Taste Of Tea Research Articles

Aerospace Mutagenesis Increases the Content of Characteristic Metabolites of Tea Tree Leaves and Enhances Taste Characteristics of Tea Leaves

Aerospace mutagenesis can alter the physiological metabolism and growth of tea trees and affect tea leaf quality. In this study, the effect of aerospace mutagenesis on the metabolite content and taste characteristics of Dahongpao fresh leaves and raw tea were analyzed. The results showed that aerospace mutagenesis had little effect on the composition and total amount of metabolites in fresh leaves and raw tea, but significantly changed the content of different metabolites. Aerospace mutagenesis improved the content of lipids, lignans and coumarins, and amino acids and derivatives, which in turn enhanced the aroma and fresh and brisk taste of fresh leaves. Aerospace mutagenesis increased the content of alkaloids, tannins, flavonoids, lignans and coumarins, amino acids and derivatives, and organic acids in raw tea, and enhanced the bitterness, mellowness, and fresh and brisk taste of raw tea. This study provides a basis for the development of aerospace mutagenesis Dahongpao tea products and the establishment of processing techniques.

Comprehensive analysis reveals the contribution of “rolling-anaerobic” processing to the improved aroma, taste and color of GABA black tea

GABA black tea (GABT), produced by the combination of anaerobic treatment and Chinese traditional black tea processing technology, has a unique flavor and health benefits. However, how to manufacture high-quality GABT efficiently is the major challenge for this area. In this study, a processing improvement of multiple rolling-anaerobic treatment cycle was applied to prepare tailored GABTs, and their comprehensive quality including aroma, taste and color were analyzed. The sensory evaluation results showed that the improvement significantly optimized the overall GABT quality. The accumulation of linalool oxide Ⅰ, citronellol, etc. was the main reason for the superior aroma of tailored GABT, while the dynamic changes of sweet/umami amino acids, catechins and tea pigments played critical roles in the GABT taste and color quality formation during processing. Furthermore, correlation analysis was applied to determine the contribution of various processing steps. These findings provide a novel manufacturing method for high-quality GABT products.

Thermochemical reactions in tea drying shape the flavor of tea: A review

Drying is the final and essential step in tea processing. It contributes a lot to the formation of tea flavor quality by a series of complicated and violent thermochemical reactions, such as degradation reaction, Maillard reaction, redox reaction, isomerization reaction, etc. However, the mechanism of specific thermochemical reaction is unclear. Here, by comprehensively summarizing the thermochemical reactions of the main chemicals, including polyphenols, lipids, amino acids and carbohydrates, etc., during tea drying with particularly focus on their contributions of thermal drying on the flavor including color, aroma, and taste, we found that thermal degradation is the dominant thermochemical reaction, directly affecting the taste and color of tea, and thermal oxidation of lipids and Maillard reaction mainly contribute to form tea aroma. More interesting was that high temperature enhanced nucleophilicity of phenolics, allowing them to easily trap carbonyl substances to form small molecular adducts (i.e. EPSFs) or polymers, which could interfere other thermochemical reactions, and then alter the flavor quality of tea. Over all, this review provides updated scientific evidence for in-depth exploration of thermochemical reactions towards tea precision processing.

Study on metabolic variation reveals metabolites important for flavor development and antioxidant property of Hainan Dayezhong black tea

To illustrate the development of chemical properties and characteristic flavor of Hainan Dayezhong black tea, the tea shoots under various manufacturing process were sampled and applied to targeted/widely-targeted metabolomic, transcriptomic, chemometric, and electronic sensory determinations. Totally, 2419 metabolites were identified in this study, of which 20 metabolites were selected as the biomarkers, mainly including amino acids, lipids, and pyrimidine derivatives. The metabolomic-transcriptomic integrated analysis indicated carbon fixation, flavonoid biosynthesis and amino acid metabolism were the major metabolic pathways over manufacturing process of Hainan Dayezhong black tea. The targeted metabolomic detection indicated the accumulations of free amino acids and reduction of total catechins, flavonol glycosides collectively contributed to the development of black tea taste; additionally, the antioxidative properties were decreasing along the production process. These results suggest that the tradeoff between bioactivity components and antioxidative capacity contribute to the characteristic flavor of Hainan Dayezhong black tea.

