Emulsifying Properties of Polysaccharide Conjugates Prepared from Chin-Brick Tea

Extraction methods, chemical compositions, molecular structure, health functions, and potential applications of tea polysaccharides as a promising biomaterial: a review

Tea polysaccharides (TPS) have attracted much attention due to their multiple biological activities, excellent biocompatibility and good biodegradability, creating a wide range of potential applications in the food and pharmaceutical industries. However, the high molecular weight and complexity of TPS components have restricted its purification and bioactivity, limiting its potential applications. In this review, the effects of various extraction methods, tea processing, and degree of fermentation on the composition and structure of TPS were thoroughly investigated to overcome this dilemma. Through a comprehensive analysis of in vivo and in vitro studies, the health benefits of TPS are discussed in detail, including antioxidant, anti-obesity, modulation of gut microbial communities, and anticancer bioactivities. Typical structural characterization techniques of TPS are also summarized, and interactions with common food components are discussed in depth, providing a deeper perspective on the overall knowledge of TPS. Finally, this review offers an extensive overview of the wide range of applications of TPS, including its strong emulsifying properties and bio-accessibility, in various fields such as food nutrition, drug delivery, encapsulation films, and emulsifiers. This review aims to provide a theoretical basis for the profound development of TPS for productive utilization.

Theabrownins in dark tea form complexes with tea polysaccharide conjugates

BACKGROUND

Theabrownins (TBs) are one of most important quality components in dark tea, but have not been produced industrially. In this study, the aqueous extract was obtained from Pu-erh ripe tea, one kind of dark tea. Caffeine, theaflavin, catechin and saponin were removed by trichloromethane, ethyl acetate and n-butanol in turn to obtain a TB isolate. The TB isolate was subjected to column chromatography using a macroporous resin HPD-750 and eluted with a gradient of 0-700 g kg-1 ethanol aqueous solution. Four fractions were obtained, and named as TBs-FC1, TBs-FC2, TBs-FC3 and TBs-FC4.

RESULTS

These four fractions contained polysaccharides and no small molecules such as catechins, caffeine and theaflavins as well as average molecular weights of 123.000 kDa, 23.380 kDa, 89.870 kDa and 106.600 kDa. It was revealed that they were complexes of TBs and tea polysaccharide conjugates (TPCs). Ultraviolet-visible (UV-visible) and infrared (IR) spectra showed the properties of TBs and TPCs. Their zeta potentials ranged from -13.40 mV to -38.80 mV in aqueous solutions at pH 3.0-9.0.

CONCLUSION

This study reveals that TBs do not exist in free state but in combined state in dark tea, which provide the theoretical basis for the industrialization of TBs. © 2024 Society of Chemical Industry.

Characterization, stability, and curcumin bioaccessibility of buckwheat flower polysaccharide conjugate emulsion

In this study, buckwheat flower polysaccharide conjugates (BFPCs) were synthesized and evaluated for their emulsification properties. The stability of BFPC-stabilized emulsions was assessed through particle size analysis, zeta potential measurements, microscopic observations, and rheological tests. Gum Arabic served as a control to compare BFPC's emulsifying efficacy across varying storage conditions, including exposure to metal ions, pH variations, and different heat treatment temperatures. Results showed that BFPC significantly lowered interfacial tension (16.2 mN/m) and effectively stabilized emulsions containing 60 wt% medium-chain triglycerides at a concentration of 1.0 wt%. Over a 20-day storage period, BFPC emulsions demonstrated robust resistance to heat (60-90°C), acidic conditions (pH 2.0-9.0), and ion concentrations (Na+, Ca2+). Moreover, in a high oil phase emulsion, BFPC enhanced the bioavailability of curcumin to 27.05%, markedly higher than the 7.10% observed without emulsification, underscoring its potential in nutrient delivery applications. PRACTICAL APPLICATION: Due to its excellent resistance, long-time emulsifying stability under different conditions, and its good effect in curcumin embedding, BFPC has a broad prospect and can be widely used under various conditions in food industry.

