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• Steamed green tea had higher concentrations of sucrose and free amino acids. • Steaming retained more compounds associated with sweet and fresh tastes, such as free amino acids. • Frying produced more compounds with bitter tastes, such as catechin. Fixation is a crucial step in green tea processing that can impact quality. In this study, we explored the differences in the chemical components of steamed and fried green teas made from the same batch of fresh tea leaves using different fixing methods. Results showed that concentrations of sucrose and free amino acids were significantly higher in steamed green tea. Abundances of 12 compounds including purine nucleoside, pyrimidine nucleoside derivatives, and catechins were higher in fried green tea, while 34 compounds such as amino acids and their derivatives, benzofurans and flavonoids were higher in steamed green tea. Thus, steaming retained more compounds associated with sweet and fresh tastes, such as free amino acids, while frying produced more compounds with bitter tastes, such as catechin. This might explain why steamed green tea is mellower than fried tea. [ABSTRACT FROM AUTHOR]

• 10 μmol/g of catechin did not affect the stability of emulsion. • Catechin (50–200 μmol/g) decreased the stability of emulsion. • Catechin (50–200 μmol/g) caused excessive expansion and aggregation between myosins. • Catechin (50–200 μmol/g) hindered the myosin adsorption at the oil–water interface. • Catechin (50–200 μmol/g) reduced the elasticity of interfacial protein film. The effects of different concentrations of catechin on the stability of myofibrillar protein-soybean oil emulsions and the related mechanisms were investigated. Adding 10 μmol/g catechin had no obvious effects on the emulsion stability and myosin structure, but 50, 100 and 200 μmol/g catechin decreased the emulsion stability. The microstructure observations showed that 10 μmol/g catechin caused a dense and uniform emulsion to form, whereas 50, 100 and 200 μmol/g catechin induced the merging of oil droplets. The addition of 50, 100 and 200 μmol/g catechin caused a decline in both the total sulfhydryl content and surface hydrophobicity, suggesting protein aggregation, which decreased the adsorption capacity of myosin and the elasticity of interfacial film. These results suggested that higher concentrations of catechin were detrimental to the emulsifying properties of myosin and that the dose should be considered when it is used as an antioxidant. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first electroanalytical method for the estimation of total phenolic and alkaloid contents in tea samples. • The method utilized catechin and caffeine oxidation signals. • A boron-doped diamond electrode was employed. • Through the analysis of black and green tea samples, the applicability was demonstrated. This work outlines the simultaneous estimation of the total phenolic and alkaloid contents in the tea samples by using catechin (C) and caffeine (CAF) oxidation signals at a non-modified boron-doped diamond (BDD) electrode. Two irreversible oxidation peaks, about + 1.03 (for C) and + 1.45 V (for CAF) vs Ag/AgCl in acetate buffer solution at pH 4.7, were seen in the cyclic voltammetric profile of the binary mixtures of C and CAF. In optimal conditions and utilizing the square-wave mode, the BDD electrode allows for simultaneous quantification of C and CAF within the concentration ranges of 5.0–100.0 µg mL−1 (1.72 × 10-5 − 3.45 × 10-3 mol/L) and 1.0–50.0 µg mL−1 (5.15 × 10-6 − 2.57 × 10-4 mol/L) respectively. The corresponding detection limits are 1.22 µg mL−1 (4.21 × 10-6 mol/L) for C and 0.11 µg mL−1 (5.66 × 10-7 mol/L) for CAF. Other phenolic compounds (like tannic acid, gallic acid, epicatechin, and epigallocatechin gallate) and other alkaloids (theophylline and theobromine) present in tea samples were examined for selectivity assessment. Ultimately, the applicability of the proposed approach was demonstrated by estimating the total phenolic and alkaloid contents in the black and green tea samples, expressed as C and CAF equivalents. The results obtained were contrasted against those acquired using UV–Vis spectrometry. [ABSTRACT FROM AUTHOR]

• Nitrogen application affects tea flavor components. • High nitrogen levels increase polyphenols and amino acids, but decrease catechins. • Chlorophyll, caffeine, and theanine accumulate with nitrogen application. • Linalool and cis -linalool oxide are key compounds for tea aroma. Our study investigated the impact of nitrogen fertilization at 0, 150, 300, and 450 kg/ha on the non-volatile and volatile substances, as well as gene expression in fresh leaves from Lingtou tea plants. We found that applying nitrogen at 450 kg/ha notably increased total polyphenols (TPs) and free amino acids (AAs) while decreasing the TP to AA ratio (TP/AA) and total catechins (TC) contents. Chlorophyll, caffeine (CAF) and theanine accumulated to a greater extent with nitrogen application rates of 150, 300, and 450 kg/ha, respectively, six substances – TP, CAF, TC, theanine, epigallocatechin (EGC), and AA – as key contributors to the taste quality of LTDC. Additionally, five substances with variable importance in projections (VIP) ≥ 1 and odor activation values (OAV) ≥ 1, notably linalool and cis -linalool oxide (furanoid), significantly contributed to the tea's overall aroma. Furthermore, applying 300 kg/ha nitrogen upregulated the dihydroflavonol reductase (DFR)gene, likely causing catechin decrease. [ABSTRACT FROM AUTHOR]

Theaflavins are beneficial to human health due to various bioactivities. Biosynthesis of theaflavins using polyphenol oxidase (PPO) is advantageous due to cost effectiveness and environmental friendliness. In this review, studies on the mechanism of theaflavins formation, the procedures to screen and prepare PPOs, optimization of reaction systems and immobilization of PPOs were described. The challenges associated with the mass biosynthesis of theaflavins, such as poor enzyme activity, undesirable subproducts and inclusion bodies of recombinant PPOs were presented. Further strategies to solve these challenges and improve theaflavins production, including enzyme engineering, immobilization enzyme technology, water-immiscible solvent-water biphasic systems and recombinant enzyme technology, were proposed. • Enzyme engineering can used to improve the properties of polyphenol oxidase. • Enzyme engineering and immobilized enzyme enhance yield of theaflavins. • Water-immiscible solvent-water biphasic systems can improve theaflavins production. • The subproducts can be reduced by controlling catechin composition and reaction time. • The use of fusion tags and molecular chaperones prevent formation of inclusion body. [ABSTRACT FROM AUTHOR]

Whole grains (WG) are beneficial to health but have reduced sensory quality, partly attributable to inhibition of Maillard reaction products (MRP) by WG phenolics. The study investigated how major flavonoid classes in cereals affect Maillard reaction pathways. Flavonoids were reacted with xylose-lysine aqueous system at 160 °C/12 min. Additionally, breads were made with catechin, and wheat and sorghum bran fortification. Low M w MRP were profiled using UPLC-MS/MS, while melanoidins were characterized using fluorescence spectroscopy and HPSEC-MALS. The flavonoids significantly (p < 0.05) reduced both melanoidin content (by 33–86%) and M w (3.5–15 kDa vs 20 kDa control), leading to lighter bread crust. Flavonoids inhibited MRP via direct condensation with early-stage amines and carbonyls into stable adducts, and reduction of late-stage polymerization reactions, increasing accumulation of cyclic N-containing intermediates. Inhibitory trend was flavones>flavanones>flavanols. C-Ring π-bond dramatically enhance flavonoid MRP inhibition; thus flavone-rich cereal grains are likely to strongly impact MRP-dependent sensory attributes of WG products. • Flavonoids common in grains highly inhibitory or Maillard reaction products (MRP). • Flavonoids reduce melanoidin content and M w , along with bread crust color. • C-Ring π-bond on flavonoids enhanced inhibition of melanoidins and MRP intermediates. • Inhibitory trend flavones>flavanones>flavanols. • Flavonoid profile of ingredients may be used to modulate MRP during food processing. [ABSTRACT FROM AUTHOR]

