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The unsaturated nature of flaxseed oil renders it susceptible to oxidation during storage. Glycated myofibrillar protein (MP)-polyphenol conjugates were used to improve the emulsifying characteristics of MP-flaxseed oil emulsion. The role of polyphenols, namely, (−)-epigallocatechin-3-gallate (EGCG), catechin (C) and gallic acid (GA), conjugated to MP-dextran (DX) covalent complex on emulsifying properties, stability characteristics and interfacial behavior of MP-flaxseed oil emulsion was investigated. MP-DX-polyphenol covalent complexes were more effective in decreasing creaming index within 24 h while increasing apparent viscosity, oxidation stability and forming more uniform emulsion. Furthermore, the concentration of interfacial proteins around oil droplets increased with polyphenols conjugation (from 3.78 to 9.52 mg/m2), especially with conjugation by EGCG (9.52 mg/m2), thereby contributing to an enhancement in flaxseed emulsion stability. Glycated MP-polyphenol conjugate was a promising emulsion stabilizer to effectively increase emulsion characteristics of flaxseed emulsion. • Polyphenols improved emulsifying properties of glycated myofibrillar protein. • Emulsions stabilized by ternary conjugates showed lower creaming index. • Ternary conjugates improved oxidation stability of flaxseed oil emulsions. • Ternary conjugates increased the interfacial proteins surrounding oil droplets. [ABSTRACT FROM AUTHOR]

Foods containing proteins or unsaturated fatty acids can generate toxic formaldehyde upon exposure to high thermal. Polyphenol-fortified food has been proved to be has less heat-induced toxic aldehydes formation (including formaldehyde), however, the chemical mechanism underlie such effect has not been fully revealed. In the present research, whether Mannich reaction mechanism is responsible for natural polyphenols's inhibition on formaldehyde production on cooking meat was explored. It is validated that green tea marination can suppress the accumulation of formaldehyde of pan-fried porks. By using HPLC, LC-ESI-MS and LC-ESI-HRMS analysis, members of catechins from tea polyphenols were found has high activity for Mannich addition. Besides, a serial of polyphenol-formaldehyde-amino acid three-component adducts were found in the extract of green tea marinated pork. Herein, we proposed firstly that tea polyphenols' inhibitory effect on formaldehyde was accounted for (at least in part) the formation of Mannich adducts. [Display omitted] • Green tea marination can suppress the accumulation of formaldehyde of pan-fried porks. • A serial of polyphenol-formaldehyde-amino acid adducts were found in green tea marinated pork. • Tea polyphenols' inhibitory effect on formaldehyde was partly accounted for the formation of Mannich adducts. • Members of catechins from tea polyphenols has high activity for Mannich addition. [ABSTRACT FROM AUTHOR]

This study investigates the pivotal role of withering in shaping the quality of white tea. We used a single-factor experimental design to optimize both the light quality and intensity during the withering process. Using gas chromatography-mass spectrometry (GC-MS), sensory evaluation, and physical and chemical analyses, we identified the ideal parameters as yellow light at an intensity of 5000 lx. Subsequently, we used non-targeted metabolomics and transcriptomics to analyze the mechanism of white tea quality formation at various stages of withering. The results showed significant changes to flavonoids during the withering process, with heightened F3′5′H (flavonoid3,5-hydroxylase) gene expression leading to increased levels of quercetin, myricetin, and luteolin. Conversely, the decreased catechin content was attributed to the decreased expression of most genes in the catechin synthesis pathway. The elevated levels of leucine, isoleucine, and GABA in free amino acids were due to a significant increase in the expression of the genes that synthesize them. Hormone and WGCNA analyses substantiated the importance of ABA, JA, and other key genes in shaping white tea quality during withering. These combined factors orchestrate the gradual formation of the distinctive characteristics of high-quality white tea. • The optimum withering light condition of white tea is yellow light 5000 lx, and the aroma and taste of white tea are the best. • The content of tea leaves changed during withering, and finally the unique quality of white tea was formed. • ABA and JA in plant hormones are involved in regulating the formation of the final quality of white tea. [ABSTRACT FROM AUTHOR]

