Interaction of environmental moisture with powdered green tea formulations: effect on catechin chemical stability

Release and MMP-9 Inhibition Assessment of Dental Adhesive Modified with EGCG-Encapsulated Halloysite Nanotubes

Degradation of the collagen fibrils at the dentin-resin interface by the enzymatic activity of matrix metalloproteinases (MMPs) has been known to permit some dental restoration complications, such as microleakage, secondary caries, and, ultimately, restoration failures. This study aimed to evaluate a modified adhesive by adding an MMP inhibitor from green tea extract with and without nanotube encapsulation to sustain the drug release. Epigallocatechin-3-gallate (EGCG) and Halloysite nanotubes (HNTs) were prepared to produce three variant combinations of modified adhesive (EGCG, EGCG-encapsulated HNT, and EGCG-free HNT). The drug loading efficiency and EGCG release over time were evaluated using UV-vis spectrometry. MMP-mediated β-casein (BCN) cleavage rate assays were used to determine the ability of the EGCG in eluates of the adhesive to inhibit MMP-9 activities. For up to 8 weeks, HNT encapsulation reduced release to a statistically significant level. MMP-mediated β-casein cleavage rate assays showed a significant decrease for the EGCG groups compared to the non-EGCG adhesive groups. Furthermore, the use of HNT for EGCG encapsulation to modify a dental adhesive helped slow down the rate of EGCG release without impacting its MMP inhibitory capabilities, which may help to maintain the dentin-resin interface's integrity over the long term after dental restoration placement.

Shelf-Life Stability of Ready-to-Use Green Rooibos Iced Tea Powder-Assessment of Physical, Chemical, and Sensory Properties

Green rooibos extract (GRE), shown to improve hyperglycemia and HDL/LDL blood cholesterol, has potential as a nutraceutical beverage ingredient. The main bioactive compound of the extract is aspalathin, a C-glucosyl dihydrochalcone. The study aimed to determine the effect of common iced tea ingredients (citric acid, ascorbic acid, and xylitol) on the stability of GRE, microencapsulated with inulin for production of a powdered beverage. The stability of the powder mixtures stored in semi-permeable (5 months) and impermeable (12 months) single-serve packaging at 30 °C and 40 °C/65% relative humidity was assessed. More pronounced clumping and darkening of the powders, in combination with higher first order reaction rate constants for dihydrochalcone degradation, indicated the negative effect of higher storage temperature and an increase in moisture content when stored in the semi-permeable packaging. These changes were further increased by the addition of crystalline ingredients, especially citric acid monohydrate. The sensory profile of the powders (reconstituted to beverage strength iced tea solutions) changed with storage from a predominant green-vegetal aroma to a fruity-sweet aroma, especially when stored at 40 °C/65% RH in the semi-permeable packaging. The change in the sensory profile of the powder mixtures could be attributed to a decrease in volatile compounds such as 2-hexenal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,Z)-2,6-nonadienal and (E)-2-decenal associated with "green-like" aromas, rather than an increase in fruity and sweet aroma-impact compounds. Green rooibos extract powders would require storage at temperatures ≤ 30 °C and protection against moisture uptake to be chemically and physically shelf-stable and maintain their sensory profiles.

Opportunities and challenges for the nanodelivery of green tea catechins in functional foods

Green tea, the least processed tea product, is scientifically known for its rich antioxidant content originating from polyphenols, especially catechins. The most potent green tea catechin is epigallocatechin-3-gallate (EGCG), which is responsible for a wide range of health benefits including anticancer, antidiabetics, and anti-inflammatory properties. However, green tea catechins (GTCs) are very labile under both environmental and gastrointestinal conditions; their chemical stability and bioavailability primarily depend on the processing and formulation conditions. Nanocarriers can protect GTCs against such conditions, and consequently, can be applicable for designing nanodelivery systems suitable for GTCs. In this review, the latest findings about both opportunities and limitations for the nanodelivery of GTCs and their incorporation into various functional food products are discussed. The scientific findings so far confirm that nanodelivery of GTCs can be an efficient approach towards the enhancement of their health-promoting effects with a minimal dose, controlled and targeted release, lessening the dose-related toxicity, and the efficient incorporation into functional foods. However, further investigation is yet needed to fully explain the cellular mechanisms of action of GTCs on human health and to elucidate the effect of encapsulation on their bioefficacy using well-designed, systematic, long-term, and large-scale clinical interventions. There also exists a substantial concern regarding the safety of the manufactured nanoparticles, their absorption, and the associated release mechanisms.