Tetrastigma hemsleyanum root is a popular functional food in China, and the price varies based on the origin of the product. The link between the origin, metabolic profile, and bioactivity of T. hemsleyanum must be investigated. This study compares the metabolic profiles of 254 samples collected from eight different areas with 49 potential key chemical markers using plant metabolomics. The metabolic pathways of the five critical flavonoid metabolites were annotated and enriched using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. Moreover, a random forest model aiding the spectrum-effect relationship analysis was developed for the first time indicating catechin and darendoside B as potential quality markers of antioxidant activity. The findings of this study provide a comprehensive understanding of the chemical composition and bioactive compounds of T. hemsleyanum as well as valuable information on the evaluation of the quality of various samples and products in the market. [Display omitted] • Different areas T. hemsleyanum were effectively distinguished by plant metabolomics. • Significant differential metabolites were mapped to KEGG for metabolic pathways. • Potential biomarkers were screened by random forest assisted spectrum-effect analysis. [ABSTRACT FROM AUTHOR]

The autoxidation of tea catechins by dissolved oxygen proceeds in pH-neutral aqueous solutions, and the major products are oligomers. However, the reaction mechanisms have not been clarified. In this study, the autoxidation of (−)-epigallocatechin-3- O -gallate (1) was examined. The autoxidation with β-cyclodextrin, which includes the A-ring of 1 , significantly suppressed oligomer production and increased the formation of products generated by the oxidative cleavage of the B-ring, indicating the participation of the A-ring in the oligomerization. Further, the autoxidation of 1 in the presence of phloroglucinol, a mimic of the catechin A-ring, yielded products via the nucleophilic addition of phloroglucinol to the B-ring quinone of 1. These results indicated that the oxidative A–B ring couplings accounted for the major oligomerization mechanism. • Autoxidation of epigallocatechin gallate (1) yields oligomers as major products. • The oligomerization was suppressed by presence of β-cyclodextrin. • Autoxidation of 1 with phloroglucinol, a mimic of catechin A-ring, yielded coupling products. • The products were produced by addition of phloroglucinol to B-ring quinone of 1. • The key mechanism of oligomerization is coupling between B-ring quinones and A-rings. [ABSTRACT FROM AUTHOR]

Most teas, including white tea, are produced from tender shoots containing both leaf and stem. However, the effect of the stem on white tea quality remains unclear, especially during withering, an essential process. Therefore, this study investigated the withering-induced changes in the leaves and stems of Camellia sinensis cv. 'Fudingdabai' by multi-group analysis. During withering, the levels of catechin and theobromine (i.e., major flavor-related compounds) decreased slightly, mainly in the leaves. The abundance of some proteinaceous amino acids related to fresh taste increased in stems due to increased protein hydrolysis. In addition, changes in biosynthetic pathways caused a decrease in theanine (a major non-proteinaceous amino acid) and an increase in gamma-aminobutyric acid in stems. Terpenes, mainly in the stems, were partially affected by withering. Phenylacetaldehyde, a major contributor to white tea aroma, increased mainly in the stems. These findings reflect the positive contribution of the stem to white tea quality. • Catechin and theobromine decreased during withering, which mainly occurred in leaf. • Some protein hydrolysis-derived amino acid contents increased in withering stems. • Theanine synthesis decreased and GABA synthesis increased in withering stems. • Stem is vital for bud-leaf type white tea quality, because of its abundant terpenes. • Withering increased the aroma-related phenylacetaldehyde content mainly in the stem. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microwave hydrodiffusion and gravity evaluated for pomegranate juice production. • MHG can increase the juice yield up to 55%. • MHG gave a juice rich in catechin and delphinidin-3,5-glucoside. • The lyophilized juices possess anti-glucosidase and anti-glycation activity. Green technologies based on microwaves have been developed by the food industry to produce organoleptically acceptable fruit juices without preliminary processing. Microwave irradiation coupled with hydrodiffusion and gravity (MHG) combines microwave heating with the earth's gravity, allowing the collection of hydrophilic substances released from the irradiated matrix. To the best of our knowledge, MHG extraction has never been experimented to produce pomegranate juice. In this work, we have evaluated it as a potential alternative to the conventional squeezing. A central composite design study (CCD) allowed the selection of the best extractive conditions (irradiation power and extraction time) to obtain a pomegranate juice with higher yield, polyphenol (e.g., catechin and delphinidin-3,5-glucoside) content, and related bioactivities (antioxidant and antidiabetic) than the one obtained by squeezing while maintaining the chemical-physical properties. Thus, this technique appears to be a functional alternative to producing high value pomegranate juice. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different taste and aroma characteristics were presented in 4 white tea and their processing samples. • The maturity of fresh tea leaves was the primary factor that promoted the formation of milky flavor. • The processing method was the key to inducing milky aroma under mature fresh tea leaves conditions. Targeted metabolomics combined with chemometrics were applied to investigate the flavor profiles of 4 white tea samples, which were produced from different maturity fresh tea leaves with different withering methods. Mature leaves that underwent novel withering process at higher temperature (28-30℃) and humidity (75 ± 3 %) (MN) were characterized by intense milky flavor. The content of free amino acids, catechins, and soluble sugars in MN were significantly lower than that in the other 3 tea samples, resulting in a sweet and mellow taste with low bitterness. Meanwhile, MN possessed the highest intensity of milky aroma, which could be mainly attributed to the existence of dihydro-5-pentyl-2(3H)-furanone and 2-pentyl-furan as the key volatile substances with coconut and creamy fragrance. These findings provide insight into the substance foundations of milky flavor, and identified leaf maturity and processing method as the determining factors of the milk-flavored white tea (MFWT). [ABSTRACT FROM AUTHOR]

• 124 volatile compounds during the storage of organic green tea by SDE-GC–MS were identified. • Variations of volatile compounds in organic green tea during storage (1–16 years) were explored. • Key volatile compounds related to the storage years were screened. • The content of six volatile compounds showed good predictive ability for the storage years. In the present study, the volatile compounds in organic green tea with a continuous storage period (ranging from 1 to 16 years) were comprehensively analyzed and compared through SDE-GC–MS and chemometrics. The results revealed that the total of 124 volatiles were identified, and their total amount was increased with the prolongation of the storage years. Ketones, alcohols, esters, and aromatic hydrocarbons were the main types of volatiles in organic green tea, among which 26 volatile compounds were significantly correlated with storage years, and six volatile compounds that were most seriously affected by the storage years. The results of the support vector machine classification combined with multiple linear regression analysis showed that the content-period prediction model for the six volatile compounds can accurately predict the storage years of organic green tea. Therefore, this study offers novel insights into volatile compounds changes during the storage of green tea. [ABSTRACT FROM AUTHOR]

