Publications by authors named "Jun-Feng Yin"

31 Publications

Effects of Hydrogen Peroxide Produced by Catechins on the Aroma of Tea Beverages.

Foods 2022 Apr 27;11(9). Epub 2022 Apr 27.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Biology, Genetics and Breeding of Special Economic Animals and Plants, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou 310008, China.

Hydrogen peroxide has a significant effect on the flavor of tea beverages. In this study, the yield of hydrogen peroxide in (-)-epigallocatechin gallate (EGCG) solution was first investigated and found to be significantly enhanced under specific conditions, and the above phenomenon was amplified by the addition of linalool. Then, an aqueous hydrogen peroxide solution was added to a linalool solution and it was found that the concentration of linalool was significantly reduced in the above-reconstituted system. These findings were verified by extending the study system to the whole green tea infusions. The results suggested that the production of hydrogen peroxide in tea beverages may be dominated by catechins, with multiple factors acting synergistically, thereby leading to aroma deterioration and affecting the quality of tea beverages. The above results provided a feasible explanation for the deterioration of flavor quality of green tea beverages with shelf life.
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http://dx.doi.org/10.3390/foods11091273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9102859PMC
April 2022

Optimization of a tannase-assisted process for obtaining teas rich in theaflavins from leaves.

Food Chem X 2022 Mar 3;13:100203. Epub 2022 Jan 3.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China.

This work aimed at optimizing the extraction of theaflavins for the development of a potentially functional tea beverage using different technological parameters as factors. Green tea leaves treated with tannase provided a beverage with significant higher amount (4.7-fold) of theaflavin (TF) compared to the pure withered leaf fermentation. For black tea, the optimized process conditions to produce a beverage with high TF (0.269 μg/mL) concentration were: 6 g of leaves/400 mL, a low fermentation temperature of 25 °C with the absence of buffer and pH control, an intermediate fermentation time (60 min) and a relatively low aeration rate (0.8-1.0 L/min). The tea liquid produced under optimized fermentation conditions appears to be ideal for making a black tea beverage with surplus summer tea leaves and brings economic benefits.
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http://dx.doi.org/10.1016/j.fochx.2022.100203DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9039937PMC
March 2022

Optimization of brewing conditions for Tieguanyin oolong tea by quadratic orthogonal regression design.

NPJ Sci Food 2022 Apr 25;6(1):25. Epub 2022 Apr 25.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, 310008, Hangzhou, China.

Tieguanyin is one of the most consumed oolong teas because of its distinctive flavor. The brewing process is crucial for the flavor performance of traditional teas, thus the effects of brewing conditions, including water/tea ratio (R), brewing temperature (T), and time (S) on the sensory traits, chemical composition, and antioxidant activity of Tieguanyin tea infusion were investigated using quadratic orthogonal regression design. Results showed that R affected all the quality variables most, its reduction could lead to the promotion of tea infusion concentration, antioxidant activity, and taste intensity, which was favored by the tea consumers drinking tea almost daily (DTD) but unacceptable for those drinking tea hardly (DTH). Based on the optimization of brewing conditions in response surface methodology (RSM), we recommended several brewing schemes for diverse consume goals: R = 34 mL/g, T = 80 °C, S = 80 s for DTH; R = 39 mL/g, T = 100 °C, S = 127 s for DTO (the consumers drinking tea occasionally); R = 20 mL/g, T = 100 °C, S = 100 s for DTD; R = 26 mL/g, T = 100 °C and S = 127 s for the common consumers seeking for flavor and health benefits. These results would be helpful for tea consumers with multiple demands.
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http://dx.doi.org/10.1038/s41538-022-00141-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9038793PMC
April 2022

Effects of baking treatment on the sensory quality and physicochemical properties of green tea with different processing methods.

Food Chem 2022 Jun 22;380:132217. Epub 2022 Jan 22.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Seven batches of raw tea leaves, processed by different methods (steaming, pan-frying) and from two different harvesting seasons (spring, autumn), were used to investigate the effect of baking treatment on changes in the composition and content of nonvolatile and volatile compounds. The results showed that baking had a greater impact on sensory and flavor quality, which chemically modified some of taste and aroma components. The aroma concentrations of steamed teas (4,168-10,706 μg/L) were significantly higher than those of pan-fried teas (959-2,608 μg/L), and the aroma concentrations of baked green teas (2,608-10,706 μg/L) were significantly higher than those of unbaked teas (959-4,213 μg/L). Based on VIP > 1 and ACI > 1, (E, E)-3,5-octadien-2-one, hexanal, β-ionone, 5-methylfurfural, β-cyclocitral, and linalool were identified as the main aroma compounds. Chemical changes resulting from Maillard reaction were greater during baking of steamed, than pan-fried green tea. These results help improve the quality of green tea with baking.
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http://dx.doi.org/10.1016/j.foodchem.2022.132217DOI Listing
June 2022

Effects of phenolic acids and quercetin-3-O-rutinoside on the bitterness and astringency of green tea infusion.