Chemometric Analysis of Extracts and Fractions from Green, Oxidized, and Microbial Fermented Teas and Their Correlation to Potential Antioxidant and Anticancer Effects

Previous reports on phytochemicals in green tea (GT) and processed teas mainly focused on more representative compounds such as catechins. Here, we focus on the insignificantly studied non-catechin components in tea extracts, and explore the multivariate correlation between diverse phenolic compounds in tea and the in vitro antioxidant and anticancer effects. Extracts from GT and four types of processed teas were further divided into hydrophilic and hydrophobic fractions, whose phenolic compositions and antioxidant capacities were quantified using HPLC-MS and three antioxidant assays, respectively. For three types of teas, the anticancer effects of their extracts and fractions were assessed using cancer cell lines. The hydrophobic fractions had lower antioxidant capacities than the corresponding hydrophilic fractions, but exhibited superior antiproliferative effects on cancer cells compared with the whole extract and the hydrophilic fraction. Partial least squares-discriminant analysis revealed a strong correlation between the anticancer effects and the theaflavins and flavonols. Therefore, in addition to catechins, the hydrophobic fraction of tea extracts may have beneficial health effects.

Development and Characterization of Gelled Double Emulsions Based on Chia (Salvia hispanica L.) Mucilage Mixed with Different Biopolymers and Loaded with Green Tea Extract (Camellia sinensis)

The aim of this research was to develop and characterize five gelled double emulsions based on chia mucilage (CM) and different biopolymers (κ-carrageenan, C; locust bean gum, L; thixogum, T; and whey protein concentrate, W) loaded with green tea extract (GTE). Gelled double emulsions consisted of W₁ (whey-protein-concentrate/sodium-azide/NaCl/GTE)/O and (PGPR/canola-oi)/W₂ (CM, CMC, CML, CMT and CMW), and were characterized based on physicochemical properties during 35 days of storage. Optical microscopy clearly showed the drops of the internal phase surrounded by droplets of oil dispersed in the second aqueous phase; the droplet size was higher for CMT and lowest for CMW. In addition, all emulsions were highly stable at creaming and were effective in reducing the loss of antioxidant activity (88.82%) and total phenols (64.26%) during storage; CMT, CML and CM were the most effective. Furthermore, all emulsions showed a protective effect by modulating the release of the GTE in a simulated gastrointestinal environment, allowing a controlled release during the gastric-intestinal digestion phases and reaching its maximum release in the intestinal phase (64.57–83.31%). Thus, gelled double emulsions are an alternative for the preservation of GTE and could be a potential alternative for their application in the development of functional foods.

Antioxidative, Anti-Inflammatory, and Anticancer Effects of Purified Flavonol Glycosides and Aglycones in Green Tea

(1) Background: Extensive research has focused on flavan-3-ols, but information about the bioactivities of green tea flavonols is limited. (2) Methods: In this study, we investigated the antioxidative, anti-inflammatory, and anticancer effects of flavonol glycosides and aglycones from green tea using in vitro cell models. The fractions rich in flavonol glycoside (FLG) and flavonol aglycone (FLA) were obtained from green tea extract after treatment with tannase and cellulase, respectively. (3) Results: FLG and FLA contained 16 and 13 derivatives, respectively, including apigenin, kaempferol, myricetin, and quercetin, determined by mass spectrometry. FLA exhibited higher radical-scavenging activity than that of FLG. FLG and FLA attenuated the levels of intracellular oxidative stress in neuron-like PC-12 cells. The treatment of RAW 264.7 murine macrophages with FLG and FLA significantly reduced the mRNA expression of inflammation-related genes in a dose-dependent manner. Furthermore, FLG and FLA treatments decreased the viability of the colon adenoma cell line DLD-1 and breast cancer cell line E0771. Moreover, the treatment with FLG or FLA combined with paclitaxel had synergistic anticancer effects on the DLD-1 cell line. (4) Conclusions: Flavonols from green tea exerted beneficial effects on health and may be superior to flavan-3-ols.

