Effect of Fermentation Humidity on Quality of Congou Black Tea

From water migration to aroma development: Revealing the influence of environmental airflow on the aroma of white tea during withering

Environmental airflow is an important factor affecting withering, primarily influencing the development of white tea's aroma. To examine how the aroma of white tea develops under the effect of environmental airflow during withering, tea shoots exposed to airflow (0.5 ± 0.2 m/s) were sampled and analyzed for water distribution, antioxidant enzyme activity, and volatiles content. The results indicated that environmental airflow hastened the evaporation of free water from witheing leaves during the pre-withering stage, facilitated the transformation of free water to bound water, stimulated antioxidant enzyme activity. Additionally, volatiles associated with green and grassy notes in white tea were dramatically reduced, including 3-hexen-1-ol, methyl salicylate, and (Z)-3-hexen-1-ol acetate. In contrast, volatiles responsible for floral and fruity scents, including linalool and nerolidol, became more concentrated. These findings provide important theoretical insights into increasing white tea manufacturing efficiency and quality.

Effect of oxygen concentration on volatile compounds and their formation in Keemun black tea fermentation

Fermentation is a key process in the production of Keemun black tea (KBT), and oxygen, time, temperature, and humidity are key factors affecting black tea fermentation. However, the effect of oxygen concentration on the aroma quality of KBT remains unclear. To deeply investigate the effect of oxygen concentration (16 %, 21 %, 35 %, and 45 %) on the volatile compounds of KBT during fermentation, the aroma characteristics of tea fermented with different oxygen concentrations were assessed. A total of 80 volatile compounds were detected based on gas chromatography-mass spectrometry. Gas chromatography-olfactometry, modified detection frequency, odor activity value, and p-values demonstrated that ten aroma-active compounds, including phenylethyl alcohol, geranyl alcohol, and linalool, that were more significantly altered by oxygen were the key compounds contributing to the differences in the aroma of KBT, and their aroma contributions were confirmed by subsequent aroma addition experiments. Additionally, the role of oxygen in the formation of key compounds was further investigated. The results revealed that oxygen-enriched fermentation significantly increased the total concentration of volatile compounds and yielded stronger sweet and fruity aromas, whereas low-oxygen fermentation resulted in weak and single aromas. This study provides new insights into the effect of oxygen on the volatile compounds of KBT and provides theoretical support for the production of high-flavor KBT.

Substance basis and fermentation mechanism study of the analgesic and anti-inflammatory effects of Tibetan medicine Wuwei Ganlu based on JiuQu fermentation

ETHNOPHARMACOLOGICAL RELEVANCE

Wuwei Ganlu, as an integral part of the Tibetan medical system known as "Sowa Rigpa" originates from the formulations documented in the "Four Tantras". It is recognized by UNESCO as an intangible cultural heritage, representing a body of traditional knowledge and practice. Fermentation, a crucial step in the preparation of Wuwei Ganlu, has not been fully understood in terms of its mechanisms and its impact on the material basis and pharmacological efficacy of the medicine.

AIM OF THE STUDY

By investigating the effects of fermentation on the chemical components and pharmacological activities of Tibetan medicine Wuwei Ganlu, this study aims to reveal the scientific basis for the enhanced efficacy induced by fermentation.

MATERIALS AND METHODS

An analgesic and anti-inflammatory animal model was employed to investigate the effects of Tibetan medicine Wuwei Ganlu at different fermentation stages (from 0 to 5 days) on the number of twisting and serum IL-6 levels in mice, aiming to explore the influence of fermentation on the potentiation of its analgesic and anti-inflammatory effects. Based on this, a systematic analysis of the substance basis of Wuwei Ganlu before and after fermentation was conducted using UPLC-Q-Exactive Orbitrap MS and HPLC-MS/MS methods, identifying key differences in the substance composition and determining the indicative components. Additionally, fungal community changes before and after fermentation were studied using ITS rRNA sequencing, which revealed the differences in the fungal community. The integrity of the plant cell walls in Wuwei Ganlu before and after fermentation was examined under a microscope, and the effects of fermentation on the plant cell walls and cellulase activity were assessed by measuring the enzyme activity during the fermentation process. Finally, the fermentation mechanism of Wuwei Ganlu was further corroborated by studying the changes in content and transformation patterns of specific components, including Rutin, Quercitrin, Hyperoside, Quercetin, and Ephedrine, under the same fermentation conditions.