• The flavor wheel of aged Jinhua white tea (AJWT) was established. • A fungus fragrance and stale flavor were the unique aroma characteristics of AJWT. • Eighteen components contributed significantly to the taste attributes of AJWT. • Thirty-nine VOCs contributed significantly to the aroma attributes of AJWT. • Long-term aging reduced the comprehensive antioxidant activity of AJWT. This study explored the sensory characteristics, metabolites and antioxidant capability of aged Jinhua white tea (AJWT) over different years of aging and revealed the transformation mechanism of these characteristics during the long-term aging process. The flavor wheel of AJWT was constructed, and its unique flavor was dominated by mellowness, smoothness, a fungus fragrance, and a stale flavor. The high content of theabrownine, soluble sugar, flavonoids and 25 aroma components made important contributions to the formation of the unique flavor of the AJWT, and their content significantly increased during the long-term aging process of 5–10 years. This was related to the microbial bioconversion, the oxidative degradation of catechins, the hydrolysis of flavonosides and the decomposition of polysaccharides. Contrary to folk experience, AJWT had weak comprehensive antioxidant capacity, mainly due to its low content of tea polyphenols, catechin components and caffeine, which decreased significantly during the long-term aging of 5–10 years. [ABSTRACT FROM AUTHOR]

• Six tea categories could be distinguished based on differences in compound accumulation. • Fermentation significantly reduced total polyphenols, catechins, and theanine content in tea. • The amounts of compounds in tea samples were closely related to the geographical origins. • Amino acids in green tea accumulate more in spring, while polyphenols more in summer and autumn. The processing techniques, geographical origins, and harvesting seasons have a significant impact on tea compound accumulation, leading to different flavor characteristics and consumer preferences for tea. Herein, six categories of tea involving 1329 samples revealed the distribution characteristics via compound accumulation, as well as the impact of production regions and harvesting seasons on flavor chemicals. With the increasing fermentation degree, the average content of tea polyphenols, catechins, and theanine in dark tea decreased by 57.78%, 94.64%, and 98.57% compared to green tea, respectively. The compounds in tea fluctuate with the geographical origins and seasons, with theanine and free amino acids being more accumulated in the Jiangnan tea region in spring tea, while total polyphenols and catechins were more abundant in Southwest China's tea region in summer and autumn tea. This study comprehensively understands the accumulation characteristics of tea compounds corresponding to processing techniques and the geographical origins of Chinese tea. [ABSTRACT FROM AUTHOR]

[Display omitted] • Increasing the yellowing temperature and relative humidity can shorten the time. • The optimal yellowing process of yellow tea (YT) improved its quality. • Hydrolysis of catechins and flavonoid glycosides enhanced the sweetness of YT. • The oxidative polymerization of catechins contributed to the yellowness of YT. In this study, an optimized yellowing process for yellow tea (YT) was developed by response surface methodology. The results showed that increasing the yellowing temperature from 20 °C to 34 °C, increasing the relative humidity from 55% to 67%, and reducing the yellowing time from 48 h to 16 h, caused a 40.5% and 43.2% increase in the yellowness and sweetness of YT, respectively, and improved the consumer acceptability by 36.8%. Moreover, metabolomics was used to explore the involved mechanisms that resulted in the improved YT quality. The optimized yellowing promoted the hydrolysis of 5 gallated catechins, 6 flavonoid glycosides, theogallin and digalloylglucose, resulting in the accumulation of 5 soluble sugars and gallic acid. Meanwhile, it promoted the oxidative polymerization of catechins (e.g., theaflagallin, δ-type dehydrodicatechin and theasinensin A), but decelerated the degradation of chlorophylls. Overall, this optimized yellowing process could serve as a guide to a shorter yellowing cycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • Catechin dimers revealed to be the first products of the reaction between acetaldehyde and (+)-catechin. • Time affected the reaction products distribution and the chemical composition of the solution. • The dissociation of the dimers over time caused vinyl-catechins to accumulate. Acetaldehyde plays a key role in determining some wine properties. Interesting is the reaction of acetaldehyde with flavonoids, as the ensuing products can alter wine color, astringency, colloidal stability. Many studies reported on the formation of ethylidene-bridged flavan-3-ols as products of the reaction between acetaldehyde and either (+)-catechin or (-)-epicatechin. In white wines after one year of incubation with acetaldehyde only vinyl-(+)-catechin and vinyl-(-)-epicatechin were observed, while no ethylidene linked oligomers were detected. This observation prompted us to study the reaction of (+)-catechin with acetaldehyde in wine model solution through an experimental and theoretical approach, with the purpose of exploring the nature of the species involved along with the mechanisms leading to them. The products of the reaction were observed over 38 days. The results showed that ethylidene-bridged catechins are the first products to be formed but over time the dissociation of these dimers causes vinyl-catechins to accumulate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Targeted metabolism of phenolics of pecan storage were conducted for the first time. • A total of 118 metabolites were identified, nine were newly found in pecan. • Phenolics with similar structures have similar change patterns during storage. • Fresh kernel seemed to lead to more changes to hydrolysable tannins. • Metabolite markers were selected out which can be used in future researches. Pecan nuts are highly enriched in phenolic compounds, which contribute to the health benefits of pecans. Phenolic compounds represent the main oxidation reaction substrates, thus leading to quality deterioration, namely pellicle browning or a decrease in beneficial effects during pecan storage. Hence, four different storage conditions were performed for 180 d to simulate real production situations. Targeted metabolomics was chosen to identify the specific phenolic compounds involved in quality deterioration under different storage conditions in 0, 90, and 180 d samples. A total of 118 phenolic compounds were detected, nine of which were identified for the first time in pecan. The total phenolic content (TPC) and antioxidant capacities initially demonstrated high scores, after which they tended to decrease during the storage process. The significantly modified phenolic compounds during storage were selected as the metabolite markers of pecan quality deterioration, including catechin, procyanidin (PA) trimer, PA tetramer, trigalloyl hexahydroxydiphenoyl (HHDP) glucose, and tetragalloyl hexoside. Fresh pecan kernels resulted in more pronounced changes in hydrolysable tannins (HTs), whereas dry kernels resulted in the most accentuated changes in condensed tannins (CTs). To the best of our knowledge, this is the first attempt to study individual phenolic changes during storage of pecan in such massive amounts. The results can offer a valuable theoretical basis for future control of pecan quality deterioration through phenolics during storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fucoidan/chitosan effectively coated nanoliposomes-embedded catechin and juglone. • The physicochemical properties and stability of nanoliposomes were investigated. • Fucoidan coating improved nanoliposomes' stability and encapsulation efficiency. • In simulated digestion, fucoidan coating provided a sustained release profile. This study aimed to improve the thermodynamic performance of nanoliposomes (NLs) using fucoidan (F) as the second-layer coating biopolymer along with chitosan (CS), to control the delivery and bioavailability of catechin (C) and juglone (J). The stabilized liposomal carrier of F/CS-conjugated JC-NL (F-CS-JC-NL) was developed with optimum concentrations of CS (0.09 wt%) and F (0.10 wt%), with the highest encapsulation efficiency of juglone (95.47%) and catechin (90.88%). Physicochemical characterization revealed that F-CS-JC-NL disclosed improved stability under different pH and ionic strengths, with the maximum juglone/catechin retention under thermal, oxidative and storage conditions. In vitro digestion revealed that NL double-coating (F-CS-JC-NL) significantly reduced compound leakage in the gastrointestinal tract, providing a controlled release and better bioavailability of juglone/catechin compared to CS-JC-NL and JC-NL. Conclusively, this study provides a novel NL-based delivery carrier with enhanced physicochemical stability and controlled release that might have promising use in delivering functional ingredients. [ABSTRACT FROM AUTHOR]