Extrusion yields either an expanded product or a non-expanded pellet. Non-expanded pellets undergo subsequent indirect expansion in a separate thermal device, such as a microwave oven, resulting in a third-generation (3G) snack. The utilization of milder conditions, makes this an encouraging approach for functional food development. Currently, the effects of both processes on retaining functional ingredients and the evolution of their structure are not yet fully understood. Accordingly, this work aimed to analyze how extrusion temperature (110, 135, and 150 °C) and moisture content (27 and 31%) affect the physical characteristics of 3G expanded rice-flour products enriched with catechins, using a microstructural approach, to better understand the relationship between catechin retention, antioxidant capacity, and structure development. The results showed that products with catechin exhibited higher expansion and increased crispiness/crunchiness, with a relatively higher percentage of small pores, as revealed by X-ray microtomography. Additionally, there was a remarkable retention of catechin and antioxidant capacity (DPPH) in the expanded products, reaching nearly 100%. The preservation of antioxidant capacity in the expanded products may be attributed to the high-temperature-short-time process, which favors catechin stability, along with the dense glassy structure of the extruded pellets obtained, protecting them through encapsulation until their subsequent expansion. [Display omitted] • 3G expanded rice-flour extruded pellets enriched with catechins were analyzed. • Lowest moisture and higher extrusion temperature led to higher expansion. • Catechin improved expansion and crispness/crunchiness. • Catechin retention and antioxidant capacity in expanded products neared 100%. • The dense glassy structure of pellets might preserve catechins. [ABSTRACT FROM AUTHOR]

The purpose of present study is to investigate the inhibitory effects of epicatechin (EC) on the formation of ALEs. A chemical model containing bovine serum albumin (BSA, 1 mg/mL) and fish oil (0.5 mg/mL) under accelerated metal-catalyzed oxidation (37 °C, 72 h) was established to mimic the generation of ALEs. The incorporation of EC (0.25, 0.5, 1, and 2 mmol/L) significantly reduced TBARS content in a dose-dependent manner (P < 0.05). The enhanced protein fluorescence associated with the formation of ALEs was also attenuated by EC. Visualization of the inhibitory effects of EC on the formation of protein carbonyls and MDA-related ALEs was achieved by Western blot analysis which showed the fading of signal intensity in the native BSA monomer and protein cross-linking and aggregation at higher molecular weights. However, EC could not restore the protein total sulfhydryl, surface hydrophobicity and microstructure to their original state due to the complicated interaction between proteins and natural phenolic compounds in the presence of lipid oxidation products. Findings of the present study highlight EC as a promising inhibitor on the formation of dietary ALEs. • A fish oil oxidation model was established to mimic the generation of ALEs. • TBARS content was significantly reduced by epicatechin in ALEs generating system. • Lipofuscin-like pigments formation was restrained by epicatechin. • Epicatechin interrupted the formation of protein carbonyls and MDA-related ALEs. [ABSTRACT FROM AUTHOR]

Cocoa bean husk extract (CBHE) was obtained by thermal treatment at 170 °C for 30 min. The CBHE was added to a virgin olive oil jam in a freeze-dried form or encapsulated. Phenols, theobromine, and antioxidant activity were determined over 28 days in both jams and compared to a control jam. Total phenols, epicatechin, and theobromine were higher in the water fraction of the jam with non-encapsulated extract (J-CBHE) at day 28: 1140, 19.14 and 70 ppm, respectively. For the oil fraction of J-CBHE, total phenols, epicatechin, and theobromine contents were 120, 2.54, and 0.13 ppm at day 28, respectively. The oil content in jam with the non-encapsulated extract showed the best Rancimat induction time, with a 32% increase compared to the control, keeping for longer without becoming rancid. Nevertheless, the jam with encapsulated extract showed the best retention of bioactive compounds during the storage time. • Cocoa bean extract improved the stability and antioxidant activity of formulated food. • Main active compounds of cocoa bean extract were theobromine and epicatechin. • The encapsulation of cocoa bean extract improved foods with a higher content of fat. • Cocoa bean extract non encapsulated improved foods with a higher content of water. • Cocoa bean husk extracts enhance the stabilization of heterogeneous foods. [ABSTRACT FROM AUTHOR]

Abstract The solution absorbance ratios were determined to investigate the effects of high pressure processing on the copigmentation reaction of pelargonidin-3-glucoside and catechin. The theoretical spectra and molecular dynamic simulation were used to calculate the catechin/anthocyanin complex concentration, explore the intrinsic relationship between complex structure and absorbance. Results showed that when interacted with catechin at pH 1.5, the catechin/flavylium had the molar absorption coefficient of 1.78 times at 520 nm. Higher catechin concentration increased the solution absorbance about 1.3 times at pH 3.6 (100, 300, 500 MPa; 60 °C); high pressure processing could significantly accelerate the copigmentation rates at pH 1.5, 25 °C with the ratio of 10:1, and 60 °C with the ratio of 1:1. The solution absorbance at 60 °C was about 1.27 times of the corresponding ones at 20 °C (catechin/anthocyanin ratio of 10:1; 300 and 500 MPa). Higher catechin concentration, pressure and temperature could accelerate the copigmentation reactions. Highlights • High pressure processing (HPP) was conveyed to explore the copigmentation reaction. • Copigmentation reactions of Pg-3-Glc and catechin under HPP were investigated. • Theoretical spectra were established to calculate the complex concentration. • Molecular dynamic simulations of copigmentation reactions were carried out. [ABSTRACT FROM AUTHOR]

