Tea Polysaccharide Conjugates Research Articles

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The cover image is based on the Research Article Theabrownins in dark tea form complexes with tea polysaccharide conjugates by Xiaoqiang Chen et al., https://doi.org/10.1002/jsfa.13431.image

Physicochemical characterization of the fraction components of the theabrownin isolates from Pu'er tea

This study focuses on the isolation of theabrownins (TBs) from Pu'er tea. This isolation process involves low temperature water extraction, membrane separation, and multi-stage extraction with organic solvents. Subsequently, purification was performed using column chromatography with macroporous adsorbent resin D-101 and ethanol aqueous solution with a concentration of 0–64.81 g/100g. Five purified fractions were obtained, namely TBs-D1, TBs-D2, TBs-D3, TBs-D4, and TBs-D5, collectively referred to as TBs-D(1–5). These fractions were found to contain TBs and polysaccharides but lacked catechins, caffeine, theaflavin, and free protein. The average molecular weights of these fraction components exceeded 104 Da. These results indicated that TBs-D(1–5) were not free, but combined with tea polysaccharide conjugates (TPC), that is, TBs-TPC complexes. Furthermore, ultraviolet–visible spectrophotometry and Flourier transformation infrared spectroscopy confirmed the nature of TBs-D(1–5) as TBs-TPC complexes. Fluorescence spectra revealed that polysaccharides exert a quenching effect on the intrinsic fluorescence of TBs. Atomic force microscopy indicated that the sample forms a spherical cluster due to the aggregation of theabrownin molecules. Additionally, measurements of interfacial tension and water contact angle demonstrated that TBs-D(1–5) exhibit some amphiphilic properties. This research provides a theoretical foundation for the industrial production and utilization of TBs.

Theabrownins in dark tea form complexes with tea polysaccharide conjugates.

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. 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. 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.

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 50.00wt% 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.

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.

Reinforcing alginate matrixes by tea polysaccharide conjugates or their stabilized nanoemulsion for probiotics encapsulation: Characterization, survival after gastrointestinal digestion and ambient storage

Tea polysaccharide conjugates (TPC) were used as fillers in the form of biopolymer or colloidal particles (TPC stabilized nanoemulsion, NE) for reinforcing alginate (ALG) beads to improve the probiotic viability. Results demonstrated that adding TPC or NE to ALG beads significantly enhanced the gastrointestinal viability of encapsulated probiotics when compared to free cells. Moreover, the survivability of free and ALG encapsulated probiotics markedly decreased to 2.03 ± 0.05 and 2.26 ± 0.24 log CFU/g, respectively, after 2 weeks ambient storage, indicating pure ALG encapsulation had no effective storage protective capability. However, adding TPC or NE could greatly enhance the ambient storage viability of probiotics, with ALG + NE beads possessing the best protection (8.93 ± 0.06 log CFU/g) due to their lower water activity and reduced porosity. These results suggest that TPC and NE reinforced ALG beads have the potential to encapsulate, protect and colonic delivery of probiotics.

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.

A combination of green tea polysaccharide conjugate and bovine serum albumin and its emulsion-stabilizing characteristics

Tea polysaccharide conjugates (TPC) and bovine serum albumin (BSA) have emulsifying properties, but they have certain shortcomings when used alone as emulsifiers. This study aimed to combine TPC and BSA to form a complex for applications to achieve the complementary advantages between them. The TPC/BSA complex was physicochemically characterized, and the results showed an improvement in its surface hydrophobicity. TPC/BSA emulsions with different concentrations (0.20–1.00 wt%) were prepared using TPC/BSA complex as the emulsifier. The effects of heat treatment, pH, and metal ions on the stability of TPC/BSA and BSA emulsions were investigated, and TPC/BSA emulsion systems loaded with epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were constructed. TPC/BSA emulsion droplets were smaller than 1.00 wt% TPC emulsion droplets, and the particle size of 0.20 wt% TPC/BSA emulsion increased slightly during storage at 25 °C. Further, 0.20 wt% TPC/BSA emulsions became less stable after heat treatment, whereas the particle size of other concentrations did not change significantly after treatment at 70 ℃–90 °C. TPC/BSA emulsions were more stable at pH 6.0–9.0. Both were less affected by Na+, weakly affected by Ca2+ than BSA emulsion, and significantly affected by Al3+. TPC/BSA emulsion had a good protection effect on EGCG and EGC. The presence of EGCG and EGC improved the stability of the emulsion system, which remained stable for 90 days.

