Brick Tea Research Articles

Multistarter fermentation of glutinous rice with Fu brick tea: Effects on microbial, chemical, and volatile compositions

A higher fermentation efficiency was achieved, using multistarter fermentation of glutinous rice supplemented with Fu brick tea (FGR-FBT), than when using traditional fermentation. The effects of multistarter fermentation on the microbial, chemical, and volatile compositions were determined. When FBT was incorporated during glutinous rice fermentation, increased population of yeasts and fungi, as well as enhanced α-amylase, proteinase and β-glucosidase activities, were observed. Specific fungi were isolated and identified as Aspergillus spp., which are known to secrete extracellular enzymes that modify the chemical properties, including ethanol levels, pH, total acids, and total soluble solids. The aroma profile of fermented glutinous rice was studied in the absence and presence of FBT, using HS-SPME-GC-MS and the electronic-nose. This analysis indicated that 35 characteristic volatile compounds were only found in FGR-FBT. The results show that FBT can be added during the fermentation of food products to enhance microbial biotransformation and modify flavour metabolism.

Fuzhuan Brick Tea Attenuates High-Fat Diet-Induced Obesity and Associated Metabolic Disorders by Shaping Gut Microbiota.

An increasing amount of evidence suggests that the metabolic improvement of high-fat diet (HFD)-induced obese mice by Fuzhuan brick tea (FBT) is associated with gut microbiota. However, the causalities between FBT and gut microbiota have not yet been elucidated and the underlying mechanisms of action remain unclear. To impart direct evidence for the essential role of gut microbiota in the attenuation of obesity by FBT, the effects of FBT on healthy mice and microbiota-depleted mice that were treated with antibiotics were compared in an HFD-induced obesity mouse model. The results showed that FBT dramatically ameliorated obesity, serum lipid parameters, blood glucose homeostasis, hepatic steatosis, adipocyte hypertrophy, and tissue inflammation. However, the microbiota-depleted mice with single bacterium (Escherichia-Shigella) after antibiotic treatment were resistant to FBT-induced antiobesity and metabolic improvement. The beneficial effects of FBT resulted from its shift on gut microbiota composition and structure in mice. HFD-induced increase in the phyla Firmicutes/Bacteroidetes (F/B) ratio was remarkably restored by FBT. Furthermore, FBT-induced increase in abundances of beneficial bacteria Clostridiaceae, Bacteroidales, and Lachnospiraceae and decreases in harmful Ruminococcaceae, Peptococcaceae, Peptostreptococcaceae, and Erysipelotrichaceae were causal antecedents for FBT to reduce obesity and improve metabolic disorders.

Energy-saving operation strategy of air conditioning system in tea brick fermentation room under different outdoor meteorological parameters

In the process of tea brick production, the major energy consumption lies in the air-conditioning system of the tea fermentation chamber. Under the condition of satisfying the fermentation process, the energy-saving operation of the air-conditioning system is an effective method to reduce the energy consumption and to improve the economic benefit of the tea brick. However, due to lack of quantitative calculation of the indoor heat and moisture load during the fermentation process, the air conditioning system of the tea brick fermentation chamber is mainly based on the CAS (circulating air system) or the ORCS (One return air conditioning system). Consequently, in this study, the heat and moisture transfer model of the tea brick was built based on the heat and moisture coupling transfer theory for porous media. The COMSOL Multiphysics was implemented to solve the heat and moisture exchange rate between tea bricks and the fermentation environment. Based on the rate and the heat transfer of the envelope structure, the heat and moisture load of the fermentation chamber was calculated under different meteorological parameters. According to the indoor heat and moisture load and outdoor weather parameters, the energy consumption and exergy loss of the two air conditioning systems were analyzed during the fermentation cycle. The results show that the ORCS energy efficiency is 30.8%–55.8% greater than that of the CAS, and the irreversible exergy loss is also reduced by 19.6%–57.0% when the residual heat Q inside the fermentation chamber is less than zero. On the other hand, when the residual heat Q is greater than zero, the CAS energy efficiency is 16.1%–22.3% greater than that of the ORCS, and the exergy loss is reduced by 37.8%–43.3%. According to the energy and exergy analyses of the two air-conditioning systems, an energy-saving operation strategies of air conditioning system for brick fermentation were determined in different tea brick production areas.

