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

Characterization of physicochemical properties of different epigallocatechin-3-gallate nanoparticles and their effect on bioavailability

Epigallocatechin-3-gallate (EGCG), a major catechin in green tea, exhibits potent antioxidant and disease-preventive properties, but its application is limited by poor stability and bioavailability. This study aimed to address these challenges by preparing and characterizing three EGCG-loaded nanoparticles: chitosan-EGCG-tripolyphosphate nanoparticles (CE-NPs), β-cyclodextrin-EGCG (BE-NPs), and EGCG-nanostructured lipid carriers (NE-NPs). BE-NPs exhibited the highest loading performance and retention rate under thermal environment (89.78 % after 10 h at 80 °C). NE-NPs had the highest EGCG stability in alkaline condition (45 % after 4 h at pH 7.4). Compared to free EGCG, all NPs significantly improved in vitro bioaccessibility following incubation in simulated gastrointestinal digestion for 4 h; BE-NPs enhanced oral bioavailability by 1.71 times in vivo. Additionally, CE-NPs and NE-NPs increased the relative abundance of Faecalibaculum, Erysipelotrichaceae, and Bifidobacterium in the colons of Sprague-Dawley rats. These findings suggest that BE-NPs are a promising nano-delivery system for enhancing EGCG stability and bioavailability in healthy organisms.

Optimizing brewing conditions for low-temperature green tea infusions: Insights into functional and nutritional properties

In response to growing demand for functional, minimally processed foods and rising energy costs, various brewing conditions for low-temperature green tea production were explored as an alternative to high-temperature processing. Optimal polyphenol extraction was achieved at 85 °C for 30 min using distilled water and finely ground leaves (< 500 μm). Although similar conditions are recommended for tap water, this resulted in a tremendous reduction in both catechin yields and antioxidant capacity (AC), as determined by spectrophotometric and chromatographic analyses. Lowering extraction temperature to 20 °C and brewing for 12 h with distilled water led to exceptionally high AC, along with higher yields of vitamin C, vitamin B2, epicatechin, and epigallocatechin compared to any high-temperature brewing method. Notably, these benefits were evident only when whole leaves were used, rather than tea powder. Further research is needed to address technological challenges for industrial green tea production with distilled water.

Dynamic changes in chemical components, volatile profile and antioxidant properties of Xanthoceras sorbifolium leaf tea during manufacturing process

In order to elucidate the dynamic changes of quality characteristics in Xanthoceras sorbifolium leaf tea (XLT), this work investigated the chemical components, volatile profile, and antioxidant properties at key stages of fixation, shaping, and drying. The process of fixation and drying emerged as critical stages that affected the chemical components and taste of XLT. Total polyphenols, reducing sugars and chlorophyll were the differential compounds, which decreased by 29.1 %, 63.3 % and 69.5 % during processing, respectively. Threonine, glycine, arginine, reducing sugar, caffeine, catechin (C), and epicatechin gallate (ECG) were primary taste characteristic compounds. A total of 95 volatile organic components (VOCs) and 24 key odorants with relative odor activity value (ROAV) > 1.0 were identified in XLT, ethyl 2-methylbutanoate-D, dimethyl disulfide, and ethyl isobutyrate (ROAV = 100) were the central contributors to volatiles profile. Moreover, tea manufacturing enhanced the antioxidant potency composite (APC) by 1.1 %, primarily due to its high water extract content.

Characteristic Changes and Potential Markers of Flavour in Raw Pu-Erh Tea with Different Ageing Cycles Analysed by HPLC, HS-SPME-GC-MS, and OAV

To investigate the flavour evolution mechanism of raw Pu-erh tea (RPT) during storage, the volatile and non-volatile compounds of RPT with different storage years (1-10 years) from the same raw material origin, manufacturer, and storage location in Wenshan Prefecture, Yunnan Province, were systematically analysed by HPLC, HS-SPME-GC-MS, and OAV. The results showed that both cluster analyses based on non-volatile and volatile compounds could classify RPT of different storage years into three ageing cycles, with key turning points in the third and eighth years of storage, which is also accompanied by the colour changing from green to orange or brown, the aroma changing from a faint scent to woody and ageing, the astringency diminishing, and the sweet and mellow increasing. Theophylline was identified as the potential marker of RPT stored 1-3 years, while (-)-catechin gallate, (-)-gallocatechin gallate, quercetin, and rutin as those for a storage of 9-10 years. The volatile compounds indicate a general trend of an initial increase followed by a decrease. Forty-four key aroma compounds (OAV ≥ 1) were identified. Eucalyptol, β-Caryophyllene, 2-Amylfuran, Copaene, Estragole, and α-Terpinene originated as potential markers for RPT stored 1-3 years, while (Z)-Linalool oxide (furanoid), α-Terpineol, Terpinen-4-ol, and cis-Anethol were for RPT stored 8-10 years. This study revealed the flavour characteristics and quality changes of RPT over the course of storage, and constructed a sensory flavour wheel, providing theoretical underpinnings for the quality control and assessment of RPT.

Pectin as the carrier for the spray drying of green tea extracts: Tailoring microencapsulation to obtain a prospective nutraceutical

In this study, microencapsulated green tea (GT) extracts, as prospective nutraceuticals, were obtained using spray drying with pectin in different pectin-to-extract (P:E) ratios. Pectin was selected as wall material based on its previously reported superiority to encapsulate phenols, low cost/sustainability of production and intrinsic hypoglycemic and antioxidant potential. A significant degradation (13.74 %) of epigallocatechin was observed in powder without pectin, in contrast to pectin-loaded samples, suggesting its role in chemical stability enhancement of stated compound. FTIR and DSC indicated GT extract bioactives to remain stable during drying. Addition of pectin significantly increased encapsulation efficacy (EE) of epigallocatechin-3-gallate (up to 8.94 %), epicatechin-3-gallate (up to 7.68 %) and caffeine (up to 12.39 %) compared to pectin-free sample. Significant EE enhancement for epigallocatechin-3-gallate was observed until the P:E ratio of 1:1 compared to pectin-free sample, while further increase of pectin share did not lead to a comparative increase in EE. Similar trend was observed for powder flowability, probably due to excess of pectin in the highest P:E ratio (2:1), preventing proper droplets formation, which was also confirmed by SEM. Sample with P:E ratio of 1:1 revealed the slowest release of bioactives, which may be important for facilitating potential GT therapeutic usage. Stated microencapsulate further revealed satisfactory antioxidant (IC50 of 23.70 μg/ml vs. 4.45 μg/ml for ascorbic acid) and hypoglycemic activities (IC50 of 39.48 μg/ml vs. 156.64 μg/ml for acarbose). These findings represent the basis for further experiments regarding usage of the developed GT microencapsulate as nutraceutical applicable in diabetes-related impairments.

