Search

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., (© 2024 Society of Chemical Industry.)

Summary: Tea processing often generates significant waste, resulting in resource inefficiency. However, extracting green tea polysaccharide conjugate (gTPC) from this waste has shown promising bioactivity. Previous studies have confirmed the emulsifying properties of gTPC. Yet, its use as an emulsifier is limited due to its requirement for high surface activity. The findings revealed that a 0.40 wt% soy protein isolate (SPI) and 0.50 wt% gTPC conjugate required 300 °C for complete decomposition, demonstrating the highest stability among other ratios. The Pickering emulsion, using a 0.30 wt% emulsifier ratio, exhibited exceptional stability. Moreover, it showed remarkable zeta potential and particle size stability under stressful conditions (temperature, pH and metal ions). Additionally, it effectively protected curcumin from adverse pH, light and temperature effects, with a retention rate of over 74.00%. These results highlight the gTPC/SPI combination as an effective stabiliser, offering new prospects for gTPC development and utilisation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Bamboo leaf polysaccharide is an active polysaccharide. Alkali-extracted bamboo leaf polysaccharide conjugates have been demonstrated to exhibit emulsification properties. However, the disparity in emulsification between aqueous and alkali-extracted bamboo leaf polysaccharide conjugates remains unclear. In this study, we extracted two bamboo leaf polysaccharide conjugates using aqueous and alkaline extraction, termed BLPC-W and BLPC-A, respectively. The physicochemical characterization revealed significant differences in monosaccharide and amino acid composition, molecular weight, and microstructure between BLPC-W and BLPC-A (p <0.05). Moreover, BLPC-A demonstrated a more pronounced ability to reduce interfacial tension between oil and water. Oil-in-water emulsions were produced using BLPC-W, BLPC-A, and medium chain triglycerides (MCT) at varying concentrations (0.5, 1.0, 1.5, 2.0, and 2.5 %wt). At 2.0 wt%, both BLPC-W and BLPC-A emulsions exhibited the smallest average particle size (d 3,2) of 0.528 μm and 0.304 μm, respectively. Additionally, BLPC-W/WP and BLPC-A/WP emulsions were prepared by incorporating whey protein (WP) at a 3:1 mass ratio with BLPC-W or BLPC-A. After ten days of storage at 25 °C, the average particle size (d 3,2) of BLPC-W, BLPC-A, BLPC-W/WP, and BLPC-A/WP emulsions increased from 0.528 μm to 1.212 μm, 0.304 μm to 0.535 μm, 0.417 μm to 0.534 μm, and 0.213–0.324 μm, respectively. The zeta potentials of BLPC-W, BLPC-A, BLPC-W/WP, and BLPC-A/WP emulsions remained stable around −31 mV, −34 mV, −33 mV, and −36 mV, respectively. Furthermore BLPC-A exhibited superior emulsifying properties compared to BLPC-W, and the addition of WP enhanced the emulsification ability of both BLPC-W and BLPC-A. These findings offer valuable insights into the potential applications of bamboo leaf polysaccharide conjugates in emulsification processes. • Water-extracted (BLPC-W) and alkali-extracted (BLPC-A) polysaccharides conjugates, were prepared from bamboo leaves and physicochemical characterized. • BLPC-W and BLPC-A were prepared from bamboo leaves and physicochemical characterized. • BLPC-W and BLPC-A can stabilize nanoemulsions. • The properties and mechanism of BLPC-W and BLPC-A stabilized emulsions were studied. [ABSTRACT FROM AUTHOR]

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. • TPC and BSA complex was prepared and characterized. • TPC and BSA plays a synergistic effect to improve emulsification. • TPC/BSA emulsion had a good protection effect on EGCG and EGC. [ABSTRACT FROM AUTHOR]

• gTPC-A can stabilize high internal phase emulsions (HIPEs). • The stability of gTPC-A HIPEs under pH, heat and UV irradiation was investigated. • The HIPEs loaded curcumin and protected it from UV radiation and in vitro digestion. • The bioaccessibility of curcumin reached 56.29% in the HIPEs and 8.73% in oil. 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. [ABSTRACT FROM AUTHOR]