Effects of β-Cyclodextrin and Sodium Ascorbate on the Chemical Compositions and Sensory Quality of Instant Green Tea Powder during Storage

The physicochemical changes of the instant green tea powders added with β-cyclodextrin and sodium ascorbate stored at 4°C and 25°C were investigated by determining moisture, polyphenols, caffeine, amino acids, catechins, color, sensory quality, and the total microbial count. The results showed that addition of both β-cyclodextrin (6%, w/w) and sodium ascorbate (2%, w/w) reduced the changes of moisture, polyphenols, and catechins contents, helped to maintain the sensory quality, and limited the microbial count. The low temperature (4°C) was also found to maintain the sensory quality and limit of the microbial count of instant green tea powder. The combination of low temperature and addition of β-cyclodextrin with sodium ascorbate were the best treatment for the storage of instant green tea powder. These results could provide useful information for the quality improvement of instant green tea powder during storage.

Impact of Bioconversion of Gallated Catechins and Flavonol Glycosides on Bioaccessibility and Intestinal Cellular Uptake of Catechins

Two bioconversions were applied to green tea extracts (GTE) and flavonol glycoside rich fraction (FVNg) derived from insoluble green tea extract by tannase and cellulase treatment in order to obtain gallated catechins (EnzGTE) and flavonol aglycone rich fraction (FVNa), respectively. The bioaccessibility of epicatechins from GTE increased with the addition of FVNg, FVNa, and flavonol aglycone rich fraction of commercial production (FVNap). Epigallocatechin-gallate (EGCG) and epicatechin-gallate (ECG) were highly recovered 4- and 125-fold, respectively, by adding FVNap. They were mostly affected by the radical scavenging activity provided from FVNap, showing remarkable 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (10769.3 μg/g) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) (8341.5 μg/g) values. The intestinal cellular uptake of epicatechins in GTE increased with the FVNap addition as follows: EGCG (332.46 ± 136.18%) > ECG (273.92 ± 97.92%) > epicatechin (EC) (150.22 ± 12.59%) > epigallocatechin (EGC) (131.21 ± 8.51%). EnzGTE and EnzGTE + FVNa were revealed to have a significant downregulation on the expression of P-glycoprotein (P-gp), up to 0.06- and 0.6-fold, respectively. The gene expression of multidrug resistance associated proteins 2 (MRP2) was reduced in EnzGTE + FVNap. The results suggest that coconsumption GTE or EnzGTE with GTE-derived flavonols could improve the bioavailability of epicatechins.

Phenolic and physicochemical stability of a functional beverage powder mixture during storage: effect of the microencapsulant inulin and food ingredients

BACKGROUND

The need for a convenience herbal iced tea product with reduced kilojoules merited investigation of the shelf-life of powder mixtures containing a green Cyclopia subternata Vogel (honeybush) extract with proven blood glucose-lowering activity and alternative sweetener mixture.

RESULTS

Prior to long-term storage testing, the wettability of powder mixtures containing food ingredients and the compatibility of their components were confirmed using the static sessile drop method and isothermal microcalorimetry, respectively. The powders packed in semi-sealed containers remained stable during storage at 25 °C/60% relative humidity (RH) for 6 months, except for small losses of specific phenolic compounds, namely mangiferin, isomangiferin, 3-β-d-glucopyranosyliriflophenone, vicenin-2 and 3',5'-di-β-d-glucopyranosylphloretin, especially when both citric acid and ascorbic acid were present. These acids drastically increased the degradation of phenolic compounds under accelerated storage conditions (40 °C/75% RH). Accelerated storage also caused changes in the appearance of powders and the colour of the reconstituted beverage solutions. Increased moisture content and a_w of the powders, as well as moisture released due to dehydration of citric acid monohydrate, contributed to these changes.

