Retrospective evaluation of three types of expanded polytetrafluoroethylene grafts for upper limb vascular access.

Currently, three expanded polytetrafluoroethylene (ePTFE) prosthetic graft types are most commonly used for patients with end-stage kidney disease (ESKD) who require long-term vascular access for hemodialysis. However, studies comparing the three ePTFE grafts are limited. This study compared the clinical efficacy and postoperative complications of three ePTFE prosthetic graft types used for upper limb arteriovenous graft (AVG) surgery among patients with ESKD. Patients with ESKD requiring upper limb AVG surgery admitted to our center between January 2016 and September 2019 were enrolled. Overall, 282 patients who completed the 2-year follow-up were included and classified into the following three groups according to the ePTFE graft type: the GPVG group with the PROPATEN® graft, the GAVG group with the straight-type GORE® ACUSEAL, and the BVVG group with the VENAFLO® II. The patency rate and incidence of access-related complications were analyzed and compared between groups. The patients were followed up postoperatively, and data were collected at 6, 12, 18, and 24 months postoperatively. Respective to these follow-up time points, in the GPVG group, the primary patency rates were 74.29%, 65.71%, 51.43%, and 42.86%; the assisted primary patency rates were 85.71%, 74.29%, 60.00%, and 48.57%; and the secondary patency rates were 85.71%, 80.00%, 71.43%, and 60.00%. In the GAVG group, the primary patency rates were 73.03%, 53.93%, 59.42%, and 38.20%; the assisted primary patency rates were 83.15%, 68.54%, 59.55%, and 53.93%; and the secondary patency rates were 85.39%, 77.53%, 68.54%, and 62.92%, respectively. In the BVVG group, the primary patency rates were 67.24%, 53.45%, 41.38%, and 29.31%; the assisted primary patency rates were 84.48%, 67.24%, 55.17%, and 44.83%; and the secondary patency rates were 86.21%, 81.03%, 68.97%, and 60.34%, respectively. The differences in patency rates across the three grafts were not statistically significant. Overall, 18, 4, and 12 patients in the GPVG, GAVG, and BVVG groups, respectively, experienced seroma. Among the three grafts, GORE® ACUSEAL had the shortest anastomosis hemostatic time. The first cannulation times for the three grafts were GPVG at 16 (±8.2), GAVG at 4 (±4.9), and BVVG at 18 (±12.7) days. No significant difference was found in the postoperative swelling rate between the GPVG group and the other two groups. Furthermore, no statistically significant differences were found across the three graft types regarding postoperative vascular access stenosis and thrombosis, ischemic steal syndrome, pseudoaneurysm, or infection. In conclusion, no statistically significant differences in the postoperative primary, assisted primary, or secondary graft patency rates were observed among the three groups. A shorter anastomosis hemostatic time, first cannulation time, and seroma occurrence were observed with the ACUSEAL® graft than with its counterparts. The incidence of upper extremity swelling postoperatively was greater with the PROPATEN® graft than with the other grafts. No statistically significant differences were observed among the three grafts regarding the remaining complications.

Variation Patterns of the Volatiles during Germination of the Foxtail Millet (Setaria Italic): The Relationship between the Volatiles and Fatty Acids in Model Experiments.

Functional and nutritional compounds are increased during foxtail millet germination while bad smell is produced due to the fatty acid oxidation. To eliminate the unpleasant aroma, the origins of the volatiles must be known. A comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry showed forty-nine volatiles containing 8 ketones, 10 aldehydes, 20 alkanes, 4 alcohols, 5 alkenes, and 2 furans were tentatively identified, and they increased during the germination of the foxtail millet. To identify the origin of some volatiles, model experiments by adding 6 fatty acids to the crude enzymes of the foxtail millet was designed, and 17 volatiles could be detected. The saturated fatty acids (palmitic acid and stearic acid) had no contributions to the formation of the volatiles, whereas the unsaturated fatty acid played important roles in the formation of volatiles. Among the unsaturated fatty acids, palmitoleic acid and linoleic acid produced most aldehydes, alcohols, and ketones, while linolenic acid produced the most alkanes and alkenes. This study will be helpful for controlling the smell of germinated seeds from the raw material selection.

Metabolomic analysis reveals the composition differences in 13 Chinese tea cultivars of different manufacturing suitabilities.