Among all types of tea beverage, tea wine uniquely combines the flavor of tea and wine, and its consumption is increasing in recent years. "Ziyan" tea wine is a new type of fermented tea wine rich in anthocyanins. The information about the dynamic changes of major chemical and volatile components in its processing is scarce. This study aimed to reveal the changes in sugar, total acids, catechins, anthocyanins and volatile components during "Ziyan" tea wine processing. Results showed that the total sugar, anthocyanin, and total catechins contents of the fermented tea wine were dramatically decreased, while epigallocatechin and epigallocatechin gallate retention remained high and the contents of caffeine and amino acids were not significantly impacted. 27 volatile fragrance compounds were generated during the fermentation process. Most of the volatile compounds in the tea leaves remain in the tea wine. The unique sweet and fruity aroma of "Ziyan" tea wine is mainly due to phenylethanol, octanoic acid, citric acid, and phenylacetaldehyde, which contain rosin, alcohol, etc. Overall, the findings provide systematic insights into the quality formation mechanism of "Ziyan" tea wine, especially in terms of aroma. • Variations in the quality components of "Ziyan" tea wine during fermentation. • The formation of characteristic aroma components of "Ziyan" tea wine. • Fundamental production process of anthocyanin-rich fermented tea wine. [ABSTRACT FROM AUTHOR]

To produce edible films with excellent antioxidant properties, soy protein isolate (SPI) was pretreated using ohmic heating (OH) to create more catechin binding sites. Compared with untreated SPI, ohmic heating-pretreated SPI (OH-SPI) had a looser secondary structure, higher fluorescence intensity, more free sulfhydryl groups, higher hydrophobicity (H 0), and lower protein particles, all of which facilitated covalent binding between SPI and catechin. The binding equivalent of OH-SPI and catechin increased from 128.90 to 237.43 nmol/mg protein. The above results proved that ohmic heating pretreatment benefited the covalent binding between SPI and catechin and the development of the antioxidant film. Scanning electron microscopy (SEM) showed that catechin-modified OH-SPI (OH-SPI-CC) films had a rough and aggregated structure. As the concentration of catechin increased, the mechanical properties of the film improved while the barrier properties slightly decreased. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) confirmed that the cross-linking between catechin and OH-SPI was covalent. In application testing of OH-SPI-CC film, OH-SPI-CC film at a catechin concentration of 4.0 mg/mL (OH-SPI-CC-4) showed the best DPPH and ABTS free radical scavenging rate and the highest cumulative release in food simulators. Therefore, cross-linking catechin with OH-SPI was an effective method for preparing antioxidant films. • SPI was pretreated with OH to provide more catechin binding sites. • The modified SPI film was prepared by catechin and OH for the first time. • Antioxidant property of SPI film prepared by OH and catechin increased obviously. • OH-SPI-CC film had better mechanical properties than OH-SPI film. [ABSTRACT FROM AUTHOR]

Tea grade evaluation plays an important role in detecting the quality of tea. In this work, we proposed a method for black tea grade discrimination, which is based on the hyperspectral (HSI) technique, chemometric algorithms and data fusion strategies. Standard Normal Variable (SNV) and Multiple Scattering Correction (MSC) were used for the pretreatment of HSI-NIR data. Moreover, the spectral features of catechins, tea polyphenols and soluble sugars were extracted separately by the Uninformative Variable Elimination (UVE). To improve the accuracy of the model, the spectral data were secondarily downscaled by the Successive Projection Algorithm (SPA) and Kernel Principal Component Analysis (KPCA), respectively. Image features were extracted by Principal Component Analysis (PCA) and Gray Level Co-generation Matrix (GLCM). Simultaneously, the image features had been fused with the spectral features in order to realize data fusion. Partial Least Squares Discriminant Analysis (PLS-DA), Support Vector Machines (SVM) and Probabilistic Neural Networks (PNN) were utilized to build the discriminant models. The results show that hyperspectral techniques combined with data fusion strategies could improve the model accuracy. The UVE-SPA-GLCM-SVM was chosen as the optimal model with 98.33% accuracy of the validation set. The method provides a theoretical basis for online black tea grade differentiation. • The black tea grades were detected by the HSI technique. • The spectral information of catechins and tea polyphenols were extracted by UVE-SPA method. • The spectral information corresponding to the multiple chemical components of tea was fused. • Image information was extracted from the GLCM. • The fusion of image and spectral information improves the classification accuracy of black tea. [ABSTRACT FROM AUTHOR]