Green Tea: Current Knowledge and Issues

Green tea possesses antioxidant, anti-inflammatory, anticancer, and antimicrobial activities, reduces body weight, and slows down aging. These effects are primarily attributed to catechins contained in green tea leaves, particularly epigallocatechin-3-gallate. However, in humans, the realization of green tea's beneficial effects is limited. In order to summarize and critically analyze the available scientific information about green tea's health benefits and issues related to its use, we conducted an in-depth literature review in scientific databases. A number of in vitro studies reported that green tea catechins modulate various signaling pathways in cells, which is thought to underlie their beneficial effects. However, data on the effects of catechins in humans are scarce, which is partly due to their low stability and oral bioavailability. Furthermore, catechins may also participate in pharmacokinetic interactions when co-administered with certain drugs such as anticancer agents, drugs for cardiovascular diseases, immunosuppressors, etc. As a result, adverse drug reactions or therapy failure may occur. In conclusion, over the years, various approaches have been investigated to optimize catechin intake and to achieve beneficial effects in humans, but to date, the use of catechins for prophylaxis or disease treatment remains limited. Therefore, future studies regarding the possibilities of catechins administration are needed.

Catechins in cancer therapy: integrating traditional and complementary approaches

Catechin is a group of bioactive flavonoids found in various plant sources such as tea, cocoa, and fruits. Recent studies have suggested that catechins has significant potential in preventing and treating cancer. Catechin exhibits a variety of biological activities that may contribute to its anticancer effects, including antioxidant, anti-inflammatory, and pro-apoptotic properties. Studies have demonstrated that catechin can inhibit cancer cell proliferation, induce cell cycle arrest, and promote apoptosis across multiple cancer types, including skin, breast, lung, liver, prostate, and colon cancers. Furthermore, catechin has shown the ability to inhibit angiogenesis, a critical process for tumor growth and metastasis, by restricting new blood vessel formation. Catechin's impact on cancer extends beyond its direct effects on cancer cells. It modulates various signaling pathways involved in cancer progression, such as those associated with cell survival, inflammation, and metastasis. Despite these promising findings, additional research is needed to clarify the precise mechanisms of catechin's anticancer action, optimal dosing strategies, and long-term safety in cancer prevention and treatment. This review will explore the current research landscape on tea polyphenols, particularly catechin, and their potential role in cancer prevention and therapy.

Effect of different drying temperature settings on the color characteristics of Tencha

Color is critical factor in the commercialization of Matcha. In this study, sensory evaluation, color difference analysis, as well as targeted and non-targeted analyses were employed to investigate the impact of different drying temperature settings on the color characteristics of Tencha. The findings revealed that compared to a single drying temperature setting, a two-stage or multi-stage drying process more effectively preserved the color quality of Tencha. Specifically, a setting involving an initial period of high-temperature drying followed by low-temperature drying (samples T_6, T_7, T_10, and T_13) resulted in superior tea color quality, characterized by higher chlorophyll content and lower levels of lutein and β-carotene. Chemometric analysis identified chlorophylls and their derivatives (chlorophyll a/b, pheophytin a/b, pyropheophytin a/b) as the key factors influencing Tencha's color. These results can provide valuable insights for optimizing tea processing methods to enhance quality.

Mechanism of red pigment formation in lotus rhizome soup during cooking: The role of polyphenols, iron and organic acids

Lotus rhizome soup, renowned as a unique delicacy made from lotus rhizome, is cherished by many consumers. However, the varying colors of soup are sure to influence individuals' appetites. This research focused on the Miancheng lotus Rhizome (MLR) and Elian No. 6 lotus rhizome (ELR) to investigate the relationship between the variations in polyphenols, organic acids and iron levels in MLR and ELR soups during the cooking process. The findings indicated that cooking MLR for 12 min resulted in a red soup with a* value of 8.65 ± 0.12, whereas the soup made from ELR remained white with a* value of 3.43 ± 0.08. The correlation analysis results indicated that polyphenols, specifically epigallocatechin (0.0169 ± 0.00029 μg/100 mL FW after cooking for 12 min) and epicatechin (0.0211 ± 0.00047 μg/100 mL FW after cooking for 12 min), exhibited a significant positive relationship with a* (p < 0.05). Moreover, lowering the pH, removing polyphenols and incorporating metal-chelating agents can also prevent the development of red pigment. The analysis from HPLC-MS, UV-Vis, FT-IR spectra and ESI-Q-TOF-MS indicated that the development of the red soup color involved i) the generation of epicatechin gallate through the enantiomeric reaction of epigallocatechin, ii) the co-chromic red interaction between anthocyanin cations and catechol structures, and iii) the formation of polyphenol oligomers (i.e., procyanidin A2, (+)-procyanidin B2, procyanidin C1 and prodelphinidin B4) due to heating, while the creation of phenol-iron chelates could inhibit the development of red coloration. In sum, this research introduces a new idea for managing the color of lotus rhizome soup and similar soup products.

Targeted quantitative metabolomic and flavor objective quantification technique reveal the impact mechanism of shaking on black tea quality and non-volatile metabolites

Shaking constitutes a pivotal technique for enhancing black tea quality; nevertheless, its impact on the transformation mechanism of non-volatile metabolites (NVMs) in black tea remains obscure. The present study aimed to investigate the impact of shaking-withering methods (SWM) and traditional-withering methods (TWM) on black tea quality and NVMs conversion. A total of 57 NVMs and 14 objective quantitative indicators were obtained. SWM enhanced sweetness and umami taste, as well as appearance and liquor color brightness of black tea. Eight key differential NVMs were identified by multivariate statistical and dose over threshold value analysis. Metabolic pathway and evolution law analysis revealed that SWM enhanced the oxidation of catechins and flavonol glycosides, promoted the decarboxylation of glutamic acid, then facilitated the formation of theaflavin-3,3'-digallate, finally enhanced the taste and color quality of black tea. This study offers theoretical guidance and technical support for the targeted processing of high-quality black tea.

Comprehensive assessment of matcha qualities and visualization of constituents using hyperspectral imaging technology

Matcha, made from different tea leaves as raw material, exhibits diverse aromas and flavors. Therefore, there is an urgent need for a rapid, non-destructive method to assess the quality of matcha to ensure that these different characteristics are accurately assessed without compromising the integrity of the product. In this study, hyperspectral imaging technology (HSI) combined with machine learning methods enabled the first visual in situ assessment of matcha quality. The physicochemical contents of matcha were determined chemically. Qualitative and quantitative detection models for different types and grades were developed using HSI (containing Vis-NIR and NIR band). The results showed that hyperspectral data in the Vis-NIR were better than in the NIR band. The accuracy of XGBoost in modelling the classification of matcha grades reached 98.10 %. After feature selection using the random forest (RF) method, partial least squares regression (PLSR) was built to predicted the quality of matcha, which showed high prediction accuracy (test set Rp2 > 0.95). The model uses HSI to visually visualize spatial variations in constitutions (catechins, free amino acids, caffeine, soluble proteins, and soluble sugars) to show compositional differences between different types of matcha, providing a rapid non-destructive method for comprehensive assessment of matcha quality.