The biochemical characteristics of a novel fermented loose tea by Eurotium cristatum (MF800948) and its hypolipidemic activity in a zebrafish model

Fuzhuan brick tea is a distinctive Chinese dark tea for its significant health benefits and unique quality characteristics by a unique fungal fermentation stage, in which Eurotium cristatum strains play a crucial role in the post-fermentation process. In this study, the biochemical characteristics and lipid-lowing activity of E. cristatum (MF800948)-fermented loose tea (FT) were investigated. The results showed that total phenolics, flavonoids, catechins and free amino acids were decreased after fermentation, while three purine alkaloids, soluble carbohydrates and theabrownins were significantly increased compared to green tea. In addition, d-limonene (27.71%) and β-myrcene (11.55%) were the predominant volatiles in FT, giving the characteristic fruity and balsamic scent to the fermented loose tea. Correspondingly, the aqueous extract of FT showed potent lipid-lowering activity in a high-fat zebrafish model and the optimum effective concentration was 500 μg/mL, at which the lipid level declined to 51.49% compared to control group. Hence, it was suggested that loose tea fermented by E. cristatum (MF800948) could provide valuable insights for developing a high-quality and hypolipidemic dark tea.

Purified fraction of polysaccharides from Fuzhuan brick tea modulates the composition and metabolism of gut microbiota in anaerobic fermentation in vitro

One purified fraction from crude Fuzhuan brick tea polysaccharides (FBTPS), FBTPS-3, was obtained through column chromatography of DEAE Sepharose Fast Flow. The chemical properties and probiotic effects of FBTPS-3 were evaluated by fermentation in vitro. Moreover, the effects of FBTPS-3 on the function and metabolic pathway of gut microbiota were investigated by metagenomic sequencing. The results showed that FBTPS-3 was an heteropolysaccharide with molecular weight of 741 kDa, which was mainly composed of Man, Rha, GalA, Gal and Ara in molar ratio of 8.7:15.5:42.2:19.7:13.9. The contents of carbohydrates and uronic acid in FBTPS-3 were 44.78 ± 2.85% and 40.4 ± 2.11%, respectively. After fermentation, the molecular weight of FBTPS-3 and content of carbohydrates were significantly decreased, indicating that FBTPS-3 could be utilized by gut microbiota. Furthermore, the relative abundances of Bacteroides, Megasphaera and Prevotella were significantly increased by FBTPS-3. FBTPS-3 also significantly promoted the production of acetic, propionic and n-butyric acids. Based on the metagenomic sequencing, it was found that FBTPS-3 significantly enriched the metabolic pathway of starch and sucrose. All the results suggest that FBTPS-3 is expected to be developed as functional ingredients or foods to improve the host health through regulating the gut microbiota and physiological metabolic functions.

Simulated digestion and fermentation in vitro by human gut microbiota of intra- and extra-cellular polysaccharides from Aspergillus cristatus

Fuzhuan brick tea is characterized in unique “golden flower” of Aspergillus cristatus. However, little information is available for intra- and extra-cellular polysaccharides from A. cristatus (IPS and EPS, respectively). Therefore, simulated digestion and fermentation in vitro were carried out to investigate whether IPS and EPS could be broken down in digestive system. Furthermore, their interactions with gut microbiota were investigated. It was found that IPS and EPS were utilized by gut microbiota to metabolize into short-chain fatty acids (SCFAs). The contents of total acids (SCFAs and lactic acid) in IPS and EPS groups increased to 39.30 ± 0.66 and 45.18 ± 1.68 mmol/L, respectively. IPS and EPS could obviously modulate the composition of gut microbiota. Thereinto, IPS could maintain the growth of OTU26 and OTU69 (Prevotella) and increase the relative levels of OTU30, OTU31, OTU35 and OTU56 (Bacteroides), whereas, EPS could maintain the growth of OTU26 and OTU48 (Prevotella) and increase the relative levels of OTU35, OTU56 and OTU63 (Bacteroides). OTU26, OTU61 and OTU69 (Prevotella) showed significantly positive correlations with propionic acid, OTU48 (Prevotella) and OTU56 (Bacteroides) showed significantly positive correlations with acetic acid. Hence, IPS and EPS could regulate the composition of gut microbiota, thereby promote production of SCFAs.