Polysaccharide Conjugates' contribution to mellow and thick taste of Pu-erh ripe tea, besides Theabrownin

Mellow and thick taste (MTT) is considered to be a typical taste characteristic of high-quality Pu-erh ripe tea. However, the role of polysaccharide conjugates remains unclear. In this study, the infusion of different grades of Pu-erh ripe tea was isolated to fractions by sensory-guided ultrafiltration technology and the key taste substances of MTT in Pu-erh ripe tea were identified and confirmed in the sensory reconstruction experiment. Further separation, purification and structural identification of the polysaccharide conjugates were carried out. Involving in aggregation morphology, the ultrafiltration fraction exhibited obvious MTT than other fractions. The main MTT compound (PRTPS-5), mainly composed of the rhamnose, galactose, arabinose and mannose, had a molecular weight of 22.93 kDa. The main chain of PRTPS-5 comprised α-L-Araf-(1→, →2,4)-α-L-Rhap-(1→, →2)-α-L-Rhap-(1→, α-D-Galp-(1→, →4)-α-D-GalpA-6-OMe-(1→, →4)-α-D-Manp-(1→, →3,6)-β-D-Galp-(1 → and →5)-α-L-Araf-(1 → and contained multiple pectic characteristic peaks. This result had scientific guiding significance for the quality enhancement of Pu-erh ripe tea.

The Light-Intensity-Affected Aroma Components of Green Tea during Leaf Spreading.

Leaf spreading is a key processing step that affects the aroma formation of green tea. The effects of a single-light wavelength on the aroma and taste of tea have been extensively studied. Less attention has been paid to the effect of different complex light intensities on the formation of green tea's volatile aroma during leaf spreading. The current study was designed to evaluate how leaf spreading under different complex light intensities relates to the quality of green tea. Using headspace solid-phase micro-extraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS), volatile flavor compounds in green tea were analyzed during leaf spreading in five different light conditions. Multivariate statistical analysis and odor activity values (OAVs) were used to classify these samples and identify key odors. Eight distinct groups, including ninety volatile compounds, were detected. The most prevalent volatile compounds found in green tea samples were hydrocarbons and alcohols, which accounted for 29% and 22% of the total volatile compounds, respectively. Fourteen volatile compounds (OAV > 1) were identified as key active differential odorants. The chestnut-like aroma in green tea was mostly derived from 3-methyl-butanal and linalool, which were significantly accumulated in medium-intensity light (ML).

Is the tea or teacup good? The effect of visual and haptic sensory processing of teacups on the perception of tea flavor.

Prior research on the relationship between the taste, aroma and drinking utensils of beverages tends to focus on topics such as alcohol, sparkling beverages, juice, coffee, and hot chocolate. There is limited research focused on the interdependence between the perception of teacups and the tea taste. The literature has not yet found any research covering the impact of visual shape and the tactile sensation of teacups on the perception of tea flavor. Therefore, this study proposed six hypotheses related to the teacup shape and texture, teacup preference and taste and smell of tea. This study involved experimental design and questionnaire data collection, using a convenience sampling method to recruit 102 participants voluntarily. The research results are: (1) Age and gender have an impact on the taste and aroma perception of tea; (2) The width, height, rim thickness and smoothness of the teacup surface do have an impact on the perception of taste and fragrance of tea. (3) The preference of teacup played an intermediary effect between tea taste and the shape and texture of teacup. The implications of these findings on the perception of tea flavor are discussed.

Effects of isolated scenting on the taste quality of broken green tea based on metabolomics

Liquid chromatography-mass spectrometry (LC-MS) combined with multivariate analysis were used to characterize the nonvolatile compounds of broken green tea and explore the effect of isolated scenting on metabolic profile and taste quality of broken green tea in this research. A total of 236 nonvolatile compounds were identified and 13 compounds were believed to be the key characteristic taste compounds of scented broken green tea. Meanwhile, the optimal isolated scenting time of broken green tea was determined to be 10 h based on the sensory evaluation and PLS results. The contents and types of flavonoids, organic acids and catechins lead to the difference of taste quality at different scenting times. Overall, these findings provided a theoretical basis for scenting to improve the taste of broken green tea, and provide a new idea for improving the taste of broken green tea.

Key umami taste contributors in Longjing green tea uncovered by integrated means of sensory quantitative descriptive analysis, metabolomics, quantification analysis and taste addition experiments

Umami taste is a key criteria of green tea quality evaluation. The aim of this study was to comprehensively explore the key umami taste contributors in Longjing tea. The taste and molecular profiles of 36 Longjing green tea infusions were characterized by sensory quantitative descriptive analysis and LC-MS based metabolomics, respectively. By uni−/multi-variate statistical analysis, 84 differential compounds were screened among tea infusions with varied umami perceptions. Among them, 17 substances were identified as candidate umami-enhancing compounds, which showed significant positive correlations with umami intensities. Their natural concentrations were accurately quantified, and their umami taste-modifying effects were further investigated by taste addition into glutamic acid solution. Glutamic acid, aspartic acid, glutamine, theanine, phenylalanine, histidine, theogallin, galloylglucose, 1,2,6-trigalloylglucose significantly enhanced the umami taste. This study uncovered for the first time of some bitter amino acids and galloylglucose homologous series as important umami-enhancers, which provided a novel perspective into the tea taste.

