Tea Fermentation Process Research Articles

Processing of oolong tea from passion fruit buds of Passiflora edulis

The research aimed to create oolong tea products from passion fruit buds, diversifying this product line and improving the usage value of this bioactive material. The tea fermentation process was conducted at a temperature of 25 ± 2°C for 4 h, while the semi-drying and final-drying were performed at 50 ± 2°C for 4 h and 90 ± 2°C for 4 h, respectively. Tea product had a moisture content of 5.45%, a reducing sugar content of 1.21 mg/g, and a total polyphenol content of 22.38 mg/g. Tea was brewed at a tea to water ratio of 2.5% for 3 min at 95°C. In sensory evaluations of the brewed tea, color scored 4.93, clarity scored 3.91, smell scored 4.81, and taste scored 4.89. Thus, the product was graded as “good” according to TCVN 12713:2019.

IMPROVEMENT OF TRADITIONAL BALINESE "ONG" TEA-MAKING PROCESS TO EXTEND SHELF LIFE TO SUPPORT ECOTOURISM IN BANJAR LANTANGIDUNG, GIANYAR, BALI

“Ong” tea contains vitamins B1, B2, B6, B12, folic acid, and vitamin C, in addition to several essential amino acids, organic acids, minerals, vitamins, amino acids, and active polyphenol compounds, and various important enzymes that have many benefits for the body. “Ong” tea is a type of probiotic drink produced from the tea fermentation process. The bacteria contained in SCOBY (Symbiotic Consortium of Bacteria and Yeast) are Acetobacter xylinum bacteria. The purpose of implementing the activities proposed in the training to improve the process of making “Ong” tea through PKM activities is to ensure that the people of Br. Lantangidung, Batuan, Sukawati have the skills and insight to manage local natural resources and have an entrepreneurial spirit so that they can open up business opportunities related to the conditions of the Batuan Village area. Improving product quality, expanding marketing reach, and using more hygienic and modern packaging techniques are also important. Thus, it is hoped that Balinese “ong” tea can become a superior product that can improve the community's economy and support the development of ecotourism in Banjar Lantangidung

Comparison Of Functional Groups in Green Tea Kombucha (Camellia sinensis) and Lavender Flower Kombucha (Lavandula angustifolia L) Using Fourier Transform Infrared Spectroscopy (FTIR)

Kombucha is a fermented beverage produced through the fermentation process of tea and sugar by SCOBY (Symbiotic Culture of Bacteria and Yeast). Kombucha can be produced from various raw materials such as green tea (Camellia sinensis) and lavender (Lavandula angustifolia L.), which have different chemical compositions. The aim of this study is to compare the functional groups of green tea kombucha and lavender kombucha. The method used is Fourier Transform Infrared Spectroscopy (FTIR). The results of this study indicate that both green tea kombucha and lavender kombucha show the presence of phenolic and flavonoid compounds. Additionally, both have the same functional groups, namely O-H (alcohol), C=C (alkena), and C≡C (alkuna). The FTIR results of lavender kombucha also show the presence of C-H (alkana) groups, indicating the presence of nonpolar compounds such as terpenoids and steroids.

Multienzyme-like MnO2@Ag aerogel as SERS/colorimetric sensing platform for the fermentation process of tea and assess the total antioxidant capacity

The unique feature of tea fermentation is the oxidation of polyphenols, which contributes to the distinct total antioxidant capacity (TAC) of different teas. In this study, we designed and synthesized a MnO2@Ag nanosheet aerogel with diverse enzyme-like activity. It exhibits an intrinsic laccase-like activity, capable of effectively oxidizing catechins to mimic the tea fermentation process, thereby generating quinone-type oxidation products (oxCC). Additionally, the MnO2@Ag aerogel exhibits surface-enhanced Raman scattering (SERS) activity, which allows for the sensitive detection of epigallocatechin gallate (EGCG) down to 1 µM. By utilizing the EGCG-induced MnO2@Ag aerogel, we have established an EGCG-TAC sensing platform to evaluate the TAC of various teas. The results indicate that the TAC of green tea > oolong tea > black tea > Pu'er tea, with Xinyang Maojian exhibiting the strongest TAC in green tea, reaching 889 µM EGCG.