NPJ Sci Food 2022 Jan 27;6(1). Epub 2022 Jan 27.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou, 310008, China.

Phenolic acids are important taste components in green tea. The aim of this study was to analyze the taste characteristics of phenolic acids and their influence on the bitterness and astringency of green tea by sensory evaluation and chemical determination. The major tea phenolic acids and quercetin-3-O-rutinoside (Que-rut) were significantly positively correlated with the bitterness (r = 0.757, p < 0.01; r = 0.605, p < 0.05) and astringency (r = 0.870, p < 0.01; r = 0.576, p < 0.05) of green tea infusion. The phenolic acids have a sour and astringent taste, whereas Que-rut has a mild astringent taste. Phenolic acids and Que-rut can increase the bitterness of epigallocatechin gallate (EGCG). However, these components behaved differently for astringency on EGCG. Gallic acid (GA) enhances the astringency throughout all the concentrations in this study. While it seemed to be double effects of caffeic acid (CA), chlorogenic acid (CGA), and Que-rut on that, i.e., the inhibition at lower concentrations (CA: 0-0.2 mM; CGA: 0-0.2 mM; Que-rut: 0-0.05 mM) but enhancement at higher ones. The phenolic acids and Que-rut interacted synergistically with tea infusion and as their concentration increased, the synergistic enhancement of the bitterness and astringency of tea infusion increased. These findings help provide a theoretical basis for improving the taste of middle and green tea.
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http://dx.doi.org/10.1038/s41538-022-00124-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8795203PMC
January 2022

A targeted and nontargeted metabolomics study on the oral processing of epicatechins from green tea.

Food Chem 2022 Jun 11;378:132129. Epub 2022 Jan 11.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Oral processing (OP), referring to the whole process of food digestion in human mouth, has a major influence on food flavor perception. This study focused on the compositional changes of the four green tea epicatechins (viz., EC, EGC, ECG, EGCG) during OP, based on targeted and nontargeted metabolomics. It was found that the four epicatechins were all extensively lost through transformation undergoing OP, among which EC was the most stable one, whereas EGCG the least. EGCG was further revealed to be susceptible to human oral cavity in the simulated OP in vitro. It could be converted physically by precipitating with mucin in saliva, and chemically through hydrolysis and dimerization, mediated mainly by the neutral pH condition. The OP of epicatechins also caused salivary composition changes possibly involving health benefits of green tea. These findings could raise awareness of the interactions between epicatechins, or any other food materials, with human mouth.
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http://dx.doi.org/10.1016/j.foodchem.2022.132129DOI Listing
June 2022

Sensory and chemical characteristics of oolong tea after roasting.

Food Chem X 2021 Dec 2;12:100178. Epub 2021 Dec 2.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China.

Roasting, a critical process for oolong tea, has been applied to tea to improve flavor attributes. To investigate the effects of the roasting on the flavor of , the global metabolomics analysis on the non-volatile and volatile components were proceeded. The weakening of bitterness and astringency, caused by roasting, may be attributed to the decreasing of flavonoids glycosides and procyanidins, whereas the enhancing of sweet aftertaste to the increasing of gallic acid. Besides, l-theanine flavan-3-ols adducts (-ehtyl-2-pyrrolidinone substituted flavan-3-ols) increased dramatically at 130 °C compared with 105 °C, with the reduction of l-theanine and flavan-3-ols. Meanwhile, high temperature hampered the volatiles' diversity and intensity, resulting from the lowering of floral volatiles, i.e., β-ionone, jasmine, and nerolidol, yet the nitrogen-containing heterocyclic compounds increased, e.g., pyrroles and pyrazines. The results can help to comprehensively understand the influences of roasting technology on the flavor and chemistry of oolong tea.
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http://dx.doi.org/10.1016/j.fochx.2021.100178DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8651997PMC
December 2021

Effect of Ferrous Ion on Heat-Induced Aroma Deterioration of Green Tea Infusion.

Molecules 2021 Jul 13;26(14). Epub 2021 Jul 13.

Key Laboratory of Tea Biology and Resources Utilization, National Engineering Research Center for Tea Processing, Tea Research Institute Chinese Academy of Agricultural Sciences, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China.

Aroma deterioration is one of the biggest problems in processing tea beverages. The aroma of tea infusion deteriorates fast during heat sterilization and the presence of ferrous ion (Fe) aggravates it. The underlying mechanism remains unveiled. In this study, Fe was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe-mediated aroma deterioration. By enhancing the degradation of catechins, Fe dramatically increased the production of hydrogen peroxide (HO). Fe and HO together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe enhanced the loss of green/grassy volatiles and promoted the formation of new volatiles with diversified aroma characteristics, resulting in a dull scent of green tea infusion. Our results revealed how Fe induced aroma deterioration of green tea infusion with heat treatment and could help guide tea producers in attenuating the aroma deterioration of tea infusion during processing.
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http://dx.doi.org/10.3390/molecules26144255DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8304355PMC
July 2021

Effects of brewing water on the sensory attributes and physicochemical properties of tea infusions.