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.

Structural properties of Phoenix Oolong tea polysaccharide conjugates and the interfacial stability in nanoemulsions.

Tea Polysaccharide conjugate (TPC) is a naturally occurring active substance that is extracted from tea. Due to its benefits in enhancing human immunity and antioxidant effects, TPC is widely used in culinary products. The binding mode of polysaccharides and proteins in TPC, however, hasn't been well studied, it may be closely related to their functional properties, especially emulsification. The molecular weights and monosaccharide compositions of TPC was determined by ion chromatography and high-performance gel permeation chromatography. Although the functional groups of polysaccharides and proteins were confirmed by infrared spectroscopy; the presence of proteins couldn't be detected by SDS-PAGE and UV spectroscopy. It was hypothesized that the hydrophobic groups of the proteins in TPC were wrapped by polysaccharide chains, thus making the proteins undetectable. The rheology and interfacial protein adsorption results show that TPC forms a viscoelastic film at the oil-water interface to prevent the aggregation of oil droplets, thereby enhancing the stability of the emulsion. Based on these structural and emulsifying properties of TPC, the binding mode of polysaccharides and proteins along with their phase behavior at the oil-water interface of the emulsion was speculated. In TPC, the hydrophilic groups of the proteins are linked to polysaccharides by covalent interactions, where the hydrophobic groups are wrapped with the polysaccharide chains with the help of hydrophobic forces to form a hydrophobic core. The unique binding of polysaccharides and proteins in TPC enhances its amphiphilic properties, which can be effectively distributed at the oil-water interface and form stable emulsions. This article is protected by copyright. All rights reserved.

Green tea polysaccharide conjugates and gelatin enhanced viability of L. acidophilus by layer-by-layer encapsulation

Adverse environments such as the gastrointestinal tract can affect the efficacy of probiotics. Therefore, the adequate protection of probiotics and their total effect exertion are probiotics application research hotspots. Green tea polysaccharide conjugate (gTPC), an anionic polymer, and gelatin as the encapsulation materials, and layer-by-layer self-assembly technology as the method, were applied to encapsulate Lactobacillus acidophilus. Microscopic results showed that with the increase in the number of deposited layers, the encapsulation was more complete. After continuous exposure to simulated gastrointestinal fluid for 120 min, the survival rate of unencapsulated cells was 53.26%, and encapsulated cells with different deposited layers were 66.00%, 71.99%, 76.94%, and 79.89%, respectively. In addition, Gel/gTPC bilayers can efficiently improve cell thermotolerance and freezing resistance. Results indicated that the more the number of Gel/gTPC bilayers, the more significant the protection is. Therefore, gTPC and Gel are viable materials to protect probiotics through microencapsulation by Layer-by-layer self-assembly.

Effects of high-pressure homogenization extraction on the physicochemical properties and antioxidant activity of large-leaf yellow tea polysaccharide conjugates

This paper, discussed the high-pressure homogenization (HPH) method for the preparation of large-leaf yellow tea polysaccharide conjugates (LYTP), and the effects of LYTP on physicochemical properties as well as antioxidant activity were investigated. The results show that HPH extraction time was less than 0.5 h, and extraction rate reached 15.4%, which was nearly 1.8 times faster than that of hot water extraction (HWE). Component analysis showed that the total polysaccharide content of LYTP was higher, while the contents of polyphenols and free protein were lower than those of HWE. It is noteworthy that the 9.1% free protein content at 40 MPa was lower than that of the Sevag method (11.2%), indicating that HPH can eliminate the cumbersome protein removal process and is more environmentally. The small-molecule polysaccharide content extracted by HPH increased, but the monosaccharide composition did not change. Meanwhile, HPH decreased the particle size of the polysaccharides, and the changes in the surface topography of LYTP upon homogenization were confirmed with scanning electron microscopy. As a consequence, HPH extraction can improve the antioxidant capacity of LYTP. HPH extraction is an efficient, rapid and environmentally method for the preparation of polysaccharides, which could be widely used in the food industry.