• Phenolic compounds interfere with the Ampliflu Red-HRP assay of H 2 O 2. • The extent of inhibition is the higher the lower is H 2 O 2 concentration. • Assays employing HRP may underestimate H 2 O 2 in plant-based food/beverages. Methods employing horseradish peroxidase (HRP) are popular for quantification of hydrogen peroxide. This communication reports interference of the Ampliflu Red-HRP assay by phenolic compounds, abundant in food and beverages of plant origin. Concentrations of catechin, propyl gallate, quercetin and gallic acid lowering the yield of the product, resorufin, in this system by 50% were lower than 10 μM. The extent of inhibition increased with decreasing hydrogen peroxide concentration. These results point to the necessity of a careful interpretation of results concerning the quantification of hydrogen peroxide in materials containing phenolic compounds with methods employing HRP, especially when low concentrations of hydrogen peroxide are concerned. [ABSTRACT FROM AUTHOR]

• Widely targeted metabolomics reveals chemical periodic change in whole process. • 568 Differential metabolites (VIP > 1.0, P < 0.05, FC > 1.50 or < 0.67) selected. • Anaerobic fermentation is regarded as critical process for the quality formation. • 7 Amino acids, 4 phenolic acids, 6 flavonoids and their glycosides accumulated. • N -, O -methylation, hydrolyzation, glycosylation, oxidation involved in fermentation. Yunnan pickled tea is produced from fresh tea-leaves through fixation, rolling, anaerobic fermentation and sun-drying. In this study, widely targeted metabolomics using UHPLC-QQQ-MS/MS and HPLC analysis were carried out to elaborate its quality formation during the whole process. Results confirmed the contribution of preliminary treatments and anaerobic fermentation to the quality formation. A total of 568 differential metabolites (VIP > 1.0, P < 0.05, FC > 1.50 or < 0.67) were screened through OPLS-DA. (-)-Epigallocatechin and (-)-epicatechin significantly (P < 0.05) increased from the hydrolyzation of ester catechins, such as (-)-epigallocatechin gallate and (-)-epicatechin gallate in anaerobic fermentation. Additionally, the anaerobic fermentation promoted vast accumulations of seven essential amino acids, four phenolic acids, three flavones and flavone glycosides, pelargonidin and pelargonidin glycosides, flavonoids and flavonoid glycosides (i.e. kaempferol, quercetin, taxifolin, apigenin, myricetin, luteolin and their glycosides) through relevant N -methylation, O -methylation, hydrolyzation, glycosylation and oxidation. [ABSTRACT FROM AUTHOR]

• Procyanidin B 2 and catechin has synergistic inhibitory effect on acrylamide. • Ratio of 1:3 and 1:9 have great synergistic inhibitory effect on acrylamide. • Optimal synergistic inhibitory effect (70.11 ± 2.07%) was achieved when ratio of 1:9. • Compared with single use, combined use of procyanidin B 2 decrease the dosage to 1/10. • Composite inhibitor achieve great inhibitory effects on acrylamide at a lower cost. The potential synergistic effects of Flavan-3-ols to inhibit the formation of acrylamide have attracted wide attention. This study aims to investigate the synergistic inhibitory effects of the B-type procyanidin and flavan-3-ols monomer on acrylamide production in food matrix. By comparing the inhibitory effects of different compounds in food matrix, procyanidin B 2 and catechin were screened out for examining their synergistic inhibitory effects on acrylamide by Isobologram analysis. When the interaction index (γ) was lower than 1, the interaction was synergistic reaction. The results showed the procyanidin B 2 /catechin ratio of 1:3 (γ = 0.57) had similar synergistic effect to that of 1:9 (γ = 0.53), both of which showed better effects than the ratio of 1:1 (γ = 0.71). The optimal synergistic inhibitory effect (70.11 ± 2.07%) was achieved when the procyanidin B 2 and catechin concentrations were 0.6 µg/mL and 5.4 µg/mL, respectively. Compared with single use, the combined use of B 2 and catechin could decrease the dosage of B 2 to 1/10 and that of catechin to 1/3. [ABSTRACT FROM AUTHOR]

• A nondestructive methodology was used to study the distribution of tea metabolites. • A Teflon imprint method was suitable for tea leaf metabolite analysis using DESI-MSI. • Catechin distributions on both sides of tea leaf were not significantly different. • Different catechins showed different distributions within the tea leaf. • L -Theanine and valinol were distributed around the outer root cross-section. Although specialized metabolite distributions in different tea (Camellia sinensis) tissues has been studied extensively, little is known about their within-tissue distribution owing to the lack of nondestructive methodology. In this study, desorption electrospray ionization imaging mass spectrometry was used to investigate the within-tissue spatial distributions of specialized metabolites in tea. To overcome the negative effects of the large amount of wax on tea leaves, several sample preparation methods were compared, with a Teflon-imprint method established for tea leaves. Polyphenols are characteristic metabolites in tea leaves. Epicatechin gallate/catechin gallate, epigallocatechin gallate/gallocatechin gallate, and gallic acid were evenly distributed on both sides of the leaves, while epicatechin/catechin, epigallocatechin/gallocatechin, and assamicain A were distributed near the leaf vein. L -Theanine was mainly accumulated in tea roots. L -Theanine and valinol were distributed around the outer root cross-section. The results will advance our understanding of the precise localizations and in-vivo biosyntheses of specialized metabolites in tea. [ABSTRACT FROM AUTHOR]

Highlights • Roasting of green tea decrease astringency by catechin oligomerization. • Spectroscopic studies suggested the presence of sugar units in the oligomers. • Model experiments using 13C-labeled glucose confirmed the participation of sugars. • Model experiments were performed using tea catechin and phloroglucinol. • Reactions of carbonyl groups with catechin A-rings causes the oligomerization. Abstract Roasting of green tea causes oligomerization of tea catechins, which decreases the astringency. The aim of this study was to elucidate the oligomerization mechanism. The 13C NMR spectrum of the oligomer fraction showed signals arising from catechin and sugar residues. Heating of epigallocatechin-3- O -gallate with 13C-labeled glucose (150 °C for 2 h) suggested that condensation of sugars with catechin A-rings caused the oligomerization. The dimeric product obtained by heating for a shorter period (30 min) suggested cross-linking occurred between sugars and catechin A-rings. Furthermore, heating of phloroglucinol, a catechin A-ring mimic, with glucose, methylglyoxal, and dihydroxyacetone, confirmed that the basic mechanism included reaction of the catechin A-ring methine carbons with carbonyl carbons of glucose and their pyrolysis products. [ABSTRACT FROM AUTHOR]

• An HPLC-MS method for simultaneously detecting 13 phenolics in fermented jujube puree. • S. thermophilus fermentation increased most phenolics in jujube puree. • Dynamic model was employed to evaluate the digestibility of phenolics. • Fermentation reduced the decrease of most phenolics during in vitro digestion. • Fermentation treatment increased the antioxidant properties of digestive fractions. Health benefits of fruit products fermented with probiotics are partially attributed to their increased contents of phenolic compounds. In this study, the effect of in vitro dynamic gastrointestinal digestion on the release of phenolic compounds and changes in the antioxidant activity of jujube puree fermented with Streptococcus thermophilus was investigated. Thirteen target phenolic compounds were characterized by high-performance liquid chromatography-tandem mass spectrometry. The recovery of this developed method ranged from 87.41% to 111.03%, and the limits of detection and quantification were low. Fermentation with Streptococcus thermophilus significantly increased the contents of most phenolic compounds in jujube puree. Fermentation reduced the decrease in the contents of most phenolic compounds in jujube puree during gastrointestinal digestion and, as a consequence improved the antioxidant capacity of digested fractions. These findings indicated that fermentation could increase the bioaccessibility of specific phenolics in jujube, as well as the antioxidant activity of this fruit. [ABSTRACT FROM AUTHOR]

