Yuexiang Longjing Tea and Its Quality Characteristics

Shengzhou is a major tea producing county in China and the major tea produced in Shengzhou is Yuexiang Longjing tea.Environment and tea cultivar are two important factors influencing tea quality.Chemical composition of tea samples prepared using materials from cultivars ‘Zhenong-117＇ and ‘ Baiye-1＇ were investigated.It showed that concentrations of total amino acids and catechins were more than 4.4％ and 129 mg/g respectively,suggesting that Yuexiang Longjing had a good quality potential.     

Analysis of the Volatile Chemicals of Longjing Tea from Different Production Locations Using Electronic Nose

Electronic nose has been applied in analysis of food products by monitoring their flavours.But it gives an overall response to a mixture of volatile components.In this work,multianalysis and chemometrics technique were employed to analyse the E-nose and GC-MS data of Longjing tea produced in different locations in Zhejiang province,China.A good discrimination of Longjing tea samples was obtained by E-nose according to the producing area,and a total of 38 compounds were commonly identified from the GC-MS data.Each individual volatile component was related to E-nose response using PLSR and the significance of each component was evaluated by the coefficient R2.Results indicated that isoamyl isovalerate,cis-3-hexenyl hexanoate,cadinene,phenylethylalcohol and linalool played an important role in response on E-nose sensors.It was possible to give a complementary information concerning the individual chemicals interacts with the sensors of E-nose instead of the total volatile components.     

Effect of Different Drying Methods on the Volatile Compounds Jinmudan Oolong Tea

Jinmudan,a new tea variety from Fujian Province has an excellent quality with a unique aroma like magnolia frogrance.To monitor the changes in the tea volatile compounds during the Jinmudan Oolong tea manufacturing （drying） process,the volatiles of tea samples were extracted and analyzed.Characteristic volatile compounds in Jinmudan Oolong tea were nerolidol,α-famesene,linolenic acid,palmitic acid,indole,phenylacetaldehyde,cisjasmone,β-phenylethanol,etc.The content of nerolidol was the highest in four tested samples.The composition of the volatile compounds in microwave drying sample was simple,but its concentration was high,in which the main volatile compounds were alcohols and esters.The processing with combination of traditional drying craft and modem aroma-improvement technique could obviously improve the tea aroma,especially in level of epoxy linalool and jasmine lactone.     

Stability of Tea Catechins and Antioxidant Properties of Green Tea Extracts as Affected by Boiling-treatment

Stability of tea catechins and the antioxidant properties of green tea extracts as affected by boiling-treatment from 1 to 5h were studied.Green tea catechins were partially epimerized from epi-form to nonepi-form under boiling-treatment.Total phenolic compounds of the samples under the boiling-treatment for 1 to 4h showed the same statistically significant （P ＞ 0.05） comparing with the untreated samples and there was no significant reduction （P ＞ 0.05） of total catechins when the green tea extracts were boiling-treated for 1 h.There were no significant （P ＞ 0.05） reduction of the antioxidant capacity when the samples were boiling-treated for 1 h,no significant （P ＞ 0.05） reduction of the scavenging ability against DPPH and O2-when treated for 2h,and no difference on scavenging ability against OH when treated even for 5h.The results indicated that boiling-treatment for 1h had limited effect on total catehins and phenols content in green tea extracts.Green tea extracts still remained excellent in antioxidant properties and free radical scavenging activity after boiling-treated for 1 h.     

A Study on Physiological Character of Fresh Tea Leaves in Different Cold-Resistant Varieties简

In order to reveal the cold resistant mechanism of tea plant,two varieties with different cold resistances were studied.The activities of catalase （CAT）,peroxidase （POD）,superoxide dismutase （SOD） and polyphenol oxidase （PPO） were investigated,and the contents of soluble protein,sugar and malondialdehyde （MDA） were determined in fresh tea leaves in the autumn.The results showed that the activities of POD and the content of soluble sugar were both much higher in the variety with strong cold resistance,and the content of soluble protein was associated with the cold resistance,while the cold resistance of the plant was not related with the activities of the CAT,SOD and PPO,and the content of MDA.It is considered that the activity of POD and contents of soluble sugar could be used as indicators to identify the cold resistance of tea varieties.     