Mn(II)-Mediated Self-Assembly of Tea Polysaccharide Nanoparticles and Their Functional Role in Mice with Type 2 Diabetes.

Tea polysaccharide (TPS) is a bioactive compound that has attracted increasing attention for its health effect on regulating the metabolism of glucose and lipid. Moreover, due to their good biocompatibility and biodegradability, TPS-based nanoparticles have emerged as effective nanocarriers for the delivery of bioactive molecules. In this study, we developed a TPS-based biocarrier system for the orally targeted administration of Mn(II) ions and investigated their antidiabetic effects in C57BL/6 mice with HFD/streptozotocin (STZ)-induced T2DM. Mn(II)-loaded TPS-based nanoparticles (MTNPs) were synthesized, in which negatively charged functional groups in protein and uronic acid in TPS conjugates would act as binding sites for Mn(II) ions, which is responsible for the cross-linking reaction of MTNP. The resulting MTNP had a spherical shape and a mean particle size of around 30 nm with a Mn(II) ion content of 2.24 ± 0.13 mg/g. In T2DM mice, we discovered that MTNP treatment significantly lowered blood glucose levels and improved glucose intolerance. Furthermore, the impact of MTNP on the recovery of FINS, the homeostatic index of insulin resistance (HOMA-IR), and the homeostatic index of β-cell (HOMA β-cell) levels was significantly larger (p < 0.05) than TPS alone, demonstrating that Mn(II) ions can enhance TPS's ability to repair HFD/STZ-induced β-cell damage. Mn(II) ions in MTNP not only acted as cofactors to increase the exocytosis of insulin secretory cells by upregulating the expression of Ca(II)/calmodulin-dependent protein kinase II (CaMK II) but also promoted TPS's lipid-lowering effect in T2DM mice by inhibiting glucogenesis and regulating the lipid metabolism. Our findings suggest that Mn(II) ions can be used not only as cross-linkers in the formation of nanoparticulated TPS but also as cofactors in improving the functional role of TPS in regulating the glucose and lipid metabolism, which will provide insights into the development of TPS-based drug delivery systems for the prevention of type 2 diabetes.

Purification, characterization, and emulsification stability of high- and low-molecular-weight fractions of polysaccharide conjugates extracted from green tea

Tea polysaccharide conjugates (TPCs) are macromolecular polymers comprising polypeptides covalently bound to polysaccharides with a wide range of molecular weights that are found in tea leaves. We previously found that TPCs had emulsifying properties, but the difference in the emulsification stabilities between the high- and low-molecular-weight TPCs was unknown. In this study, the total polysaccharide conjugates (gTPC-T) with average molecular weight of 258,900 Da were extracted from low-grade green tea, from which two separate fractions with average molecular weights of 989,600 Da (22.43%) and 47,780 Da (77.57%), which were referred to as gTPC-1 and gTPC-2, respectively, were separated using an ultrafiltration membrane. The polypeptide chains of the three TPCs (gTPC-T, gTPC-1, and gTPC-2) contained 17 out of the 20 canonical amino acids. In addition, gTPC-1 had the highest acidic monosaccharide content. Circular dichroism (CD) an analysis showed that the secondary structures of the protein moieties of the three TPCs were dominated by α-helices. The nano-differential scanning calorimetry (Nano-DSC) results showed that the transition midpoints (Tm) of the three samples were 86.69, 59.53, and 68.59 °C, respectively. The zeta potential of gTPC-T at weakly acidic or neutral pH (4.0–7.0) was the highest, followed by gTPC-1 and then gTPC-2. Of all three gTPCs, gTPC-1 had the smallest interfacial tension, the highest interfacial pressure, and the best interfacial activity. In addition, gTPC-T slightly better-stabilized the MCT oil-in-water emulsions than gTPC-1, while the emulsification stability of gTPC-2 was the worst. This trend was likely attributed to the synergistic effect between gTPC-1 and gTPC-2.