We studied how high pressure processing (HPP) affects various properties of Rosa roxburghii Tratt juice (RrT), such as SOD, Vc, polyphenols, sugar, acid, soluble solids, odor, and color using non-linear models. Results showed that HPP (>100 MPa) increased levels of beneficial compounds like SOD (3202–3697 U/mL), ascorbic acid (12.39–14.08 mg/mL), total phenolics (7.46–12.81 mg GAE/mL) and flavonoids (89.26–648.48 μg RE/mL), gallic acid (53.55–61.46 μg/mL), catechin (23.89–51.41 μg/mL) and ferulic acid (10.82–51.34 μg/mL). The change rules of these bio-active compounds could be well fitted by cubic equations (R 2 = 0.815–0.999). HPP also enhanced the aroma intensity of certain compounds while reducing the flavor concentration of nitrogen oxides. RrT juice treated at 100 MPa had similar odor to untreated juice. 200 MPa treatment resulted in aroma similar to 300 MPa, and 400 MPa treatment produced aroma similar to 500 MPa. High correlation coefficient values (r = 0.67–0.90) between antioxidant compounds (SOD, Vc, catechin, gallic acid) indicated their positive correlations during HPP. • HPP (400 MPa, 20 min) boosted RrT juice SOD activity from 2217 U/mL to 3697 U/mL. • HPP at 200–500 MPa well retained vitamin C levels at 12.39–14.08 mg/mL. • HPP (>200 MPa) maintained gallic acid (53.55–61.46 μg/mL) and catechin (23.89–51.41 μg/mL). • HPP's effect on SOD, Vc, phenolic compounds well fitted cubic equations. • RrT juice smell depended on pressure:100 MPa similar to control, 200 MPa to 300 MPa, and 400 MPa to 500 MPa. [ABSTRACT FROM AUTHOR]

Abstract We have previously reported that the antioxidant activity of catechin degraded dramatically in a protein rich matrix compared to a sugar or oil-based matrix, and that this degradation was significantly retarded by β-cyclodextrin (β-CD) encapsulation. In the present study, we have probed the nature of this interaction of catechin and its β-CD inclusion complex with protein, sugar and oil models using fourier-transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. The former technique revealed a shift and increase in the intensity of the protein amide absorption bands upon mixing with catechin that was not observed with β-CD or with the corresponding encapsulated catechin, suggesting hydrogen bonding between this antioxidant and the protein amide groups. Catechin fluorescence was quenched by all three food models in a concentration dependent manner and this relationship was used to calculate binding constants in each matrix, which also revealed a strong interaction between catechin and protein that was reduced by encapsulation with β-CD. These new results help to explain our earlier observation of catechin degradation by protein and have implications for the use of this important antioxidant in food formulations. Highlights • Free catechin degraded dramatically in protein compared to a sugar and oil model. • Strong interaction was observed between catechin and protein. • Weak interaction was observed between β-CD encapsulated catechin and protein. • β-CD encapsulation helps to protect catechin from degradation. [ABSTRACT FROM AUTHOR]

Ultrasound-assisted aqueous extraction (UAE) of soluble matter (°Brix), catechin and total phenolic contents (TPC) from flesh and peel of apple tissues were studied. The commercial green (Granny Smith) and red (Red delicious) apples were used in the investigation. All extractions were done at fixed temperature, T  = 50 °C, and protocols with different specific energy inputs, S 1 ( W  = 0 kJ/kg), S 2 ( W  ≈ 6.5 kJ/kg), S 3 ( W  ≈ 10.6 kJ/kg), S 4 ( W  ≈ 21.3 kJ/kg), and S 5 ( W  ≈ 26.8 kJ/kg) during the initial period of extraction (first 300–350 s). The total aqueous extraction time was up to 3 h. The kinetics of extractions, and correlations o Brix and concentration of catechin, C , were compared for flesh and peel tissues. The increase of energy resulted in increase of o Brix and C values. For both green and red apples, the values of °Brix and C were noticeably higher for peel as compared to flesh. The distinct correlations between saturation levels of C m and TPC m at the long extraction time (≈3 h) were observed. However, the relative content of catechin in TPC (i.e., ratio C m /TPC m ) evidenced the presence of selectivity in extraction of catechin. This selectivity depends from the type of tissue (flesh or skin), apple variety (green or red) and applied treatment protocols. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the interaction between catechins and glycated porcine hemoglobin (G-PHb). The effects of the interaction on the antioxidant function and structural characteristics of the complex (CG-PHb) of catechin and G-PHb were discussed. Porcine hemoglobin (PHb) and G-PHb were used as controls. The solubility, turbidity, emulsifying property, surface hydrophobicity, and oxidation resistance of CG-PHb were studied. The structural characteristics of the CG-PHb were analyzed via UV–visible spectroscopy, fluorescence spectrometry, fourier transform infrared spectroscopy, scanning electron microscope and molecular docking technology. Compared with the control group, these properties of the CG-PHb are significantly improved. The UV absorption peak of CG-PHb had a larger peak and a slight red shift. The fluorescence peak intensity was in the following order: CG-PHb > PHb > G-PHb. The β-sheet content of CG-PHb increased significantly (P < 0.05). Moreover, SEM showed that the structure of CG-PHb had changed. The surface pore structure increased, which facilitated its functional properties. Molecular docking showed that catechin likely interacted with PHb residues HEM-950, PHE-41, GLU-43, ARG-40 and LEU-96. Catechin and PHb formed a more stable complex because of hydrogen bonds. This study can provide new ideas for protein modification research and provide theoretical basis and reference for the property changes of the CG-PHb during food processing. • Glycation can improve some physical or chemical properties of protein. • The interaction between protein and catechin can also modify protein function. • The combination of the two methods makes it have better performance. [ABSTRACT FROM AUTHOR]