High-internal-phase emulsions stabilized by alkali-extracted green tea polysaccharide conjugates for curcumin delivery

Exploring the emulsification capabilities of tea polysaccharide conjugates (TPCs) in high-internal-phase emulsions (HIPEs) would further expand the utilization value of TPCs. This study aimed to prepare 0.1-0.5 wt% alkali-extracted green tea polysaccharide conjugate (gTPC-A)-stabilized HIPEs containing 75-87 wt% medium chain triglycerides (MCTs) to investigate their stability, rheology, microstructure, and loading and protective effects on curcumin. The findings revealed that only 0.1 wt% of gTPC-A could stabilize HIPEs containing 85 wt% oil for 30 days. HIPEs had better storage stability in a weakly acidic environment at pH 5.0-6.0 and at temperatures less than 70 °C. HIPEs could load curcumin and protect it from ultraviolet (UV) radiation and in vitro digestion. The half-life of curcumin loaded in HIPEs was 65 h under UV radiation. The curcumin bioaccessibility of HIPEs (56.29 %) was higher than that in MCT (8.73 %). These results provided a theoretical basis for the extensive use of TPCs.

Elevated fucose content enhances the cryoprotective performance of anionic polysaccharides

Biological cryopreservation often involves using a cryoprotective agent (CPA) to mitigate lethal physical stressors cells endure during freezing and thawing, but effective CPA concentrations are cytotoxic. Hence, natural polysaccharides have been studied as biocompatible alternatives. Here, a subset of 26 natural polysaccharides of various chemical composition was probed for their potential in enhancing the metabolic post-thaw viability (PTV) of cryopreserved Vero cells. The best performing cryoprotective polysaccharides contained significant fucose amounts, resulting in average PTV 2.8-fold (up to 3.1-fold) compared to 0.8-fold and 2.2-fold for all non-cryoprotective and cryoprotective polysaccharides, respectively, outperforming the optimized commercial CryoStor™ CS5 formulation (2.6-fold). Stoichiometrically, a balance between fucose (18-35.7 mol%), uronic acids (UA) (13.5-26 mol%) and high molecular weight (MW > 1 MDa) generated optimal PTV. Principal component analysis (PCA) revealed that fucose enhances cell survival by a charge-independent, MW-scaling mechanism (PC1), drastically different from the charge-dominated ice growth disruption of UA (PC2). Its neutral nature and unique properties distinguishable from other neutral monomers suggest fucose may play a passive role in conformational adaptability of polysaccharide to ice growth inhibition, or an active role in cell membrane stabilization through binding. Ultimately, fucose-rich anionic polysaccharides may indulge in polymer-ice and polymer-cell interactions that actively disrupt ice and minimize lethal volumetric fluctuations due to a balanced hydrophobic-hydrophilic character. Our research showed the critical role neutral fucose plays in enhancing cellular cryopreservation outcomes, disputing previous assumptions of polyanionicity being the sole governing predictor of cryoprotection.

Structurally Modified Polysaccharides: Physicochemical Properties, Biological Activities, Structure-Activity Relationship, and Applications

Polysaccharides are an important class of biomolecules derived from several sources. However, the inherent structure of polysaccharides prevents them from exhibiting favorable physicochemical properties, which restricts their development in agriculture, industry, food, and biomedicine. This paper systematically summarizes the changes in the primary and advanced structures of modified polysaccharides, and focuses on the effects of various modification methods on the hydrophobicity, rheological properties, emulsifying properties, antioxidant activity, hypoglycemic, and hypolipidemic activities of polysaccharides. Then there is a list the applications of modified polysaccharides in treating heavy metal pollutants, purifying water resources, improving beverage stability and bread quality, and precisely delivering the drug. When summarized and reviewed, the information above can shed further light on the relationship between polysaccharide structure and function. Determining the structure-activity relationship provides a scientific basis for the direction of molecular modifications of polysaccharides.

Green tea polysaccharide conjugates and bovine serum albumin have a synergistic effect in improving the emulsification ability

Our previous study revealed that green tea polysaccharide conjugate (gTPC) has emulsion effect, but its emulsifying ability is weak. In order to improve the emulsification ability of gTPC, gTPC and bovine serum albumin (BSA) were combined to form five different mass proportions of the TPC/BSA (TB) complex: TPC/BSA: 5:1, 5:2, 5:3, 5:4, and 5:5 w/w. We observed that the 5:5 w/w TB emulsion was more hydrophobic and surface-active. Furthermore, the emulsions prepared using 50.00 wt% medium-chain triglycerides exhibited the best stability. In addition, the TB emulsion exhibited stability in adverse environments of pH, salt, and heat; in particular, under salt conditions, no significant changes were observed in zeta potential. Subsequently, in vitro simulated digestion experiments were performed to investigate the use of TB emulsions for β-carotene encapsulation. We observed that the encapsulation efficiency for β-carotene was approximately 90.0 %; it was subsequently released in the intestine.