RESULTS

The analgesic and anti-inflammatory experiments indicated that fermentation significantly enhanced the analgesic and anti-inflammatory effects of Tibetan medicine Wuwei Ganlu, as evidenced by a marked reduction in the number of twisting and IL-6 levels (P < 0.05). Fermentation caused significant changes in the Chemical Compotents of Wuwei Ganlu, increasing the levels of Ephedrine (19.69%), Rutin (16.71%), Quercitrin (21.54%), Quercetin (132.54%), and Hyperoside (110.16%). Fungal community analysis revealed that Saccharomycetaceae was the dominant fungal genus during fermentation, with its abundance significantly increasing after fermentation, while Aspergillus showed relatively low abundance on day 3 of fermentation. The cellulase produced by Saccharomycetaceae promoted the hydrolysis of the plant cell walls. Microscopic observation demonstrated that fermentation led to plant cell walls rupture and fiber structure transparency in the raw materials, which enhanced cellulase activity between days 1 and 3, promoting the release of Ephedrine, Rutin, Quercitrin, Quercetin, and Hyperoside. Under the catalytic action of JiuQu fermentation starter, Rutin, Quercitrin, and Hyperoside were hydrolyzed into Quercetin, while Ephedrine was transformed into Methylephedrone and Cathinone, confirming the fermentation-induced transformation pathways of these compotents. The heatmap of the correlation between chemical components, microbial community, and pharmacological indicators showed that the abundance of Saccharomycetaceae in the fermented samples was significantly correlated with the Twisting inhibition rate and IL-6 levels in mice, as well as Ephedrine and Quercetin, suggesting that Ephedrine and Quercetin may have potential analgesic and anti-inflammatory effects.

CONCLUSION

The fermentation process significantly enhances the analgesic and anti-inflammatory effects, primarily due to the chemical components changes in Tibetan medicine Wuwei Ganlu induced by fermentation. Fermentation regulates the abundance of dominant microbial communities, particularly Saccharomycetaceae species, and enhances cellulase activity. This enhances the breakdown of plant cell walls, promoting the release of chemical components. Additionally, fermentation facilitates the conversion of glycosides (water-soluble) into aglycones (lipid-soluble), such as the hydrolysis of Rutin, Hyperoside, and hypericin into Quercetin. In summary, the fermentation mechanism of Wuwei Ganlu involves an increase in Saccharomycetaceae abundance and enhanced cellulase activity under the influence of JiuQu fermentation, leading to plant cell walls breakdown and the subsequent release of chemical components. Moreover, the conversion of glycosides to lipid-soluble aglycones during fermentation enhances transdermal absorption, which may also contribute to the potentiation of its effects.

Effects of Different Kinds of Fruit Juice on Flavor Quality and Hypoglycemic Activity of Black Tea

At present, the heavy bitter taste, poor flavor quality and low functional activity of summer and autumn tea are the bottleneck problems restricting the low utilization rate of summer and autumn tea resources. The research and development of new products of fruit-flavored black tea is conducive to expanding the utilization of summer and autumn tea resources. Different kinds of fruit juice were added during the fermentation and processing of classic black tea, such as bananas, apples, fragrant pear and Sydney pear, in this study. The effects of fruit juice on the flavor quality and amylase inhibitory activity of fruity black tea were researched. The sensory quality, flavor chemicals and α-amylase inhibitory activity were evaluated. The results showed that the sensory evaluation scores of black tea treated with fruit juice were significantly higher than those of black tea treated without fruit juice, especially the crown pear juice. The amylase inhibition rate of black tea treated with fruit juice was significantly higher than the control treated without fruit juice (p < 0.05). The sensory evaluation scores, polyphenol oxidase activity, water extract content, soluble sugar content, free amino acid content, theaflavin content, thearubigin content and inhibition rate of amylase activity of black tea treated with pear juice were significantly higher than those of the apple and banana juices (p < 0.05), especially crown pear juice. Tea polyphenol content and theaflavin content of black tea treated with added pear juice were significantly lower (p < 0.05) than the black tea control treated with added apple juice and banana juice, especially crown pear juice. The fruity black tea treated with crown pear juice had a redder broth, more pronounced sweet fruit aroma, sweet and mellow taste and reduced astringency. Therefore, the black tea treated with crown pear juice was preferred. The research hopes to provide a theoretical basis for the research of black tea quality control and the research of summer and autumn tea resources utilization technology.