Highlights • EGCG esterification with stearic acid was partial and yielded a mixture of esters. • NaCl (1.6–8 %wt) was added to a 0.8 %wt PGPR-0.25 %wt BC-1 %wt WPI double emulsion. • Droplet size, viscosity and stability of emulsions depended on salt concentration. • Storage reduced EGCG and esterified EGCG encapsulation in the 4.3 %wt NaCl emulsion. • Neither of the catechins made the emulsion more resistant to oxidation. Abstract Double (W1/O/W2) emulsions of 0.8 %wt PGPR-0.25 %wt BC-1 %wt WPI and NaCl (1.6–8 %wt) were characterized regarding their microstructure, droplet size, stability and viscosity. Droplet size increased with salt concentration. Salt addition at 4–5% wt limited the instability rate. Viscosity increased with NaCl concentration up to 4.8 %wt, above which it decreased. Eventually, the emulsion with 4.3 %wt salt was selected for catechin incorporation. In order to increase its antioxidant activity, Epigallocatechin Gallate (EGCG) was esterified with stearic acid. Esterification was partial and a mixture of esters was obtained. Both EGCG and its esterified derivatives were incorporated in the double emulsion. Storage reduced encapsulation. Encapsulation efficiency was reduced in the order "EGCG in the W1 phase" emulsion > "EGCG in the O phase" emulsion > "esterified EGCG in the W1 phase" emulsion. The presence of both catechins did not have a great effect on retarding emulsion oxidation. [ABSTRACT FROM AUTHOR]

Highlights • Guarana is a natural source of caffeine and polyphenols. • Crude and waste seeds of guarana are products with strong antioxidant capacity. • Hot hydroalcoholic solution enhanced extraction of bioactives from guarana. • High yields in extract were attributed to enzyme-assisted extraction. Abstract Catechins and methylxanthines are natural molecules in guarana (Paullinia cupana) that are associated with antioxidant and stimulatory effects in the human body. There are few natural sources of these antioxidants. The most popular molecule used in foods and beverages is caffeine, which, most of the time, is derived from synthetic sources. In this work, cold hydroalcoholic (CHM), hot hydroalcoholic (HHM), and aqueous enzymatic maceration (AEM) were applied to crude (CG) and waste guarana seeds (WG) to process these materials into natural added-value products with enhanced levels of catechin, epicatechin, epicatechin gallate, caffeine, theobromine and theophylline. The highest level of catechins and methylxanthines was extracted with HHM. Nevertheless, AEM enhanced the global yield in the extract, probably due to the solubilization of other substances. The maceration procedures applied to guarana contributed to the valorization of this plant crop by providing antioxidant sources with clear applications in food and nonfood industries. [ABSTRACT FROM AUTHOR]

Highlights • Catechin inhibited protein oxidation in linoleic acid-lipoxygenase reaction system. • Catechin promoted gastrointestinal digestibility of oxidized β -conglycinin. • Catechin improved antioxidant activity of oxidized β -conglycinin digest. • Catechin increased abundance of di-/tripeptide in oxidized β -conglycinin digest. Abstract The aim of the present study was to enhance oxidative stability and bioaccessibility of β -conglycinin (7S) prepared from low denatured defatted soybean flours with residual lipids and high lipoxygenase (LOX) activity. The model system consisting of linoleic acid (LA), LOX and unheated 7S (UH-7S)/heated 7S (H-7S) or UH-7S-catechin/H-7S-catechin complex, and in vitro gastrointestinal (GI) digestion model were used to investigate the effect of complexation with catechin on protein oxidation and characterisation of GI digest. The interaction of UH-7S/H-7S with catechin dramatically inhibited LOX-catalyzed LA peroxidation-induced protein oxidation. The interaction also promoted the degree of proteolysis in GI digestion and intestinal absorption for oxidized UH-7S/H-7S, increasing the antioxidant activity of oxidized UH-7S/H-7S, bioaccessibility for catechin and release of di-/tripeptides with dipeptidyl peptidase-IV/angiotensin converting enzyme inhibitory effects or antioxidant activities during GI digestion. The complexation with catechin is a potential strategy to enhance the oxidative stability, GI digestibility and bioaccessibility of 7S. [ABSTRACT FROM AUTHOR]

Highlights • Co-pigmentation of aronia anthocyanins with 10 phenolic co-pigments was studied. • The highest effect was with rosmarinic acid, syringic acid, catechin and chlorogenic acid. • The effect was most profound at high co-pigment/pigment ratios not achievable in plants. • Herbal extracts, in low concentrations were better co-pigments than pure compounds. • Results could be applied for the development of aronia foods with improved color. Abstract The co-pigmentation of black chokeberry (Aronia melanocarpa) anthocyanins with ten phenolic co-pigments was studied. Tested compounds provoked different co-pigmentation effect, manifested by hyperchromic and batochromic shifts. The co-pigmentation was accompanied by a magnification of color intensity and decrease of color hue, both related to a more pleasant color. The hyperchromic effect was the most significant for rosmarinic acid (51.02%), syringic acid (43.24%) and catechin (39.73%). However, it was observed at the highest pigment/co-pigment ratio (1:50), not achievable in plant matter. Targeting the potential practical application of co-pigmentation, we tested eight herbal extracts for their co-pigmentation ability with aronia anthocyanins. The use of herbal extracts led to a significant hyperchromic effect at much lower pigment/co-pigment ratios, compared to pure compounds. The use of selected herbal extracts as co-pigments opens realistic prospects for development of aronia functional foods with improved sensory properties and biological effects, due to enhanced color and anthocyanin stability. [ABSTRACT FROM AUTHOR]

Highlights • Grape seed PPCs were converted into OPCs by simultaneous reaction with C and EC. • The semisynthetic method was efficient and simple to gain dimers and trimers. • 13 individual procyanidins were obtained by one-step HSCCC and prep-HPLC. • The method could be applied to grape pomace and other procyanidin-rich plants. Abstract Polymeric procyanidins (PPCs) were the major constituents of procyanidins, while they have poor bioactivity. To better utilize PPCs, a semisynthetic approach for converting PPCs to oligomeric procyanidins (OPCs) was proposed. Grape seed PPCs were simultaneously reacted with catechin (C) and epicatechin (EC) under acid condition. Combining response surface methodology (RSM) and single-factor experiments, an optimized semisynthetic condition was confirmed with the ratio of PPCs with C and EC of 1:1:1, temperature of 40 °C, reaction time of 20 min and 0.1 M methanolic HCl. High-speed counter-current chromatography (HSCCC) was adopted to obtain three fractions from semisynthetic products and preparative-HPLC was used to isolate individual procyanidins. Thirteen B-type procyanidins including monomers, dimers and trimers were got with high yield of 0.8–17.8 mg from 200 mg semisynthetic products and high purity over 91%. The developed semisynthesis combined with separation method was efficient to obtain individual OPCs in preparative scale. [ABSTRACT FROM AUTHOR]