The application of untargeted metabolomics coupled with chemometrics for the analysis of agitation effects on the sensory profiles of matcha tea

In the study, the effects of agitating parameters (different agitating rates and time) on the aroma and taste profiles of matcha tea were systematically investigated by the combination of untargeted metabolomics and chemometrics. The aroma profiles of matcha tea agitated at low rates (500 rpm) and for 30 s were more richness than that agitated with other parameters by sensory analysis and gas chromatography-ion mobility spectrometry. The key aroma compounds contributed to the sensory differences of matcha tea agitated at different rates and time were analyzed by gas chromatography-mass spectrometry and partial least square-discriminate analysis (PLS-DA), which were further verified by the triangle test. Thereinto, 2,4-decadienal associated with the sweet, brown and seaweed aroma significantly affected the aroma profiles of matcha tea with different agitating rates and time. The levels of bitterness and astringency were also higher in matcha tea with low agitating rates and time by sensory evaluation, which were attributed to the variations of phenolic compounds. Flavonol glycosides, gallic acid and (-)-gallocatechin were determined the key compound to the taste differences of matcha tea with different agitating parameters by the analysis of PLS-DA based on the results of high performance liquid chromatography and the sensory verification. And flavonol glycosides were mainly contributed to the bitterness and astringency, and gallic acid and (-)-gallocatechin influenced the umami and sweetness of matcha tea. Consequently, agitation has the potential to affect the sensory profiles of matcha tea by changing aroma and taste substances.

The enhanced affinity of moderately hydrolyzed whey protein to EGCG promotes the isoelectric separation and unlocks the protective effects on polyphenols

The instability and discoloration of (-)-epigallocatechin-3-gallate (EGCG) constrain its application in functional dairy products. Concurrently, challenges persist in the separation and utilization of whey in the dairy industry. By harnessing the interactions between polyphenols and whey proteins or their hydrolysates, this study proposed a method that involved limited enzymatic hydrolysis followed by the addition of EGCG and pH adjustment around the isoelectric point to obtain whey protein hydrolysates (WPH)-EGCG. Over 92 % of protein-EGCG complexes recovered from whey while ensuring the preservation of α-lactalbumin. The combination between EGCG and WPH depended on hydrogen bonding and hydrophobic interactions, significantly enhanced the thermal stability and storage stability of EGCG. Besides, the intestinal phase retention rate of EGCG in WPH-EGCG complex was significantly increased by 23.67 % compared to free EGCG. This work represents an exploratory endeavor in the improvement of EGCG stability and expanding the utilization approaches of whey.

Biological activity, limitations and steady-state delivery of functional substances for precision nutrition

Food-related functional substances with biological activity serve as a crucial material foundation for achieving precision nutrition, which has gained increasing attraction in regulating physiological functions, preventing chronic diseases, and maintaining human health. Nutritional substances typically include bioactive proteins, peptides, polysaccharides, polyphenols, functional lipids, carotenoids, probiotics, vitamins, saponins, and terpenes. These functional substances play an essential role in precise nutrition. This chapter introduces and summarizes typical functional substances to demonstrate the challenges in precision nutrition for their stability, solubility, and bioavailability. The current status of delivery systems of functional substances is described to give an insight into the development of desirable characteristics, such as food grade status, high loading capacity, site targeting, and controlled release capacity. Finally, the applications of food-borne delivery systems of functional substances for precision nutrition are emphasized to meet the requirement for precision nutrition during nutritional intervention for chronic diseases.

Aroma and taste analysis of pickled tea from spontaneous and yeast-enhanced fermentation by mass spectrometry and sensory evaluation

Anaerobically fermented pickled tea (PT) can be produced by spontaneous fermentation (SF) or yeast-enhanced fermentation (YF). Aroma and taste characteristics of PT during YF and SF were investigated using sensory evaluation, odour activity, aroma character impact values, HS-SPME-GC-MS, UPLC-QQQ-MS/MS, and spectrophotometry, annotating 198 volatile and 115 non-volatile components. The main contributing volatile components were β-ionone, and 1-octanol, promoted by YF and SF, and yielding floral and fruity aromas respectively. Additionally, compared with SF, YF promoted the formation of citronellol yielding a floral aroma, inhibited the stale aroma of methoxybenzenes, and reduced bitter, astringent, and sour tastes. Furthermore, partial least-squares regression analysis identified the main components related to the 'acides aroma' of PT as linalool oxide, n-decanoic acid, hexanoic acid, 3,7-dimethyl-2,6-octadienoic acid, 3-methyl-1-dodecyn-3-ol, and nerolidol. This application could be used as methodology for the comprehensive analysis of tea aroma and taste and these results can act as guidelines for PT production and quality control.

Quality characteristics and cooking-induced changes on phenolic compounds of dried green tea noodles

Incorporating green tea powder (GTP) into wheat flour-based noodles can significantly improve nutritional value. So, this study investigated the effects of GTP (0%, 0.5%, 1%, 1.5%, and 2.0%) on the quality properties of dried green tea noodles (DGTN) and cooking-induced changes to phenolic compounds. Mixolab analysis of wheat flour with GTP showed more water absorption of dough, and the developed dough had a firmer structure. GTP markedly increased the toughness of the noodle sheet. DGTN fortified with GTP showed more stable textural properties during cooking and storage, representing higher hardness and tensile strength. The viscosity and thermal properties of DGTN showed that GTP affected the gelatinization and retrogradation behavior of starch, which were closely related to the textural properties. Overall, DGTN prepared with 1.5% GTP showed better quality properties. However, ultra-performance liquid chromatography-time (UPLC/Q-TOF-mass spectrometry [MS]/MS) analysis showed that cooking by boiling significantly decreased phenolic content in 1.5% DGTN; further analysis revealed that the thermal degradation is a key factor in the loss of polyphenols. Therefore, further studies are necessary to focus on the mechanism of cooking-induced polyphenol loss, which is of great significance for improving the nutritional value of cooked DGTN.

Identification and quality evaluation of Lushan Yunwu tea from different geographical origins based on metabolomics

The relationship between the chemical composition and quality of Lushan Yunwu tea (LYT) from different geographical origins is not clear. Sensory evaluation, metabolomics analyses combined with chemometrics were conducted on LYT from 8 different geographical origins, and altitude was identified as the main factor responsible for the differences among LYT. A total of 32 non-volatile and 27 volatile compounds were identified as marker metabolites to distinguish the origins of high altitudes from those of low altitudes. LYT samples from higher altitude areas contained more free amino acids, sugars, and organic acids, and less catechins, which may contribute to the reduction of bitterness and astringency and the enhancement of umami. The contents of geranylacetone, ethyl hexanoate, ethyl caprylate, 3-carene, d-cadinene, linalool, nerol, and nerolidol in high altitude areas were higher than those in low altitude areas, indicating that LYT from high altitude had strong floral and fruity aroma. The altitudes were positively correlated with pH value, total flavonoids, soluble protein, total free amino acids, and the antioxidant capacities of the LYT. This study provided a theoretical basis for the study of the effect of altitude on tea quality.