At present, several novel pile-fermentation styles have been developed for ripened Pu-erh tea (RPT) processing. In this study, tea pigments, phenolic compounds, purine alkaloids and amino acids in six RPTs produced through three various fermentation styles were determined by using HPLC and amino acid analyzer to reveal chemical differences caused by fermentation style, respectively. Additionally, dynamic changes of phenolic compounds and purine alkaloids were explored during a whole new-type fermentation. Despite three various fermentation styles, these RPTs demonstrated consistent sensory and major quality components including three tea pigments, two flavonoids and three purine alkaloids. However, RPTs of the new-type fermentation had relatively higher contents of seven catechins, gallic acid, two flavonols (i.e. quercetin and kaempferol), two other flavonoids (i.e. rutin and luteolin) and 10 amino acids such as l -theanine and l -arginine. The new-type fermentation decelerated the degradation of four galloylated catechins, rutin, amino acids and soluble sugars, but contributed to the accumulations of three non-galloylated catechins, two flavonols, luteolin and gallic acid. Therefore, the new-type fermentation could be a potential style for RPT processing with a shorter fermentation cycle. • Sensory, quality constituents exhibit consistency among various fermentation styles. • Fermentation style affect phenolic compounds, amino acids in ripened Pu-erh teas. • New-type fermented tea contain higher catechins, flavonols, gallic acid, amino acids. • New-type fermentation accumulated 3 catechins,2 flavonols, luteolin and gallic acid. [ABSTRACT FROM AUTHOR]

Separation of individual green tea catechins has the limitation due to their structural resemblance and unequal distribution. Hence, the objective of this study was to develop separation methods based on 1.Preparative Thin Layer Chromatography (TLC) using oxalic acid impregnation and 2. Microwave (MW) mediated acetylation followed by classical silica gel column chromatography separation. The yield of total catechins by different extraction techniques was, conventional (7.3%), liquid-liquid (7.8%), Soxhlet (8.3%) and microwave (8.8%). Acetylation of total catechins under various MW conditions explored with acetic anhydride, triethylamine and standardized at 15 min at 1g scale and subjected to separation. Subsequently, the individual catechin acetates deacetylated under MW conditions and characterized by TLC, High-Resolution Mass Spectrometry (HRMS), Fourier Transform Infrared Spectroscopy (FT-IR), 1 H and 13 C Nuclear Magnetic Resonance (NMR) spectroscopic studies. The total polyphenol content of the extract was 931.17 ± 0.67 g GAE kg −1 . The antioxidant activity of deacetylated catechins was evaluated by Ferric-Reducing Antioxidant Potential (FRAP) in terms of Trolox equivalence (TE) and % inhibition of 1, 1-diphenyl-2-picryl-hydrazyl (DPPH). Accordingly, the TE and DPPH % inhibition was epigallocatechingallate (12.3 and 71.9%), epicatechingallate (11.5 and 55.5%), epigallocatechin (9.10 and 46.0%), epicatechin (7.40 and 35.1%) respectively. [ABSTRACT FROM AUTHOR]

The potential applications of catechin in food products are limited by its astringent taste, sparing solubility in water and sensitivity to oxygen, light and pH. A finishing formulation that is capable of protecting catechin is needed to deliver this antioxidant to its physiological targets with minimal loss of bioactivity. The aims of this study were to optimize the yield, microencapsulation efficiency and antioxidant properties of the inclusion complex (IC) and to determine the physicochemical properties and stability of β-CD-, HPβ-CD and Mβ-CD-complexed-catechin for potential functional food and health supplement applications. An inclusion complex prepared from 0.006 mol/L catechin and β-cyclodextrin (β-CD) with a 1:1 core to wall ratio showed the highest yield, encapsulation efficiency and antioxidant activity. Catechin complexed with β-CD more efficiently than with hydroxypropyl- β-cyclodextrin (HPβ-CD) or methyl- β-cyclodextrin (Mβ-CD). Encapsulation with β-CD was observed to double the water solubility of catechin. Particles of complexes ranging from 5 to 100 μm with spherical morphology were produced. 1 H NMR spectroscopy and DSC confirmed the host – guest complexation of catechin in the β-CD cavity. The current study shows that encapsulation of catechin with β-CD provides protection against temperature, light and oxygen. These inclusion complexes have potential applications as functional foods and health supplements. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effect of the addition of β-cyclodextrin, catechin or inclusion complexes (catechin: β-CD) (physical mixture or with supercritical carbon dioxide) on prebiotic green tea beverage characteristics during storage at ambient temperature (90 days/25 °C). The prebiotic (oligofructose) stability was also evaluated. The addition of cyclodextrin and/orcatechin resulted in products with higher acidity. The physical process of complexation, which is simple and cheap, gave the best results in relation to the stability of the phenolic compounds content in the product. The supercritical carbon dioxide did not improve the protection of the phenolic compounds. A portion of 200 mL of the green tea had sufficient oligofructose content to be considered a prebiotic product during 90 days of storage. It was possible to formulate green tea beverages with high total phenolic compounds (2525–3307 mg CE/L) and oligofructose content (3.1 g/200 mL) sufficient to consider them prebiotic products, being recommended the physical process of complexation (catechin: β-CD). The green teas would maintain the beneficial effects for 90 days at ambient temperature (25 °C). [ABSTRACT FROM AUTHOR]