Food Chem 2021 Dec 20;364:130235. Epub 2021 Jun 20.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

The effects of brewing water on the sensory attributes and physicochemical properties of tea infusions made from Chinese teas were investigated. The tea infusions brewed in water with higher pH and total dissolved solids (TDS), generally had a darker color and lower overall sensory acceptability. Moreover, those infusions had less catechins, particularly galloylated-catechins, and lower antioxidant capacity. The teas with less fermentation contained more galloylated-catechins and had higher antioxidant capacity, but were much more susceptible to high mineral brewing water. Green tea was proved to be the most susceptible one, whereas dark tea the most stable one. Green tea infusions prepared with higher pH/TDS water were more rapidly oxidized, resulting in a darker color due to polymerization of catechins, when exposed to the air. These findings suggested that low mineral brewing water was better for Chinese tea, both from the sensory and health benefit perspectives.
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http://dx.doi.org/10.1016/j.foodchem.2021.130235DOI Listing
December 2021

Zijuan tea- based kombucha: Physicochemical, sensorial, and antioxidant profile.

Food Chem 2021 Nov 9;363:130322. Epub 2021 Jun 9.

Tea Research Institute Chinese Academy of Agricultural Sciences, National Engineering Research Center for Tea Processing, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Zijuan tea is a representative anthocyanin-rich tea cultivar in China. In this study, Zijuan tea was used to produce a novel kombucha beverage (ZTK). The physicochemical, sensory properties, and antioxidant activity of ZTK were compared with that of black tea kombucha (BTK) and green tea kombucha (GTK). Results indicated that after fermentation, the color of ZTK changed from yellowish-brown to salmon-pink, because its anthocyanins (4.5 mg/L) appeared red in acidic conditions. Meanwhile no significant changes of color were observed in BTK and GTK. The dynamic changes of pH, biomass, and concentrations of sugars, amino acids, and main organic acids were similar in three kombucha beverages, except catechins showing different trends. Moreover, ZTK showed the highest overall acceptability score, antioxidant activity, and concentration of volatiles among the three kombucha beverages. Therefore, Zijuan tea is suitable for the preparation of kombucha beverage with attractive color and health benefits.
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http://dx.doi.org/10.1016/j.foodchem.2021.130322DOI Listing
November 2021

Effect of chemical composition of black tea infusion on the color of milky tea.

Food Res Int 2021 01 5;139:109945. Epub 2020 Dec 5.

Tea Research Institute Chinese Academy of Agricultural Sciences, National Engineering & Technology Research Center for Tea Industry, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Milky tea is popular in many countries and its color is an important sensory property. The effects of black tea infusion on the color of milky tea prepared with non-dairy creamer were investigated. The results showed that the redder black tea infusion produced milky tea with more redness, and the color of milky tea was a pleasant pink when the a* value (redness indicator) was in the range of 6.0-7.0. Correlation analysis revealed that the respective theaflavins (TFs), thearubigins (TRs), thearubigins (TBs), (-)-epigallocatechin-3-gallate (EGCG) and chlorogenic acid contents significantly correlated with the a* values of milky tea. A series of complementary experiments were performed to elucidate that TFs and EGCG contributed to the redness of milky tea. The color formation was mainly associated with the binding of phenols to the proteins in the non-dairy creamer. These results contribute to understand the mechanism of color formation in milky tea.
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http://dx.doi.org/10.1016/j.foodres.2020.109945DOI Listing
January 2021

A predictive model for astringency based on in vitro interactions between salivary proteins and (-)-Epigallocatechin gallate.

Food Chem 2021 Mar 26;340:127845. Epub 2020 Aug 26.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture and Rural Affairs, 9 South Meiling Road, Hangzhou, Zhejiang 310008, China. Electronic address:

Astringency is an important quality attribute of green tea infusion, and (-)-Epigallocatechin gallate (EGCG) is the main contributor to astringency. Turbidity was used to predict the intensity of astringency for EGCG. The interactions between the selected proteins and EGCG, and the impacts of temperature, pH, protein structure, and EGCG concentration were studied. Mucin was selected as the protein in study for the prediction of EGCG astringency intensity. A predictive model (R = 0.994) was developed based on the relationship between the astringency of EGCG and the turbidity of EGCG/mucin mixtures at pH 5.0 and 37 °C. The fluorescence quenching analyses showed the interactions between EGCG and the selected proteins, which induced the reversible protein molecule conformational changes. The interactions were considered as the main reason that causes the astringency of tea infusions. The results provided a biochemical approach to explore the sensory qualities of green tea.
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http://dx.doi.org/10.1016/j.foodchem.2020.127845DOI Listing
March 2021

Effect of baking on the flavor stability of green tea beverages.

