Stability Of Catechins Research Articles

Enhancement of catechin loaded in BSA-pullulan nanoparticles on the oxidation stability of pickering emulsion: Effect of concentration

Preventing and delaying the lipid rancidity especial O/W emulsion system is an important task in the food industry. Low solubility in aqueous/lipid phases and poor stability of catechins limited the antioxidant effect in O/W emulsion. To enhance the oxidative stability of O/W emulsions, bovine serum albumin (BSA)-pullulan (PUL) nanoparticles (BPNs) and catechins-loaded BPNs (BPCNs) were successfully fabricated via self-assembly in this paper. Fourier transform infrared (FTIR) spectra of BPNs and BPCNs indicated that self-assembly of BSA and PUL to form nanoparticles and loading of catechins in BPNs are all maintained through non-covalent interactions. Particle size distribution, zeta-potential, structural characterization and interfacial properties of BPNs and BPCNs showed that catechins act as cross-linking “bridge” among BSA molecules, leading to an increase in the mean particle size, surface charges, interfacial properties, radical scavenging activity of BSA-PUL nanoparticles. Compared with BPNs, BPCNs can significantly enhance the storage stability and oxidative stability of Pickering emulsions. In conclusion, enhancement of BPCNs on oxidative stability of the Pickering emulsions not only because of the radical scavenging activity of the loaded catechins, but also attributed to the effect of catechin loading on the increased interfacial charge and balanced the amino acids distribution of BSA in the BPCNs. This study highlights the excellent properties of BSA-pullulan-catechin nanoparticles as novel emulsifiers with high antioxidant activity and potential applications in the food industry.

Encapsulation and characterization of catechin and epicatechin microcapsules using yeast cell biocarriers

In this study, catechin and epicatechin compounds were encapsulated using Saccharomyces cerevisiae yeast cell and fabricated yeast cell microcarriers were subjected to bioactive analysis, conformational and morphological characterization. Encapsulation efficiency values of the yeast cell microcarriers were 24.74 and 31.87% for the epicatechin and catechin loaded yeast cell microcapsules, respectively. Total flavonoid content of the epicatechin and catechin loaded yeast cell microcapsules were determined to be 79.67 and 61.86 mg CE/g while the antiradical activity of the samples was in the range of 4.16-39.24%. FT-IR and XRD spectrum revealed that the catechin and epicatechin were encapsulated by the yeasts cell successfully.

Microwave-Assisted Extraction Optimization and Effect of Drying Temperature on Catechins, Procyanidins and Theobromine in Cocoa Beans.

Cocoa beans (Theobroma cacao L.) are an important source of polyphenols. Nevertheless, the content of these compounds is influenced by post-harvest processes. In this sense, the concentration of polyphenols can decrease by more than 50% during drying. In this study, the process of procyanidins extraction was optimized and the stability of catechins, procyanidins, and theobromine to different drying temperatures was evaluated. First, the effectiveness of methanol, ethanol, acetone, and water as extract solvents was determined. A Box-Behnken design and response surface methodology were used to optimize the Microwave-Assisted Extraction (MAE) process. The ratios of methanol-water, time, and temperature of extraction were selected as independent variables, whereas the concentration of procyanidins was used as a response variable. Concerning the drying, the samples were dried using five temperatures, and a sample freeze-dried was used as a control. The quantitative analyses were carried out by HPLC-DAD-ESI-IT-MS. The optimal MAE conditions were 67 °C, 56 min, and 73% methanol. Regarding the drying, the maximum contents of procyanidins were obtained at 40 °C. To our knowledge, this is the first time that the stability of dimers, trimers, and tetramers of procyanidins on drying temperature was evaluated. In conclusion, drying at 40 °C presented better results than the freeze-drying method.

Effects of catechin types found in tea polyphenols on the structural and functional properties of soybean protein isolate–catechin covalent complexes

Soy protein isolate (SPI) has useful functional properties, such as gelation, emulsification, and foaming. However, SPI is usually dense and has a unique spherical structure, which hinders its practical application. In this study, the effects of three typical catechins (epigallocatechin gallate (EGCG), epigallocatechin (EGC), and epicatechin (EC)) on the structure and functional properties of soy protein isolate (SPI) under alkali conditions were investigated. Compared with the native SPI, the fluorescence intensity of SPI–EC, SPI–EGC, and SPI–EGCG complexes decreased, while their fluorescence quenching rate and binding sites increased, indicating the formation of covalent complexes. The SPI–EGCG complex has a higher fluorescence quenching rate and more binding sites than those of SPI–EC and SPI–EGCG complexes. The emulsifying activity and stability of the SPI–EGCG complex were 1.16 m2/g and 147 min, respectively, higher than those of latter two complexes. Hence, the functional property of SPI and the stability of catechins could be improved by the covalent interaction between the two. This study provides new insights into the relationship between the type of polyphenol and the structure of SPI.