Comparison of different aroma-active compounds of Sichuan Dark brick tea (Camellia sinensis) and Sichuan Fuzhuan brick tea using gas chromatography–mass spectrometry (GC–MS) and aroma descriptive profile tests

Sichuan dark brick tea (Camellia sinensis) and Sichuan Fuzhuan brick tea have significantly different aroma characteristics although both of them have almost the same processing methods. Thus, these two types of tea were used as the research materials to determine the differences in their aroma compounds. The volatile compounds in the two types of tea were identified and quantified by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME–GC–MS), results showed that they both had 37 common volatile compounds. Then the aroma-active components were identified by odour activity value (OAV). It was found that SFBT had 20 aroma-active components, of which β-ionone had the largest OAV (199547.72). SDBT has 21 aroma-active ingredients (including all 20 aroma-active components of SFBT), of which β-ionone again has the largest OAV (114800.66). Finally, the aroma profile differences between the two tea samples were studied by aroma profile tests, and the results showed that the main aroma differences of SDBT and SFBT were caused by β-ionone, epoxydihydrolinalool II, methyl salicylate, geranylacetone, nerolidol, benzaldehyde, benzyl acetate, nonanal, trans,trans-2,4-heptadienal and 1-octen-3-ol, in addition, defined SFBT’s ‘fungi flower aroma’ and SDBT’s ‘aged fragrance’ from the level of aroma monomer.

Analysis of bacterial and fungal communities by Illumina MiSeq platforms and characterization of Aspergillus cristatus in Fuzhuan brick tea

Fuzhuan brick tea (FBT) is an indigenous dark tea fermented by fungal and bacterial communities, and the special favor of FBT attributes to the actions of microbiota, while the correlation between bacteria and fungi attracts little attention. In the present study, therefore, the compositions of microbial communities in 10 samples of FBT from four tea processing factories were evaluated by Illumina MiSeq sequencing. Bacterial taxonomy analysis revealed that the phylum Firmicutes and Proteobacteria were the predominant bacteria in all samples. Fungal taxonomy analysis revealed that the phylum Ascomycota, family Trichocomaceae, genus Aspergillus was the dominant fungus in all samples. Moreover, Aspergillus (OTU1, OTU2, OTU16, OTU30, OTU31 and OTU37), Wallemia (OTU3), Penicillium (OTU32), Candida (OTU33, OTU35, OTU40 and OTU43), Debaryomyces (OTU48) and Rhodotorula (OTU68) showed higher correlation with bacteria in FBT. Furthermore, a strain Aspergillus cristatus was isolated from FBT, and its morphology and molecular taxonomy were observed and analyzed by scanning electron microscopy and sequencing. Hence, this is the first report to reveal the correlation between bacterial and fungal communities in FBT, and A. cristatus may have potential application to improve the quality of FBT.

Isolation and Characterization of Benzaldehyde Derivatives with Anti-Inflammatory Activities from Eurotium cristatum, the Dominant Fungi Species in Fuzhuan Brick Tea

Eurotium cristatum is the dominant fungi species in Fuzhuan brick tea (FBT), which may be responsible for the color, taste, and associated health benefits. In this study, eight E. cristatum strains...

The Core Role of Bacillus subtilis and Aspergillus fumigatus in Pile-Fermentation Processing of Qingzhuan Brick Tea.