BACKGROUND: Green tea and black tea are manufactured using appropriate tea cultivars in China. However, the metabolite differences relating to the manufacturing suitability of tea cultivars are unclear. In the present study, we performed a non-targeted metabolomic analysis on 13 Chinese tea cultivars using ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry to investigate comprehensively the metabolite differences between cultivars suitable for manufacturing green tea (GT cultivars) and cultivars suitable for manufacturing both green tea and black tea (G&BT cultivars). RESULTS: Multivariate statistical analysis and cluster analysis divided the 13 cultivars into two groups, namely GT cultivars and G&BT cultivars, which correlated with their manufacturing suitability. The GT cultivars contained higher levels of flavonoid glycosides, whereas the G&BT cultivars contained higher levels of catechins, dimeric catechins, phenolic acids and alkaloids. CONCLUSION: Metabolic pathway analysis revealed that the flavonoid pathway inclined toward the synthesis of flavonoid glycosides in GT cultivars, whereas it inclined toward the synthesis of catechins and phenolic acids in G&BT cultivars. The results of the present study will be helpful for discriminating the manufacturing suitability of tea cultivars and investigating their breeding. © 2017 Society of Chemical Industry.

The impact of magnetic field-assisted freeze-thaw treatment on the quality of foxtail millet sourdough and steamed bread.

Foxtail millet and sourdough are used to make foxtail millet sourdough steamed bread to improve the flavor and taste. Compared with the conventional freeze-thaw treatment (CFT), the effect of magnetic field-assisted freeze-thaw treatment (MFT) on the storage quality of foxtail millet sourdough and steamed bread is explored. The results showed that compared with CFT, MFT shortened the phase transition time of dough; decreased the water loss rate, the water mobility, and the freezable water content; increased the fermentation volume; stabilized the rheological properties; and minimized the damage of freezing and thawing to the secondary structure and microstructure of the gluten. In addition, an analysis of the specific volume, texture, surface color, and texture structure showed that MFT was beneficial to slowing the deterioration of the steamed bread texture. Finally, MFT effectively inhibited the growth and recrystallization of ice crystals during freezing and thawing, improving the quality of millet dough and steamed bread.

Insights into the starch and proteins molecular structure changes of foxtail millet sourdough: Effect of fermentation from grains of cereal to pre-meal.

This study investigated the effects of foxtail millet sourdough fermentation time (0, 8, 16, and 24 h) on the protein structural properties, thermomechanical, fermentation, dynamic rheological, starch granules crystalline regions molecular mobility, and starch microstructural characteristics. The fermentation led to a significant increase in the concentration of free amino acids from protein hydrolysis. Fourier transform infrared spectroscopy (FTIR) revealed changes in protein secondary structure and the presence of functional groups of different bioactive compounds. The result of thermomechanical properties showed a significant increase in the stability (0.70-0.79 min) and anti-retrogradation ability (2.29-3.14 Nm) of lactic acid bacteria (LAB) sourdough compared to the control dough, showing a wider processing applicability with radar profiler index. In contrast, sourdoughs with lower tan δ values had higher elasticity and strength. Scanning electron microscopy showed that the surface of the starch appeared from smooth to uneven with patchy shapes and cavities, which declined the crystallinity from 34.00 % to 21.57 %, 23.64 %, 25.09 %, and 26.34 % respectively. Fermentation changed the To, Tp, Tc, and ΔH of the starch. The results of the study will have great potential for application in the whole grain sourdough industry.

The effect of heat moisture treatment times on physicochemical and digestibility properties of adzuki bean, pea, and white kidney bean flours and starches.

The effects of heat moisture treatment (HMT) times on the physicochemical properties of three bean flours and their starch were analyzed. The colors of L*, b* and ΔE values increased significantly with time. The adzuki bean and pea flours showed better WAI and SP, and better gelation of starch at 2 h. The rheological properties of mixed HMT dough (3:7) exhibited the typical solid-like weak gel behavior. HMT had a significantly decreased on the pasting viscosity of bean flour starch with treated time. HMT caused the starch granules damage, but did not radically change the crystal type. FTIR results showed more proteins attached to the surface of starch granules, and the short-range molecular order decreased the DO at 2 h. In vitro digestibility inferred that RDS converted into SDS and RS. These results indicated that HMT significantly affected the digestibility and physicochemical properties of bean flours.

Upregulation of outer membrane porin gene ompC contributed to enhancement of azithromycin susceptibility in multidrug-resistant Escherichia coli.