Effect of hydrophobic property on antibacterial activities of green tea polysaccharide conjugates against Escherichia coli

We previously found that green tea polysaccharide conjugates (gTPCs) have antibacterial activity against Escherichia coli. In this study, the effect of hydrophobic property on the antibacterial activities of gTPCs was evaluated to elucidate their property-activity relationship. Three gTPCs (gTPCs-5 h, gTPCs-12 h and gTPCs-24 h) were extracted from green tea with the ethanol precipitation time of 5 h, 12 h and 24 h, respectively. These three gTPCs did not differ significantly in terms of molecular weight distribution, amino acids composition and zeta potentials. Fourier transform infrared spectroscopy results revealed that gTPCs-5 h and gTPCs-12 h processed more hydrogen bonds than gTPCs-24 h. The surface hydrophobicity and contact angle of gTPCs-5 h were larger than that of gTPCs-12 h and gTPCs-24 h. The antibacterial activity of gTPCs against E. coli decreased in the order of gTPCs-5 h > gTPCs-12 h > gTPCs-24 h. There wasn't significant difference among the zeta potentials of E. coli treated by gTPCs-5 h, gTPCs-12 h and gTPCs-24 h, but the bacterial contact angles of E. coli treated by gTPCs-5 h were higher compared with those of the other two gTPCs. Furthermore, gTPCs-5 h exhibited higher activity to decrease bacterial membrane proteins, and increase bacterial membrane permeability than the other two gTPCs. In conclusion, gTPCs with higher hydrophobicity property exhibited stronger antibacterial activity against E. coli.

Regulating effects of phytosterol esters-loaded emulsions stabilized with green tea polysaccharide conjugates and Tween on lipids in KKAy mice

Phytosterol esters (PSE) have been shown to have cholesterol-lowering effects, but their insolubility in water limits their applications. Green tea polysaccharide conjugates (gTPC) have hypoglycemic and emulsifying effects. To address lipid dysregulation in diabetic patients, we developed PSE-loaded emulsions stabilized with gTPC and Tween-20 (gTPC-PSE emulsions) and evaluated their physicochemical properties. We subsequently investigated the lipid-regulating potential of these emulsions to in KKAy mice. The KKAy mice were randomly assigned to eight groups: the model group, the Lipitor (10 mg·kg^-1)-acarbose (30 mg·kg^-1) combination group, two gTPC groups, two PSE groups, and two gTPC-PSE groups with a 1:2 mass ratio of gTPC to PSE. The administered doses were 90 and 270 mg kg^-1, respectively. Administration of a 270 mg·kg^-1 dose of gTPC-PSE emulsions led to the most significant effects including increased levels of liver and serum high-density lipoprotein cholesterol (HDL-CH), reduced serum leptin and insulin, and improved liver superoxide dismutase (SOD) and reduced malondialdehyde (MDA). In general, gTPC and PSE demonstrated a synergistic effect on lipid regulation in mice. Our results indicate that gTPC-PSE emulsions hold potential as a nutritional intervention for diabetes by modulating lipid levels.

Effects of pile fermentation on the physicochemical, functional, and biological properties of tea polysaccharides

This study investigated the influence of pile fermentation on the physicochemical, functional, and biological properties of tea polysaccharides (TPS). Results indicated that the extraction yield, uronic acid content, and polyphenol content of TPS greatly increased from 1.8, 13.1 and 6.3 % to 4.1, 27.9, and 7.8 %, respectively, but the molecular weight markedly decreased from 153.7 to 76.0 kDa after pile fermentation. Additionally, the interfacial, emulsion formation, and emulsion stabilization properties of TPS were significantly improved after pile fermentation. For instance, 1.0 wt% TPS isolated from dark tea (D-TPS) can fabricate 8.0 wt% MCT oil-in-water nanoemulsion (d₃₂ ≈ 159 nm) with potent storage stability. Moreover, the antioxidant and α-glucosidase inhibitory activities of D-TPS was higher than that of TPS isolated from sun-dried raw tea (R-TPS). Overall, this study indicated that pile fermentation markedly affected the physicochemical and structural characteristics of TPS, thereby improving their functional and biological properties.

