2-MIL-53 (Fe) nanocomposite was synthesized for magnetic dispersion micro-solid phase extraction (M-d-µSPE) of cadmium in water, spice, chocolate, tea, and tobacco samples prior to the detection by flame atomic absorption spectrometry. Fe3O4-SiO2-MIL-53 (Fe) nanocomposite fabricated using the solvothermal technique was characterized using a field emission scanning electron microscope and X-ray diffraction. The extraction efficiency of the method was improved by optimizing the experimental factors. After optimization, the linearity range for Cd (II) was 4.3-500µgL-1. The limits of detection and quantification were 1.3 and 4.3µgL-1, respectively. The presented magnetic dispersion-micro solid phase extraction method was applied to Cd (II) analysis in food and some environmental samples.

Au-Ag OHCs-based SERS sensor coupled with deep learning CNN algorithm to quantify thiram and pymetrozine in tea.

Pesticide residue detection in food has become increasingly important. Herein, surface-enhanced Raman scattering (SERS) coupled with an intelligent algorithm was developed for the rapid and sensitive detection of pesticide residues in tea. By employing octahedral Cu2O templates, Au-Ag octahedral hollow cages (Au-Ag OHCs) were developed, which improved the surface plasma effect via rough edges and hollow inner structure, amplifying the Raman signals of pesticide molecules. Afterward, convolutional neural network (CNN), partial least squares (PLS), and extreme learning machine (ELM) algorithms were applied for the quantitative prediction of thiram and pymetrozine. CNN algorithms performed optimally for thiram and pymetrozine, with correlation values of 0.995 and 0.977 and detection limits (LOD) of 0.286 and 29ppb, respectively. Accordingly, no significant difference (Pgreater than0.05) was observed between the developed approach and HPLC in detecting tea samples. Hence, the proposed Au-Ag OHCs-based SERS technique could be utilized for quantifying thiram and pymetrozine in tea.

Ag-containing metal organic framework reacted with AsH3: Mechanism and application for inorganic arsenic detection by hydride generation-smartphone RGB readout colorimetric system.

The reaction mechanism of Ag-containing metal organic framework (Ag-BTC) and hydrogen arsenide (AsH3) was discussed in detail in this work. Silver ions in Ag-BTC were reacted with AsH3, and silver nanoparticles were generated on the surface of Ag-BTC, causing its color changed. This property was further applied to a hydride generation-colorimetric analytical system. As(III) was converted to AsH3via hydride generation and then reacted with the Ag-BTC (immobilized on test paper), leading to the test paper changed from white to black. Visual colorimetric and smartphone RGB readout mode were used for this analytical system. The results could be readout by naked-eye in visual colorimetric mode and a smartphone in RGB readout mode. Under the optimized conditions, As(III) concentration as low as 10μg/L and 50μg/L could be readout by smartphone and naked-eye, respectively. This method was further successful applied to As(III) determination in real samples (drinking water samples and scented tea samples), with recoveries of 91-113%.

A simple microwave-assisted synthesis of cobalt ferrite nanoparticles and its application for the determination of lead ions in rooibos (Aspalathus linearis) tea.

In this study, a magnetic sorbent assisted dispersive solid phase extraction (DSPE) method was used to preconcentrate lead ions from rooibos tea samples for determination by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS). Cobalt ferrite magnetic nanoparticles (CoFe2O4 MNPs) were synthesized by microwave assisted digestion. Limits of detection and quantification were calculated as 5.3 and 17.6µg/L, respectively, in a linear dynamic range of 20-800µg/L. The enhancement factor of the developed method was found to be 80-folds when compared to the detection limit of the regular FAAS system. The percent recoveries obtained for rooibos tea samples spiked at different concentrations were in the range of 77 - 125%, with high repeatability as indicated by low standard deviations. The findings of the study demonstrated that the CoFe2O4 MNPs-based extraction method is a straightforward, fast, affordable, safe, and eco-friendly approach to qualifying/quantifying lead with high precision in the selected beverage sample.

Occurrence of Aspergillus chevalieri and A. niger on Herbal Tea and Their Potential to Produce Ochratoxin A (OTA)

Herbal teas, including Camellia sinensis (black and green teas), are popular beverages with health benefits for consumers worldwide. These products are prepared from natural materials of different plant parts containing antioxidant properties and vitamins. The aim of this study was to investigate fungal contaminants and their ability to produce ochratoxin A (OTA) in herbal tea samples. Seven herbal teas were obtained from local markets in Chiang Rai, northern Thailand. Samples were incubated on potato dextrose agar (PDA), and the growing mycelia were isolated into a pure culture. The cultures were identified via both morphology and molecular analysis to confirm species identification. The identified species were subjected to OTA analysis using high-performance liquid chromatography (HPLC) with a fluorescence detector. Ochratoxin A was produced by Aspergillus chevalieri and A. niger, isolated from seven herbal tea samples (black tea, green tea, bael fruit, goji berry, jasmine, lavender, and rose). This finding raises concerns about the safety of herbal tea and should be investigated further for potential health implications.

Simultaneous Screening and Quantification of 479 Pesticides in Green Tea by LC-QTOF-MS.

A high-throughput screening and quantification method for 479 pesticides in green tea was established based on solid-phase extraction combined with liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Pesticides were extracted from samples using an optimized SPE (TPT cartridges) procedure. LC-QTOF-MS in All Ions MS/MS scan mode acquired full MS data for quantification and product ion spectra for identification. LC-QTOF-MS quantification was achieved using matrix-matched standard calibration curves to achieve the optimal method accuracy. The method performance characteristics included the linearity, overall recovery, precision, and measurement uncertainty being evaluated. The validation results exhibited a good sensitivity with the LOQs of 5-55 µg/kg, which was satisfactory for their MRLs in China or the EU. The recoveries of more than 92.7% of the 479 pesticides in green tea were 70-120% at the three spiked levels with a precision of ≤20%. Finally, this method was employed to analyze 479 pesticides in 95 tea samples from markets in China. The test results of the tea samples showed that tolfenpyrad, buprofezin, and pyridaben were found with lower concentrations. The method has effectively improved the determination efficiency of pesticide residue screening by high-resolution mass spectrometry in green tea.

Pyrrolizidine Alkaloids in Tea (Camellia sinensis L.) from Weeds through Weed-Soil-Tea Transfer and Risk Assessment of Tea Intake.

Pyrrolizidine alkaloids (PAs) have been detected in tea and can threaten human health. However, the specific source of PAs in tea is still unclear. Here, 88 dried tea products collected from six major tea-producing areas in Anhui Province, China, were analyzed. The detection frequency was 76%. The content of total PAs in dried tea was between 1.1 and 90.5 μg/kg, which was all below the MRL recommended by the European Union (150 μg/kg). In the Shexian tea garden, PAs in the weeds and weed rhizospheric soil around tea plants and the fresh tea leaves were analyzed. Intermedine (Im), intermedine-N-oxide (ImNO), and jacobine-N-oxide (JbNO) were transferred through the weed-to-soil-to-tea route into the fresh tea leaves; only Im and ImNO were detected in dried tea samples. Potential risk of the total PAs in the tea infusion was assessed according to the margin of exposure method, and it might be a low concern for public health.