In this work extraction kinetics of typical ingredients in representative white teas was investigated. Aqueous extraction of 4 epicatechins (EGC, EC, EGCG, ECG), 4 trans -catechins (GC, C, GCG, CG), gallic acid (GA) and caffeine at 65 °C, 75 °C, 85 °C, 95 °C respectively from Fuding Silver Needle (FSN), Fuding White Peony (FWP), Zhenghe Silver Needle (ZSN) and Zhenghe White Peony (ZWP) was examined. The total catechins, gallic acid, caffeine, EGCG, epicatechins, trans -catechins were compared in terms of rate, peak value, peak time and the extraction kinetics at different temperatures. It is exhibited that the contents of 8 catechins in ZWP, ZSN and FSN follow the order of EGCG > ECG > GC > EGC > GCG > CG > EC > C, and that in FWP is EGCG > ECG > EGC > GC > EC > GCG > CG > C. Structural transformation from epicatechins to trans -catechins and dissociation of gallic acid were observed during extraction by data analysis. Extraction kinetics over 240 min period were successfully modeled using Peleg's model with low MSR (0–2.232) and high R2 adj (0.903–0.999). Optimal extraction conditions (FSN(43.3 min, 95 °C); FWP(43.3 min, 95 °C); ZSN(53.8 min, 95 °C); ZWP(41.5 min, 95 °C)) were suggested by Peleg's model. As a result, this study will facilitate quality control of white tea during processing. [ABSTRACT FROM AUTHOR]

In this work, a green tea extract (GTE) was encapsulated within electrosprayed protein (i.e. gelatin and zein) microparticles, and the protective ability of both systems on the green tea catechins was assessed. The microparticles (with encapsulation efficiencies ∼90 g/100 g), proved to be very effective in stabilizing the catechins during a thermal treatment at 180 °C (12 min), preserving 85–90 g/100 g of their initial catechins content, while free GTE lost almost 40 g/100 g of its catechins content. In order to assess the impact of microencapsulation in a real food system, the GTE-loaded electrosprayed microparticles were added to biscuits dough. Results showed that microencapsulation did not significantly protect during biscuit processing and emphasized the need of assessing the behaviour of microencapsulation systems in real food processing conditions. The sensorial analysis of the biscuits indicated that addition of the GTE-loaded microparticles did not impact the acceptability of the biscuits, as perceived by consumers. [ABSTRACT FROM AUTHOR]

In recent years, biodegradable materials (carbohydrates, proteins, and lipids) have similar properties to plastic materials, which can be decomposed and will not cause environmental pollution. Thus, they can be developed into edible films as food packaging materials; however, their manufacturing costs have increased several folds. Taiwanese tilapia (Oreochromis mossambicus) contains considerable gelatin, a by-product of the food processing industry, which can be made into an edible film combined with catechin and guava leaf extract as the principal polyphenol and flavonoid, respectively, with antioxidant and antibacterial activities. Therefore, this study investigates the properties of edible films combined with catechin-guava leaf extract at different ratios. Results showed that the film's thickness ranged from 0.053 to 0.068 mm. The film had a good barrier effect on UV rays. In addition, the edible film exhibited good antioxidant ability; it had more evident antibacterial activity against E. coli and S. aureus. Consequently, the catechin-guava leaf extract ratio of 30–70 had a better elongation at break and film thermal stability, indicating its great application potential. However, further development is required compared with polyvinyl chloride, particularly with regard to mechanical efficiency and transparency. • Edible films of gelatin, catechins, and guava-leaf extracts have potential application for food packaging. • Catechins and guava-leaf extracts promote film elongation, antioxidant activity, and microbial resistance. • The film will degrade to achieve environmental friendliness. • The film can prevent UV radiation within a certain range. • No microbial growth has been found on the contact surface of the edible film. [ABSTRACT FROM AUTHOR]