Dietary Fiber from Navel Orange Peel Prepared by Enzymatic and Ultrasound-Assisted Deep Eutectic Solvents: Physicochemical and Prebiotic Properties

Dietary fiber (DF) was extracted from navel orange peel residue by enzyme (E-DF) and ultrasound-assisted deep eutectic solvent (US-DES-DF), and its physicochemical and prebiotic properties were characterized. Based on Fourier-transform infrared spectroscopy, all DF samples exhibited typical polysaccharide absorption spectra, indicating that DES could separate lignin while leaving the chemical structure of DF unchanged, yielding significantly higher extraction yields (76.69 ± 1.68%) compared to enzymatic methods (67.27 ± 0.13%). Moreover, ultrasound-assisted DES extraction improved the properties of navel orange DFs by significantly increasing the contents of soluble dietary fiber and total dietary fiber (3.29 ± 1.33% and 10.13 ± 0.78%, respectively), as well as a notable improvement in the values of water-holding capacity, oil-holding capacity, and water swelling capacity. US-DES-DF outperformed commercial citrus fiber in stimulating the proliferation of probiotic Bifidobacteria strains in vitro. Overall, ultrasound-assisted DES extraction exhibited potential as an industrial extraction method, and US-DES-DF could serve as a valuable functional food ingredient. These results provide a new perspective on the prebiotic properties of dietary fibers and the preparation process of prebiotics.

Preparation of Fucoxanthin Nanoemulsion Stabilized by Natural Emulsifiers: Fucoidan, Sodium Caseinate, and Gum Arabic

This study was proposed to investigate the possibility of O/W nanoemulsion stabilization via natural emulsifiers as a delivery system for fucoxanthin. Nanoemulsions were prepared using ultrasonic treatment (150 W, amplitude 80%, 10 min) with different levels (0.5%, 1%, and 2% wt) of fucoidan, gum Arabic, and sodium caseinate as natural emulsifires and they were compared with tween 80. Then, the creaming index, stability, encapsulation efficacy, Fourier-transform infrared (FT-IR) spectroscopy, and in vitro release were evaluated. The best stability and lowest creaming index were observed at 2% wt of emulsifiers. Nanoemulsions with droplet sizes (113.27−127.50 nm) and zeta potentials (−32.27 to −58.87 mV) were prepared. The droplet size of nanoemulsions was reduced by increasing the emulsifier concentration, and the best nanoemulsion stability after 15 days of storage was in the following order: tween 80 > sodium caseinate > fucoidan > gum Arabic. The encapsulation efficacy of nanoemulsions stabilized by sodium caseinate, fucoidan, and gum Arabic were 88.51 ± 0.11%, 79.32 ± 0.09%, and 60.34 ± 0.13%, respectively. The in vitro gastrointestinal fucoxanthin release of nanoemulsion stabilized with tween 80, sodium caseinate, fucoidan, and gum Arabic were 85.14 ± 0.16%, 76.91 ± 0.34%, 71.41 ± 0.14%, and 68.98 ± 0.36%, respectively. The release of fucoxanthin from nanoemulsions followed Fickian diffusion. The FTIR also confirmed the encapsulation of fucoxanthin.

Astragaloside Ⅳ alleviates ulcerative colitis by regulating the balance of Th17/Treg cells

BACKGROUND

Restoring immune homeostasis by targeting the Th17/Treg response is a potentially valuable therapeutic strategy for ulcerative colitis (UC). Astragaloside IV (AS-Ⅳ) is a phytochemical naturally occurring in Astragalus membranaceus that has good anti-inflammatory, anti-oxidant and anti-stress properties. However, the effects of AS-IV on the homeostasis of Th17/Treg cells in colitis mice remains unknown.

PURPOSE

To investigate the protective effects and potential immunomodulatory mechanisms of AS-IV on UC.