The outer membrane (OM) in gram-negative bacteria contains proteins that regulate the passive or active uptake of small molecules for growth and cell function, as well as mediate the emergence of antibiotic resistance. This study aims to explore the potential mechanisms for restoring bacteria to azithromycin susceptibility based on transcriptome analysis of bacterial membrane-related genes. Transcriptome sequencing was performed by treating multidrug-resistant Escherichia coli T28R with azithromycin or in combination with colistin and confirmed by reverse transcription-quantitative PCR (RT-qPCR). Azithromycin enzyme-linked immunosorbent assay (ELISA) test, ompC gene overexpression, and molecular docking were utilized to conduct the confirmatory research of the potential mechanisms. We found that colistin combined with azithromycin led to 48 differentially expressed genes, compared to azithromycin alone, such as downregulation of tolA, eptB, lpxP, and opgE and upregulation of ompC gene. Interestingly, the addition of colistin to azithromycin differentially downregulated the mph(A) gene mediating azithromycin resistance, facilitating the intracellular accumulation of azithromycin. Also, overexpression of the ompC elevated azithromycin susceptibility, and colistin contributed to further suppression of the Mph(A) activity in the presence of azithromycin. These findings suggested that colistin firstly enhanced the permeability of bacterial OM, causing intracellular drug accumulation, and then had a repressive effect on the Mph(A) activity along with azithromycin. Our study provides a novel perspective that the improvement of azithromycin susceptibility is related not only to the downregulation of the mph(A) gene and conformational remodeling of the Mph(A) protein but also the upregulation of the membrane porin gene ompC.IMPORTANCEUsually, active efflux via efflux pumps is an important mechanism of antimicrobial resistance, such as the AcrAB-TolC complex and MdtEF. Also, bacterial porins exhibited a substantial fraction of the total number of outer membrane proteins in Enterobacteriaceae, which are involved in mediating the development of the resistance. We found that the upregulation or overexpression of the ompC gene contributed to the enhancement of resistant bacteria to azithromycin susceptibility, probably due to the augment of drug uptakes caused and the opportunity of Mph(A) function suppressed by azithromycin with colistin. Under the combination of colistin and azithromycin treatment, OmpC exhibited an increased selectivity for cationic molecules and played a key role in the restoral of the antibiotic susceptibility. Investigations on the regulation of porin expression that mediated drug resistance would be important in clinical isolates treated with antibiotics.

Unraveling the Enantiomeric Distribution of Glycosidically Bound Linalool in Teas (Camellia sinensis) and Their Acidolysis Characteristics and Pyrolysis Mechanism.

Glycosidically bound linalool plays important roles in the formation of excellent tea flavor, while their enantiomeric distribution in teas and the actual transformations with free linalool are still unclear. In this study, a novel chiral ultrahigh performance liquid chromatography-mass spectrometry/mass spectrometry approach to directly analyze linalyl-ß-primeveroside and linalyl-ß-d-glucopyranoside enantiomers in teas was established and then applied in 30 tea samples. A close transformation relationship existed between the two states of linalool for their consistent dominant configurations (most S-form) and corresponding distribution trend in most teas (r up to 0.81). The acidolysis characterization indicated that free linalool might be slowly released from linalyl-ß-primeveroside with stable enantiomeric ratios during long-term withering of white tea in a weakly acidic environment, along with other isomerized products, e.g., geraniol, nerol, α-terpineol, etc. Furthermore, a novel online thermal desorption-gas chromatography-mass spectrometry approach was established to simulate the pyrolysis releasing of linalyl-ß-primeveroside during tea processing. Interestingly, free linalool was not the selected pyrolysis product of linalyl-ß-primeveroside but rather trans/cis-2,6-dimethyl-2,6-octadiene during the high-fire roasting or baking step of oolong and green teas. The identification of above high-fire chemical marks presented great potential to scientifically evaluate the proper thermal conditions in the practical production of tea.

Nutrient and metabolite characteristics of the husk, bran and millet isolated from the foxtail millet (Setaria italica L.) during polishing.

The utilization of byproducts from foxtail millet polishing can reduce food loss and waste. Thus, it is necessary to know the chemical compounds from the millet and the segregation of the layers. The nutrients including minerals were compared among the husk, bran, and millet, and a LC-MS metabolomics analysis was also performed among them. The results showed that the protein, crude fat and 4 fatty acids, seven minerals, the nitrogen-containing compounds and phenolic acids were at much higher levels in the bran part than the husk and millet, whereas the husk only contained higher levels of dietary fibre, and some minerals. The millet section, as the edible part, contained the lowest level of chemical constituents. It illustrated that the bran part contained more functional and nutritional components than the millet and husk part. Therefore, the bran of the foxtail millet should be a food resources instead of wasting.