Food Chem 2020 Nov 7;331:127258. Epub 2020 Jun 7.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Flavor stability is important for the quality of tea beverages. Baking is a typical processing technology to improve the flavor of tea leaves. In present study, seven raw tea materials, including steamed spring and autumn tea leaves, pan-fired spring tea leaves, and their corresponding baked tea leaves, were used to investigate the effect of baking on flavor stability of green tea beverages. The results showed that tea beverages prepared with baked tea had better flavor stability. The baking process obviously changed the concentrations of some important flavor substances, especially the aromatic pyrrole substances from 0 (unbaked) to 338.13 μg/L (baked) in tea beverages. Heat treatment had little influence on the flavor of tea beverages prepared from baked tea, but caused great changes in non-volatile and volatile components in those prepared from unbaked leaves. These results could help guide the processing of tea beverages which would improve their flavor quality stability.
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http://dx.doi.org/10.1016/j.foodchem.2020.127258DOI Listing
November 2020

Chemical composition, sensory properties and bioactivities of Castanopsis lamontii buds and mature leaves.

Food Chem 2020 Jun 6;316:126370. Epub 2020 Feb 6.

Tea Research Institute, Chinese Academy of Agricultural Sciences, National Engineering Research Center for Tea Processing, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Castanopsis lamontii is used as functional herbal tea in southwest China. Usually, only buds rather than mature leaves are applied. To figure out whether mature leaves were suitable for producing herbal tea, chemical composition, sensory properties and bioactivities of Castanopsis lamontii bud infusion (CLB) and mature leaf infusion (CLM) were investigated. According to the results, CLB and CLM had similar non-volatile composition, but in different proportion. Meanwhile, CLB contained more types of volatiles than CLM, leading to distinguishable volatile profiles between them. Sensory assessment showed that CLB had sweet aftertaste and floral aroma. CLM tasted astringent and smelled grassy. Bioactivity evaluation indicated that CLB exhibited higher activities in scavenging free radicals and suppressing lipopolysaccharide-induced inflammation. Taken together, CLB had better overall acceptability in sensory quality and higher bioactivity, implying that Castanopsis lamontii buds were more suitable for producing herbal tea.
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http://dx.doi.org/10.1016/j.foodchem.2020.126370DOI Listing
June 2020

Improving the taste of autumn green tea with tannase.

Food Chem 2019 Mar 2;277:432-437. Epub 2018 Nov 2.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Green tea processed from autumn leaves is more bitter and astringent than that from spring leaves, mainly due to gallated catechins. The present study aimed to improve the taste of autumn green tea and green tea infusion by using tannase to treat tea leaves and tea infusion. The results showed that, after hydrolysis, the sweet aftertaste and overall acceptability improved, and the ratio of gallated catechins decreased, as did the bitterness and astringency of the autumn green tea. The pH value was significantly correlated with the concentrations of gallated catechins (r = 0.930, p < 0.01), non-gallated catechins (r = -0.893, p < 0.01), and gallic acid (r = 0.915, p < 0.01), as well as with the intensities of bitterness, astringency, and sweet aftertaste during hydrolysis. Gallic acid contributed to the sweet aftertaste of green tea infusion. These results will help to improve autumn green tea products with tannase.
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http://dx.doi.org/10.1016/j.foodchem.2018.10.146DOI Listing
March 2019

Quantitative analyses of the bitterness and astringency of catechins from green tea.

Food Chem 2018 Aug 12;258:16-24. Epub 2018 Mar 12.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

Bitterness and astringency are two important quality attributes of green tea infusion, and catechins are the main contributor to the bitterness and astringency. The aim of this work was to quantitatively analyse the bitterness and astringency of green tea infusion according to the concentrations of catechins. The concentration-taste curves of catechins showed a pattern that fit the cubic functions, and their R values were higher than 0.956. The bitterness of green tea was highly correlated with the concentrations of (-)-epigallocatechin gallate and (-)-epicatechin gallate (ECG) (R = 0.7769, p < 0.01), and the astringency (R = 0.7878, p < 0.01) was highly correlated with the concentrations of ECG and flavonol glycosides (myricetin 3-O-galactoside and quercetin-3-O-rutinoside). Taste interactions between different catechins and between catechins and other substances were determined. These results may enhance the understanding of tea chemistry for improving the taste of products from green tea.
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http://dx.doi.org/10.1016/j.foodchem.2018.03.042DOI Listing
August 2018

Flavor characteristics and chemical compositions of oolong tea processed using different semi-fermentation times.

J Food Sci Technol 2018 Mar 12;55(3):1185-1195. Epub 2018 Jan 12.

1Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou, 310008 China.