Polyphenol Encapsulates from the Waste Biomass of C. sinensis and Their Simulated Oral, Gastric, and Intestinal Stability Studies: Nutraceutical Application

Extraction of bioactive metabolites from waste biomass is a recent area of research; hence purification and HPLC-DAD-based quantification of polyphenols from neglected parts (fruit, flower, and coarse leaves) of Camellia sinensis were carried out. Purification of polyphenols was performed via fractionation process, and purity was attained up to 77%, while the quantified content of catechins attained up to 63.3% with excellent free radical inhibition (78.89–97.20%). Aiming the controlled release of polyphenols with improved shelf life, microencapsulates were prepared by spray-drying and freeze-drying processes. Maltodextrin and soy lecithin were used as two different wall materials, and maximum encapsulation efficiency was attained up to 69.05%. Furthermore, in vitro simulated studies presented maximum release (>50%) of catechins in the gastric phase followed by intestine and oral phases. Stability studies of free and microencapsulated polyphenols were performed with respect to quantified content of catechins and free radical scavenging activity. The findings resulted in a significant effect of microencapsulation on the release profile and stability of catechins as well as retention of antioxidant activity. Hence, this study suggests a new perspective for the utilization of bioactive microencapsulates from waste tea plant biomass to develop value-added products.

Structure, stability and antioxidant activity of dialdehyde starch grafted with epicatechin, epicatechin gallate, epigallocatechin and epigallocatechin gallate.

Catechins, a member of the flavonoids, exist widely in teas, and have health benefits. However, catechins have poor stability, which greatly limits their application. In order to improve the stability of catechins, different catechins including (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) were conjugated onto dialdehyde starch by acid-mediated coupling method. The structure, stability and antioxidant activity of dialdehyde starch-catechin conjugates were determined. Thin-layer chromatography and ultraviolet-visible spectroscopy, fluorescence, nuclear magnetic resonance and infrared spectra revealed that catechins were successfully conjugated onto dialdehyde starch, coupling between 6-H/8-H of catechins' A ring and dialdehyde starch's aldehyde groups. The conjugates presented an amorphous structure and sheet-like and/or blocky morphologies. As compared to dialdehyde starch, the conjugates showed enhanced thermal stability. Furthermore, the stability of catechins in pH 7.4 phosphate-buffered saline was improved after conjugating onto dialdehyde starch. The conjugates exhibited significantly higher antioxidant activities than dialdehyde starch, decreasing in the following order: dialdehyde starch-ECG, dialdehyde starch-EGCG, dialdehyde starch-EC, dialdehyde starch-EGC and dialdehyde starch. Dialdehyde starch-catechin conjugates have great potential as stable antioxidant agents. © 2022 Society of Chemical Industry.

An alternative strategy for enhancing stability and antimicrobial activity of catechins by natural deep eutectic solvents

The low stability and loss of antimicrobial activity of catechins limited their application in food preservation. In this study, four kinds of catechins including (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG), and (−)-epigallocatechin-3-gallate (EGCG) were selected as model compounds. Natural deep eutectic solvents (NADES) are a new generation of green solvents that have attracted much attention due to their unique characteristics. The effects of NADES on the stability and antimicrobial activity of catechins were investigated in the present study. Eight typical NADES, especially choline chloride/glycerol (ChG), were found to significantly enhance the thermal and storage stability of catechins. This finding accounted for by hydrogen bonding network formation between ChG and catechins, confirmed by FT-IR and 2D NMR analysis. Additionally, ChG decreased the minimum inhibitory concentration of catechins on Gram-positive and Gram-negative bacteria, which may be associated with its stabilizing property. The stability of catechins combined with NADES revealed their potential of applications in the food industry.