Effects of Hydrogen Blending Ratio and Equivalence Ratio on the Dynamic Characteristics of Deflagration Shock Waves of CH4/H2 Mixtures.

To evaluate the explosion hazard of CH4/H2 mixtures, experiments were conducted in a long and closed pipeline with a length-to-diameter ratio of 51 and built-in obstacles, and the characteristic parameters of deflagration shock waves were analyzed under different hydrogen blending ratios (0 ≤ λ ≤ 100%) and equivalence ratios (0.5 ≤ Φ ≤ 3). The results indicate that within the range of Φ = 0.8-1.2, the explosion overpressure (P P) exhibits a "two-zone" structure distribution. When 0 ≤ λ ≤ 80%, P P shows an initial increase and then a decrease in both regions, while deflagration to detonation transition (DDT) occurs in the second evolution region when λ = 100%, which is caused by the different strengths of the positive feedback mechanism coupled with flames and shock waves. The P max, (dP/dt)max, and V a show a trend of first increasing and then decreasing and monotonically increasing with the increase of the equivalence ratio and hydrogen blending ratio, respectively, and reach their maximum values at Φ = 1.0 and λ = 100%. For CH4/H2 mixtures with low hydrogen blending ratios (λ = 0 and 20%), the P max and (dP/dt)max in the fuel-lean conditions (Φ = 0.9 and 0.8) are higher than those in the fuel-rich conditions (Φ = 1.1 and 1.2), while the CH4/H2 mixtures under high hydrogen blending ratios (λ = 80 and 100%) are the opposite. Overall, the increase in H2 at a high hydrogen blending ratio and the increase in the equivalence ratio at a fuel-lean condition significantly enhance the average V a. In addition, chemical kinetics analysis found that R38 and R52 elementary reactions are the dominant elementary reactions that promote and inhibit temperature increase, respectively. Their temperature sensitivity coefficients are negatively correlated with the hydrogen blending ratio and positively correlated with the equivalence ratio. The research results provide vital information for evaluating the explosion hazards of CH4/H2 mixtures and developing safety protection measures.

The Damage to Thick Steel Plates by Local Contact Explosions.

The paper presents the damage results of thick steel plates subjected to local blast loading using experimental and numerical approaches. Three steel plates with a thickness of 17 mm under the local contact explosion of trinitrotoluene (TNT) explosives were tested, and the damaged parts of the steel plates were scanned using a scanning electron microscope (SEM). ANSYS LS-DYNA software was used to simulate the damage results of the steel plate. By analyzing and comparing the experimental results with the numerical simulation results, the influence law of the TNT acting on the steel plate, the damage mode of the steel plate, the reliability verification of the numerical simulation, and the criterion for judging the damage mode of the steel plate were obtained. Results show that the damage mode of the steel plate changes with the changes in the explosive charge. The diameter of the crater on the surface of the steel plate is mainly related to the diameter of the contact surface between the explosive and the steel plate. The fracture mode of the steel plate in the process of generating cracks is a quasi-cleavage fracture, and the process of generating craters and perforations in the steel plate is a ductile fracture. The damage mode of the steel plates can be divided into three types. The numerical simulation results have minor errors and high reliability, and numerical simulation can be used as an auxiliary tool for experiments. A new criterion is proposed to predict the damage mode of the steel plates under contact explosion.

Experimental study on the leakage temperature field of buried CO2 pipelines.

The leakage of small holes in the buried CO2 pipeline is not easy to detect, which leads to the problem of the inability to accurately trace the source of the pipeline repair in the later stage. This paper designs and builds an experimental system to simulate the leakage of buried CO2 pipelines and conducts experiments on the leakage of small holes in buried CO2 pipelines to investigate the changes in the surrounding soil temperature when they leak. The results showed that the type of movement of CO2 in porous media after it is released from the leak is "funneling." At a distance of about 50 mm from the horizontal, the temperature difference in the horizontal surface is smallest at the 50 cm closest to the vertical distance of the leak, while at a distance of 225 mm from the horizontal, the temperature difference in the horizontal surface is largest at the 70 cm farthest from the vertical distance of the leak. The research results can provide a theoretical basis for the later development of technologies that can quickly locate the leakage points of buried CO2 pipelines and accurately determine their leakage status.

Experimental and Numerical Study of Natural Gas Leakage and Explosion Characteristics.