THE STATE OF PLAY: SYMBIOTIC CULTURE OF BACTERIA AND YEASTS (SCOBY) IN TEXTILE INDUSTRY

The fermentation of Kombucha tea produces SCOBY, or Symbiotic Culture of Bacteria and Yeast, as a result of the interaction between bacteria and yeast. In order to fully explore the potential of employing this cellulose as a viable raw material in many applications of industry, numerous studies on the Kombucha SCOBY are now being done. According to studies, Zygosaccharomyces and Acetobacter xylinum are the most frequent bacteria found throughout the SCOBY fermentation process. At the air-liquid interface, these microorganisms help produce cellulose fibrils extracellularly, resulting in a biofilm. An overview of the favourable conditions for SCOBY manufacture is provided in more specific, as well as the aspects that may influence the product, and its suitability for textile and fashion sector applications is appraised. The advantages of this biofilm are being explored, including in several industries especially in textile and fashion industry. The microbial consortium's tea fermentation process was able to demonstrate an increase in specific biological activities that had previously been researched. However, there are some limitations in the applications of SCOBY in the textile that need to be highlighted. Thus, this review focuses on the SCOBY properties, challenges and potential available to make it feasible in textile industries.

Study on the Trend in Microbial Changes during the Fermentation of Black Tea and Its Effect on the Quality.

The role of tea endophytes in black tea fermentation and their impact on black tea quality remain unclear. We collected fresh leaves of Bixiangzao and Mingfeng tea and processed them into black tea, while testing the biochemical composition of both the fresh leaves and the black tea. We also used high-throughput techniques, such as 16S rRNA, to analyze the dynamic changes in the microbial community structure and function during black tea processing in order to investigate the influence of dominant microorganisms on the quality of black tea formation. Our results showed that bacteria, such as Chryseobacterium and Sphingomonas, and Pleosporales fungi dominated the entire black tea fermentation process. Predicted functional analysis of the bacterial community indicated that glycolysis-related enzymes, pyruvate dehydrogenase, and tricarboxylic acid cycle-related enzymes were significantly elevated during the fermentation stage. Amino acids, soluble sugars, and tea pigment content also increased considerably during fermentation. Pearson's correlation analysis revealed that the relative bacterial abundance was closely related to the content of tea polyphenols and catechins. This study provides new insights into the changes in microbial communities during the fermentation of black tea and demonstrates understanding of the basic functional microorganisms involved in black tea processing.

Hands on Biofilm! Utilizing a public audience in a citizen science project to assess yield variability when culturing kombucha pellicle.

The pellicle biofilm generated during the Kombucha tea fermentation process has, when dried, textile-like properties that may have real-life applications. However, pellicle yield can vary depending on inoculation and incubation conditions, which affects research investigations on the properties of the pellicle. To generate data on variability to help define optimum pellicle growth conditions, as part of a public engagement event about biofilm, a citizen science activity was hosted whereby visitors to a science festival were invited to select incubation conditions and inoculate different media with liquid or solid (pellicle). More than 220 samples were inoculated (in excess of 1200 visitors, mainly in family groups). The most popular incubation conditions were coconut water or tea medium, 30°C/room temperature and liquid inoculum. The most productive/reproducible in terms of yield and variability were tea medium, 30°C, and liquid inoculum, which reflect some of the conditions most used in the domestic setting for kombucha culture. The event provided both useful research data and generated public interest in a research area of which many will have been unaware. Interest in the results of the activity, available several weeks after the activity, was sustained using email contact and FlickR for the dissemination of images and data.

Analysis of D-amino acid in Japanese post-fermented tea, Ishizuchi-kurocha.

The D-amino acid content of Ishizuchi-kurocha, a post-fermented tea produced in Ehime, Japan, was measured. Ishizuchi-kurocha mainly contains D-glutamic acid and D-alanine, but it also contains a small amount of D-aspartic acid. Two types of lactic acid bacteria, Lactiplantibacillus plantarum and Levilactobacillus brevis, are the main species involved in lactic acid fermentation during the tea fermentation process. Therefore, the D-amino acid-producing abilities of strains of these two species isolated from Ishizuchi-kurocha were examined. Specifically, the production of D-aspartic acid, D-alanine, and D-glutamic acid by L. brevis and L. plantarum strains was observed. The amount of D-aspartic acid produced by L. plantarum was low. D-glutamine was detected in culture supernatant but not in bacterial cells. D-arginine was detected in bacterial cells of the L. plantarum strains but not in the culture supernatant. Both the L. brevis and L. plantarum strains possessed at least three kinds of putative racemase genes: alanine racemase, glutamate racemase, and aspartate racemase. However, their expression and enzyme activity remain unknown. L. plantarum and L. brevis could play an important role in the production of D-amino acids in Ishizuchi-kurocha. In fact, Ishizuchi-kurocha is expected to possess the effective physiological activities of D-amino acids.