Flavor characteristics and chemical compositions of Tieguanyin oolong tea processed using different semi-fermentation times were investigated. Six flavor attributes of the teas, namely, astringency, bitterness, umami, sweet aftertaste, floral flavor, and green fruity flavor, were analysed. With extended semi-fermentation time, the taste intensity of sweet aftertaste increased, and the aroma intensity of floral and green fruity flavors increased, while the intensities of astringency, bitterness, and umami showed no clear trend. With increasing semi-fermentation time, the concentrations of gallated catechins, myricetin-rhamnose, quercetin-rutinoside, myricetin, and theanine greatly decreased, while those of total theaflavins, vitexin-rhamnose, kaempferol-galactose, kaempferol-rutinoside, vitexin, quercetin, and kaempferol increased significantly. The intensity of bitter taste was positively correlated with the concentrations of total catechins and gallated catechins. The intensity of astringent taste strongly correlated with the flavonoid concentrations, and that of sweet aftertaste positively correlated with the concentrations of (-)-epigallocatechin and (-)-epicatechin. However, dose-over-threshold analysis revealed that catechins, theaflavin, flavonol glycosides, and caffeine are the main taste-active compounds contributing to the taste of Tieguanyin oolong tea. The concentrations of total volatiles and most of the esters increased markedly with the semi-fermentation time, while the concentrations of low aldehydes showed a significant decrease. The flavor index was consistent with the intensity of floral aroma, increasing from 0.59 (12 h) to 0.84 (24 h) and then decreasing to 0.63 (32 h). Results of this work suggest that the flavor change is mainly due to the variation of taste-active and aroma-active compounds in oolong tea.
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http://dx.doi.org/10.1007/s13197-018-3034-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5821678PMC
March 2018

Quality development and main chemical components of Tieguanyin oolong teas processed from different parts of fresh shoots.

Food Chem 2018 May 3;249:176-183. Epub 2018 Jan 3.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

The Tieguanyin oolong tea is popular in China. However, the quality development and chemical change during processing were still unclear. This study aimed to investigate the chemical compositions and quality of Tieguanyin oolong teas processed from different leaves of fresh shoots. The results showed the fermentation degree of oolong teas decreased from the first leaves to the fourth-fifth leaves, and was associated with the changes in infusion color (b) and chroma, as well as the contents of total theaflavins, (E)-nerolidol and indole. After shaking and setting, the differences in the water contents and the activities of polyphenoloxidase, peroxidase, and β-glucosidase of the tea leaves, significantly influenced the oxidation of catechins. The hydrolysis of volatile compounds might influence the fermentation degrees of the oolong teas processed from different leaves of fresh shoots. The results generated from the present study can be used in guiding the production of oolong teas.
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http://dx.doi.org/10.1016/j.foodchem.2018.01.019DOI Listing
May 2018

Effect of extraction methods on the chemical components and taste quality of green tea extract.

Food Chem 2018 May 16;248:146-154. Epub 2017 Dec 16.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

The physicochemical properties of tea extracts are significantly affected by the extraction method. The aim of this study was to compare the effects of static and dynamic extractions on the concentrations of chemical components and taste quality of green tea extracts. Our results show that extraction of chemical components using static extraction follows a pseudo-second-order reaction, while that of dynamic extraction follows a first-order reaction. The concentrations of the solids, polyphenols, and free amino acids in green tea extract prepared by dynamic extraction were much higher, although the overall yields were not significantly different between the two extraction methods. Green tea extracts obtained via dynamic extraction were of lower bitterness and astringency, as well and higher intensities of umami and overall acceptability. These results suggest that dynamic extraction is more suitable for the processing of green tea concentrate because of the higher concentration of green tea extract.
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http://dx.doi.org/10.1016/j.foodchem.2017.12.060DOI Listing
May 2018

Strengthening Gastric Cancer Therapy by Trastuzumab-Conjugated Nanoparticles with Simultaneous Encapsulation of Anti-MiR-21 and 5-Fluorouridine.

Cell Physiol Biochem 2017 12;44(6):2158-2173. Epub 2017 Dec 12.

Department of Oncology, Affiliated Lianyungang Hospital of Xuzhou Medical University, Lianyungang, China.

Background/aims: MicroRNA-21 is an oncogenic miR (oncomiR) frequently elevated in gastric cancer (GC). Overexpression of miR-21 decreases the sensitivity of GC cells to 5-fluorouridine (5-Fu) and trastuzumab, a humanized monoclonal antibody targeting human epidermal growth factor receptor 2 (HER2). Receptor-mediated endocytosis plays a crucial role in the delivery of biotherapeutics including anti-miRNA oligonucleotides (AMOs). This study is a continuation of earlier findings involving poly(ε-caprolactone) (PCL)-poly (ethylene glycol) (PEG) nanoparticles (PEG-PCL NPs), which were coated with trastuzumab to target GC with HER2 receptor over-expression using anti-miRNA-21 (AMO-21) and 5-Fu.