Predictive models for sensory score and physicochemical composition of Yuezhou Longjing tea using near-infrared spectroscopy and data fusion

In this study, NIR quantitative prediction model was established for sensory score and physicochemical components of different varieties and quality grades of Yuezhou Longjing tea. Firstly, L, a, b color factors and diffuse reflection spectral data are collected for each sample. Subsequently, the original spectrum is preprocessed. Three techniques for selecting variables, CARS, BOSS, and SPA, were utilized to extract optimal feature bands. Finally, the spectral data extracted from feature bands were fused with L, a and b color factors to build SVR and PLSR prediction models. enabling the rapid non-destructive discrimination of different varieties and grades of Yuezhou Longjing tea. The outcomes demonstrated that BOSS was the best variable selection technique for sensory score and the distinctive caffeine wavelengths, CARS, however, was the best variable selection technique for catechins distinctive wavelengths. Additionally, the middle-level data fusion-based non-linear prediction models greatly outperformed the linear prediction models. For the prediction models of sensory score, catechins, and caffeine, the relative percent deviation (RPD) values were 2.8, 1.6, and 2.6, respectively, suggesting the good predictive ability of the models. In conclusion, evaluating the quality of the five Yuezhou Longjing tea varieties using near-infrared spectroscopy and data fusion have proved as feasible.

Caffeoylquinic acid profiling: comparative analysis in yerba mate, Indian camphorweed, and stevia extracts with emphasis on the influence of brewing conditions and cold storage in yerba mate infusion

Herbal infusions exhibit diverse pharmacological effects, such as antioxidant, anti-inflammatory, anticancer, antihypertensive, and antineurodegenerative activities, which can be attributed to the high content of phenolic compounds (e.g., caffeoylquinic acids (CQAs)). In this study, we used ultraperformance liquid chromatography to determine the content of CQAs in the methanolic extracts of model herbs, namely, yerba mate (Ilex paraguariensis), stevia (Stevia rebaudiana), and Indian camphorweed (Pluchea indica (L.) Less.). The results revealed that yerba mate had the highest total CQA content (108.05 ± 1.12 mg/g of dry weight). Furthermore, we evaluated the effect of brewing conditions and storage at 4 °C under dark and light conditions on the antioxidant property and total phenolic and CQA contents of a yerba mate infusion. The analysis of the yerba mate infusions prepared with different steeping times, dried leaf weights, and water temperatures revealed that the amount of extracted CQAs was maximized (∼175 mg/150 mL) when 6 g of dried leaves were steeped in hot water for 10 min. A total of 10-day refrigerated storage resulted in no significant changes in the antioxidant activity and total phenolic and CQA contents of an infusion kept in a brown container (dark). However, the antioxidant properties and total phenolic and CQA contents were negatively affected when kept in a clear container, suggesting the detrimental effect of light exposure. Our study provides practical recommendations for improving the preparation and storage of herbal infusions, thus catering to the needs of consumers, food scientists, and commercial producers. Moreover, it is the first study of the influence of light exposure on the content of crucial quality attributes within plant-based beverages.

Study on color, aroma, and taste formation mechanism of large-leaf yellow tea during an innovative manufacturing process

This study used samples processed with an innovative manufacturing process to explore the dynamic changes of large-leaf yellow tea (LYT) in color, aroma, and taste substances, and the quality components were most significantly affected in the stages of first pile-yellowing (FP) and over-fired drying (TD). In this process, the moisture and temperature conditions caused chlorophyll degradation, Maillard reactions, caramelization reactions, and isomerization of phenolic substances, forming the quality of LYT. Specifically, chlorophyll degradation favored the formation of color quality; the taste quality was determined by the content of soluble sugars, amino acids, catechins, etc.; the aroma quality was dependent on the content changes of alcohols and aldehydes, as well as the increase of sweet and roasting aroma substances in the third drying stage. Additionally, twelve key aroma components, including linalool, (E)-β-ionone, 2,3-diethyl-5-methyl-pyrazine, etc., were identified as contributors to revealing LYT rice crust-like and sweet aroma formation mechanism.

Mechanism of aroma enhancement methods in accelerating Congou black tea acidification subjected to room temperature storage

Acidification of aroma-enhanced black tea during storage was studied. UPLC-Q-TOF/MS (Ultra Performance Liquid Chromatography and Quadrupole-Time of Flight Mass Spectrometer) and HPLC (High-Performance Liquid Chromatography) analysis of non-volatile substances and organic acids revealed a decrease of soluble sugars and amino acids in aroma-enhanced black tea, while an increase in organic acids such as oxalic acid, malic acid and quinic acid. Further in vitro experiments indicated that the acidification of aroma-enhanced tea during storage can be attributed to decomposition of sugars and amino acids by heating, oxidation of aromatic aldehydes. Meanwhile, the amino acids, catechins, soluble sugars and flavonoids that constitute the taste of black tea are further reduced, changing the taste composition of tea infusion and further increasing its acidity. This study revealed the reasons for black tea acidification during aroma enhancement and storage and provided a theoretical basis for improving black tea quality.

Storage stability and degradation mechanism of xanthohumol in Humulus lupulus L. and beer

Xanthohumol (XN), possessing potent physiological activity, is exclusively derived from hops (Humulus lupulus L.) and exhibits high instability. However, its inherent instability often results in degradation during storage, leading to a decline in its activity due to the formation of various products. This study aimed to explore the stability of XN in beer under different storage conditions, establish or clarify degradation kinetic models, and understand the degradation mechanism. Our findings revealed that XN would degrade rapidly when exposed to high temperature and light. Its degradation followed a first-order kinetic model, involving reactions such as isomerization, hydration and ortho-position cyclization, resulting in the formation of five products. These insights shed light on the factors and mechanisms underlying the instability and degradability of XN, serving as a foundation for the development of a stable beer product enriched with functional XN.

Effects of Different Expansion Temperatures on the Non-Volatile Qualities of Tea Stems

Tea stems are a type of tea by-product, and a considerable amount of them is discarded during picking, with their value often being overlooked. To enhance the utilization of tea stems, we investigated the effects of different expansion temperatures on the non-volatile compounds of tea stems. The results showed that the contents of EC, EGC, EGCG, tea polyphenols, and amino acids all decreased with the expansion temperature, while the contents of GA and C increased. The best effect was observed at 220 °C for 20 s. Additionally, as the temperature increased, the umami and aftertaste of astringency values of tea stems decreased, and the value of bitterness increased. Meanwhile, the value of sweetness decreased first and then increased. EGC was identified as the key differential compound of tea stems at different temperatures. In this investigation, determining the optimum expansion temperature was deemed advantageous for enhancing the flavor quality of tea stems, consequently elevating the utilization efficacy of tea stems and tea by-products.

Understanding the physical breakdown and catechin bioaccessibility of third generation extruded snacks enriched with catechin using the human gastric simulator

The nutritional quality of third-generation snacks prepared from rice flour by extrusion can be improved by the addition of polyphenols such as catechins, which are known to be more stable at high temperatures. However, the extrusion parameters can impact the breakdown and release of bioactive compounds and decrease the catechin bioaccessibility. Accordingly, this study investigated the impact of different extrusion parameters, including different extrusion temperatures (110, 135, and 150 °C) and moisture content prior to extrusion (27 and 31%), on the breakdown and bioaccessibility of catechin-enriched snacks during in vitro dynamic digestion using the Human Gastric Simulator (HGS). The extrusion parameters did not significantly impact most measured variables by themselves, indicating that within the tested ranges, any of the processing conditions could be used to produce a product with similar digestive behavior. However, the interaction of extrusion parameters (temperature and moisture content) played a significant role in the snack behavior during digestion. For example, the combination of 27% moisture content and 150 °C extrusion temperature had higher catechin bioaccessibility and higher starch hydrolysis than the other treatments. Overall, these findings suggest that the processing conditions of third generation snacks enriched with catechin can be optimized within certain ranges with limited modifications in the digestive properties.