To identify the microorganisms responsible for the formation of the main quality components of Qingzhuan brick tea (QZBT) during solid-state fermentation (SSF), predominant thermoduric strains were isolated from the tea leaves collected during SSF. According to their capability of releasing cellulase, pectase, protease, and polyphenol oxidase, four strains were selected as starter cultures to ferment sun-dried tea leaves during artificially inoculated SSF. According to the major enzymatic activities and quality components content (tea polyphenols, catechins, amino acids, soluble sugar, and theabrownin), it was found that Aspergillus fumigatus M1 had a significant effect on the transformation of polyphenols and Bacillus subtilis X4 could enhance the ability of bioconversion of strain M1. Strain X4 and M1 may be the core microbes responsible for developing these biochemical components of QZBT, as the values of quality components of tea leaves fermented by these two strains for 6days was very close to that of the sample naturally fermented for 35days in the tea factory. The results could be significant in developing industrial starters for the manufacture of QZBT and stabilizing the product quality of different batches.

Online extraction–HPLC–FRAP system for direct identification of antioxidants from solid Du-zhong brick tea

Du-zhong brick tea (DBT), a new post-fermented functional tea, is marketed in China for its prevention of diseases from oxidative stress. However, antioxidant compounds in DBT are not clear. Here, a novel online extraction–HPLC–ferric reducing antioxidant power (OLE–HPLC–FRAP) has been developed to screen antioxidants in DBT. For OLE, guard column is packed with DBT (1.0 mg), then compounds are extracted directly by HPLC mobile phase for HPLC–FRAP analysis without sample pretreatment procedures. Eleven antioxidants have been screened and identified, three of which are detected in Du-zhong for the first time. Contributions of eleven antioxidant compounds to total antioxidant activity are evaluated using chlorogenic acid as antioxidant marker. Results indicate that the developed OLE–HPLC–FRAP system is a simple and powerful tool to analyze antioxidant compounds from solid complex mixtures, which also contribute to the enhancement of the value of DBT as a good functional tea.

Fu Brick Tea Alleviates Chronic Kidney Disease of Rats with High Fat Diet Consumption through Attenuating Insulin Resistance in Skeletal Muscle.

Fu brick tea is a unique post-fermented dark tea product which undergoes controlled fermentation by "golden flower" fungus Eurotium cristatum. This study examined the effects of Fu brick tea aqueous extract (FTE) to alleviate insulin resistance, chronic kidney disease (CKD), and its regulatory mechanism in high fat diet (HFD)-induced obese rats. Sixteen-week administration of FTE at 400 mg/kg bw in rats significantly antagonized HFD-induced insulin resistance and CKD with elevations in serum leptin, TC, TG, LDL-C, blood urea nitrogen, uric acid, and creatinine levels, respectively ( p < 0.05). FTE treatment decreased the glomerular area, the thickness of basement membrane of renal tubules, and kidney fibrosis in HFD-fed rats. FTE alleviated insulin resistance through down-regulation of SIRP-α expression and activation of the insulin signaling Akt/GLUT4, FoxO1, and mTOR/S6K1 pathways in skeletal muscle. Furthermore, FTE prevented the HFD-caused kidney dysfunction and lipid or collagen accumulation, which was accompanied by the inhibition of GSK-3β phosphorylation and the action of PI3K/Akt and nuclear accumulation of Nrf2 in kidney. These results indicated that FTE alleviated insulin resistance and CKD through modulating insulin signal transduction cascades in skeletal muscle and enhanced the Nrf2 expression in kidney.

Lexicon development and quantitative descriptive analysis of Hunan fuzhuan brick tea infusion

Twenty-seven representative Hunan fuzhuan brick teas were collected to develop a terminology lexicon and a quantitative descriptive analysis (QDA) method suitable for the sensory evaluation of Hunan fuzhuan brick tea infusion. Ten trained panelists developed a terminology lexicon comprised of eleven aroma and six taste attributes and evaluated the intensities of sensory attributes of each sample by conducting the QDA method. The QDA results showed that seventeen attributes listed in the final lexicon can be used to evaluate the quality of Hunan fuzhuan brick tea infusion properly, among which five aroma attributes, overall aroma, smoky, floral, fermented, and sweet (fruit), and one taste attribute, bitter, were the characteristic attributes to distinguish the differences in the sample qualities. Another panel made up of four professional cuppers evaluated samples by the cupping method to analyze the applicability and accuracy of the lexicon and the QDA method. The results showed that both the cupping method and QDA can be effectively used to evaluate Hunan fuzhuan brick tea quality, and their evaluation results showed high consistency and mutual complementation. This information will be beneficial for developing a sensory evaluation method and quality control for Hunan fuzhuan brick tea.