Frequent occurrence of indoor natural gas explosion accidents seriously threatens the safety of people and property. To determine the law of indoor natural gas leakage and explosion hazards, based on experiment and simulation, the nature of natural gas explosion, the distribution law of natural gas volume fraction, flame propagation, temperature, and shock wave overpressure were studied. The results show that the flame structure can be divided into three zones, i.e., preheat zone, reaction zone, and product zone. OH + CO ⇔ H + CO2 is the main exothermic reaction in the combustion process. The overall distribution law of natural gas volume fraction shows that the higher the position, the greater the volume fraction, and the closer the distance to the leak source at the same height, the greater the volume fraction, and the natural gas volume fraction of the hose falling off is the largest under different leakage conditions. The difference in the wrapping structure of the kitchen package has a significant impact on the diffusion distribution of natural gas. The flame development goes through five stages of ignition, slow burning, detonation, slow burning, and extinguishing. The indoor temperature reaches about 1400 °C. Although the simulated value of shock wave overpressure is larger than the experimental value, the relationship between overpressure and distance is expressed by Y = A + B * ln(X + C). This study can provide certain technical support for natural gas accident rescue. The research can provide certain technical support for natural gas accident rescue and can also be used for accident investigation to form the determination procedure and method of leakage location and leakage amount.

Dynamics of Microbial Communities, Flavor, and Physicochemical Properties during Ziziphus jujube Vinegar Fermentation: Correlation between Microorganisms and Metabolites.

Jujube pulp separated from Ziziphus jujube is often discarded after processing, resulting in a serious waste of resources and environmental pollution. Herein, Ziziphus jujube pulp was used as a raw material for vinegar fermentation. To investigate the dynamic distribution of microorganisms and flavor substances in ZJV, correlations between environmental variables (e.g., total acid, reducing sugar, temperature) and flavor substances (organic acids, amino acids, volatile substances) and microorganisms were analyzed. Physicochemical indicators (temperature, total acid, alcohol) were the main factors affecting ZJV fermentation. The middle and later stages of ZJV fermentation were the periods showing the largest accumulation of flavor substances. Organic acids (acetic acid, malic acid, citric acid, lactic acid), amino acids (Asp, Glu, Arg) and volatile substances (ethyl phenylacetate, phenethyl alcohol) were important odor-presenting substances in ZJV. In the bacterial community, the Operational Taxonomic Units (OTUs) with an average relative abundance of more than 10% in at least one fermentation stage were mainly Acetobacter, Lactobacillus and Saccharopolyspora, while it was Thermomyces in the fungal community. Pearson correlation coefficients showed that Penicillium, Lactobacillus and Acetobacter were the core microorganisms, implying that these microorganisms contributed to the flavor formation greatly in ZJV fermentation. This study reveals the correlation between physicochemical indexes and flavor substances and microorganisms in ZJV fermentation. The results of the study can provide a theoretical basis for the development of the ZJV industry.

Nutritional Components of Millet Porridge Cooked by Different Electric Cookers Based on Principal Component and Cluster Analyses.

(1) Background: In order to study the effects of different electric cookers on the nutritional components of millet porridge, five different electric cookers (No. 1-5) were selected to cook millet porridge, then sensory and nutritional components in millet porridge, millet soup, and millet grains were analyzed; (2) Methods: Using principal component and cluster analysis, a variety of nutritional components were comprehensively compared; (3) Results: The results showed that among the different cooked samples, the content of amylose and reducing sugars was the highest in the samples cooked by electric cooker No. 3. The electric cooker No. 4 samples had the highest sensory evaluation score, crude fat, and protein content. The contents of ash, fatty acids, bound amino acids, and minerals were the highest in the electric cooker No. 5 samples. The sensory evaluation score and content of crude fat, ash, reducing sugars, direct starch, and Cu were higher in millet grains than in millet soup or porridge. The content of fatty acids, protein, amino acid, Zn, Fe, Mg, Mn, and Ca was highest in millet soup. Different electric cookers produced millet porridge with varying nutritional levels; (4) Conclusions: This study provides a reference for the further development of new electric cookers.

Preparation of an Intelligent Oleophobic Hydrogel and Its Application in the Replacement of Locally Damaged Oil Pipelines.