Substance basis of selenium (Se) enriched green tea (Se-GT) plays a crucial role in imparting numerous health benefits to the consumer, however, the complex relationship between minerals, chemical ingredients, and Se in tea leaves remains largely unknown. Here, the contents of 14 minerals and 29 bioactive components (including 19 amino acids, 8 polyphenols, and 2 alkaloids) were determined in five green tea samples with different Se levels. Marked differences were observed in the elemental and chemical profiles of the five groups of teas. Pearson correlation analysis demonstrated that Se was likely to be synergistic with Zn, while antagonistic with Mg, Al, Cr, Fe, and As. Inconspicuous correlations between amino acids and Se in tea leaves were discussed via this extended study. Moreover, Se showed positive correlations with gallic acid, (+)-catechin, and gallated catechins (like (−)-epigallocatechin gallate, (−)-gallocatechin gallate, and (−)-epicatechin gallate), but negatively correlated with some non-gallated catechins (including (−)-gallocatechin and (−)-epigallocatechin) in tea leaves. These results suggested that Se has significant effects on the accumulation of minerals and polyphenols in tea leaves. Overall, this study elucidates the elemental and chemical basis of Se-GT and provides a rationale for the quality evaluation of Se-GT, which is of crucial importance for tea industry. Minerals and bioactive components of five green tea samples were analyzed, and the relationships between these elemental and chemical components and Se were evaluated by Pearson correlation analysis. [Display omitted] • 14 minerals and 29 bioactive components in 5 green tea samples were analyzed. • There was a positive association between Zn and Se levels in green tea leaves. • Mg, Al, Cr, Fe, and As contents in tea leaves were negatively related with Se level. • Catechins and gallic acid showed significant correlations with Se in tea leaves. [ABSTRACT FROM AUTHOR]

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

Catechin (CA) is a natural polyphenol with antioxidant activity. However, it is difficult to maintain stability and easy to release rapidly in active films. Novel zein edible films containing nano-sized CA/α-, β-, γ-cyclodextrin-metal-organic frameworks (CD-MOFs) were developed, and their physicochemical properties, antioxidant stability and release behavior were characterized. FT-IR revealed the CA/CD-MOFs and film matrix formed intermolecular hydrogen bonding interactions. XRD analysis detected that the film matrix was successfully embedded by CA/CD-MOFs. With the incorporation of CA/CD-MOFs, the microstructure of zein film was more compact, and significantly improved the water resistance, barrier and mechanical properties of zein film. Zein film containing CA/β-CD-MOFs showed good physical properties because of good compatibility of the CA/β-CD-MOFs with zein. Compared with zein film containing free CA, zein-CA/CD-MOFs films still have higher antioxidant capacity after 80 days of storage. Since CA was encapsulated into the porous structure of CD-MOFs by intermolecular force, the release of CA from zein films was controlled. These results suggest that the developed nanoedible films have potential application value as food packaging, which can be directly in contact with foods, and the longer active ingredient availability can effectively extend the food shelf life. • Active edible film was developed by adding different CA/CD-MOFs into zein films. • The structure and function of films containing different CA/CD-MOFs were compared. • CA/CD-MOFs elevated the mechanical and barrier properties of the films. • Films containing CA/CD-MOFs showed excellent antioxidant stability. • The release of CA encapsulated by CD-MOFs from the film was controlled. [ABSTRACT FROM AUTHOR]