Increased Phenolic Content and Enhanced Antioxidant Activity in Fermented Glutinous Rice Supplemented with Fu Brick Tea.

Glutinous rice-based foods have a long history are consumed worldwide. They are also in great demand for the pursuit of novel sensory and natural health benefits. In this study, we developed a novel fermented glutinous rice product with the supplementation of Fu brick tea. Using in vitro antioxidant evaluation and phenolic compounds analysis, fermentation with Fu brick tea increased the total phenolic content and enhanced the antioxidant activity of glutinous rice, including scavenging of 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical, 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical, and hydroxyl radical, ferric-reducing antioxidant power, and ferric ion reducing power and iron chelating capability. Besides, compared with traditional fermented glutinous rice, this novel functional food exhibited a stronger activity for protecting DNA against hydroxyl radical-induced oxidation damage. Quantitative analysis by HPLC identified 14 compounds covering catechins and phenolic acids, which were considered to be positively related to the enhanced antioxidant capability. Furthermore, we found that 80% ethanol was a suitable extract solvent compared with water, because of its higher extraction efficiency and stronger functional activities. Our results suggested that this novel fermented glutinous rice could serve as a nutraceutical food/ingredient with special sensory and functional activities.

New Acylglycosides Flavones from Fuzhuan Brick Tea and Simulation Analysis of Their Bioactive Effects.

Four novel acylglycosides flavones (AGFs) including two quercetin acylglycosides and two kaempferol acylglycosides were isolated from Fuzhuan brick tea (FBT) as follows: quercetin 3-O-[α-l-rhamnopyranosyl (1→3)] [2-O’’-(E)-p-coumaroyl] [β-d-glucopyranosyl (1→3)-α-l-rhamnopyranosyl (1→6)]-β-d-galactoside was named as camelliquercetiside E (1), quercetin 3-O-[α-l-rhamnopyranosyl (1→3)] [2-O’’-(E)-p-coumaroyl] [α-l-rhamnopyranosyl (1→6)]-β-d-galactoside was named as camelliquercetiside F (2), kaempferol 3-O-[α-l-arabinopyranosyl (1→3)] [2-O’’-(E)-p-coumaroyl] [β-d-glucopyranosyl (1→3)-α-l-rhamnopyranosyl (1→6)]-β-d-glucoside was named as camellikaempferoside D (3), kaempferol 3-O-[α-l-arabinopyranosyl (1→3)] [2-O’’-(E)-p-coumaroyl] [α-l-rhamnopyranosyl (1→6)]-β-d-glucoside was named as camellikaempferoside E (4). Chemical structures of AGFs were identified by time-of-flight mass (TOF-MS) and NMR spectrometers (1H NMR, 13C NMR, 1H-1H COSY, HMBC and HSQC), and the MS2 fragmentation pathway of AGFs was further investigated. The inhibitory abilities of AGFs and their proposed metabolites on α-glucosidase and HMG-CoA reductase were analyzed by molecular docking simulation, and the results suggested that inhibitory activities of AGFs were significantly affected by acyl structure, number of glycosyl and conformation, and part of them had strong inhibitory activities on α-glucosidase and HMG-CoA reductase, suggesting that AGFs and their metabolites might be important ingredients that participate in the regulation of hypoglycemic and hypolipidemic effects. The results provided new AGFs and research directions for the practical study of FBT health functions in future.

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.

Consumption of post-fermented Jing-Wei Fuzhuan brick tea alleviates liver dysfunction and intestinal microbiota dysbiosis in high fructose diet-fed mice.