Transcriptome analysis of salt-stress response in three seedling tissues of common wheat

Xiaoyan 60(XY60) is a new wheat variety bred in the laboratory of Zhensheng Li.After salt treatment, seedlings of XY60 maintain green leaves and produce longer roots than the high yielding cultivar Zhongmai 175(ZM175).To explain these different phenotypes we carried out an RNA-Seq analysis using 12 samples from three tissues of both varieties subjected to salt and control treatments.By comparing data from the salt treated plants with the control, 703, 979, and 1197 differentially expressed genes(DEGs) were detected in new leaves, old leaves, and roots of XY60, respectively.The corresponding numbers for ZM175 were 613, 1401, and 1301.The most significantly enriched Gene Ontology(GO) terms and KEGG pathways were associated with polyunsaturated fatty acid(PUFA) metabolism in both new and old leaves from XY60.They were associated with photosynthesis and energy metabolism in ZM175.The most significantly enriched KEGG pathway in roots of both varieties was “glucosinolate biosynthesis”.In addition, jasmonic acid(JA) concentration in XY60 was higher than in ZM175, although it increased significantly in both varieties following salt treatment.Trends in relative expression levels of AOS, MYC2, and JAZ revealed by qRT-PCR were concordant with those from RNA-Seq.Our results suggest that PUFAs may contribute to salt tolerance in common wheat by enhancing the photosynthetic system and JA-related pathways.     

Different Aluminum Tolerance among Indica,Japonica and Hybrid Rice Varieties

Hydroponic cultures were conducted to compare the aluminum(Al) tolerance among different rice(Oryza sativa L.) varieties, including indica, japonica and their hybrids. The results showed that the root growth of rice plant was inhibited in different degrees among Al treated varieties. The Al tolerance observed through relative root elongation indicated that five japonica varieties including Longjing 9, Dharial, LGC 1, Ribenyou and Koshihikari were relatively more tolerant than indica varieties. Most indica varieties in this study, such as Aus 373 and 9311(awnless), were sensitive to Al toxicity. The Al tolerance of most progenies from japonica × indica or indica × japonica crosses was constantly consistent with indica parents. The differences of Al tolerance among Longjing 9(japonica), Yangdao 6(indica) and Wuyunjing 7(japonica) were studied. Biomass and the malondial-dehyde content of Yangdao 6 under Al exposure decreased and increased, respectively, while there was no significant effect on those of Longjing 9 and Wuyunjing 7. Remarkable reduction of root activities was observed in all these three rice varieties. Significantly higher Al content in roots was found in Yangdao 6 compared to Longjing 9 or Wuyunjing 7.     

Association of Phytate Formation with Grain Filling in Rice

The grain-filling characteristics of six rice varieties (combinations) and the relationships between their relative biochemistry composition during phytate synthesizing and grain plumpness were studied. Regarding results for ISHR1,ISHR2, R198 and JW21, with good grain plumpness, the two-step-filling in superior spikelets and inferior spikelets was not clear, while for ISHR3 and 559, with poor grain plumpness, it was very clear. From booting stage to flowering stage, the contents of phytate and inositol in varieties with good grain plumpness was obviously higher than those in varieties with poor grain plumpness. While at grain filling stage, the content of inorganic phosphorus in varieties with poor grain plumpness was obviously higher than that in varieties with good grain plumpness. The contents of phytate and inositol from booting stage to flowering stage was highly significantly correlated with the initial filling power (R0), the mean filling rate (RM) and grainfilling percentage (PGF), and the content of inorganic phosphorus at grain filling stage was negatively significantly correlated with R0, FM and PGF. Furthermore, effective approach to improving grain filling was put forward.     