METHODS

This study was constructed for DSS-induced acute colitis and recurrent colitis, with AS-IV administered prophylactically and therapeutically, respectively. The balance of Th17/Treg cells was analyzed by flow cytometry, their specific nuclear transcription factors were detected by RT-PCR as well as their secreted inflammatory cytokines were detected by ELISA and RT-PCR. Notch signaling-related proteins were detected by RT-PCR and Western blotting. Oxidative stress indicators were measured by biochemical technology.

RESULTS

In this study, AS-IV treatment not only effectively prevented and alleviated the clinical symptoms of DSS-induced colitis mice, including weight loss, DAI soaring, colon length shortening and colon weight gain, but also significantly improved ulcer formation, inflammatory cell infiltration and index, and regulated the expression of inflammatory cytokines in colon tissues. Importantly, the efficacy of high-dose AS-IV (100 mg/kg/day) in mice with recurrent colitis in this study was comparable to that of 5-ASA. AS-IV early administration was able to reshape the homeostasis of Th17/Treg cells in mice with acute colitis; meanwhile, AS-IV inhibited Th17 cell responses and promoted Treg cell responses in mice with recurrent colitis. Moreover, AS-IV not only inhibited the activation of Notch signaling pathway in colitis mice, but also prevented and ameliorated DSS-induced oxidative stress injury.

CONCLUSION

In conclusion, AS-IV effectively prevented and alleviated UC by reshaping Th17/Treg cell homeostasis and anti-oxidative stress.

Physicochemical and Colon Cancer Cell Inhibitory Properties of Theabrownins Prepared by Weak Alkali Oxidation of Tea Polyphenols

Existing studies on the biological activity of theabrownins are not based on their free state but on the complexes of theabrownins, polysaccharides, proteins, and flavonoids. In this study, theabrownins (TBs-C) were prepared by weak alkali oxidation of tea polyphenols. The ultraviolet-visible scanning spectrum of TBs-C showed two characteristic absorption peaks at 203 and 270 nm. The zeta potential of the TBs-C aqueous solution was negative, and the values varied from - 6.26 to -19.55 mV with a solution pH of 3-9. Storage conditions of pH 5.0-7.0 and around 25 °C were beneficial for the physical and chemical stability of the TBS-C solution. Cells were treated with series concentrations and examined by MTT, HE staining, PI immunofluorescence staining, flow cytometry, and real-time PCR to investigate the antiproliferative effect of TBs-C on human colon cancer HT-29 cells. The results showed that TBs-C, particularly at 500 µg/mL, inhibited cell growth. TBs-C induced HT-29 cell apoptosis, as confirmed by morphological changes, nucleus propidium iodide staining, and distributions of the cell cycle. The apoptotic mechanism may be due to the intracellular redox imbalance induced by TBs-C.

Development of Millettia speciosa champ polysaccharide conjugate stabilized oil-in-water emulsion for oral delivery of β-carotene: Protection effect and in vitro digestion fate

In this study, a natural antioxidant emulsifier, Millettia speciosa Champ polysaccharide conjugates (MSC-PC), was used for fabricating oil-in-water emulsion, and the influences of MSC-PC on β-carotene stability and bioaccessibility were studied. Results suggested that MSC-PC stabilized emulsion exhibited excellent resistance to a wide range of salt levels (0-500 mM of Na⁺), thermal treatments (50-90 °C) and pH values (3.0-11.0). MSC-PC also exhibited an outstanding inhibition capacity on lipid oxidation. Besides, MSC-PC stabilized emulsion had a better protective effect on β-carotene than other systems. Interestingly, in spite of similar lipolysis extent, β-carotene bioaccessibility in MSC-PC fabricated emulsion (14.75 %) was markedly higher than that in commercial Tween 80 fabricated emulsion (10.08 %), likely due to the steric-hindrance effect and antioxidant ability of MSC-PC, building interfacial layers that prevented β-carotene from degradation. This work supplied a deep insight into elucidating the mechanisms of emulsifying performance and β-carotene protection effect of MSC-PC fabricated emulsion.