In the pipeline transportation process for crude oil, the most important and popular maintenance method for perforated and ruptured oil pipelines is the replacement of the damaged pipeline segment. However, this method has several disadvantages, including a complex process, large time consumption, and excessively high costs. The present study reported the preparation of a strong cross-linking hydrogel that served as a temporary blocking material during the long-distance oil pipeline partial replacement process. The prepared product was characterized by infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy to analyze the microscopic reactions and structures. Orthogonal experiments for shear stress were performed to determine the optimal synthesis condition. The relevant experiments indicated that the proposed product can effectively isolate oil and oil gas, and a 4.5 m long hydrogel can resist the force of a 0.57 MPa overpressure. The blocked pipeline turned to a dredged state on changing the pipeline pressure. The flame resistance experiment showed that the hydrogel exhibited excellent flame resistance and could therefore ensure the safety of the hot work. On the basis of this hydrogel material, a new method for replacing the partially damaged oil pipeline was proposed.

Experimental study on vented explosion overpressure of methane/air mixtures in manhole.

Gas explosion in manhole often occurs in cities. Many previous researches on gas explosion are not suitable for manhole explosion because of the particularity of manhole structure. To investigate the gas explosion in manhole, a full-scale manhole model was established, in which the explosion overpressure of methane/air mixtures were studied experimentally. The variation of blast wave overpressure with time at different distances was analyzed. In addition, the effects of methane concentration, ignition location and manhole cover weight on the external overpressure after manhole explosion were obtained. The results showed that at the experimental conditions in this paper, under the influence of vent mode and flame propagation, the maximum peak overpressure caused by manhole explosion was mostly at the third measuring point. And there were two peaks in the overpressure histories. It was also found that when the methane concentration was close to stoichiometric ratio, the ignition location was further away from the manhole head, and the weight of manhole cover increased, the peak overpressure of blast wave caused by explosion increased. Besides, some suggestions were put forward for the risk control of manhole explosion accident based on the experimental results.

Effects of corrosion defect and tensile load on injection pipe burst in CO2 flooding.

Highly pressurized injection pipelines in CO2 flooding often suffer from different types of corrosion defects and mechanical stresses and can easily cause serious damage to the environment. Currently, the descending rule of pipe burst pressures under different defect parameters and tensile loads has not been studied systematically. In this study, a section of injection pipe was used to simulate the burst process of pipe with groove and general corrosion defects. The crack appearance showed that the fracture began at the centre of the longitudinal defect line as an instantaneous ductile rupture and then extended along both sides as a rapid brittle rupture under high stress. The burst pressure in the groove corrosion defect tests showed that the defect depth played a more dominant role in pipe burst than the defect length did, and when a 30 MPa axial tensile load was added, the pipe burst pressure was reduced approximately 20-30%. In general corrosion defect tests, the burst pressures were generally much lower than the groove corrosion defect tests produced, and when adding the axial tensile load, the burst mode changed. Moreover, the value of the burst pressure can be a sign of BLEVE (boiling liquid expanding vapor explosion) severity.

Aroma formation and dynamic changes during white tea processing.

The formation of and dynamic changes in aroma during white tea processing have not previously been systematically investigated. In this study, advanced comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry was employed to investigate the mechanism of white tea aroma formation. A total of 172 volatiles were identified and mainly comprising endogenous volatiles, which displayed diverse change trends during the withering period. In this process, free aroma precursor amino acids and glycosidically bound volatiles (GBVs) were found to contribute to the formation of white tea aroma, with the differential expression of aroma-related key genes accounting for various accumulation of endogenous volatiles and GBVs. In addition, the drying was also shown to play an important role in the formation of white tea aroma. Our study provides the first characterization of white tea aroma formation and establishes a theoretical basis for quality control during white tea processing operations.

Variation patterns in the content of glycosides during green tea manufacturing by a modification-specific metabolomics approach: Enzymatic reaction promoting an increase in the glycosidically bound volatiles at the pan firing stage.

The glycosides are presumed to influence the quality of green tea but the molecular mechanism behind remains unclear. To elucidate the contribution of glycosides to the flavor formation of green tea, changes of both glycosidically bound non-volatiles (GBNVs) and glycosidically bound volatiles (GBVs) during the manufacturing of green tea were investigated using a modification-specific metabolomics method. A total of 64 glycosides (47 GBNVs and 17 GBVs) were identified and their contents mainly changed during the pan firing and drying stages of green tea manufacturing. Notably, the contents of GBVs significantly increased by 1.12-4.46-fold during pan firing. Correlation analysis showed that the GBVs contents were negatively related to the contents of volatiles and glucose. Model experiments revealed that enzymatic synthesis contributed to the increase in the content of GBVs during the pan firing. This comprehensive study on the glycosides changes revealed the molecular bases for GBVs increments during the pan firing.