Widely targeted metabolomic analysis reveals effects of yellowing process time on the flavor of vine tea (Ampelopsis grossedentata)

The bitter and astringent taste and miscellaneous smell of vine tea prevent its further development. In this study, we used a processing technology that mimics yellow tea to improve the flavor of vine tea and revealed its internal reasons through metabolomics. Sensory evaluation showed the yellowing process for 6–12 h reduced the bitterness and astringency significantly, and enriched the aroma. The improvement of taste was mainly related to the down-regulation of anthocyanins (54.83–97.38%), the hydrolysis of gallated catechins (34.80–47.81%) and flavonol glycosides (18.56–44.96%), and the subsequent accumulation of d-glucose (33.68–78.04%) and gallic acid (220.96–252.09%). For aroma, increase of total volatile metabolite content (23.88–25.44%) and key compounds like geraniol (239.32–275.21%) induced the changes. These results identified the positive effects of yellowing process on improvements in vine tea flavor and the key compounds that contribute to these changes.

A functional study reveals CsNAC086 regulated the biosynthesis of flavonols in Camellia sinensis.

CsNAC086 was found to promote the expression of CsFLS, thus promoting the accumulation of flavonols in Camellia sinensis. Flavonols, the main flavonoids in tea plants, play an important role in the taste and quality of tea. In this study, a NAC TF gene CsNAC086 was isolated from tea plants and confirmed its regulatory role in the expression of flavonol synthase which is a key gene involved in the biosynthesis of flavonols in tea plant. Yeast transcription-activity assays showed that CsNAC086 has self-activation activity. The transcriptional activator domain of CsNAC086 is located in the non-conserved C-terminal region (positions 171-550), while the conserved NAC domain (positions 1-170) does not have self-activation activity. Silencing the CsNAC086 gene using antisense oligonucleotides significantly decreased the expression of CsFLS. As a result, the concentration of flavonols decreased significantly. In overexpressing CsNAC086 tobacco leaves, the expression of NtFLS was significantly increased. Compared with wild-type tobacco, the flavonols concentration increased. Yeast one-hybrid assays showed CsNAC086 did not directly regulate the gene expression of CsFLS. These findings indicate that CsNAC086 plays a role in regulating flavonols biosynthesis in tea plants, which has important implications for selecting and breeding of high-flavonols-concentration containing tea-plant cultivars.

Effect of drying methods on aroma, taste and antioxidant activity of Dendrobium officinale flower tea: A sensomic and metabolomic study

Dendrobium officinale flower tea (DFT) is a traditional health product of geographical identity known for its unique aroma and taste. The effects of different drying methods on sensory properties, metabolic profiles and antioxidant activity of DFT were compared using sensomics and metabolomics approaches. Twenty-seven aroma-active compounds were identified and more than half of the volatiles responsible for the “green” and “floral” scent lost after drying. Sensory evaluations revealed that vacuum freeze-dried DFT showed a significant preference in taste and fifty-eight metabolites with higher levels of glutamine were observed, possibly contributing to a “fresh” taste and increased preference. Among the three drying methods, natural air drying retained the fresh flower scent better, while freeze drying preserved the color and shape of the flowers better and enhanced the taste and antioxidant activity of DFT. The research results may provide a foundation for the selection of DFT processing method and quality detection.

Comparison of different drying technologies for coffee pulp tea: Changes in color, taste, bioactive and aroma components

Drying is a crucial process in the production of tea. The effects of sun drying (SD), hot air drying (HAD), microwave drying (MD), vacuum drying (VD) and freeze drying (FD) on the color, taste, bioactive, and aroma of coffee pulp tea (CPT) were evaluated systematically. The results showed that FD could better retain the original color, total phenolics (4.75 mg/mL), trigonelline (0.31 mg/mL), chlorogenic acid (0.067 mg/mL), protocatechuic acid (0.81 mg/mL), and total soluble sugars (24.33 mg/mL) of CPT, but its drying time was longer (32.56 h), and the taste and flavor were the worst. HAD and SD displayed the highest loss rates of most bioactive components, exceeding 40%. In contrast, MD can better improve the quality of CPT, giving it a better color, superior retention of bioactive components, and the most attractive taste and aroma, and decrease the drying time by 66.1% and 96.5%, respectively. Overall, MD is a promising production method for obtaining high-value-added CPT products.