CONCLUSION

A low-kilojoule honeybush iced tea powder mixture will retain its functional phenolic compounds and physicochemical properties during shelf-life storage at 25 °C for 6 months. © 2017 Society of Chemical Industry.

Amorphization of thiamine chloride hydrochloride: A study of the crystallization inhibitor properties of different polymers in thiamine chloride hydrochloride amorphous solid dispersions

Amorphous solid dispersions of thiamine chloride hydrochloride (THCl) were created using a variety of polymers with different physicochemical properties in order to investigate how effective the various polymers were as THCl crystallization inhibitors. THCl:polymer dispersions were prepared by lyophilizing solutions of THCl and amorphous polymers (guar gum, pectin, κ-carrageenan, gelatin, and polyvinylpyrrolidone (PVP)). These dispersions were stored at select temperature (25 and 40°C) and relative humidity (0, 23, 32, 54, 75, and 85% RH) conditions and monitored at different time points using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Moisture sorption isotherms of all samples were also obtained. Initially amorphous THCl was produced in the presence of ≥40% w/w pectin, κ-carrageenan, gelatin, and guar gum or ≥60% w/w PVP. Trends in polymer THCl crystallization inhibition (pectin≥κ-carrageenan>gelatin>guar gum≫PVP) were primarily based on the ability of the polymer to interact with THCl via hydrogen bonding and/or ionic interactions. The onset of THCl crystallization from the amorphous dispersions was also related to storage conditions. THCl remained amorphous at low RH conditions (0 and 23% RH) in all 1:1 dispersions except THCl:PVP. THCl crystallized in some dispersions below the glass transition temperature (T_g) but remained amorphous in others at T~T_g. At high RHs (75 and 85% RH), THCl crystallized within one day in all samples. Given the ease of THCl amorphization in the presence of a variety of polymers, even at higher vitamin concentrations than would be found in foods, it is likely that THCl is amorphous in many low moisture foods.

Green Tea Leaves Extract: Microencapsulation, Physicochemical and Storage Stability Study

Green tea polyphenols have been reported to possess many biological properties. Despite the many potential benefits of green tea extracts, their sensitivity to high temperature, pH and oxygen is a major disadvantage hindering their effective utilization in the food industry. Green tea leaves from the Cameron Highlands Malaysia were extracted using supercritical fluid extraction (SFE). To improve the stability, green tea extracts were encapsulated by spray-drying using different carrier materials including maltodextrin (MD), gum arabic (GA) and chitosan (CTS) and their combinations at different ratios. Encapsulation efficiency, total phenolic content and antioxidant capacity were determined and were found to be in the range of 71.41%–88.04%, 19.32–24.90 (g GAE/100 g), and 29.52%–38.05% respectively. Further analysis of moisture content, water activity, hygroscopicity, bulk density and mean particles size distribution of the microparticles were carried out and the results ranged from; 2.31%–5.11%, 0.28–0.36, 3.22%–4.71%, 0.22–0.28 g/cm³ and 40.43–225.64 µm respectively. The ability of the microparticles to swell in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was determined as 142.00%–188.63% and 207.55%–231.77%, respectively. Release of catechin polyphenol from microparticles in SIF was higher comparable to that of SGF. Storage stability of encapsulated catechin extracts under different temperature conditions was remarkably improved compared to non-encapsulated extract powder. This study showed that total catechin, total phenolic content (TPC) and antioxidant activity did not decrease significantly (p ≥ 0.05) under 4 °C storage conditions. The half-life study results were in the range of 35–60, 34–65 and 231–288 weeks at storage temperatures of 40 °C, 25 °C and 4 °C respectively, therefore, for improved shelf-life stability we recommend that microparticles should be stored at temperatures below 25 °C.