Metabolic improvements of novel microbial fermentation on black tea by Eurotium cristatum.

Due to its traditional fermentation, there are obvious limits on the quality improvements in black tea. However, microbial fermentation can provide an abundance of metabolites and improve the flavor of tea. The "golden flower" fungi are widely used in the microbial fermentation of tea and has unique uses in healthcare. To further explore the improvements in black tea quality achieved via microbial fermentation, we used widely targeted metabolomics and metagenomics analyses to investigate the changes in and effects of metabolites and other microorganisms during the interaction between the "golden flower" fungi and black tea. Five key flavor metabolites were detected, the levels of catechin, epigallocatechin gallate, (-)-epicatechin gallate were decreased by different degrees after the inoculation of the "golden flower" fungus, whereas the levels of caffeine and (+)-gallocatechin increased. Botryosphaeriaceae, Botryosphaeriales, Dothideomycetes, Aspergillaceae, Trichocomaceae, and Lecanoromycetes play a positive role in the black tea fermentation process after inoculation with the "golden flower" fungi. D-Ribose can prevent hypoxia-induced apoptosis in cardiac cells, and it shows a strong correlation with Botryosphaeriaceae and Botryosphaeriales. The interaction between microorganisms and metabolites is manifested in tryptophan metabolism, starch and sucrose metabolism, and amino sugar and nucleotide sugar metabolism. In conclusion, the changes in metabolites observed during the fermentation of black tea by "golden flower" fungi are beneficial to human health. This conclusion extends the knowledge of the interaction between the "golden flower" fungi and black tea, and it provides important information for improving the quality of black tea.

Development of a new type of Anhua black tea and its application: Black tea wine

Anhua black tea is widely consumed in China. Traditional Anhua black tea is fermented by Eurotium cristatum. In this study, Monascus and E. cristatum were used during the fermentation process to develop a new type of black tea prepared using 10 g black tea, 6 ml E. cristatum suspension, and 4 ml Monascus suspension, with fermentation at 28°C for 4 days. This new type of Anhua black tea contained more probiotics from Monascus and E. cristatum than the traditional. Furthermore, we used this new black tea to develop wine using ultrasonic methods. The best extraction process for this product was with a solid–liquid ratio of 1.6%, ultrasonic time of 120 min, ultrasonic power of 300 W, and ultrasonic temperature of 50°C. Wine products made using new black tea contained several active substances, such as lovastatin, caffeine, and other several flavor components, resulting in improved taste and health-promoting effects. Novelty Impact Statement Monascus and Eurotium cristatum were used during the Anhua black tea fermentation process to produce a new type of tea, which was developed into a rice-flavored black tea wine product. The new type of Anhua black tea and black tea wine product, produced using technology involving cooperative fermentation of two probiotics, showed better performance than traditional products.

High-sensitivity hyperspectral coupled self-assembled nanoporphyrin sensor for monitoring black tea fermentation

The rapid and scientific method for monitoring the quality of black tea fermentation is of great significance to the quality control of black tea production. This study proposed a novel method for evaluating the fermentation quality of black tea by using hyperspectral imaging technology with self-assembled nanoporphyrin (N-TPP) dyes, which were used as aroma capture probes in the black tea fermentation process. Scanning electron microscopy and ultraviolet–visible spectroscopy were performed to characterize the N-TPP. Then, the results of the colorimetric sensor array (conventional camera color method) and the proposed hyperspectral methods were compared. Finally, the hyperspectral information of N-TPP with higher sensitivity was collected, and the qualitative models of evaluating black tea fermentation quality were established using support vector machine (SVM), extreme learning machine, and linear discriminant analysis. Among these models, the SVM model exhibited the highest discriminant accuracy. The accuracy of the SVM model based on the hyperspectral information of the self-assembled N-TPP array was 98.85 %, which was considerably higher than that (68.97 %) of the SVM model based on the color information of the porphyrin array. The results revealed that the proposed method can effectively improve the monitoring accuracy of black tea fermentation quality.