Advances in the Utilization of Tea Polysaccharides: Preparation, Physicochemical Properties, and Health Benefits

Tea polysaccharide (TPS) is the second most abundant ingredient in tea following tea polyphenols. As a complex polysaccharide, TPS has a complex chemical structure and a variety of bioactivities, such as anti-oxidation, hypoglycemia, hypolipidemic, immune regulation, and anti-tumor. Additionally, it shows excellent development and application prospects in food, cosmetics, and medical and health care products. However, numerous studies have shown that the bioactivity of TPS is closely related to its sources, processing methods, and extraction methods. Therefore, the authors of this paper reviewed the relevant recent research and conducted a comprehensive and systematic review of the extraction methods, physicochemical properties, and bioactivities of TPS to strengthen the understanding and exploration of the bioactivities of TPS. This review provides a reference for preparing and developing functional TPS products.

Characterization of Theabrownins Prepared From Tea Polyphenols by Enzymatic and Chemical Oxidation and Their Inhibitory Effect on Colon Cancer Cells

Theabrownins (TBs) are prepared from dark tea and contain a large number of complex heterogeneous components, such as carbohydrates, proteins, and flavonoids, which are difficult to remove. In addition, some toxic and harmful extraction solvents are used to purify TBs. These obstacles hinder the utilization and industrialization of TBs. In this study, tea polyphenols were used as substrates and polyphenol oxidase and sodium bicarbonate (NaHCO₃) were used successively to prepare theabrownins (TBs-E). The UV-visible characteristic absorption peaks of the TBs-E were located at 203 and 270 nm and Fourier-transform IR analysis showed that they were polymerized phenolic substances containing the hydroxy and carboxyl groups. The TBs-E aqueous solution was negatively charged and the absolute values of the zeta potential increased with increasing pH. A storage experiment showed that TBs-E were more stable at pH 7.0 and in low-temperature environments around 25°C. HT-29 human colon cancer cells were used to evaluate the biological activity of TBs-E through 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT), H&E staining, propidium iodide immunofluorescent staining, flow cytometry, and real-time PCR assays. The TBs-E significantly inhibited cell growth and caused late apoptosis, particularly at the dose of 500 μg/ml. The TBs-E markedly reduced the expression of antioxidant enzyme genes and increased the generation of reactive oxygen species to break the redox balance, which may have led to cell damage and death. These results will promote research and industrialization of TBs.

Modulating storage stability of binary gel by adjusting the ratios of starch and kappa-carrageenan

This study aimed to investigate the interaction mechanism of the waxy starch and kappa carrageenan (KC) gel with different ratios during co-gelatinization and storage. Water distributions, mobilities and rheological properties of the mixture gels were studied. When KC concentration was low (0.5%KC and 4% starch), the starch dominated the system, and the gel strength was the lowest. When KC concentration increased to 0.75%, the gel had the lowest change rate of fracture force, and the most homogeneous network of the freeze-dried gel was observed. When KC concentration increased to 1.0%, the gel strength was high, but the uneven structure led to the instability of the gel. Overall, the gel with 0.75%KC and 4% starch was the most stable during storage, and the exclusion of the two components to each other was the weakest, resulting in the uniform structure of the gel.

Effects of different extraction methods on structural and physicochemical properties of pectins from finger citron pomace

The functionality and property of pectin are correlated with its structure which is affected by the extraction method used. In this study, three different methods of extracting pectin, the microwave-assisted extraction (MAE), the ultrasonic-assisted extraction (UAE) and the conventional heating extraction (CHE), were used at three different temperatures with both an acid and alkali extraction solution. It was found that temperature mainly influenced pectin yield, while pectin structures and physicochemical properties were affected by the pH condition and extraction technology. The alkali-extraction with MAE and UAE at short time promoted the yield of low-ester pectin. Monosaccharide composition analysis showed a high galacturonic acid (GalA) content in the pectin derived from MAE and UAE. The high viscosity and desirable viscoelastic properties of the acid-MAE pectin were due to its large molecular weight and particle size. The results contribute to our understanding of the association among pectin extraction, structure and properties.