Color and chemical stability of a variety of anthocyanins and ascorbic acid in solution and powder forms

The color and chemical stabilities of six anthocyanins, including cyanidin 3-glucoside, highly purified and present in semipurified extracts (also containing other anthocyanins) from grape pomace, purple corn, and black rice, were determined in combination with ascorbic acid in solutions at differing pH values (3.0 and 4.0) and temperatures (6-40 °C) and lyophilized powders at different relative humidities (43-98% RH). Color and chemical changes were analyzed using CIELAB measurements and HPLC, respectively. In liquids, stability was inversely related to increasing pH and temperature; for powders, stability was inversely related to RH. The mutual destruction of anthocyanins and ascorbic acid in solution was confirmed, with unexpected new findings showing no significant stabilizing/destabilizing effect based upon anthocyanin structure, including differing flavylium core (three types) and type of acylation (two aliphatic, one cinnamic acid), or final extract purity.

Water-solid interactions in amorphous maltodextrin-crystalline sucrose binary mixtures

Amorphous and crystalline solids are commonly found together in a variety of pharmaceutical and food products. In this study, the influence of co-formulation of amorphous maltodextrins (MDs) and crystalline sucrose (S) on moisture sorption, deliquescence, and glass transition (Tg) properties of powder blends was investigated. Individual components and binary mixtures of four different molecular weight MDs with sucrose in 1:1 w/w ratios were exposed to various relative humidity (RH) environments and their equilibrium and dynamic moisture contents were monitored. The deliquescence point (RH0) and dissolution behavior of sucrose alone and in blends was also monitored by polarized light microscopy and second harmonic generation imaging. In S:MD blends, the deliquescence RH of sucrose was lower than the RH0 of sucrose alone, and synergistic moisture sorption also occurred at RHs lower than the RH0. Intimate contact of sucrose crystals with the amorphous MDs resulted in complete dissolution of sucrose at RH < RH0. When blends were stored at conditions exceeding the Tg of the individual MDs (25 °C and 60%, 49% and 34%RH for MD21, MD29 and MD40, respectively), the Tg of the blends was lower than that of individual MDs. Thus, co-formulation of amorphous MDs with crystalline sucrose sensitizes the blend to moisture, potentially leading to deleterious changes in the formulation if storage conditions are not adequately controlled.

Kinetic study of catechin stability: effects of pH, concentration, and temperature

The degradation behaviors of catechins in dilute aqueous systems, including tea beverages and catechin solutions, have been documented; however, their reaction kinetics in green tea concentrated solutions, and impacts of pH, concentration, and temperature thereon, have not yet been established. In this study, reactions were conducted at pH levels ranging from 1.5 to 7, concentrations ranging from 1 to 1666.7 mg/mL, and temperatures ranging from 25 to 120 °C. Catechin contents were determined using high-performance liquid chromatography. Catechins were found to be more stable at high concentrations around pH 4. An empirical model for catechin content was established as a function of pH and temperature and showed good correlation between green tea concentrated solutions and previous reports of catechin stability in powder systems. These results provide useful approaches for shelf life calculations and catechin loss predictions at given temperature and pH conditions in green tea concentrates.

Effect of high relative humidity on dried Plantago lanceolata L. leaves during long-term storage: effects on chemical composition, colour and microbiological quality

INTRODUCTION

Modern phytotherapy and quality assurance requires stability data on bioactive metabolites to identify and minimise decomposing factors during processing and storage. A compound's stability in a complex matrix can be different from the stability of the purified compound.

OBJECTIVE

To test the stability of iridoids and acteoside and quantify changes in colour and microbiological quality in a common herbal tea, dried P. lanceolata leaves during exposure to high-humidity air. To test the contribution of fungi to metabolite decomposition.

METHODOLOGY

Dried P. lanceolata leaves were exposed to atmospheres of different relative humidity (75, 45 and 0%) for 24 weeks. Changes in aucubin and catalpol concentration were determined by CE-MEKC, and those in acteoside on TLC. Colour and chlorophyll-like pigments were measured by different spectrophotometric methods. The number of fungi was monitored; 10 strains were isolated from the plant drug, and their ability to decompose the analytes of interest was tested.