Fermentation quality evaluation of tea by estimating total catechins and theanine using near-infrared spectroscopy

Concentrations of total catechins and theanine are important indices for monitoring the degree of fermentation, a key factor in determining the types, qualities, and taste characteristics of tea, during manufacturing process. Until now, there has not been any near-infrared (NIR) study applying theanine as an index for monitoring the degree of fermentation of tea. It is necessary to understand and monitor the degree of fermentation according to the concentrations of total catechins and theanine in tea by using NIR spectroscopy, especially for manufacturers of tea products. NIR spectroscopy integrated with modified partial least-squares regression (MPLSR) method was used for spectral analysis of total catechins and theanine in 161 tea samples in the full visible NIR wavelength range of 400−2498 nm (25000−4003 cm−1). Both the optimal calibration models of total catechins and theanine built by MPLSR showed satisfactory predictability, with coefficient of determination of calibration (Rc2) and residual predictive deviation (RPD) up to 0.94 and 3.38, respectively. High total accuracy rates of 100 % were also achieved for the discrimination of green tea, partially fermented tea, and black tea in the validation sets by the optimal MPLSR calibration model of theanine. The results indicated that NIR spectroscopy has the potential to be adopted as an effective method of rapid and accurate inspection of the degree of fermentation of tea. This technique could contribute substantially to quality assurance during fermentation process of tea.

Bioconversion of Flavonoid Glycosides from Hippophae rhamnoides Leaves into Flavonoid Aglycones by Eurotium amstelodami.

The flowering process has been reported to play crucial roles in improving the flavor and efficacy of fermented tea. Hippophae rhamnoides leaves containing many beneficial ingredients are a suitable plant source for tea processing. In this study, we isolated a β-glucosidase-producing fungus Eurotium amstelodami BSX001 from the fermented tea and used Hippophae rhamnoides leaves (HRL) as a substrate to explore the detailed process of bioconversion of some important functional factors. The results show that the contents of total phenolic compounds and flavonoids increased significantly after seven days, especially flavonoid aglycones (e.g., quercetin, kaempferol, and isorhamnetin). Such compounds greatly enhance the antioxidative activity of fermented products. Metabolic analysis of the standard compounds (rutin, quercetin-3-glucoside, kaempferol-3-glucoside, quercetin, isorhamnetin-3-glucoside, isorhamnetin, and kaempferol) further confirmed the effective biotransformation by E. amstelodami. Mechanisms of the bioconversion could be involved in deglycosylation, dihydroxylation, and O-methylation. Our findings expand the understanding of tea fermentation process and provide further guidance for the fermented tea industry.

Shifts in diversity and function of the bacterial community during the manufacture of Fu brick tea

To better understand the effects of bacteria on the characteristics of Fu brick tea, we investigated bacterial community structure as well as the predicted functions of identified bacteria and their correlations with chemical compounds during the manufacturing process. Overall, Klebsiella species dominated during the initial stage of processing, but were quickly replaced by Pseudomonas, Lactococcus, Stenotrophomonas, Enterococcus, and Bacillus species, which remained stable until the end of the manufacturing process. Network analysis identified 11 bacterial genera as keystone taxa, which contributed to the stabilization of the microbial community in the co-occurrence network. Bacterial taxa were grouped into eight modules, with the dominant genera mainly distributed amongst modules I and Ⅵ, which were involved in metabolism of carbon and flavor compounds in the Fu brick tea ecosystem. Using bidirectional orthogonal partial least squares analysis, 19 bacterial genera were identified as core functional genera linked to the metabolism of chemical compounds during the manufacturing process, while three genera, namely Klebsiella, Lactococcus, and Bacillus, also dominated the Fu brick tea fermentation process. These findings provide new insights into Fu Brick tea bacterial community variation and increased our understanding of the core functional bacterial genera involved in the manufacture of Fu brick tea.

A new approach to automation of black tea fermentation process with electronic nose

ABSTRACTManufacturing of black tea is a complex process consisting of plucking, withering, curling, fermenting, drying, determining of quality, and packaging stages. Nowadays, tea quality is determined by two methods. Either chemical analysis method is used or tea tasters give quality scores by tasting, smelling, and visual inspection. By means of recent studies, tea quality can also be determined by electronic nose technology. The quality of tea is generally related with the fermentation stage. In this work, an electronic nose, which determines the quality of tea during the fermentation process in real time from only its odour, was made, and the fermentation band was controlled by this electronic nose. Fermentation bands of a tea factory in the Çayeli District of Rize, Turkey have been simulated and controlled via LabVIEW simulation software by using real odour values measured in the factory with the electronic nose. In the study, a new fermentation band system has been designed to function with the electronic nose. This section of the study has been performed in the simulation environment due to the high cost of physical system setup. With the method proposed in this study, tea factories will be able to increase their production capacity with higher quality.