Effect of ultra-high pressure treatment on the characteristics of a tea polysaccharide conjugate aqueous solution

Previous studies have shown that ultra-high pressure (UHP) processing technology to extract, prepare, and sterilize tea beverages (tea infusion) significantly increases the extraction rate of tea polyphenols (catechins), free amino acids, caffeine, and other small molecules in green tea, besides sterilizing and inactivating residual oxidases, such as polyphenol oxidase and peroxidase. UHP avoids the deterioration of color and aroma, as high-quality green tea infusions were obtained with nutritional value and flavor quality close to the original tea. However, the effect of UHP on polysaccharides in green tea infusions is unclear. The water-extracted tea polysaccharide conjugates (TPC-W) and alkali-extracted tea polysaccharide conjugates (TPC-A) from low-grade green tea were subjected to a UHP treatment of 100, 300, and 500 MPa for 5, 12, and 25 min. The circular dichroism (CD) spectra results showed that UHP transformed the secondary structure of the TPC-W and TPC-A from compact and ordered α-helices and β-sheets to disordered β-turns and random coils; one component of TPC-A was dissociated into two components. The absolute values of the zeta potential of TPC-W treated with 100, 300, and 500 MPa increased by 2.4–5.6, 5.3–8.0, and 5.5–9.1 mV, while those of TPC-A increased by 0.5–2.8, 3.5–5.5, and 4.8–6.9 mV, respectively. The stability of TPC-W and TPC-A aqueous solutions treated with 300 and 500 MPa was enhanced during storage at 5°C. These findings will contribute to applying UHP for tea beverage processing and in-depth investigations on the physiochemical properties of TPC, particularly the protein moiety.

Influence of thermal treatment on the physicochemical and functional properties of tea polysaccharide conjugates

With increasing consumer demand for label-friendly products, there is a push towards the identification and utilization of effective natural emulsifiers from botanical sources. In this study, we investigated the effect of controlled thermal treatments on the physicochemical and functional properties of tea polysaccharide conjugates (TPCs). Thermal treatment of the TPCs at 110 °C for 3 days (TPC-3d) markedly improved their emulsifying activity without negatively impacting their antioxidant activity. In comparison with animal-based (sodium caseinate) and synthetic (Tween 80) emulsifiers, TPC-3d stabilized emulsions were more effective at inhibiting the chemical degradation of encapsulated ω-3 oils and curcumin during storage at elevated temperatures. The improvement in the chemical stability of the bioactive lipids was mainly ascribed to the antioxidant activity of the conjugated phenolic groups in the TPC. Our results show that thermally-treated TPC has the potential to be used as a novel plant-based antioxidant emulsifier to encapsulate and protect chemically labile hydrophobic compounds.

Antibacterial activity and mechanism of green tea polysaccharide conjugates against Escherichia coli

The effect of green tea polysaccharide conjugate (gTPC) on the growth of E. coli was evaluated. gTPC has optimal antibacterial concentrations for E. coli DH5α (4.00 mg/mL) and 25,922 (1.00 mg/mL), with the antibacterial rates of 55.75 % and 50.65 % respectively. The results of scanning electron microscopy (SEM) and transmission electron microscope (TEM) indicated that gTPC-treated E. coli cells showed obvious morphological changes, part of the cell wall became blurred, and the leakage of cytoplasmic content were observed. The proportion of the propidium iodide (PI) permeable E. coli cells treated using 0.50–2.00 mg/mL gTPC was between 8.79 %–9.49 % as well as 14.10 % (4.00 mg/mL gTPC) and 15.10 % (6.00 mg/mL gTPC). Reactive oxygen species (ROS) production of 1.00–4.00 mg/mL gTPC treated E. coli increased by 26.57 %–38.19 % with a significant increase level (p < 0.01). The outer membrane disruption played a key role in the antibacterial activity of gTPC against E. coli. This research result will open a new application field of tea polysaccharide conjugates.

Effects of polysaccharides from Yingshan Yunwu tea on meat quality, immune status and intestinal microflora in chickens