Impact of Various Microbial-Fermented Methods on the Chemical Profile of Dark Tea Using a Single Raw Tea Material

In the present study, we produced Pu-erh, Liubao, Qingzhuan, and Fuzhuan teas using a single raw tea material and applied widely targeted metabolomics to study the impact of various microbial-fermented methods on the chemical profile of dark tea. The contents of catechins and free amino acids decreased drastically, whereas the contents of gallic acid and theabrownins increased significantly during microbial fermentation. Pu-erh tea had the highest content of theabrownins (11.82 ± 0.49%). Moreover, MS-based metabolomics analysis revealed that the different types of dark teas were significantly different from their raw material. A total of 85 differential metabolites were screened among 569 metabolites identified referring to self-compiled database. Glycosylated, hydroxylated, methylated, and condensed and oxidated products originating from microbial bioconversion of their corresponding primitive forms were significantly increased in dark teas. These results suggest that various microbial-fermented methods greatly affect the metabolic profile of dark tea, which can provide useful information for dark tea biochemistry research.

Polysaccharide conjugates from Chin brick tea (Camellia sinensis) improve the physicochemical stability and bioaccessibility of β-carotene in oil-in-water nanoemulsions

A natural antioxidant emulsifier, tea polysaccharide conjugate (TPC), was isolated from Chin brick tea. The impact of TPC on β-carotene stability and bioaccessibility in oil-in-water nanoemulsions was assessed. TPC exhibited strong antioxidant activity and could be used to fabricate stable nanoemulsions (d < 140 nm). The extent of lipid digestion was considerably lower for lipid droplets coated by TPC (68%) than Tween 80 (94%) or whey protein isolate (WPI) (89%), probably because TPC formed interfacial layers that hindered the access of lipases to lipids. The chemical stability of β-carotene in TPC-nanoemulsions was markedly higher than in those formulated with Tween 80 or WPI due to the high antioxidant activity of TPC. The bioaccessibility of β-carotene (20-30%) was independent of emulsifier type. TPC from Chin brick tea can therefore be used as a dual-purpose functional ingredient in emulsified foods.

Formation, structural characteristics and physicochemical properties of beeswax oleogels prepared with tea polyphenol loaded gelators

In this study, a tea polyphenol (TP) loaded beeswax gelator (TP gelator) was constructed and incorporated into soybean oil to improve the oxidative stability of oleogels. The effects of TP on the structure and storage stability of oleogels were investigated. The TP gelator prepared by embedding TP into beeswax improved the dispersity of TP in lipids. The thermal characteristics and X-ray diffraction analysis showed that the components of the TP gelator coexisted homogeneously and TP was well dispersed in beeswax. The Fourier-transform infrared spectra indicated that the phenolic hydroxyl group of TP had intermolecular force with the quaternary ammonium nitrogen in the choline portion of soybean lecithin. The formation of needle-like crystals by beeswax restricted the flow of liquid oil, and TP did not participate in the construction of the internal network structure of the oleogel. In the accelerated storage experiment at 60 °C, the peroxide value of the TP loaded oleogel decreased by 60.6% at the end of the storage period compared with soybean oil. TP was successfully embedded in the oleogel without changing its structure, which not only solved the problem of poor dispersion of TP in oil, but also showed a significant inhibitory effect on lipid oxidation.

A Ganoderma atrum polysaccharide alleviated DSS-induced ulcerative colitis by protecting the apoptosis/autophagy-regulated physical barrier and the DC-related immune barrier

Polysaccharides are one of the main active substances in Ganoderma atrum (G. atrum). The purpose of this study was to explore the protective effect of a G. atrum polysaccharide (PSG-1) on DSS-induced colitis and the underlying mechanism. The results showed that PSG-1 could maintain the integrity of the intestinal structure by promoting the expression of goblet cells and levels of tight junction proteins in the colon of DSS-induced colitis mice. Furthermore, PSG-1 relieved the inhibition of Bcl-2 and the overexpression of caspase-3 and caspase-9 caused by DSS. Simultaneously, PSG-1 restored the expression of Atg5, Atg7 and beclin-1 and inhibited the p-akt and p-mTOR levels, suggesting that PSG-1 promoted autophagy via the Akt/mTOR pathway. Moreover, PSG-1 inhibited the content of DCs in the colon and modulated the expression of IL-10 in DCs. In conclusion, PSG-1 alleviated DSS-induced ulcerative colitis by protecting the apoptosis/autophagy-regulated physical barrier and the DC-related immune barrier.