Lipase-catalyzed selective esterification of catechin

Catechins show strong antioxidant, antitumoral, antiviral, and anti-inflammatory activities. The uses of catechins in food, cosmetic, and pharmaceutical formulations seem very attractive. Unfortunately, solubility and stability of catechins are poor in apolar media, which limits their efficient uses. In order to improve the solubility of catechins in the oil phase and maintain their oxidation resistance, a regioselective enzymatic acylation was investigated. The effects of reaction medium, water content, carbon chain length of acyl donor and other factors on the acylation reaction were studied, catechins were enzymatically esterified with an aliphatic acid (stearic acid) using an immobilized lipase Novozym 435 in n-butanol. The results show that when the ratio between catechins and stearic acid was 1:5, adding molecular sieves 4A after 11 h of reaction and the temperature of 60 °C led to the maximum conversion yield of 60.36%. Studies have shown that catechin stearate has a higher antioxidant activity than vitamin E and dibutyl hydroxytoluene (BHT).

Improving the stability of catechin from gambier in β-cyclodextrin and nanoemulsion-based inclusion complexes

The application of catechin is limited due to low stability, however nanoencapsulation technology can improve catechin stability. This study aimed to determine the effect of the types and concentrations surfactants in the catechin encapsulation process on β-CD. Concentrations of surfactants used were Poloxamer 188 (NKP, 0.5%-1.5%), Tween 80 (NKT, 2,5% and 3%) without surfactants was used to control (NKB). The catechin nanoemulsion complex formed was inclusion them into β-CD (ratio 1:1), and dried by spray drying. The stability test showed a sample of NKP 1% was more stable with the lower turbidity and viscosity values, namely 175 NTU and 0.93 cP, NKT 2.5% (118 NTU and 0.94 cP), NKB (461 NTU and 4.0 cP). The size of the sample particle decreased according to an increase in the surfactant concentration, where the NKP 1% (37 nm) produced smaller particles, the appearance of clear and yellowish suspension. NKP 1% had the highest EE value, followed by that NKT 2.5%, and NKB, i.e. 91.9%, 89.5%, 77.4%, respectively. Sample NKP 1% had a morphology shape with compact structures and the highest crystallinity degree (92.4%). This research showed the use of surfactants could improve the stability of catechins compared to that without surfactants.

Dehydroascorbic Acid Affects the Stability of Catechins by Forming Conjunctions.

Although tea catechins in green tea and green tea beverages must be stable to deliver good sensory quality and healthy benefits, they are always unstable during processing and storage. Ascorbic acid (AA) is often used to protect catechins in green tea beverages, and AA is easily oxidized to form dehydroascorbic acid (DHAA). However, the function of DHAA on the stability of catechins is not clear. The objective of this study was to determine the effects of DHAA on the stability of catechins and clarify the mechanism of effects by conducting a series of experiments that incubate DHAA with epigallocatechin gallate (EGCG) or catechins. Results showed that DHAA had a dual function on EGCG stability, protecting its stability by inhibiting hydrolysis and promoting EGCG consumption by forming ascorbyl adducts. DHAA also reacted with (−)-epicatechin (EC), (−)-epicatechin gallate (ECG), and (−)-epigallocatechin (EGC) to form ascorbyl adducts, which destabilized them. After 9 h of reaction with DHAA, the depletion rates of EGCG, ECG, EC, and EGC were 30.08%, 22.78%, 21.45%, and 13.55%, respectively. The ability of DHAA to promote catechins depletion went from high to low: EGCG, ECG, EGC, and EC. The results are important for the processing and storage of tea and tea beverages, as well as the general exploration of synergistic functions of AA and catechins.

Dual effects of ascorbic acid on the stability of EGCG by the oxidation product dehydroascorbic acid promoting the oxidation and inhibiting the hydrolysis pathway

A series of incubation systems of pure (−)-Epigallocatechin gallate (EGCG), ascorbic acid (AA) and dehydroascorbic acid (DHAA) at 80 °C were performed to investigated the effect and mechanism of AA on the stability of EGCG. Results shows the dual function of AA, protect action at low concentration and promoting degradation at high concentration, and the critical concentration is about 10 mmol/L. The protective properties of AA due to the reversible reaction from AA to DHAA inhibiting oxidation pathway of EGCG to EGCG quinone or other activated intermediates, and both AA and DHAA can inhibit the hydrolysis of EGCG. The properties of promoting degradation is mainly due to the fact that DHAA, the oxidation product of AA, can react with EGCG to generate some ascorbyl adducts of EGCG. This result is helpful to control the stability of catechins and further clarify the complex interaction on healthy between EGCG and AA.