Karakteristik Teh Jelai (Coix Lacryma-Jobi.L) dengan Perlakuan Waktu dan Suhu Roasting yang Berbeda

Jelai (Coix Lacryma Jobi.L) seeds are grains that have the potential to be processed into herbal teas which are served either hot or cold. Jelai tea can be processed through a high-temperature roasting process to enhance the aroma and taste. Temperature and length of roasting time are factors that affect grain characteristics. The purpose of this study was to evaluate the effect of temperature and roasting time on water content, color of barley powder and the effect of temperature and roasting time on pH, total dissolved solids, and organoleptic of jelai tea. The study used a factorial completely randomized design (CRD) with two factors: (t) roasting temperature (180oC, 200oC, 220oC) and (f) roasting time (5 minutes, 10 minutes, 15 minutes). The roasting temperature and time reduced the water content of jelai powder from 11.04% to 1.57% (wb), increased the dissolved solids from 0.26 oBrix to 5.16 oBrix, and lowered the pH from 7.04-6.79. The higher the temperature and roasting time, the darker the color of the powder and the barley tea (brown), increase the burning aroma (burn aroma), nutty smelling, burn flavor and the sour taste of jelai tea. The highest results were obtained at 220oC combined roasting time of 10 minutes and 15 minutes. Overall, the level of panelist acceptance of jelai tea was in the rather favorable category for all treatments (2.77 – 3.42).

Mixed processing improved the theaflavin, theanine and aroma components of Congou black tea

SummaryCongou black tea is mainly processed from single variety leaves, with obvious variety characteristics. This study investigated the effects of mixed processing withered leaves varieties on sensory quality, the volatile and non‐volatile compounds of seven Congou black tea samples. Sensory quality evaluation revealed that the Congou black tea with three leaves varieties were fresher, more floral and had coordinate taste. The total quality score was in the order: MPH > H > M&H > M > M&P > H&P > P. However, samples MPH and M&H have a higher content of theaflavins and amino acids, especially theanine. Furthermore, 130 volatile substances were identified in seven black teas by using HS‐SPME/GC–MS. M&H and MPH have more aroma types and total amount than that of M, P and H. The mixed processing of withered leaves may fully use the catalysis of endogenous enzymes to increase the 19 kinds of black tea key aromas including Benzyl alcohol, trans‐2‐hexenyl hexanoate, Hexyl hexanoate and Methyl jasmonate. Thus, blended processing can enhance the taste, aroma and LC quality of black tea.

Characteristics of Takokak (Solanum torvum Sw.) Leaves Herbal Tea Based on Drying Temperature

Pokak plant, also known as takokak or prickly nightshade (Solanum torvum Sw.), belongs to the Solanaceae family. The part of the plant commonly utilized was its leaves. Takokak leaves contained numerous bioactive components that can be developed into one of the functional foods, such as herbal tea. One crucial aspect in the herbal tea-making process is the drying temperature. The aimed of this research was to investigate the effect of drying temperature variations on the characteristics of takokak leaves herbal tea and to determined the optimal temperature that can yield the best characteristics of takokak leaf herbal tea. Parameters observed in this study included total phenols, total flavonoids, total tannins, vitamin C, antioxidant activity, and sensory properties comprising hedonic tests on color, taste, aroma, and overall acceptances. Data obtained were analyzed using analysis of variance (ANOVA), and if there was a significant effect of treatment on the results (P<0.05), it would be followed by the Tukey test. The results showed that variations in drying temperature significantly affected the values of total phenols, tannins, flavonoids, vitamin C, antioxidant activity, and sensory properties regarding color, aroma, taste, and overall acceptances of takokak leaf herbal tea. The best treatment was obtained at a drying temperature of 40°C with total phenol content of 31.58 mg GAE/g, total tannin content of 0.79 mg TAE/g, total flavonoid content of 14.23 mg QE/g, total vitamin C content of 7.92 mg AAE/g, antioxidant activity of 84.26%, and sensory properties for color, aroma, taste, and overall acceptances respectively were 5.73 (like), 5.27 (slightly like), 3.77 (neutral), and 3.91 (neutral).