Highlights • Ten phenolic compounds have been identified for the first time in finger millet. • Catechin and epicatechin are the major extractable flavonoids in finger millet. • Ferulic acid is the major bound phenolic compound in finger millet. • Colored finger millets have higher phenolic compounds than non-colored ones. Abstract The profiles of phenolic compounds and antioxidant capacities of four finger millet varieties harvested in northern Malawi were investigated. The total phenolics, flavonoids and condensed tannins in the free fractions ranged from 114.43 to 179.19 mg ferulic acid equivalent (FAE)/100 g, 90.24 to 202.94 mg catechin equivalent (CE)/100 g and 31.76 to 83.59 mg CE/100 g, respectively. Total phenolic contents of the bound fractions ranged from 58.27 to 123.23 mg FAE/100 g. Twenty phenolic compounds were identified in the free fractions including eighteen flavonoids, with catechin and epicatechin being the predominant flavonoids. Seventeen phenolic compounds were identified in the bound fractions, with ferulic acid being the predominant one. Ten of the identified polyphenols were firstly reported in finger millet. Darker colored finger millet varieties had higher phenolic contents and antioxidant properties than the lighter colored ones. Finger millet can be used as healthy food material and natural antioxidant resource. [ABSTRACT FROM AUTHOR]

Highlights • IC and free catechin was more stable in a solid matric. • IC in milk and yogurt showed the highest percentage recovery of catechin. • Semi-solid matrix (yogurt) was the most suitable matrix. • Inclusion complex of catechin with β-CD masked the bitterness of catechin. Abstract Catechin is astringent in taste, sparingly soluble in water and sensitive to oxygen, light and pH. These properties restrict its application in food products. The present study investigated the stability of inclusion complex (IC) and catechin in various food matrices and investigated in vitro recovery profile of catechin and IC in liquid, semi-solid and solid food matrices. Besides, the sensory profile of IC added yogurt was also determined. Results showed that IC and catechin was more stable in solid matrix compared to semi-solid and liquid matrices. IC added in milk and yogurt show the highest percentage recovery of catechin compared to IC added in cheese and catechin added in all the matrices in in vitro digestive system. Through IC, β-CD masked the bitterness of catechin. These results suggest that protection of antioxidant such as catechin by β-CD inclusion complex may have applications in functional foods and health supplements. [ABSTRACT FROM AUTHOR]

Highlights • Integration of catechin and β-sitosterol realized by Steglich reaction. • Amphiphilic structure with excellent antioxidant activity in emulsion. • Detailed mechanistic speculation of the novel chimera antioxidant. Abstract Novel amphiphilic antioxidant, (+)-catechin-β-sitosterol (CS), was designed and successfully prepared with integration of (+)-catechin and β-sitosterol through the linkage of succinic acid. Sequential esterification was carried out to connect (+)-catechin and β-sitosterol. The identity of CS was confirmed by NMR, IR and MS spectroscopies. DSC analysis revealed that ΔH of CS was much lower than those of (+)-catechin and β-sitosterol, indicating ameliorated crystallinity. The logP measurement demonstrated significantly increased lipophilicity. Then excellent antioxidant activities of the novel antioxidant in typical polyunsaturated lipid O/W and W/O emulsions were unveiled applying β-sitosterol bleaching assay and 5-dodecanoylaminofluorescein (DAF) fluorescent probe method. The antioxidative behavior of CS in emulsion was beyond the polar paradox hypothesis and could be rationalized by effective accumulation at oil/water interface owing to its amphiphilic nature. This study offers a promising solution for development of naturally derived amphiphilic antioxidants for lipid-based systems. [ABSTRACT FROM AUTHOR]

Highlights • Effect of pistachio hulling methods on phenolic compounds were first investigated in this study. • Phenolic profiling of the cvs. Ohadi and Uzun (Pistacia vera L.) pistachios was determined by HPLC-DAD-ESI-MS n. • Dry-dry hulling method treated sample had a higher content of phenolic compounds in both pistachios. • Gallic acid and catechin were the most abundant phenolic compounds. Abstract The aim of this study was to identify phenolic compounds and measure the physicochemical properties of two pistachio (Pistacia vera L.) cultivars ('Uzun' and 'Ohadi'). For this purpose, the pistachios were subjected to four different hulling methods (wet hulling-WT, brine hulling-BR, wet-dry hulling-WD, and dry-dry hulling-DD) and a standard roasting treatment. Phenolic compounds were analyzed by HPLC-DAD-ESI-MS n. Twelve phenolics were identified and quantified in the samples, 10 of which were flavonoid and two non-flavonoid phenolic acids. In both cultivars, the major compounds were found to be gallic acid and catechin followed by eriodictyol- 7 - O -glucoside and eriodictyol. The dry-dry hulling method treated sample had higher antioxidant capacity, total phenol content, and phenolic compounds than the other hulling methods in both pistachio cultivars. After the roasting treatment, the antioxidant capacity, phenolic content, and a∗ value increased while the L∗ and b∗ values decreased. [ABSTRACT FROM AUTHOR]

Highlights • Synergic effect of bPRPs and aPRPs on the interaction with flavanols is observed. • 30 soluble aggregates flavanol-PRPs (molecular weight 4680–35,851 Da) were detected. • Catechins bind preferentially bPRPs than aPRPs. • aPRPs seem to interact preferentially with medium size aggregates flavanol-bPRPs. Abstract In this study, we have evaluated by HPLC-DAD, DLS and MALDI-TOF a synergic effect of the coexistence of two salivary-PRP fractions (basic-PRPs and acidic PRPs) on the interaction with flavanols. Results obtained showed noticeable enhancement of the interaction between (epi)catechin and PRPs when both types of proteins are blended. Up to 30 soluble aggregates have been tentatively identified with molecular weight from 4680 to 35,851. (epi)Catechins seem to bind preferentially bPRPs than aPRPs, although the medium size aggregates flavanol-bPRPs formed could favour the interaction with aPRPs giving rise to soluble mixed aggregates. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermodynamics & kinetics of catechin adsorption onto fibre was studied. • Adsorption of catechin onto pectin was higher than onto cellulose. • The adsorption was predominantly a physisorption spontaneous process. • Catechin adsorption onto fibre was accompanied by increased fluorescence. Abstract The adsorption behaviour of catechin onto cellulose and pectin was compared. The adsorption of catechin onto the two fibres involved an initial fast adsorption phase followed by a slower adsorption as the sites became saturated and the systems moved towards equilibrium. The adsorption capacity of pectin for catechin (20.71 ± 2.24 mg/g) was significantly greater than that of cellulose (2.41 ± 0.05 mg/g) after equilibration for 24 h at 37 °C. The Langmuir and Freundlich models were applied to obtain the quantitative information about the adsorption of catechins to pectin and cellulose. Thermodynamic data derived from the isothermal adsorption carried out at the temperatures of 27 °C, 32 °C, 37 °C and 42 °C suggested that the adsorption was spontaneous and the binding was driven predominantly by physisorption. Fluorescence experiments confirmed the adsorption of catechins onto cellulose and pectin. The results showed that catechin adsorption capacity and adsorption mechanism were different for pectin and cellulose. [ABSTRACT FROM AUTHOR]

Highlights • PARAFAC, LDA and DA-UPLS discriminated between irrigated and non-irrigated grapes. • PARAFAC, LDA and DA-UPLS discriminated between high and low crop load. • The resveratrol concentration predictions were better applying UPLS. • The PARAFAC results for catechin and epicatechin were comparable with LC results. • Resveratrol, catechin and epicatechin concentrations increased with irrigation. Abstract Phenolic extracts from cv Tempranillo grapes subjected to water stress and irrigation treatment, both of them with high and low crop load, were analyzed by front-face fluorescence. Excitation-emission matrices (EEMs) were analyzed by means of unsupervised parallel factor analysis (PARAFAC), PARAFAC supervised by linear discriminant analysis, and discriminant unfolded partial least-squares. All algorithms allowed to differentiate between water stress and irrigation grape samples when the fluorescence maxima region of catechin and epicatechin, and resveratrol was considered. A central composite design was employed for the calibration of catechin, epicatechin and resveratrol. Resveratrol was quantified by U-PLS in both, irrigated and water stressed samples, and levels between 3.46 ± 0.22 and 4.67 ± 0.08 μg mL−1 and 2.43 ± 0.60 and 3.03 ± 0.10 μg mL−1, respectively, were found. PARAFAC only allowed the determination of the sum of catechin plus epicatechin (R2 = 0.9397). The determination of total catechin plus epicatechin by means of PARAFAC was successfully validated by liquid chromatography. [ABSTRACT FROM AUTHOR]