Impact of storage time on non-volatile metabolites and fungal communities in Liupao tea using LC-MS based non-targeted metabolomics and high-throughput sequencing

Long-term storage of Liupao tea (LPT) is usually believed to enhance its quality and commercial value. The non-volatile metabolites variations and the fungal succession play a key role for organoleptic qualities during the storage procedure. To gain in-depth understanding the impact of storage time on the quality of LPT, two different brands of LPT with different storage time, including Maosheng LPTs (MS) with 0, 5, 10 and 15 years and Tianyu LPTs (TY) with 0, 3, 5, 8 and 10 years, were resorted to investigate the changes of non-volatile metabolites and fungi as well as their correlation by multi-omics. A total of 154 and 119 differential metabolites were identified in these two different brands of MS and TY, respectively, with the aid of high-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry. In both categories of LPTs, the transformation of differential metabolites in the various stages referred to the formation of alkaloids, increase of organic acids, biosynthesis of terpenoids as well as glycosylation and methylation of flavonoids. Thereinto, glycosylation and methylation of flavonoids were the critical stages for distinguishing MS and TY, which were discovered in MS and TY stored for about 10 and 8 years, respectively. Moreover, the results of high-throughput sequencing showed that the key fungal genera in the storage of LPTs consisted of Eurotium, Aspergillus, Blastobotrys, Talaromyces, Thermomyces and Trichomonascus. It was confirmed on the basis of multivariate analysis that the specific fungal genera promoted the transformation of metabolites, affecting the tea quality to some extent. Therefore, this study provided a theoretical basis for the process optimization of LPT storage.

Extraction of (+)-catechin from oak (Quercus spp.) bark: Optimization of pretreatment and extraction conditions

Oaks (Quercus L., Fagaceae) are a widespread tree species worldwide, and in Hungary they account for nearly 30 % of the forests. Their wood is valuable, but their bark is considered as a by-product. Oak bark, available in large quantities but with no dedicated use, contains a significant amount of valuable extractives. Its (+)-catechin content is around 1 %. (+)-Catechin is mostly used for food industry, medicine and many other industrial purposes, representing a significant financial value. The aim of the present research was to compare the (+)-catechin concentrations in the bark of the most important oak species found in Hungary and to optimize sample pretreatment (conservation) and extraction methods in order to achieve fast and efficient extraction. From these species the highest concentrations were measured in Q. robur and Q. robur ssp. slavonica (8-12 mg (+)-catechin/g dry bark). The combination of microwave sample pretreatment and microwave assisted extraction proved to be the most time- and cost-effective method. The utilization of the extracted bark powder for energetic purposes requires further investigations.

Chitooligosaccharide-catechin conjugate loaded liposome using different stabilising agents: characteristics, stability, and bioactivities

AIM

To determine the optimum condition for preparing chitooligosaccharide-catechin conjugate (COS-CAT) liposomes using different stabilising agents.

METHODS

COS-CAT liposomes (0.1-1%, w/v) were prepared using soy phosphatidylcholine (SPC) (50-200 mM) and glycerol or cholesterol (25-100 mg). Encapsulation efficiency (EE), loading capacity (LC), physicochemical characteristics, FTIR spectra, thermal stability, and structure of COS-CAT liposomes were assessed.

RESULTS

COS-CAT loaded liposome stabilised by cholesterol (COS-CAT-CHO) showed higher stability as shown by the highest EE (76.81%) and LC (4.57%) and the lowest zeta potential (ZP) (-76.51 mV), polydispersity index (PDI) (0.2674) and releasing efficiency (RE) (53.54%) (p < 0.05). COS-CAT-CHO showed the highest retention and relative remaining bioactivities of COS-CAT under various conditions (p < 0.05). FTIR spectra revealed the interaction between the choline group of SPC and -OH groups of COS-CAT. Phase transition temperature of COS-CAT-CHO was shifted to 184 °C, which was higher than others (p < 0.05).

CONCLUSION

SPC and cholesterol-based liposome could be used as a promising vesicle for maintaining bioactivities of COS-CAT.

Green Synthesis of Silver Nanoparticles: Optimizing Green Tea Leaf Extraction for Enhanced Physicochemical Properties

In this paper, we present the optimization of green tea leaf (Camellia sinensis L.) extraction, carried out using water and hydroalcoholic solvents, for the subsequent synthesis of silver nanoparticles (AgNPs). The value ranges for independent variables, including pH, time, and temperature, were selected based on single-factor experiments and used for extraction in the order presented by the Box-Behnken design. Three-dimensional response surface graphs were used to visually present the optimization results and determine the optimal extraction conditions: pH = 7, 30 min, 80 °C for water and pH = 5.5, 50 min, and 80 °C for water-ethanol. Our findings indicate that the water-ethanol mixture extracted more polyphenols. We compared the physicochemical properties of AgNPs obtained using both types of extractants via DLS and TEM analysis. We proposed a predicted mechanism for the reduction and stabilization of AgNPs based on the Fourier transform infrared data. The hydroethanolic extract leads to significant nanoparticle aggregation, which can be explained by the nucleation theory and agglomeration of nanoparticles in the presence of excess macromolecular organic substances (flocculation).

Effects of processing methods on quality, antioxidant capacity, and cytotoxicity of Ginkgo biloba leaf tea product

BACKGROUND

Ginkgo biloba leaves contain beneficial flavonoids, bilobalide (BB), and ginkgolides. However, the toxic ginkgolic acid (GA) limit its application. In this study, various traditional processing methods were used to prepare G. biloba leaf tea (GBLT), including white tea, black tea, dark tea, green tea, and freeze-dried as control, followed by investigations of their effects on quality, antioxidant capacity, bioactive components, and cytotoxicity of the tea products.

RESULTS

Results showed that different processing methods significantly impact the tea products' quality indexes and the principal component analysis (PCA) and hierarchical cluster analysis (HCA) corroborated it. White tea had the highest total sugar (TS) and GA content and the most potent cytotoxicity on HepG2 cells. However, TS and GA content and the cytotoxicity of GBLT markedly decreased during fermentation and fixation. Moreover, white tea possessed higher total phenolic content (TPC), total flavonoid content (TFC), and more vigorous antioxidant activities than green tea, black tea, and dark tea. Terpene trilactones value was stable, but different catechins contents fluctuated according to the manufacturing process of different GBLTs. Among the four GBLTs, dark tea combining fixation and fermentation had the lowest GA content and cytotoxicity, less bioactive components reduction, appropriate quality, and stronger flavor.

CONCLUSION

These findings demonstrate that fixation and fermentation help reduce GAs during the manufacturing of GBLT. However, their ability to retain bioactive substances needs further optimization in future studies. © 2023 Society of Chemical Industry.