Effect of storage temperature on the decay of catechins and procyanidins in dark chocolate

The storage stability of catechins, procyanidins, and total flavonoids in dark chocolate was investigated. The obtained results showed that the degradation of flavonoids followed first-order reaction kinetics. Temperature-dependent degradation was modelled on the Arrhenius equation. The activation energy for the degradation of dark chocolate flavonoids during storage was 61.2 kJ/mol. During storage, flavonoids degraded more rapidly at 35°C (k = 7.8 × 10<sup>–3</sup>/day) than at 22°C (k = 5.4 × 10<sup>–3</sup>/day) and 4°C (k = 2.2 × 10<sup>–3</sup>/day).

Influence of water quality on nutritional and sensory characteristics of green tea infusion

AbstractImpact of water quality on the nutritional and sensory characteristics of green tea infusion was studied. The total soluble tea solids, catechins and l‐theanine concentrations were significantly higher in infusions prepared from water having lower total dissolved solids (TDS, 0.59 to 13.0 ppm), conductivity (1.12 to 26.20 µS), and pH (6.04 to 6.90). The difference in extractability was explained using the mass transfer equation dNT/dt = kLAs(CTe − CTL); where dNT/dt‐mass transfer rate, kL‐mass transfer coefficient, As‐surface area, CTe‐equilibrium concentration, and CTL‐concentration in bulk liquid. The major catechins reduced (∼84–93%) in the infusions prepared from water with higher TDS (315 to 338 ppm), conductivity (630 to 679 µS), and pH (7.65 to 8.05), accompanied with undesirable color changes during storage following the first‐order kinetics. Tea cream and turbidity were much higher with water having higher calcium concentration (51.60 mg/L). The study recommended water with low TDS, conductivity and pH for hot‐infusions and beverages.Practical applicationsThe study was initiated to select a suitable type of water for the preparation of green tea infusion and ready‐to‐drink (RTD) beverages. For infusion, the extractability of the nutrients as well as the sensory characteristics are important. Accordingly, ultra‐pure (UP), packaged drinking (PD), or reverse osmosis (RO) water may be used for the preparation. But, in the case of RTD beverages, the physical stability and visual appearance are also equally important for consumer acceptance, as they are held in storage and distribution before being consumed. Furthermore, the results indicated that stability of catechins need to be considered as a parameter for the selection of water. Even though UP, PD, or RO meets all these criteria, economic considerations propel RO water for RTD production. Thus the inferences obtained from this scientific study has practical relevance in the selection of appropriate quality of water for the preparation of green tea beverages.

Formation and Characterization of Green Tea Extract Loaded Liposomes.

Green tea extract was encapsulated into liposomes to enhance bioavailability and stability of catechins by protecting their functional properties simultaneously. Encapsulation was achieved by dispersing 1% (w/v) soy lecithin through high pressure homogenization (microfluidization) and ultrasonication. Effects of homogenization type and pH of the dispersing medium on the physical properties and stability of the liposomes during 1-mo storage period were investigated. Mean particle size, total phenolic content by Folin-Ciocalteu method and antioxidant activity by 2-diphenyl-1-picrylhydrazyl radical scavenging and ferric reducing-antioxidant power methods, and transmission electron microscopy (TEM) experiments were conducted for characterization. Green tea extract loaded liposomes prepared by microfluidization in distilled water were determined as the most stable system which demostrated no significant difference (P > 0.05) on mean particle size, total phenolic content, and antioxidant activity between the first and final day of 1-mo storage time. Additionally, uniform size and shape in TEM images supported the results.

Effect of the type of brewing water on the chemical composition, sensory quality and antioxidant capacity of Chinese teas

The physicochemical characteristics, sensory quality, and antioxidant activity of tea infusions prepared with purified water (PW), mineral water (MW), mountain spring water (MSW), and tap water (TW) from Hangzhou were investigated. The results showed that the taste quality, catechin concentration, and antioxidant capacity of green, oolong, and black tea infusions prepared using MW and TW were significantly lower than those prepared using PW. Extraction of catechins and caffeine was reduced with high-conductivity water, while high pH influenced the stability of catechins. PW and MSW were more suitable for brewing green and oolong teas, while MSW, with low pH and moderate ion concentration, was the most suitable water for brewing black tea. Lowering the pH of mineral water partially improved the taste quality and increased the concentration of catechins in the infusions. These results aid selection of the most appropriate water for brewing Chinese teas.