Highlights • Novel starch based nano-particles were used for encapsulating catechin. • Horse chestnut starch (HSC) had highest encapsulation efficiency and produced lower particle size. • Water chestnut starch (WSC) had highest stability and displayed slower release of catechin. • Nano-encapsulation helped in retaining bioactive properties of catechin during digestion process. Abstract Novel starch-based nanoparticles from three sources: horse chestnut (HSC), water chestnut (WSC) and lotus stem (LSC) were prepared for nano-encapsulation of catechin. Average particle size of HSC, WSC and LSC based nano-particles were 322.7, 559.2 and 615.6 nm with encapsulation efficiency of 59.09, 48.30, and 55.00% and negative zeta potential of −18.05, −21.5 and −18.05 mv, respectively. Structural, physical and thermal properties were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). SEM revealed capsule formation with entrapped catechin, while broad characteristic peaks at 3475, 1650, 1383, 1148, 1083 and 790 cm−1 depicts encapsulation of catechin in starch nanoparticles without any evident interaction. XRD showed loss of crystallinity after encapsulation. Higher content of catechin in intestinal juice ensured controlled release in intestine. Bioactive properties were retained at higher level in encapsulated catechin compared to free catechin upon in-vitro digestion. [ABSTRACT FROM AUTHOR]

The study aimed at improving the antioxidant activity of β -conglycinin to enhance the oxidative and physical stabilities of safflower oil-in-water emulsion stabilized by β -conglycinin. Heating promoted binding affinity and antioxidant activity of β -conglycinin. Catechin and chlorogenic acid showed higher binding affinities towards unheated (or heated) β -conglycinin than caffeic acid and quercetin. The enhancement efficiencies of the phenolics on the antioxidant activity of unheated (or heated) β -conglycinin decreased in the order of catechin > quercetin > chlorogenic acid > caffeic acid. Hydrophobic force and hydrogen bonding were the important binding forces for the selected phenolics to β -conglycinin. The complexation with catechin has no side effect on interfacial behavior and emulsifying property of β -conglycinin. The use of heated β -conglycinin-catechin complex as an emulsifier for preparing safflower oil emulsion effectively improved the oxidative and physical stabilities of the emulsion treated with lipoxygenase through inhibition of lipid oxidation, protein carbonyl formation and sulfhydryl loss. [ABSTRACT FROM AUTHOR]

As a potential novel technique in the wine-making industry, ultrasound has received considerable attention. In this paper, a model wine system was constructed to investigate the effect of ultrasonic irradiation on the formation of xanthylium cation pigment derived from the (+)-catechin and the glyoxylic acid, an oxidation product of tartaric acid, so as to explore the changing mechanism of the wine color mediated by ultrasound. The results indicate that the long-term ultrasonic treatment can enhance the formation of the xanthylium cation pigment in the model wine, which is attributed to free radicals triggered by ultrasound, meanwhile, iron ions and oxygen can influence the ultrasonic effect. All these results suggest that ultrasound is promising to be employed in regulating the formation of the yellow pigment during wine aging thus modifying the wine organoleptic characteristic. [ABSTRACT FROM AUTHOR]

Interaction of metal, especially iron ions with flavanols is considered as an important feature of these compounds and is believed to contribute to their both antioxidant and prooxidant properties. The aim of this study was to examine how Fe 2+ binding to form a 4:1 (flavanol:Fe 2+ ) mixtures affects the antioxidant properties of flavanols. ABTS ∗ scavenging, protection against fluorescence bleaching induced by AAPH and hypochlorite, protection against lipid peroxidation and protection against hypochlorite-induced hemolysis demonstrated that flavonol-Fe 2+ mixtures retain antioxidant properties, although, in most cases, they are lower with respect to the flavanols alone. No superoxide dismutase-like or catalase-like activity of the mixtures was revealed. [ABSTRACT FROM AUTHOR]

(−)-Epicatechin (EC) and (−)-epigallocatechin gallate (EGCG) (0.001–5%) were found to reduce N ε -(carboxymethyl) lysine (CML) concentrations by up to 0.80 ± 0.11 mM and 0.85 ± 0.07 mM, respectively, as quantified by HPLC-MS during heating at 80 °C and 100 °C in a glucose-lysine model system at pH 5, 7 and 8, which mimic different food processing conditions. With the addition of 1 mM EC, the free CML concentration in coconut milk was reduced to 5.7 ± 0.1 μg/mL (∼2.8 × 10 −2  mM), which was significantly lower than that in unheated coconut milk (6.1 ± 0.2 μg/mL (∼3.0 × 10 −2  mM), p < 0.05) indicating that the free CML may be eliminated by the addition of EC in coconut milk. Products of EC/EGCG quinones reacted with CML by a Michael addition or Schiff base addition in model systems were tentatively identified by UPLC-ESI-MS/MS. [ABSTRACT FROM AUTHOR]

Our objective was to develop a robust system for anthocyanin-based color intensification, with high-encapsulation capacity and improved stability of the encapsulated natural colorant. Catechin was used to modulate the copigmentation and encapsulation of anthocyanins in counter-ionic polyelectrolyte complexes (PECs) composed of chondroitin sulfate and chitosan. Results showed that catechin copigmentation significantly intensified red color of formulations both with and without encapsulation in PECs and improved the anthocyanin encapsulation efficiency by forming additional dense network through hydrogen bonding. A series of stability assays revealed that anthocyanin stabilizing effect of system depended on the formulated pH and adding order of catechin. The strongest retaining capacity of anthocyanin was observed when catechin was copigmented with anthocyanin directly in PECs at pH 3.3, while the coated layer of catechin covered on PECs would be more effective at pH 4.0 and 5.0. Furthermore, we demonstrated that this delivery system works for anthocyanins from different sources. [ABSTRACT FROM AUTHOR]

Catechins are the major bioactive compounds existing in tea leaves ( Camellia sinensis ). Dehydroascorbic acid is (DHAA) a reactive dicarbonyl species and previous studies have demonstrated that catechins could effectively trap DHAA to form ascorbyl adducts of catechins, especially epigallocatechin gallate (EGCG). Since catechins in the aqueous solution are unstable due to their structural features, ascorbic acid (AA) is usually added to bottled tea beverages to protect catechins. However, whether ascorbyl adducts of catechins are formed in bottled tea beverages remains unclear. In this study, formation of ascorbyl adducts of EGCG increased along with increased incubation time when EGCG and AA were dissolved in the aqueous solution. Next, 6C-DHAA-EGCG and 8C-DHAA-EGCG were detected in both green tea and oolong tea beverages, and their concentrations ranged from 0.23 to 1.95 µM and 0.28 to 1.97 µM, respectively. Furthermore, an 8C-ascorbyl adduct derived from gallocatechin gallate was also found in some tea beverages. [ABSTRACT FROM AUTHOR]