Methods: HER-PEG-PCL NPs were prepared by one-step carbodiimide coupling using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDAc) and Sulfo-NHS in aqueous phase. Covalent coupling of amino groups at the surface of PEG-PCL with the carboxyl groups of trastuzumab was analyzed by X-ray photoelectron spectroscopy (XPS). AMO-21/5-Fu NPs were formulated by a double-emulsion solvent evaporation technique. The cell line specificity, cellular uptake and AMO-21 delivery were investigated through the rhodamine-B-labeled 6-carboxyfluorescein (FAM)-AMO-21-PEG-PCL NPs coated with or without the antibody in both Her2-positive (NUGC4) and negative GC cells (SGC7901) visualized by fluorescence microscopy. The cytotoxicity of the HER-PEG-PCL NPs encapsulating AMO-21 was evaluated by MTT and apoptosis. Real-time reverse-transcription polymerase chain reaction (RT-PCR) was used to examine miR-21 and phosphatase and tensin homolog (PTEN) and Sprouty2 expression in GC cell lines. The antitumor effects of AMO-21/5-Fu NPs were compared with other groups in xenograft gastric cancer mice.

Results: The antibody conjugates significantly enhanced the cellular uptake of NPs. The AMO-21/5-Fu NPs effectively suppressed the target miRNA expression in GC cells, which further up-regulated PTEN and Sprouty2. As a result, the sensitivity of HER2-expressing gastric cancer to trastuzumab and 5-Fu were enhanced both in vitro and in vivo. The approach enhanced the targeting by trastuzumab as well as antibody-dependent cellular cytotoxicity (ADCC) of immune effector cells Conclusions: Taken together, the results provide insight into the biological and clinical potential of targeted AMO-21 and 5-Fu co-delivery using modified trastuzumab for GC treatment.
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http://dx.doi.org/10.1159/000485955DOI Listing
March 2018

Improving the quality of fermented black tea juice with oolong tea infusion.

J Food Sci Technol 2017 Nov 13;54(12):3908-3916. Epub 2017 Sep 13.

Tea Research Institute Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou, 310008 China.

Fresh tea leaves were crushed into juice and then fermented (oxidation) to obtain fermented black tea juice, which can be used to prepare black tea beverage. The effects of addition of oolong tea infusion or tossing of tea leaves on the sensory quality and theaflavins (TFs) concentration of fermented black tea juice were investigated. The results showed that both addition of tea infusion and tossing of fresh tea leaves increased the TFs/thearubigins (TRs) ratio and improved the sensory quality of fermented black tea juice. The TFs/TRs ratio was found to be significantly correlated with the scores for flavor ( = 0.98), mouth feel ( = 0.94), and overall acceptability ( = 0.91) of the fermented black tea juices from different processes. This result suggested that a relatively high concentration of catechins and stepwise enzymatic oxidation were the crucial factors that increased the TFs/TRs ratio and improved the sensory quality. The combination of adding tea infusion and tossing fresh tea leaves greatly improved the quality of the fermented black tea juice by markedly increasing the TFs/TRs ratio (87%). Results of the present study provided useful information for improving the quality of fermented black tea juice.
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http://dx.doi.org/10.1007/s13197-017-2849-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5643807PMC
November 2017

Effect of the type of brewing water on the chemical composition, sensory quality and antioxidant capacity of Chinese teas.

Food Chem 2017 Dec 22;236:142-151. Epub 2016 Nov 22.

Tea Research Institute Chinese Academy of Agricultural Sciences, National Engineering Research Center for Tea Processing, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

The physicochemical characteristics, sensory quality, and antioxidant activity of tea infusions prepared with purified water (PW), mineral water (MW), mountain spring water (MSW), and tap water (TW) from Hangzhou were investigated. The results showed that the taste quality, catechin concentration, and antioxidant capacity of green, oolong, and black tea infusions prepared using MW and TW were significantly lower than those prepared using PW. Extraction of catechins and caffeine was reduced with high-conductivity water, while high pH influenced the stability of catechins. PW and MSW were more suitable for brewing green and oolong teas, while MSW, with low pH and moderate ion concentration, was the most suitable water for brewing black tea. Lowering the pH of mineral water partially improved the taste quality and increased the concentration of catechins in the infusions. These results aid selection of the most appropriate water for brewing Chinese teas.
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http://dx.doi.org/10.1016/j.foodchem.2016.11.110DOI Listing
December 2017

Upregulated expression of long noncoding RNA SNHG15 promotes cell proliferation and invasion through regulates MMP2/MMP9 in patients with GC.

Tumour Biol 2016 May 10;37(5):6801-12. Epub 2015 Dec 10.

Radiotherapy and Chemotherapy Department, The 1st Affiliated Hospital of Wenzhou Medical University, No.2 Fuxue Lane, Wenzhou, Zhejiang Province, 325000, China.