일본산 품종 녹차의 우림 조건과 품종별 주요 성분

The flavors of tea vary depending on various factors, among which the taste of tea is greatly determined by the elution rate of each component contained in tea leaves. This study analyzed the infusion characteristics of Japanese green tea such as ‘Yabukita’, ‘Fusun’, ‘Okumidori’, and ‘Benifuki’. The brewing water temperature was 20, 40, 60, 80, or 100°C, and the brewing time consisted of one and two minutes. The elution rate of amino acids increased from 22.7-76.6% and 4.0-81.8% in theanine as the brewing water temperature and time were increased. The elution rates for polyphenols, catechins, and caffeine were 4.5-74.8%, 4.9-70.4%n, and 3.5-80.1%, respectively. The result indicated that the elution of components increased as brewing water temperature and time increased from 20 to 100°C and from one to two minutes, respectively. Amino acids were eluted at a slightly higher rate even at low temperatures, whereas polyphenols, and catechins were well eluted at temperatures above 80°C. These results suggest that each component related to the taste of tea has different elution characteristics. In addition, the elution conditions can be adjusted to achieve the favorite taste of tea.

New Insights into the Umami and Sweet Taste of Oolong Tea: Formation of Enhancer N-(1-carboxyethyl)-6-(hydroxymethyl) pyridinium-3-ol (Alapyridaine) in Roasting Via Maillard Reaction.

Roasting is pivotal for enhancing the flavor of Wuyi rock tea (WRT). A study investigated a novel compound that enhances the umami taste of WRT. Metabolomics of Shuixian tea (SXT) and Rougui tea (RGT) under light roasting (LR), medium roasting (MR), and heavy roasting (HR) revealed significant differences in nonvolatiles compounds. Compared LR reducing sugars and amino acids notably decreased in MR and HR, with l-alanine declining by 69%. Taste-guided fractionation identified fraction II-B as having high umami and sweet intensities. A surprising taste enhancer, N-(1-carboxyethyl)-6-(hydroxymethyl) pyridinium-3-ol (alapyridaine), was discovered and identified. It formed via the Maillard reaction, positively correlated with roasting in SXT and RGT. Alapyridaine levels were highest in SXT among the five oolong teas. Roasting tea with glucose increased alapyridaine levels, while EGCG inhibited its formation. HR-WRT exhibited enhanced umami and sweet taste, highlighting alapyridaine's impact on WRT's flavor profile. The formation of alapyridaine during the roasting process provides new insights into the umami and sweet perception of oolong tea.

The effects of tea plant age on the color, taste, and chemical characteristics of Yunnan Congou black tea by multi-spectral omics insight

The present study comprehensively used integrated multi-spectral omics combined with sensory evaluation analysis to investigate the quality of three types of Yunnan Congou black teas from different tree ages (decades, DB; hundreds, HB; a thousand years, TB). TB infusion presented the highest scores of sweetness and umami, higher brightness, and yellow hue. Eighty-four marker metabolites were identified, including Amadori rearrangement products, catechin oxidation products, flavonoid glycosides, and organic acids, which are simultaneously related to tea infusions' color and taste. Moreover, the content of some characteristic flavonoid glycosides and organic acids was determined. Our finding implied trans-4-O-p-coumaroylquinic acid and quercetin 3-O-rutinoside contributed to bitterness and astringency, while dehydro theanine-glucose Amadori product and xylopyranosyl-glucopyranose resulted in umami and sweetness. These results provided quantitative and qualitative information for deciphering differences among black teas with different tea plant ages, conducing to the further utilization of ancient tea plants in Southwest China.

Root microbiota of tea plants regulate nitrogen homeostasis and theanine synthesis to influence tea quality

The flavor profile of tea is influenced not only by different tea varieties but also by the surrounding soil environment. Recent studies have indicated the regulatory role of soil microbes residing in plant roots in nutrient uptake and metabolism. However, the impact of this regulatory mechanism on tea quality remains unclear. In this study, we showed that a consortium of microbes isolated from tea roots enhanced ammonia uptake and facilitated the synthesis of theanine, a key determinant of tea taste. Variations were observed in the composition of microbial populations colonizing tea roots and the rhizosphere across different seasons and tea varieties. By comparing the root microorganisms of the high-theanine tea variety Rougui with the low-theanine variety Maoxie, we identified a specific group of microbes that potentially modulate nitrogen metabolism, subsequently influencing the theanine levels in tea. Furthermore, we constructed a synthetic microbial community (SynCom) mirroring the microbe population composition found in Rougui roots. Remarkably, applying SynCom resulted in a significant increase in the theanine content of tea plants and imparted greater tolerance to nitrogen deficiency in Arabidopsis. Our study provides compelling evidence supporting the use of root microorganisms as functional microbial fertilizers to enhance tea quality.