Pomegranate peel (PoP), a juice byproduct often considered as a waste, comprises nearly around 30–40% portion of the fruit. Phenolic compounds (one class of bioactive phytochemicals) are primarily concentrated in the peel portion of pomegranate fruit. In PoP, the main phenolic compounds reported in the literature include flavonoids (anthocyanins such as pelargonidin, delphinidin, cyanidin along with their derivatives and anthoxanthins such as catechin, epicatechin and quercetin), tannins (ellagitannins and ellagic acid derivatives such as punicalagin, punicalin and pedunculagin) and phenolic acids (such as chlorogenic, caffeic, syringic, sinapic, p-coumaric, ferulic, ellagic, gallic and cinnamic acid). It is generally accepted that phenolic compounds can be more efficiently recovered from PoP by improving the extraction efficiency. The curative relevance of these compounds has been mainly assessed by in vitro experimentation. Therefore, conclusive clinical trials of the phenolic compounds present in PoP are essential for correct validation of their health benefits. [ABSTRACT FROM AUTHOR]

Bitterness and astringency are two important quality attributes of green tea infusion, and catechins are the main contributor to the bitterness and astringency. The aim of this work was to quantitatively analyse the bitterness and astringency of green tea infusion according to the concentrations of catechins. The concentration–taste curves of catechins showed a pattern that fit the cubic functions, and their R 2 values were higher than 0.956. The bitterness of green tea was highly correlated with the concentrations of (−)-epigallocatechin gallate and (−)-epicatechin gallate (ECG) ( R 2  = 0.7769, p  < 0.01), and the astringency ( R 2  = 0.7878, p  < 0.01) was highly correlated with the concentrations of ECG and flavonol glycosides (myricetin 3- O -galactoside and quercetin-3- O -rutinoside). Taste interactions between different catechins and between catechins and other substances were determined. These results may enhance the understanding of tea chemistry for improving the taste of products from green tea. [ABSTRACT FROM AUTHOR]

There are eight most abundant green tea catechins (GTCs) existing in four pairs of eipimers, and carbon-3 configuration represents the only steric difference within each pair. This study aimed to use a new kinetic approach to elucidate the effect of stereochemical changes on the antioxidant activity. A mixture of eight GTCs was treated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) prepared in a series of concentrations, their relative reaction rates towards scavenging DPPH were revealed by the recently introduced parameter, i.e. D m . The 3- R configuration in (−)-epicatechin, (−)-epigallocatechin and (−)-epigallocatechin gallate gave lower D m values demonstrating faster kinetics as opposed to their 3- S counterparts, with the only exception of the pair of (−)-catechin gallate and (−)-epicatechin gallate in which 3- S configuration was faster. These results suggested that the kinetic approach adopted in this study could reflect the different antioxidant activity of GTCs attributed by minor steric changes. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the interactions between insoluble fractions of different coffee infusions and major cocoa free antioxidants, catechin and epicatechin, as well as the interactions between different coffee infusions and dark chocolate. Espresso, filtered coffee, French press and Turkish coffee were used for this purpose. Antioxidant capacity (AC) measurements were performed by monitoring the percentage inhibition of 2,2-Diphenyl-1-picrylhydrazil (DPPH) radical. Multivariate approach was adopted for experimental design and data analysis steps. In dry basis, the AC values of infusions (mmol Trolox/kg) were ranged between 953 ± 2.6 and 1184 ± 11.3, while the AC values for their insoluble fractions were ranged between 45 ± 0.0 and 105–1.3. Interactions between the insoluble fractions of coffee infusions and catechins were synergistic for espresso and additive/antagonistic for the other infusions. Interactions between coffee infusions and chocolate were synergistic for French press and Turkish coffee and additive/antagonistic for the other infusions. [ABSTRACT FROM AUTHOR]

• Acrylamide prefers having nucleophilic addition with quinones. • Acrylamide is prone to react with catechin's B ring via a redox reaction than its A ring via electrophilic addition. • Thirteen reaction products were detected by UHPLC-Q-Exactive Orbitrap Mass Spectrometry. Acrylamide (AA) elimination is significant in thermal-processing foods that rich in carbohydrate and asparagine. Here, catechin (CAT) and its quinone were utilized to investigate and evaluate the reaction rate of AA's characteristics (electrophilicity, oxidizing ability, and nucleophilicity) and trace the reaction pathways to eliminate AA in model system at 25 °C and 150 °C. It is revealed that AA prefers nucleophilic additions with quinone (k AA-CATQ = 1.1E-2 min−1 > k AA-CAT = 3.1E-3 min−1). It is prone to react with the B ring of CAT (k AA-4MC = 1.4E-3 min−1) via the redox reaction, rather than the A ring (k AA-PHL = 1.0E-4 min−1) through the electrophilic reaction. For the investigation of unknown products resulting from the above reactions, a process incorporating mechanism and tentative product speculation was implemented. Thirteen products were partially detected based on the extracted ion chromatography and MS spectrum from UHPLC-Q-Exactive Orbitrap Mass Spectrometry. These results provide a new perspective to eliminate AA in thermal-processing foods. [ABSTRACT FROM AUTHOR]

• Polyphenol–protein reactions between β-lactoglobulin (β-LG) and (−)-epicatechin. • Addition of epicatechin altered the tryptic peptide profiles of β-LG models. • Site-specificity of (−)-epicatechin o -quinones were determined. • Covalent reactions were determined at S27, S30, K60, C66, K69, and C160. • (−)-Epicatechin promoted the formation of methionine sulfoxide. Polyphenol–protein reactions in model solutions of β-lactoglobulin (β-LG) incubated with (−)-epicatechin at 37 °C and 60 °C were monitored by microLC–timsTOF Pro-MS/MS combined with bioinformatics strategies. The addition of (−)-epicatechin to the model solutions resulted in changes in tryptic peptide profiles. Covalent bond formation between (−)-epicatechin o -quinones and β-LG was identified for the residues S27, S30, K60, C66, K69, and C160, with C160 being the predominant binding site. Furthermore, the incubation of β-LG with (−)-epicatechin significantly promoted oxidation, especially for the residues M7 and M24. The reaction of monomeric (−)-epicatechin o -quinone at C160 was also identified in the milk chocolate sample. The adaptation of this study by extending the scope of the reaction products offers significant potential for comprehensive food profiling strategies. [ABSTRACT FROM AUTHOR]

• Polyproanthocyanidins was degraded by microwave-assisted nucleophilic techniques. • The increasing process parameters were favorable for the degradation reaction. • The degradation kinetics conformed to the random first-order degradation model. • The antioxidation activity of polyproanthocyanidins were improved. • The Mw distribution was narrower, and the compositions were more single. Microwave was employed to enhance the degradation of polymeric proanthocyanidins from black chokeberry using the nucleophilic technique of sulfite/catechin. Based on the degradation effect and kinetics, it was found that increasing the microwave time, microwave power, microwave temperature, sulfite concentration, and mass ratio of raw material to catechins was favourable for the degradation reaction. The degradation kinetics conformed to a random first-order degradation model. The antioxidant activity of the degraded products was analysed using DPPH and O2− assay, which suggested that the scavenging effect of the products was improved. FT-IR and 1H NMR analyses showed that the main functional groups were not destroyed. Using MALDI-TOF/MS to study the components of the degradation products, it was found that the molecular weight distribution became narrower, and the compositions were more single. Polyproanthocyanidins were reduced to oligomers. This study suggested that microwave-assisted nucleophilic techniques could produce oligomeric proanthocyanidins with remarkably improved functionalities. [ABSTRACT FROM AUTHOR]