Accumulation of data indicates that misregulated long noncoding RNAs (lncRNAs) are implicated in cancer tumorigenesis and progression and might be served as diagnosis and prognosis biomarker or potential therapeutic targets. Identification of cancer-associated lncRNAs and investigation of their biological functions and molecular mechanisms are significant for understanding the development and progression of cancer. In this study, we identified a novel lncRNA SNHG15, whose expression was upregulated in tumor tissues in 106 patients with gastric cancer (GC) compared with those in the adjacent normal tissues (P < 0.001). Furthermore, increased SNHG15 expression was positively correlated with invasion depth (P < 0.001), advanced tumor node metastasis (TNM) stage (P = 0.001), and lymph node metastasis (P = 0.019). SNHG15 levels were robust in differentiating GC tissues from controls (area under the curve (AUC) = 0.722; 95 % confidence interval (CI) = 0.657-0.782, P < 0.01). Kaplan-Meier analysis demonstrated that elevated SNHG15 expression contributed to poor overall survival (P < 0.01) and disease-free survival (P < 0.01) of patients. A multivariate survival analysis also indicated that SNHG15 could be an independent prognostic marker. Furthermore, knockdown of SNHG15 expression by siRNA could inhibit cell proliferation and invasion and induce apoptosis, while ectopic expression of SNHG15 promoted cell proliferation and invasion in GC cells partly via regulating MMP2 and MMP9 protein expression. Our findings present that elevated lncRNA SNHG15 could be identified as a poor prognostic biomarker in GC and regulate cell invasion.
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http://dx.doi.org/10.1007/s13277-015-4404-0DOI Listing
May 2016

Improving the sweet aftertaste of green tea infusion with tannase.

Food Chem 2016 Feb 10;192:470-6. Epub 2015 Jul 10.

Tea Research Institute, Chinese Academy of Agricultural Sciences, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

The present study aims to improve the sweet aftertaste and overall acceptability of green tea infusion by hydrolyzing (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) with tannase. The results showed that the intensity of the sweet aftertaste and the score of overall acceptability of the green tea infusion significantly increased with the extension of the hydrolyzing treatment. (-)-Epigallocatechin (EGC) and (-)-epicatechin (EC) were found to be the main contributors for the sweet aftertaste, based on a trial compatibility with EGCG, ECG, EGC, and EC monomers, and a synergistic action between EGC and EC to sweet aftertaste was observed. A 2.5:1 (EGC/EC) ratio with a total concentration of 3.5 mmol/L gave the most satisfying sweet aftertaste, and the astringency significantly inhibited the development of the sweet aftertaste. These results can help us to produce a tea beverage with excellent sweet aftertaste by hydrolyzing the green tea infusion with tannase.
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http://dx.doi.org/10.1016/j.foodchem.2015.07.046DOI Listing
February 2016

Improving the effectiveness of (-)-epigallocatechin gallate (EGCG) against rabbit atherosclerosis by EGCG-loaded nanoparticles prepared from chitosan and polyaspartic acid.

J Agric Food Chem 2014 Dec 17;62(52):12603-9. Epub 2014 Dec 17.

Institute of Food Chemistry, Zhejiang A&F University , 88 Huanbei Road, Hangzhou, Zhejiang 311300, China.

(-)-Epigallocatechin gallate (EGCG) is the major bioactive compound in green tea. Its effect is limited by the harsh environment of the gastrointestinal tract. The present study investigates how the effectiveness of EGCG is influenced by its encapsulation into self-assembled nanoparticles of chitosan (CS) and aspartic acid (PAA). Blank nanoparticles with a mean diameter of ca. 93 nm were prepared from 30-50 kDa PAA and 3-5 kDa CS with a mass rate of 1:1. EGCG was loaded in the nanoparticles to yield EGCG-CS-PAA nanoparticles with an average diameter of 102 nm, which were pH-responsive and demonstrated different EGCG release profiles in simulated gastrointestinal tract media. The average ratio (%) of lipid deposition for EGCG-CS-PAA nanoparticles administered orally to rabbits was 16.9 ± 5.8%, which was close to that of oral simvastatin (15.6 ± 4.1%). Orally administered EGCG alone yielded an average ratio of lipid deposit area of 42.1 ± 4.0%, whereas this value was 65.3 ± 10.8% for the blank nanoparticles. The effectiveness of EGCG against rabbit atherosclerosis was significantly improved by incorporating EGCG into the nanoformulation.
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http://dx.doi.org/10.1021/jf504603nDOI Listing
December 2014

The major factors influencing the formation of sediments in reconstituted green tea infusion.

Food Chem 2015 Apr 5;172:831-5. Epub 2014 Oct 5.

Tea Research Institute, Chinese Academy of Agricultural Sciences; Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China. Electronic address:

The effects of Ca(2+), caffeine and polyphenols on the formation of reversible tea sediments (RTS) and irreversible tea sediments (IRS) in green tea infusion were studied. Adding Ca(2+) (2 mmol/l) was found to increase the formation of RTS by 8% and IRS by 92%, while adding chelating ions of Na2EDTA significantly decreased the amount of RTS by 14.6%, but not the amount of IRS. Under acid conditions, Ca(2+) combined with oxalic ions to form indissoluble oxalate that is the principal constituent of IRS, despite the existence of the chelating ions. Decaffeination largely inhibited the formation of RTS (73%) and IRS (60%), even in the presence of Ca(2+). The amount of sediment could be reduced by removing polyphenols using polyvinyl-polypyrrolidone. The results suggest that sediment formation in green tea infusions can be inhibited by lowering the concentration of Ca(2+), caffeine or polyphenols.
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http://dx.doi.org/10.1016/j.foodchem.2014.09.143DOI Listing
April 2015

Hydrolysis of green tea residue protein using proteolytic enzyme derived from Aspergillus oryzae.