Stability of catechins in green tea nutraceutical products: Application of solid phase extraction–thin layer chromatography densitometry

Epigallocatechin gallate (EGCG) is a powerful antioxidant and commonly used nutraceutical. Accelerated stability of EGCG in tablet formulations was investigated. LLE and SPE were employed for sample clean-up and enrichment of EGCG over caffeine. Samples were analysed after spiking with fixed concentration of gallic acid (GA), in order to verify reproducibility of analysis. A TLC–densitometric assay was developed and validated for determination of % loss EGCG. EGCG, GA and caffeine were resolved with Rf values 0.54, 0.69 and 0.80, respectively. LC–MS/MS was used to verify identity and purity of the EGCG band. Determination was carried out over a concentration range of 0.50–5.00μg/band and 0.20–2.40μg/band for GA and caffeine, respectively. Results showed significant reduction in EGCG content after one, three and six months: 24.00%, 28.00% and 52.00% respectively. Results continue to demonstrate that stability of nutraceutical products should be investigated in-depth using industry-oriented protocols before granting marketing authorisation.

Degradation Kinetics of Catechins in Green Tea Powder: Effects of Temperature and Relative Humidity

The stability of catechins in green tea powders is important for product shelf life and delivering health benefits. Most published kinetic studies of catechin degradation have been conducted with dilute solutions and, therefore, are limited in applicability to powder systems. In this study, spray-dried green tea extract powders were stored under various relative humidity (RH) (43-97%) and temperature (25-60 °C) conditions for up to 16 weeks. High-performance liquid chromatography (HPLC) was used to determine catechin contents. Catechin degradation kinetics were affected by RH and temperature, but temperature was the dominant factor. Kinetic models as functions of RH and temperature for the individual 2,3-cis-configured catechins (EGCG, EGC, ECG, and EC) were established. The reaction rate constants of catechin degradation also followed the Williams-Landel-Ferry (WLF) relationship. This study provides a powerful prediction approach for the shelf life of green tea powder and highlights the importance of glass transition in solid state kinetics studies.

Green tea catechins during food processing and storage: A review on stability and detection

Green tea catechins can undergo degradation, oxidation, epimerization and polymerization during food processing. Many factors could contribute to the chemical changes of green tea catechins, such as temperature, pH of the system, oxygen availability, the presence of metal ions as well as the ingredients added. Several detection methods have been developed for tea catechin analysis, which are largely based on liquid chromatography (LC) and capillary electrophoresis (CE) methods for getting a good separation, identification and quantification of the catechins. Stability of green tea catechins is also influenced by storage conditions such as temperature and relative humidity. The stability of each catechin varies in different food systems and products. Pseudo first-order kinetic model has been developed and validated for the epimerization and degradation of tea catechins in several food systems, whereas the rate constant of reaction kinetics followed Arrhenius equation.

Covalent Binding of Tea Catechins to Protein Thiols: The Relationship between Stability and Electrophilic Reactivity

In this study, we investigated the relationship between the stability of catechins and their electrophilic reactivity with proteins. The stability of catechins was evaluated by HPLC analysis. Catechol-type catechins were stable in a neutral buffer, but pyrogallol-type catechins, such as (-)-epigallocatechin gallate (EGCg), were unstable. The electrophilic reactivity of catechins with thiol groups in a model peptide and a protein was confirmed by both mass spectrometry and electrophoresis/blotting with redox-cycling staining. In a comparison of several catechins, pyrogallol-type catechins had higher reactivity with protein thiols than catechol-type catechins. The instability and reactivity of EGCg were enhanced in an alkaline pH buffer. The reactivity of EGCg was reduced by antioxidants due to their ability to prevent EGCg autoxidation. These results indicate that the instability against oxidation of catechins is profoundly related to their electrophilic reactivity. Consequently, the difference in these properties of tea catechins can contribute to the magnitude of their biological activities.

Effect of process unit operations and long-term storage on catechin contents in EGCG-enriched tea drink

Due to the increasing market for functional foods and the chemopreventive action of ()-epigallocatechin gallate (EGCG), manufacturers produce ready-to-drink green tea infusions enriched or not in EGCG. However, the maintenance of green tea catechins stability in drinks is always a challenge. In this context, the objectives of this study were (1) to assess the catechin stability in tea drink during a 6-month storage, (2) to evaluate the impact of process unit operations on catechin stability and (3) to compare the catechin and caffeine contents of commercially available tea drinks. It appeared that the stability of catechins during long-term storage was optimum at low temperature (4 C) and acidic pH (pH 4.0). During the processing of the EGCG-enriched green tea drink, all the process unit operations, except heat-treatment, had no impact on catechin concentrations. In addition, in commercially available tea drinks, except enriched green tea drinks, their catechin contents are very low to provide health benefits.