Effect of Spice Incorporation on Sensory and Physico-chemical Properties of Matcha-Based Hard Candy

The present study was carried out to formulate and determine the sensory, proximate, phytochemical, and antioxidant properties of matcha hard candies incorporated with spices such as ginger (Zingiber officinale Rosc.), cinnamon (Cinnamomum zeylanicum and Cinnamon cassia), and holy basil (tulsi) (Ocimum sanctum L.). Standardized matcha (Camellia sinensis) hard candy was taken as a control, and spices/herbs were incorporated in different concentrations. The best formulation was GC5 (2% ginger powder) for matcha ginger hard candy, CZ10 (0.9% cinnamon powder) for matcha cinnamon hard candy, and TC7 (3% tulsi powder) for matcha tulsi hard candy. These formulations were selected based on the organoleptic evaluation. Furthermore, these selected hard candies were evaluated for the determination of proximate, phytochemical, and antioxidant profiles which exhibited significant results. This study demonstrates the excellent nutritional and phytochemical potential that spiced matcha hard candy has for use as a nutraceutical food product.

Catechins and Selenium Species-How They React with Each Other

The combination of selenium and tea infusion, both with antioxidant properties, has potentially complementary mechanisms of action. Se-enriched tea has been considered as a possible Se supplement and a functional beverage to reduce the health risk of Se deficiency. This work investigated the interactions between plant catechins present in tea infusions and selenium species based on changes in the concentration of both reagents, their stability in aqueous solutions, and the possibilities of selenonanoparticles (SeNPs) formation. Selenium species exhibited instability both alone in their standard solutions and in the presence of studied catechins; selenocystine appeared as the most unstable. The recorded UV-Vis absorption spectra indicated the formation of SeNPs in the binary mixtures of catechins and selenite. SeNPs have also formed with diameters smaller than 100 nm when selenite and selenomethionine were added to tea infusions. This is an advantage from the point of view of potential medical applications.

Synergistic Effects of Heat-Treated Green Tea Extract and Enzymatically-Modified Isoquercitrin in Preventing Obesity

Previous research has shown that both heat-treated green tea extract (HTGT) and enzymatically modified isoquercitrin (EMIQ) have anti-obesity effects. Given the absence of in vivo evidence demonstrating their synergistic effects, our study aimed to elucidate the combined obesity prevention potential of HTGT and EMIQ in mice. Mice were treated with these compounds for 8 weeks, while being fed a high-fat diet, to investigate their preventive anti-obesity effects. We demonstrated that the co-treatment of HTGT and EMIQ results in a synergistic anti-obesity effect, as determined by a Kruskal-Wallis test. Furthermore, the combined treatment of HTGT and EMIQ was more effective than orlistat in reducing body weight gain and adipocyte hypertrophy induced by high-fat diet. The co-treatment also significantly reduced total body fat mass and abdominal fat volume. Additionally, the group receiving the co-treatment exhibited increased energy expenditure and higher glucose intolerance. We observed a dose-dependent upregulation of genes associated with mitochondrial oxidative metabolism and PKA signaling, which is linked to lipolysis, in response to the co-treatment. The co-treatment group displayed elevated cAMP levels and AMPK activation in adipose tissue and increased excretion of fecal lipids. The results indicate that the co-treatment of HTGT and EMIQ holds the potential to be a promising combination therapy for combating obesity. To further validate the anti-obesity effect of the combined treatment of HTGT and EMIQ in human subjects, additional clinical studies are warranted.

Comprehensive investigation on flavonoids metabolites of Longjing tea in different cultivars, geographical origins, and storage time

In this study, four kinds of Longjing tea, the famous flat green tea and the protected geographical indication product in China, were used to explore the quality difference of the same green tea due to the cultivar, geographic origin, and storage time under the premise of consistent picking conditions and processing technology using the widely targeted metabolomics. Results showed that 483 flavonoid metabolites with 10 subgroups of flavonoids were screened and 118 differential flavonoid metabolites were identified. The number and subgroups of differential flavonoid metabolites produced by different cultivars of Longjing tea were the largest, followed by storage time, and third by the geographic origin. Glycosidification and methylation or methoxylation were the main structural modifications of differential flavonoid metabolites. This study has enriched the understanding of the effects of the cultivar, the geographic origin, and the storage time on the flavonoid metabolic profiles of Longjing tea, and provided worthy information for the traceability of green tea.

New insights of the application of water or ethanol-water plant extract rich in active compounds in food

Plants are recognized as natural sources of antioxidants (e.g., polyphenols, flavonoids, vitamins, and other active compounds) that can be extracted by green solvents like water, ethanol, or their binary mixtures. Plant extracts are becoming more used as food additives in various food systems due to their antioxidant abilities. Their application in food increases the shelf life of products by preventing undesirable changes in nutritional and sensory properties, such as the formation off-flavors in lipid-rich food. This review summarizes the most recent literature about water or ethanol-water plant extracts used as flavors, colorings, and preservatives to fortify food and beverages. This study is performed with particular attention to describing the benefits of plant extract-fortified products such as meat, vegetable oils, biscuits, pastries, some beverages, yogurt, cheese, and other dairy products. Antioxidant-rich plant extracts can positively affect food safety by partially or fully replacing synthetic antioxidants, which have lately been linked to safety and health issues such as toxicological and carcinogenic consequences. On the other hand, the limitations and challenges of using the extract in food should be considered, like stability, level of purity, compatibility with matrix, price, sensory aspects like distinct taste, and others. In the future, continuous development and a tendency to use these natural extracts as food ingredients are expected, as indicated by the number of published works in this area, particularly in the past decade.

Collagen hydrolysates improve the efficiency of sodium alginate-encapsulated tea polyphenols in beads and the storage stability after commercial sterilization

This study showed that sodium alginates (SA)-based beads reinforced with collagen hydrolysates (CHs) significantly increased an encapsulation rate of tea polyphenols (TP) from 34.54 % to 85.06 % when the mass ratio of SA: CHs increased from1.5:0 to 1.5:0.5. And after the 30-day storage at 37 °C, the retention rate of TP in beads with CHs at the solutions with pH = 4.0 or pH = 7.0 increased from 61.10 % to 80.21 %, or from 67.72 % to 80.47 % after sterilization at 98 °C or 121 °C for 30 min, respectively. Also, the addition of CHs at 0.5 % resulted in a greater retention of the polyphenolic compositions values of TP determined by UPLC-Orbitrap-MS system. Additionally, the DPPH and ABTS+ free-radical scavenging capacities and ferric-reducing antioxidant power of beads with CHs after sterilization at 98 °C or 121 °C for 30 min were significantly higher than which without CHs. Physical phenomena based on ζ-potential, particle size, fluorescence, UV spectroscopy and confocal laser scanning microscope showed that tightly non-covalent complexes of CHs in combination to TP could be uniformly and stably distributed in the network of SA solution for encapsulating TP in SA-based beads. These findings provided suggestions for the co-encapsulation design and development of hydrophilic nutritive compounds based on CHs in SA-based beads.