HS-SPME-GC-MS combined with relative odor activity value identify the key aroma components of flowery and fruity aroma in different types of GABA tea

Anaerobic processing is a crucial factor influencing the formation of flavor quality in Gamma-aminobutyric acid (GABA) tea. In this study, headspace solid-phase microextraction combined with gas chromatography and mass spectrometry was employed to explore the flavor characteristics of different types of GABA tea. We utilized multivariate analyses to identify at least 146 volatile components (VOCs) across 12 functional groups in the GABA tea samples via principal component analysis (PCA). At least 40 differential VOCs were screened from the GABA tea samples via orthogonal partial least squares-discriminant analysis. Subsequently, a minimum of four VOCs were identified in the GABA tea samples via the Pearson correlation coefficient combined with relative odor activity values as potential markers for flowery and fruity aromas, clarifying the impact of the VOCs on these characteristics. The results of this study provide a theoretical basis for understanding the formation of flowery and fruity flavor characteristics in GABA tea.

Effect of fermentation temperature on the non-volatile components and in vitro hypoglycemic activity of Jinxuan black tea

Fermentation significantly influences the chemical composition of black tea, yet the effects of different fermentation temperatures on non-volatile components and their in vitro hypoglycemic activity are insufficiently studied. This research investigates how varying temperatures (20, 25, and 30°C) affect the bioactive profile and the inhibitory activity of Jinxuan black tea against α-glucosidase and α-amylase. Our results show that lower fermentation temperatures (20°C) lead to elevated levels of key bioactive compounds, including tea polyphenols (9.24%), soluble sugars (8.24%), thearubigins (7.17%), and theasinesin A (0.15%). These compounds correlate strongly with enhanced α-glucosidase inhibition (R = 0.76-0.97). Non-targeted metabolomic analysis revealed that 36 differential metabolites, including catechins, exhibited altered levels with increasing fermentation temperature. Notably, tea fermented at 20°C exhibited superior hypoglycemic activity, with α-glucosidase inhibition (IC50 = 14.00 ± 1.00 μg/ml) significantly outperforming α-amylase inhibition (IC50 = 2.48 ± 0.28 mg/ml). The findings of this research underscore the importance of fermentation temperature in optimizing the bioactive profile of black tea. It is proposed that recommendations for future processing or formulation should emphasize the use of lower fermentation temperatures, aimed at augmenting the health benefits linked to higher polyphenol content and stronger hypoglycemic activity.

Recent Advances Regarding Polyphenol Oxidase in Camellia sinensis: Extraction, Purification, Characterization, and Application

Polyphenol oxidase (PPO) is an important metalloenzyme in the tea plant (Camellia sinensis). However, there has recently been a lack of comprehensive reviews on Camellia sinensis PPO. In this study, the methods for extracting PPO from Camellia sinensis, including acetone extraction, buffer extraction, and surfactant extraction, are compared in detail. The main purification methods for Camellia sinensis PPO, such as ammonium sulfate precipitation, three-phase partitioning, dialysis, ultrafiltration, ion exchange chromatography, gel filtration chromatography, and affinity chromatography, are summarized. PPOs from different sources of tea plants are characterized and systematically compared in terms of optimal pH, optimal temperature, molecular weight, substrate specificity, and activators and inhibitors. In addition, the applications of PPO in tea processing and the in vitro synthesis of theaflavins are outlined. In this review, detailed research regarding the extraction, purification, properties, and application of Camellia sinensis PPO is summarized to provide a reference for further research on PPO.

Effects of Pulsed Electric Field Pretreatment on Black Tea Processing and Its Impact on Cold-Brewed Tea

This study applied pulsed electric fields (PEFs) to accelerate the withering and drying processes during cold-brewed black tea production. PEF pretreatment was administered at 1.0, 1.5, and 2.0 kV/cm electric field strengths, combined with varying withering times from 8 to 12 hr. During the 12-hour withering process, the redness value (a*) and total color change (∆E) of PEF-treated leaves significantly increased (p < 0.05). Furthermore, the homogenous redness of tea leaves during fermentation depended on the PEF strength applied. In addition, PEF pretreatment remarkably reduced the drying time, up to a 50% reduction at a 2.0 kV/cm field strength. Additionally, the 2.0 kV/cm PEF-pretreated black tea exhibited a notable 42% increase in theaflavin (TF) content and a 54% increase in thearubigin (TR) content. Sensory evaluation scores were highest for black tea that received PEF pretreatment at 2.0 kV/cm. These findings highlight the significant potential of PEFs in enhancing the efficiency of withering and drying processes while positively impacting the physicochemical and sensory properties of cold-brewed black tea.