Studies on Bitter and Astringent Taste of Tea

Bitterness and astringency are important sensory properties for evaluating quality of tea.The research advances in the mechanism of tea astringency and bitterness,astringent and bitter tasting components and their evaluations were reviewed in the present paper.The astringency arises from the interaction of salivary proteins with polyphenols which depends on the structure of both the polyphenols and the proteins.Bitter and astringent compounds in tea include phenolic acids,catechins and their oxidized products,flavonol glycosides and proanthocyanidins.There are many factors influencing on astringency and bitterness including the interaction between taste substances,repeated ingestion,saliva flow and its composition and acidity.Sensory assessment and instrumental evaluation were used in the evaluation of astringency.     

A Review on Decaffeination of Tea Products

Since caffeine possesses some well-unknown adverse effects,many attempts have been conducted to remove it from tea products,including selective extraction with different solvents,enzymatic degradation and inhibition the caffeine synthesis pathway.Reports showed that caffeine can be safely and efficiently removed from fresh tea leaves by hot water blanching,however this approach is not suitable for treating the rolled or dried leaves because of the unavoidable loss of catechins.Although microwave-enhanced vacuum ice water extraction can be used for decaffeination of dried tea,time consumption seems to be the main shortage of this method.Liquefied dimethyl ether might be used as another alternative solvent for selective extraction of caffeine from tea products because of its low toxicity and residum,but its decaffeination efficiency needs to be verified furthermore.It has been proved that supercritical carbon dioxide extraction is an effective approach for removing caffeine from different types of tea products,while the application of the technique is always limited as its expensive equipments and high running costs.Decaffeination with microbe incubation or enzymatic digestion is highly hopeful since many studies showed that some microorganisms can degrade the caffeine through induced demethylase and oxidase under gentle condition in some model systems,unfortunately,this approach is far away from application since security and quality of the decaffeinated products are rarely concerned.Low-caffeine tea products can be easily produced through normal manufacture by using the leaves harvested from some low-caffeine cultivars which are derived through genetic modification or conventional breeding,but these germplasms are very limited.     

Tea Seed and Its Bioactive Functions

Tea seed is a byproduct in tea production and also a source of nutritional and bioactive compounds.There have been studies showing that extracts of tea seeds offered many physiological functions including anti-inflammatory,anti-oxidant,anti-tumor,anti-obesity,hepatoprotective and gastroprotective effects.The tea seed oil is also an acceptable biodiesel and the saponin-rich tea seed meal can be used as vermicide to expel earthworms from the soil of golf courses and sports fields.The bioactive functions of tea seed extracts and their potential uses in agricultural and industrial sectors were reviewed in the present paper.     

Effects of Brewing Conditions on Quality of Pu＇erh Tea Infusion

To brew tea correctly is very important to absorb the tea nutrition for people.The dynamic changes of the main compositions in brewing Pu＇erh tea processing with different conditions were studied.Three different temperatures and eight times were designed to study the effects on the tea infusion quality.The index t0.5 min （50％ concentration of compounds in tea infusion） was used to evaluate the extract speed of compound in this experiment.The results showed that caffeine solubility speed at 80℃ was the highest to compare with tea polyphenols,amino acid,caffeine,soluble sugar,theaflavins and theabrownine,t0.5min of caffeine was 4.8 min,amino acid 10.3min was the second,the third one was tea polyphenols,soluble sugar was the lowest.We also found in different infusion temperature the t0.5min of compounds was distinguishing.With increasing the temperature all t0.5min of six compounds were shorter.However,the change regulations of t0.5min for all compounds in 90℃ and 100℃ were similar to in 80℃.Total quality score （TQS） were applied to evaluate the quality of tea infusion.The results found the TQS score of infusion was higher with the temperature rising,and the temperature to brew best quality infusion was 100℃ for 4-5min.According to the multiple regression analysis between sensory assessments and chemical components of Pu＇erh tea we suggested the TQS was mainly affected by theaflavins,amino acid,soluble sugar and theabrowine four factors in 100℃.     