The effect of natural antioxidants, pH, and green solvents upon catechins stability during ultrasonic extraction from green tea leaves (Camellia sinensis)

BACKGROUND

This is a first-time report to evaluate the effect of natural antioxidants, pH, and green solvents upon catechins yield and stability during the active process of extraction from green tea leaves.

METHODOLOGY

Green solvents (model-A) augmented with piperine (PPN) and quercetin (QT) as natural antioxidants (model-B) at different pH 2-6 (model-C) were used to extract catechins from green tea leaves using an ultrasonic extraction process (USE). For quantification of catechins (EC; epicatechins, ECG; epicatechin gallate, and EGCG; epigallocatechin gallate), a green and sensitive UHPLC-MS/MS method was developed and validated.

RESULTS

The UHPLC-MS/MS method showed an accuracy of 98.3-102.6 % within the linearity range of 1-500 ppb for EC (m/z) 289 → 245 → 109, ECG (m/z) 441.2 → 169 → 289, and EGCG (m/z) 457.1 → 169 → 125.1. The general yield (ppb) for EC, ECG, and EGCG was observed with the ranges and sum of (N = 180) 0.06-157.80 and 6696.83, 0.04-316.93 and 12632.60 and, 0.12-584.11 and 26144.83, respectively. Model-C revealed the highest yield for catechins at the lowest pH-2 with an individual catechin yield of EGCG (584.11) > ECG (316.93) > EC (157.80) in CW2. In terms of stability, EGCG was the most unstable catechin whereas, catechins extracted in model-B exhibited more stability (%recovery of 14.70 for EC, 10.55 for ECG, and 5.36 for EGCG in BEP). Moreover, model-B showed the minimal degradation for catechins within the range of 11.81-94.64 (BEP); even the most degradable EGCG was seen with the smallest %loss of 11.81-94.64 at time 24-70 h, as compared to the loss of > 95 % in model-A and C. The ANOVA score for catechins yield was; F_11,168 = 61.06 (EC), F_11,168 = 66.53 (ECG), and F_11,168 = 48.92 (EGCG) (P = 0.00) with mean scores of (M = 94.63, SD = 25.46) for EC, (M = 194.87, SD = 51.41) ECG, and (M = 357.57, SD = 96.80) EGCG in CE2.

CONCLUSION

A significant effect on catechins yield and stability was observed with the use of natural antioxidants and lowest pH-2.

Achieving dual functions of texture modification and water retention of shrimp surimi products with the combination of epigallocatechin-3-gallate and γ-cyclodextrin

Epigallocatechin-3-gallate (EGCG) exhibits excellent cross-linking effects of myofibrillar proteins, it is prone to self-aggregation, causing excessive cross-linking and moisture loss of gels, which limits its application as a food additive in surimi products. Here, through combination γ-cyclodextrin and EGCG into one inclusion complex, we achieved proper usage of EGCG in shrimp surimi products: elevating both water holding capability and texture properties (hardness, chewiness and resilience). Moreover, the mechanism behind excellent performance was elucidated: as texture modifiers, the complexes improved gel network integrity through intermolecular interactions and moderated disulfide bonds; and as water retainer agents, the complexes promoted transformation of nitrogen in proteins towards the form of protonated amino, facilitating the occurrence of hydration. Furthermore, the inclusion complexes brought a higher phenolic retention within products in contrast with direct addition of EGCG. This work may propose novel insights for the usage of polyphenols as additives in surimi-based products.

Gut microbiota-mediated metabolism of green tea catechins and the biological consequences: An updated review

Multiple beneficial effects have been attributed to green tea catechins (GTCs). However, the bioavailability of GTCs is generally low, with only a small portion directly absorbed in the small intestine. The majority of ingested GTCs reaches the large intestinal lumen, and are extensively degraded via biotransformation by gut microbiota, forming many low-molecular-weight metabolites such as phenyl-γ-valerolactones, phenolic acids, butyrate, and acetate. This process not only improves the overall bioavailability of GTC-derived metabolites but also enriches the biological activities of GTCs. Therefore, the intra- and inter-individual differences in human gut microbiota as well as the resulting biological contribution of microbial metabolites are crucial for the ultimate health benefits. In this review, the microbial degradation of major GTCs was characterized and an overview of the in vitro models used for GTC metabolism was summarized. The intra- and inter-individual differences of human gut microbiota composition and the resulting divergence in the metabolic patterns of GTCs were highlighted. Moreover, the potential beneficial effects of GTCs and their gut microbial metabolites were also discussed. Overall, the microbial metabolites of GTCs with higher bioavailability and bioactive potency are key factors for the observed beneficial effects of GTCs and green tea consumption.

The Catechins Profile of Green Tea Extracts Affects the Antioxidant Activity and Degradation of Catechins in DHA-Rich Oil

This study investigated the effect of the catechins profile on the antioxidant activity of green tea extracts (GTEs) by comparing the antioxidant activity of an EGC-rich GTE (GTE1, catechin content: 58% EGC, 30.1% EGCG, 7.9% EC, and 3.9% ECG) and an EGCG-rich GTE (GTE2, catechin content: 60.6% EGCG, 17.7% EGC, 11.8% ECG, and 9.8% EC) in a DHA-rich oil. The effects of the individual catechins (EGC, EC, EGCG, and ECG) and reconstituted catechins mixtures (CatMix), prepared to contain the same amount of major catechins as in the GTEs, were also measured. All treatments (GTE1, CatMix1, GTE2, CatMix2, EGC250, EC250, EGCG250, and ECG250), each containing epistructured catechins at a concentration of 250 ppm, as well as the control (oil with no added antioxidant), were stored at 30 °C for 21 days with sampling intervals of 7 days. The antioxidant activity was assessed by measuring the peroxide value (PV) and p-anisidine value (p-AV) of oils. Changes in fatty acid content and catechins content were also monitored. Both GTEs enhanced the oxidative stability of the DHA-rich oil, but GTE1 demonstrated a stronger antioxidant activity than GTE2. No significant difference was observed between the PV of treatments with GTE1 and CatMix1 during storage, whereas the PV of oil with GTE2 was significantly higher than that with CatMix2 after 21 days. Among the individual catechins, EGC was the strongest antioxidant. Overall, the antioxidant activities of the extracts and catechins were observed in the decreasing order GTE1 ≈ EGC250 ≈ CatMix1 > GTE2 > EGCG250 ≈ CatMix2 > ECG250 > EC250. A significant change in fatty acid content was observed for the control and EC250 samples, and the catechins were most stable in GTE1-supplemented oil. Our results indicate that the EGC-rich GTE is a more potent antioxidant in DHA-rich oil than the EGCG-rich GTE.