Rapid determination by near infrared spectroscopy of theaflavins-to-thearubigins ratio during Congou black tea fermentation process

The theaflavin-to-thearubigin ratio (TF/TR) is an important parameter for evaluating the degree of fermentation and quality characteristics of Congou black tea. Near infrared (NIR) spectroscopy, one of the most promising techniques for evaluating large-scale tea processing quality, in association with chemometrics, can be used as a selection tool when a fast determination of the requested parameters is required. The aim of this work is to develop a unique model for the determination of TF/TR. First, 11 key wavelength variables were screened by synergy interval partial least-squares regression (SI-PLS) and competitive adaptive reweighted sampling (CARS). Based on these characteristic variables, a new extreme learning machine (ELM) combined with an adaptive boosting (ADABOOST) algorithm (ELM-ADABOOST) was applied to construct the nonlinear prediction model for TF/TR, and an independent external set was used for the validation. A determinate coefficient (Rp2) of 0.893, root mean square error of prediction (RMSEP) of 0.0044, RSD below 10%, and RPD above 3 were acquired in the prediction model. These results demonstrate that NIR can be used to rapidly determine the TF/TR value during fermentation, and it effectively simplify the model and improve the prediction accuracy when combined with the SI-CARS variable.

Understanding Kombucha Tea Fermentation: A Review.

Kombucha is a traditional fermented tea whose consumption has increased in the recent years due to its multiple functional properties such as anti-inflammatory potential and antioxidant activity. The microbiological composition of this beverage is quite complex and still more research is needed in order to fully understand its behavior. This study comprises the chemical and microbiological composition of the tea and the main factors that may affect its production.

Research on the effect of culture time on the kombucha tea beverage's antiradical capacity and sensory value.

Recent consumption trends shows high consumer acceptability and growing medicinal interest in the biological value of kombucha tea. This tea is a sweetened tea leaf brew fermented with a layer containing mainly acetic acid bacteria, yeast and lactic acid bacteria. The main antioxidants in tea leaves are polyphenols, the consumption of which is proven to be beneficial for human health, e.g. protecting from reactive oxygen species (ROS). The aim of the present research was to evaluate antiradical activity, total polyphenol content (TPC) and sensory value of kombucha tea brews. In the present study, Kombucha tea beverages were analyzed for TPC content, DPPH radical scavenging method and sensory value. The highest TPC content and DPPH radical scavenging capacity values were evaluated in yellow tea samples, both unfermented and kombucha, which did not differ within the storage time. The results of sensory evaluations of kombucha tea brews depend on the tea leaf variety used for preparing the drink. Research indicates that the fermentation process of tea brews with kombucha microbiota does not affect significantly its polyphenol content and antiradical capacity, and retains its components' biological activity.

Study of the dynamic changes in the non-volatile chemical constituents of black tea during fermentation processing by a non-targeted metabolomics approach

Fermentation is a critical manufacturing process to produce black tea, in which the chemical compositions are greatly changed. However, the dynamic changes of this sophisticated process are far from clear, and were often characterized by determining a small number of compounds. In this study, we applied a non-targeted metabolomics approach based on ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry to comprehensively profile the variations of metabolites in tea samples with various fermentation durations of 0, 1, 2, 4, 6, 8, 10, 12 and 14h. Principal component analysis indicated obvious stepwise alterations of tea metabolome during the fermentation. Relative quantitation of 61 identified metabolites including catechins, dimeric catechins, flavonol glycosides, amino acids, phenolic acids, alkaloids, and nucleosides revealed distinct changes of phenol pathway. Dynamic changes of a part of these compounds were mapped for the first time. To the best of our knowledge, this study offered the most comprehensive profiles of metabolite changes during the tea fermentation process.

Identification of novel homologous series of polyhydroxylated theasinensins and theanaphthoquinones in the SII fraction of black tea thearubigins using ESI/HPLC tandem mass spectrometry.

Thearubigins are the most abundant phenolic pigments found in black tea, produced by enzymatic oxidation of green tea flavan-3-ols in tea fermentation of until recently unknown composition. In this study electrospray ionization tandem LC-MS(n) experiments have been applied for the characterization of crude thearubigins isolated from black tea not exceeding 1000 Da. The aim of this study is to confirm the oxidative cascade hypothesis of tea fermentation. The data revealed the presence of two novel classes of compounds in thearubigin fractions. The first class of compounds revealed the presence of polyhydroxylated dimers of the theanaphthaquinone and theasinensin C structures, which were consistent with the polyhydroxylation hypothesis previously formulated. Furthermore, new classes of peroxo-/epoxy- compounds in the series of theasinensin A were identified, thus indicating the presence of H2O2 and its important contribution as a nucleophile in the tea fermentation process.