J Food Sci Technol 2013 Feb 5;50(1):171-5. Epub 2011 Feb 5.

Tea Research Institute of the Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008 China.

Free amino acids are important chemical components which impact the taste of green tea infusion. The hydrolysis of water-insoluble protein in the green tea residue helps to increase the contents of free amino acids components except theanine. Studies indicate that the hydrolysis of the tea protein could be restricted due to interaction of polyphenols with protein. The experiment indicates that the hydrolysis of tea protein by protease is the main trend when the polyphenols concentration is lower than 5 mg ml(-1), however, the proteins (including tea protein and protease) would interact with polyphenoles instead of hydrolysis when the concentration of polyphenols is higher than 5 mg ml(-1). The hydrolysis of tea protein is absolutely restrained when concentration comes to 10 mg ml(-1).
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http://dx.doi.org/10.1007/s13197-011-0239-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550956PMC
February 2013

Sediments in concentrated green tea during low-temperature storage.

Food Chem 2014 Apr 30;149:137-43. Epub 2013 Oct 30.

Institute of Food Chemistry, Zhejiang Gongshang University, 149 Jiaogong Road, Hangzhou, Zhejiang 310012, China; Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou 310008, China.

The formation and the main chemical components of sediments, including reversible tea sediments (RTS) and irreversible tea sediments (IRS), in concentrated green tea during low-temperature storage were studied. RTS was mainly formed in the first 10 days, and IRS was mainly formed between 20 and 40 days of storage. The RTS were the primary sediment, contributing more than 90% of the total sediment. The RTS comprised of polyphenols, total sugar, caffeine, flavones and proteins, while the IRS mainly comprised of oxalates of Ca, Mg, Ga and Mn. The total mineral content in the IRS (17.1%) was much higher than that in the RTS (2.6%) after 80 days of storage. The Ca, Mg, Mn and Ga contents in IRS were over 1.0% (w/w) each. About 75% of the IRS was soluble in 0.1 M aqueous HCl, with the oxalate accounting for 68%. Minerals and oxalic acid were the crucial factors in the IRS formation.
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http://dx.doi.org/10.1016/j.foodchem.2013.10.084DOI Listing
April 2014

Analysis of cream formation in green tea concentrates with different solid concentrations.

J Food Sci Technol 2012 Jun 5;49(3):362-7. Epub 2011 Feb 5.

Tea Research Institute of the Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou, 310008 China.

The formation of tea cream in the green tea concentrates of different solid concentrations (5, 10, 20, 30, 40, 50 and 60°Brix) was investigated. The results showed a good positive correlation (γ = 0.98, p ≤ 0.05) between the amount of tea cream and the solid concentrations from 5 to 40°Brix, while the amount of tea cream in the tea concentrates of 50 and 60°Brix decreased acutely. Total sugar, caffeine and catechins were found to be the main chemical components of tea cream in the green tea concentrate. The large decrease of the amount of tea cream in the tea concentrates of 50 and 60°Brix may be induced by a sharp increase of the viscosity of the tea concentrates, which helped to improve the stability of tea concentrate. It may be indicated that the stability of green tea concentrate enhanced when the concentration higher than 50°Brix, which helped to restrain the formation of tea cream.
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http://dx.doi.org/10.1007/s13197-011-0281-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614051PMC
June 2012

The impact of Ca2+ combination with organic acids on green tea infusions.

Food Chem 2013 Aug 23;139(1-4):944-8. Epub 2013 Jan 23.

Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 South Meiling Road, Hangzhou 310008, China.

The effect of Ca(2+) in brewing water on the organic acid content, turbidity, and formation of tea cream and sediment in green tea infusions was studied. When the Ca(2+) concentration of the brewing water was >40 mg L(-1), the green tea infusion became more turbid. The turbidity of the tea infusion was highly negatively correlated with the contents of oxalic acid (R=-0.89, p<0.01), quinic acid (R=-0.90, p<0.01) and tartaric acid (R=-0.82, p<0.01). Oxalic acid on its own interacted with Ca(2+) at low concentrations, whereas polyphenols and protein did not. In conclusion, Ca(2+) in brewing water influences the quality of a tea infusion by inducing tea cream and sediment formation from combination of Ca(2+) and organic acids, such as oxalic acid, quinic acid and tartaric acid. Ca(2+) and oxalate are the main metal ion and anion, respectively, involved in tea cream and sediment formation on tea infusion cooling or concentrating.
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http://dx.doi.org/10.1016/j.foodchem.2013.01.025DOI Listing
August 2013
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