Characterisation of catechins and their oxidised derivatives in Ceylon tea using multi-dimensional liquid chromatography and high-resolution mass spectrometry

Tea is a complex food matrix comprising of many structurally diverse compounds, of which catechins and their oxidised derivatives are of particular interest due to their nutritional functionality. However, these catechins and derivatives exist in various isomeric forms with few or no pure standards available, rendering their analysis challenging. A method combining multi-dimensional liquid chromatography (MDLC) and high-resolution mass spectrometry (HRMS) was developed for the characterisation of these compounds using Ceylon tea as a model. Based on a Plackett-Burman (PB) design, flow rate and initial methanol percentage were identified as the most significant factors (p < 0.05) affecting chromatogram coverage and resolution (Rs) for comprehensive two-dimensional LC (LCxLC) and heart-cutting two-dimensional LC (LC-LC) respectively. Central composite design (CCD) was then applied using these parameters for method optimisation and to identify second-order relationships between screened parameters. The optimised LCxLC (flow rate: 2.18 mL/min and initial methanol percentage: 28.0%) and LC-LC (flow rate: 0.86 mL/min and initial methanol percentage for different cuts: A- 10.0%; B- 15.8%; and C- 18.7%) methods were applied to the analysis of Ceylon tea samples from seven regions of Sri Lanka and demonstrated an improved separation of co-eluting isomeric compounds. Finally, with the mass spectral information from HRMS, a total of 31 compounds (eight monomers, 17 dimers, five trimers and one tetramer) were detected and putatively identified in Ceylon tea.

Exploring The Relative Astringency of Tea Catechins and Distinct Astringent Sensation of Catechins and Flavonol Glycosides via an In Vitro Assay Composed of Artificial Oil Bodies

Artificial oil bodies covered by a recombinant surface protein, caleosin fused with histatin 3 (a major human salivary peptide), were employed to explore the relative astringency of eight tea catechins. The results showed that gallate-type catechins were more astringent than non-gallate-type catechins, with an astringency order of epicatechin gallate > epigallocatechin gallate > gallocatechin gallate > catechin gallate > epigallocatechin > epicatechin > gallocatechin > catechin. As expected, the extension of brewing time led to an increase in catechin content in the tea infusion, thus elevating tea astringency. Detailed analysis showed that the enhanced proportion of gallate-type catechins was significantly higher than that of non-gallate-type catechins, indicating that tea astringency was elevated exponentially, rather than proportionally, when brewing time was extended. Rough surfaces were observed on artificial oil bodies when they were complexed with epigallocatechin gallate (a catechin), while a smooth surface was observed on those complexed with rutin (a flavonol glycoside) under an atomic force microscope and a scanning electron microscope. The results indicate that catechins and flavonol glycosides induce the sensation of rough (puckering) and smooth (velvety) astringency in tea, respectively.

Improvement of Sourdough and Bread Qualities by Fermented Water of Asian Pears and Assam Tea Leaves with Co-Cultures of Lactiplantibacillus plantarum and Saccharomyces cerevisiae

Qualities of sourdough and sourdough bread using fermented water from Asian pears and Assam tea leaves with Lactiplantibacillus plantarum 299v and Saccharomyces cerevisiae TISTR 5059 as starter cultures were evaluated. Changes in the growth of lactic acid bacteria and yeast, pH, sourdough height, total phenolic contents (TPCs) and antioxidant activities detected by ORAC, FRAP and DPPH radical scavenging assays were monitored during sourdough production. Mature sourdough was achieved within 4 h after 18 h retard fermentation and used for bread production. The bread was then analyzed to determine chemical and physical properties, nutritional compositions, TPCs, antioxidant activities and sensory properties as well as shelf-life stability. Results showed that fermented water significantly promoted the growth of yeast and increased TPCs and antioxidant activities of sourdough. Compared to common sourdough bread, fermented water sourdough bread resulted in 10% lower sugar and 12% higher dietary fiber with improved consumer acceptability; TPCs and antioxidant activities also increased by 2–3 times. The fermented water sourdough bread maintained microbial quality within the standard range, with adequate TPCs after storage at room temperature for 7 days. Fermented water from Asian pears and Assam tea leaves with L. plantarum 299v and S. cerevisiae TISTR 5059 as starter cultures improved dough fermentation and bread quality.

Evaluating the Nutritional Properties of Food: A Scoping Review

There are many methods or indicators used for evaluating the nutritional value of foods; however, it is difficult to accurately reflect the comprehensive nutritional value of a food with a single indicator, and a systematic evaluation system is lacking. In this article, we systematically summarize the common evaluation methods and indicators of the nutritional value of foods. The purpose of this review was to establish an evaluation procedure for nutritional properties of foodstuffs and to help scientists choose more direct and economical evaluation methods according to food types or relevant indicators. The procedure involves the selection of a three-level evaluation method that covers the whole spectrum of a food's nutritional characteristics. It is applicable to scientific research in the fields of agricultural science, food science, nutrition, and so on.

Formation and stabilization of multiple w/o/w emulsions encapsulating catechin, by mechanical and microfluidic methods using a single pH-sensitive copolymer: effect of copolymer/drug interaction

Multiple w/o/w emulsions (MEs) are promising systems for protecting fragile hydrophilic drugs and controlling their release. We explore the capacity of a single pH-sensitive copolymer, PDMS₆₀-b-PDMAEMA₅₀, and salts, to form and stabilize MEs loaded with sucrose or catechin by a one-step mechanical process or a microfluidic method. ME cytotoxicity was evaluated in various conditions of pH. Using the mechanical process, the most stable emulsions were obtained with Miglyol®812N and isopropyl myristate in a final pH range of 8-12 and [0.3 M-1 M] NaCl concentrations. Conversely, with the microfluidic method, isopropyl myristate at pH 3 without salt was more efficient. Catechin strongly affected the formation of droplets by the mechanical process but did not modify the conditions of stability of MEs obtained by the microfluidic method. The antioxidant power of catechin was preserved in the inner droplets, even in emulsions prepared by the mechanical method at pH 8. An incomplete release of sucrose and catechin from the emulsions was observed and attributed to the interaction of molecules with the copolymer through hydrogen bonding. This study highlights some of the barriers to break to formulate multiple emulsions stabilized by a PDMS-b-PDMAEMA copolymer or other polymers which can form hydrogen bonds interaction with encapsulated drugs.

Changes of some bioactive and physicochemical properties during the black tea processing

In this research, some physical and bioactive properties of tea samples collected from every processing stage of black tea production were investigated. The processing stages were significantly effective on the investigated properties (moisture content, color parameters [L^* , a^* , and b^* ], and pH values the total phenolic substance, antioxidant activity) (p < 0.01). The antioxidant activities were found to be at a high level in fresh tea but decreased during the processing stages. Furthermore, the lowest activity was observed in the drying stage for extracts prepared with water and in the drying and sorting stages for extracts prepared with ethanol. In addition, it was determined that palmitic acid, myristic acid, and capric acid as saturated fatty acids, oleic acid, heptadecenoic acid, and eicosenoic acid as unsaturated fatty acids formed the fatty acid profile. Palmitic acid was determined to be the dominant fatty acid in tea samples. PRACTICAL APPLICATION: Tea is a beverage known to have positive health effects. The chemical structure of tea is very effective in providing these positive effects on health. Black tea production takes place in five stages in general terms (withering, rolling, oxidation, drying, and sorting stages) after the harvesting. These processes are very effective in the quality properties of tea. This research provides information about effects of processing stages on black tea. Our results demonstrate that processing was significantly effective on the physicochemical and bioactive properties of tea. Functionality of bioactive compounds could be maintained by optimization of the applied processes.