Emerging evidence supports the health-promoting ability of a special microbial-fermented Fuzhuan brick tea. Epigallocatechin gallate was identified as a dominant flavonoid of Fuzhuan tea aqueous extract (FTE). Mice were treated with 30% high fructose (HF) water feeding alone or in combination with administration of FTE at 400 mg per kg bw for 13 weeks. FTE caused strong inhibition against the elevation of liver weight, serum enzymatic (aspartate aminotransferase, aspartate aminotransferase and alkaline phosphatase) activities and hepatic inflammatory cytokines (interleukin-1, interleukin-6, tumor necrosis factor-α and tumor necrosis factor-β) formation, as well as dyslipidemia (total cholesterol, total triglyceride, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol) in HF-fed mice (p < 0.05). Hepatic malonaldehyde formation was lowered, while superoxide dismutase and glutathione peroxidase activities were enhanced by FTE treatment, relative to HF-fed mice (p < 0.05), and histopathological evaluation confirmed the protection. As revealed by 16S rDNA gene sequencing, FTE notably increased abundance of Bacteroidetes and Lactobacillus, but reduced population of Firmicutes, Proteobacteria and Tenericutes in HF feeding mice. These findings suggest that FTE exerts a hepatoprotective effect by modifying hepatic oxidative stress, inflammatory response and gut microbiota dysfunction.

茯砖茶中茶褐素的抗氧化性研究

茯砖茶中茶褐素的抗氧化性研究

Characteristics and chemical compositions of Pingwu Fuzhuan brick-tea, a distinctive post-fermentation tea in Sichuan province of China

ABSTRACT Pingwu Fuzhuan brick tea (PWT), a distinctive post-fermentation tea originated from Pingwu region of Sichuan province in China, is a popular “western road” border-selling tea. In this study, we investigated characteristics and chemical compositions of PWT, together with comparing its physicochemical properties with other regions of Fuzhuan brick teas (FBTs). Firstly, inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the geographical origin of FBTs, and the profiles of mineral elements were subjected to principal component analysis (PCA) to evaluate the differences among FBTs. Results from ICP-MS showed that the compositions of mineral elements from PWT, Hunan FBT (HNT), Shaanxi FBT (SNT), and Guizhou FBT (GZT) were distinctly different. The four different types of FBTs were clearly distinguished according to the results of PCA. Furthermore, all FBT samples were assessed for physicochemical properties and heatmap method was applied to data analysis. It was found that the total colour difference was highly distinct when compared PWT with HNT, SNT and GZT. Moreover, most of contents of biochemical compounds (gallic acid, catechins, free amino acids, alkaloids and volatile components) in PWT were lower compared to others except for total essential amino acids, GABA, aldehydes and acids.

Preparation of hydrophilic, magnetic molecularly imprinted resins of chlorogenic acid and evaluation of its solid-phase extraction performance

Hydrophilic, magnetic molecularly imprinted resins (MMIRs) were fabricated inside Fe3O4@mSiO2 pores by the one-pot copolycondensation of chlorogenic acid (CGA), resorcinol, melamine, and formaldehyde. The final porous MMIRs with larger numbers of surface recognition sites were obtained by removing mSiO2. The successful preparation of MMIRs was confirmed using transmission electron microscopy, Fourier transform infrared spectroscopy, vibrating sample magnetometry, thermo-gravimetric analysis, and water contact angle analysis. The analyses suggest that the MMIRs have excellent hydrophilicity and magnetic solid-phase extraction efficiency. The MMIRs had a good adsorption capacity (50.87 mg/g), fast rate of adsorption (equilibrium was attained at 70 min), and specific recognition for CGA. The MMIRs, in combination with high performance liquid chromatography, were directly used for the selective extraction and determination of CGA in Duzhong brick tea. The limit of detection and recovery were 0.7 mg/L and 93.1%-109.4%, respectively, with relative standard deviations of less than 9.6%. The proposed strategy was extremely promising for the facile, rapid, and selective determination of CGA in real aqueous samples.