RESULTS

During incubation at 75% relative humidity (RH), aucubin, catalpol and acteoside concentrations decreased by 95.7, 97.0 and 70.5%, respectively. Strong shifts were detected in CIELAB parameters a* and b* (browning) as a result of conversion of chlorophyll to pheophytin. Intensive microbial proliferation was also observed. Changes at 45 or 0% RH were typically insignificant. Seven of the 10 isolated fungal strains could decompose both iridoids, and five could decompose acteoside in vitro.

CONCLUSION

It was shown that exposure to water results in loss of bioactive molecules of P. lanceolata dried leaves, and that colonising fungi are the key contributors to this loss.

Kinetics of moisture-induced hydrolysis in powder blends stored at and below the deliquescence relative humidity: investigation of sucrose-citric acid mixtures

Previous studies have shown that deliquescent organic compounds frequently exhibit chemical instability when stored in environmental conditions above their deliquescence relative humidity (RH). The goal of the current study was to investigate the effect of atmospheric moisture on the long-term chemical stability of crystalline sucrose-citric acid mixtures following storage at RHs at and below the mutual deliquescence relative humidity (MDRH). Interestingly, it was found that sucrose hydrolysis can occur below the MDRH of 64% and was observed for samples stored at 54% RH. However, hydrolysis was not seen for samples stored at 33 or 43% RH. The rate of sucrose hydrolysis could be modeled by taking into account the rate and extent of moisture uptake, which in turn was dependent on the composition of the powder and the storage RH. A reaction mechanism initiated by capillary condensation and involving additional deliquescence lowering by the degradation products formed as a result of sucrose hydrolysis (glucose and fructose) was proposed.

Stability of green tea catechins in commercial tea leaves during storage for 6 months

To help meet the needs of consumers, producers of dietary tea products, and researchers for information on health-promoting tea ingredients, we determined by HPLC 7 catechins [(-)-epigallocatechin (EGC), (-)-catechin (C), (+)-epicatechin (EC), (-)-epigallocatechin 3-gallate (EGCG), (-)-gallocatechin 3-gallate (GCG), (-)-epicatechin 3-gallate (ECG), and (-)-catechin 3-gallate (CG)] in samples of 8 commercial green tea leaves of unknown history sold as tea bags in the United States, Korea, and Japan. The samples were stored at 20 degrees C and sampled at 1 wk and 1, 2, 4, and 6 mo. The following ranges in the initial values (0 controls) were observed (in mg/g tea leaves): EGC and C, 0 to trace amounts; EC, 1.9 to 21.1; EGCG, 13.3 to 113.0; GCG, 0.2 to 1.6; ECG, 5.7 to 50.5; CG 0.5 to 3.7; total catechins 36.5 to 169.7. Statistical analysis of the results and plots of changes in individual and total catechin levels as a function of storage time indicate a progressive decrease in the content in the total levels, most of which is due to losses in the most abundant catechins, EGCG and ECG. Possible mechanisms of degradations of catechins during storage and the possible significance of the results to consumers of tea are discussed.

Interaction of environmental moisture with powdered green tea formulations: relationship between catechin stability and moisture-induced phase transformations

This study investigated the effect of phase transformations of amorphous and deliquescent ingredients on catechin stability in green tea powder formulations. Blends of amorphous green tea and crystalline sucrose, citric acid, and/or ascorbic acid were analyzed by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), dynamic water vapor sorption, water activity measurements, and high-performance liquid chromatography (HPLC) after storage for up to 12 weeks at 0-75% relative humidity (RH) and 22 degrees C. The glass transition temperature (T(g)) of green tea was reduced to below room temperature (<22 degrees C) at 68% RH. Dissolution of deliquescent ingredients commenced at RH values below deliquescence points in blends with amorphous green tea, and these blends had greater water uptake than predicted by an additive model of individual ingredient moisture sorption. Catechin degradation was affected by T(g) of green tea powder and both dissolution and deliquescence of citric and ascorbic acids.