Studies on Aftertaste of Tea

Aftertaste is a taste perceiption after a food or beverage is either swallowed or spat out.The primary taste processing area located in the insula was considered to be involved in aftertaste perception.The changes in chemical compositions lead to the changes in aftertaste of tea.Tea fermentation,in which tea catechins are transformed into thearubigins,lead to a strong,distinctive flavor but a plain aftertaste.Theanine has a sweet taste,with little or no aftertaste.The bitter aftertaste of transglucosylated steviosides was reduced when they were converted through transglucosylation of stevioside by α-amylase.Characteristics of aftertaste include quality,intensity,and duration.Foods that have lingering aftertastes typically have long sensation durations.A surface plasmon resonance （SPR） system immobilized β-cyclodextrin indicated larger responses for the gallate-type catechins in comparison to the non-gallate-type catechins.The β-cyclodextrin/SPR system can sense the bitter-astringent taste intensity of the green tea.The SPR system detected the stability of the complex between the gallate-type catechins and β-cyclodextrin,which can be interpreted as the aftertaste produced in humans by the gallate-type catechins.     

Applications of Green Tea Extract in Bakery Products

Green tea extract （GTE） is a rich source of tea catechins with antioxidative,anticarcinogenic and antiarteriosclerotic activities and it has been applied in food such as bakery products to provide health benefits and extend the shelf life.This review outlines the stability of green tea catechins during baking process of bakery products supplemented with GTE and the effects of GTE on the functional properties,sensory properties,physical characteristics and Maillard reaction of bakery products.     

Studies on Umami Taste of Tea

Umami is one of the five basic tastes and an important taste attribute of green tea.Amino acids are major components contributing to umami taste and the top three amino acids in tea are theanine,glutarnic acid and aspartic acid.Trace of umami taste components adenosine monophosphate （AMP） and guanosine monophosphate （GMP） were detected in tea.Levels of umami taste components varied with tea cultivar,environmental conditions,fertilizer and processing method.The taste threshold of amino acids differentiated greatly and its DOT （dose over threshold） is an important indicator evaluating its contribution to umami taste.     

The 30-Day Oral Administration Studies of Liposoluble Tea Polyphenols in Rats

Tea polyphenols is a natural antioxidant with a variety of biological activity.However,the weak liposolubility and low bioavailability limit their application.As a result,structural modification of tea polyphenols comes into being.The prepared liposoluble tea polyphenols was suggested as a good candidate antioxidant for edible-oil and fats products.But,safety studies on liposoluble tea polyphenols are limited.The objective of the present study was conducted to synthesize liposoluble tea polyphenols and evaluate its toxicity in Sprague-Dawley rats on oral administration at dietary levels of 1,2 and 4％ for 30 days.There were no adverse effects on general condition,growth,food intake,feed conversion efficiency,haematology parameters,clinical chemistry values and organ weights.High-dose males exhibited a higher haemoglobin concentration and a lower alanine aminotransferase levels,and high-dose females showed a lower albumin and globulin levels.These slight changes were considered of no toxicological significance.Necropsy and histopathology findings revealed no treatment-related changes in any of the organs.Thus,the results allowed us to conclude that the liposoluble tea polyphenols properly utilized in the oral administration could be devoid of any toxic risk.     

Study on the Retention Rate of Green Tea Catechins Components and Tea Polyphenol by Different Processing Technology

The aim of this research was to explore the effect of fixation,rolling,and drying processing technology on the retention rate of green tea catechins components and tea polyphenol.Different fixation processes （rotary drum-firing,microwave,steam-blasting）,rolling process （weight of rolling,gently press rolling and traditional rolling）,drying process （stove drying,roasting dehydration,baked fried drying） were adopted.The effect of different tea processing technology on the retention rate of catechins component and tea polyphenol was analyzed.It showed that the microwave fixation process,gently press rolling process,baked fried dry process were beneficial to keep high levels of EGCG,C,EGC,EC,ECG.