The present study was aimed to investigate the effects of the addition of Yingshan Yunwu green tea polysaccharide conjugates (GTPC) on meat quality, immune response and gut microflora in chickens. A total of 200 chickens with average initial body weight were randomly allotted to 4 groups. Intestinal samples were collected at the end of experiment for bacterial culture and microbial community analysis by 16S rDNA gene sequencing using Illumina MiSeq. Chicken breast muscle and serum were also sampled for analysis of meat quality and immune function. The results showed that dietary GTPC addition increased (P < 0.05) chicken breast muscle pH and redness-greenness (a*) value and decreased (P < 0.05) the values of lightness (L*), yellowness-blueness (b*), hardness, toughness and adhesiveness. In addition, dietary supplementation of GTPC increased (P < 0.05) the weight of thymus and bursa and serum concentrations of IgA and IgG. Furthermore, of the 10 bacterial phyla, the predominant taxa across all sampling time-points were Bacteroidetes, Firmicutes, Proteobacteria, and Deferribacteres, representing >97% of all sequences. GTPC increased the abundance of Bacteroidetes and Lactobacillus, and decreased the abundance of Proteobacteria. These findings provided some references of the application of GTPC in the poultry industry.

Emulsifying Properties of Polysaccharide Conjugates Prepared from Chin-Brick Tea.

Chin-brick tea polysaccharide conjugates (TPC-C) were prepared to study their emulsion capabilities. Interfacial tension and the effects of some factors, such as storage time, metal ion concentrations (Na+, Ca2+), pH (2.0-8.0), and heat treatment (70-100 °C) on the emulsions stabilized by TPC-C were studied. The interfacial tension of TPC-C (10.88 mN/m) was lower than that of gum arabic (15.18 mN/m) at a concentration of 0.08%. As the TPC-C concentration increased from 0.1 to 3.0 wt %, the mean particle diameter (MPD) (d32) of emulsions stabilized by TPC-C decreased from 1.88 to 0.16 μm. Furthermore, at a concentration of 0.5 wt % or higher, the MPD (d32) of emulsions stabilized by TPC-C at 25 and 60 °C for 10 days was between 0.20 and 0.50 μm. In the tested pH conditions from 2.0 to 8.0, the MPD (d32) of emulsions stabilized by 2.0 wt % TPC-C was less than 0.20 μm. At Na+ concentration conditions between 0.10 and 0.50 mol/L, the MPD (d32) of emulsions was between 0.19 and 0.20 μm, and the zeta potential values varied from -34.10 to -32.60 mV. However, with an increasing Ca2+ concentration from 0.01 to 0.05 mol/L, the MPD (d32) of emulsions was between 0.20 and 21.65 μm, and the zeta potential raised sharply from -34.10 to -28.46 mV. The emulsions stabilized by TPC-C have a decent storage stability after a high-temperature heat treatment. Overall, tea polysaccharide conjugates strongly stabilized the emulsions, which support their new application as natural emulsifiers.

Characteristics of the emulsion stabilized by polysaccharide conjugates alkali-extracted from green tea residue and its protective effect on catechins

Alkali-extracted tea polysaccharide conjugates, termed TPC-A, are obtained from the residue derived from tea after water extraction. Oil-in-water emulsions stabilized by different concentrations of TPC-A (0.5 wt%, 1.0 wt %, 1.5 wt %, 2.0 wt %, and 3.0 wt%) were prepared using medium chain triglycerides (MCT). The optimal concentrations of TPC-A were 2.0 wt % and 3.0 wt %. We investigated the effects of the storage time of 10 days, pH 2.0–10.0, and metal ions (Na+ and Ca2+) on the emulsion stabilized using 2.0 wt % TPC-A at 25 ℃. During the 10-day storage period, the mean particle diameter (MPD) (d32) of the emulsion stabilized using 2.0 wt % TPC-A slightly increased from 0.31 μm to 0.37 μm, and the absolute value of the zeta potential increased from 44.9 mV to 41.4 mV. Under neutral or alkaline conditions, the emulsion stabilized using TPC-A had the MPD (d32) of less than 0.30 μm and the absolute value of the zeta potential ranging from 40.52 to 41.53 mV. The MPD (d32) of the emulsion in different Na+ concentrations from 0 mmol/L to 500 mmol/L, increased from 0.30 μm to 2.80 μm, and their absolute value of zeta potential decreased from 41.0 mV to 37.7 mV. The emulsion stabilized using TPC-A had a favorable protective effect on EGCG and EGC, and the retention rates of EGCG and EGC during the 10 days were 7 and 6 times higher than those without TPC-A emulsion protection, respectively. TPC-A extracted from tea residue, which is abundantly available and cheap, can be used as a natural emulsifier, in order to develop a milky food or beverage products with excellent health benefits.