The aim of this study was to fabricate dual-function antioxidant emulsifiers using natural ingredients. Catechin-dextran-egg white protein (EC-Dex-EWP) conjugates were prepared using a two-step method: (i) free radical grafting of dextran to EC; (ii) attachment of EC-Dex to EWP using the Maillard reaction. The total phenolic equivalent of the conjugates formed was 4.91 mg EC per gram of conjugate and the free amino content decreased by 19.2% compared to EWP. The formation of EC-Dex-EWP conjugates was confirmed by electrophoresis, infrared spectroscopy, and fluorescence spectroscopy. The interfacial tension of the conjugates was higher than for pure proteins, which was attributed to their larger molecular weight and lower hydrophobicity that EWP. The conjugation of EC-Dex to EWP did not affect the solubility of the protein but it did improve its emulsifying properties. The thermal stability of proteins was improved through Maillard reaction. Moreover, the conjugates also exhibited a stronger antioxidant activity, which was attributed to the presence of polyphenols. Our results suggest that the protein-polysaccharide-polyphenol conjugates developed in this study have potential as novel surface-active antioxidants for improving the physicochemical stability of emulsion-based foods. • EC-Dex-EWP conjugates were prepared using a two-step method. • The formation of conjugates was confirmed by structural analysis. • Presence of dextran in conjugates improved their physical stability of emulsions. • EC provide a strong antioxidant activity for the conjugates. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of rain-shelter on microbial diversity in spontaneous fermentation of Cabernet Sauvignon wines, and the correlations of core microbial taxa with biological parameters and monomeric phenols, with an open-field mode as the control. Firstly, rain-shelter increased the contents of 2.6% alcohol, 6.8% glycerol, 10.3% malic acid and 20.3% catechins in resulting wines, respectively (P < 0.05). As fermentation advanced, bacterial diversity decreased and then increased, while fungal diversity decreased (P < 0.05), regardless of cultivation. Besides, significant correlations were identified between Acetobacter , Pseudonocardia , Leuconostoc , Starmerella , Aspergillus and Saccharomyces and biological properties and monomeric phenols. Finally, the functions of bacterial genes were predicted to be primarily related to carbohydrate and amino acid metabolisms; fungi were more abundant in glycolytic pathway, and coenzyme A biosynthesis fatty acid elongation pathway. Overall, this information provides important insights into the succession and metabolism of indigenous microbes mediated by rain-shelter. [Display omitted] • Rain-shelter increased the alcohol, glycerol, malic acid and catechin levels of the final wine. • The variations in biological parameters were concentrated in MF and EF, with monomeric phenols at EF. • OPLS-DA model identified glycerol, lactic acid and benzoic acid as differential metabolites. • Microbial community succession during spontaneous fermentation of wine under rain-shelter mode was confirmed. • Relationships between biological parameters, monomeric phenols and microbial communities were established. [ABSTRACT FROM AUTHOR]

In this work, silver nanoparticles (AgNPs) were synthesized solely using catechin (Ct), a natural polyphenol, then their effects on the growth and metabolism of Aspergillus niger GM13 were investigated using 7.5 and 15 ppm of nanoparticles. AgNPs-Ct, induced physio-metabolic changes activating different stress compensation mechanisms that affect the fungal growth and survival. In particular, 15 ppm of AgNPs-Ct leads to a reduction of 81% of the mycelia biomass. The stress responses in the presence of AgNPs-Ct were further determined by overall cell changes through the production of reactive oxygen species (ROS) by the fungal hyphae. The increase in ROS production confirmed cellular oxidative stress which, together with membrane damage, can be considered to be the main antifungal effect. Adaptative fungal responses during AgNPs-Ct treatment were linked to a high accumulation of trehalose, glycerol, citric and oxalic acid, and several important enzymes involved in the catabolism of nutrients for cell growth, such as acid phosphatase, Naphthol-ASBI phosphohydrolase. The exposure to AgNPs-Ct also triggers changes in the production of VOC derivating from the α- or β-oxidation of fatty acids as alcohols, aldehydes, alkanes, and acids. Herein, the antifungal effect of AgNPs-Ct is demonstrated, elucidating the impact on its physio-metabolic profile. • Surfactant-free AgNPs were synthesized in water exclusively using catechin (Ct). • AgNPs-Ct physio-metabolic effects on A. niger growth were monitored. • AgNPs-Ct induces a redox homeostasis imbalance and osmotic disequilibrium. • Adaptation and defense mechanisms of A. niger were evidenced. • AgNPs-Ct are sustainable emerging biocontrol agents with promising features. [ABSTRACT FROM AUTHOR]

Catechin and curcumin have high potential health benefits. In contrast, these free polyphenolic compounds are susceptible to the external environment, and curcumin's poor solubility further lowers its biological activity. Herein, catechin or curcumin was pre-emulsified with soybean protein isolate (SPI) and encapsulated in co-crystallized sucrose, respectively. The different encapsulated co-crystals were applied to beef meatballs as antioxidants and emulsifiers. DSC, XRD, FTIR, and SEM confirmed the modification from crystalline to irregular agglomerates after co-crystallization treatment. Co-crystallization with encapsulated catechin (CCA, CSCA) showed higher total phenolic content (over 210 mg GAE/100 g) and free radicals scavenging activity (over 87%) than that in encapsulated curcumin. The beef meatballs added with encapsulated catechin (MCCA) had the lowest TBARS (0.158 mg MDA·kg−1) and carbonyl content (0.282 nmol/mg) but the highest total sulfhydryl content (995.88 nmol/mg), and total in vitro digestibility (96.47%). Notably, encapsulated SPI-catechin or SPI-curcumin (CSCA, CSCU) significantly improved the emulsification effect of beef meatballs by maintaining the lower cooking loss, higher water-holding capacity, and better texture properties, as evident from LF-NMR, light microscopy images and protein solubility. In conclusion, co-crystallization significantly improved the stability of catechin and curcumin, and applying these co-crystals in meat products as natural antioxidants and emulsifiers is feasible. • Co-crystallization process does not change the chemical structure of active compound. • The presence of SPI enhances the co-crystals antioxidation and emulsification. • Co-crystallized catechin is better for improving the quality of beef meatball. [ABSTRACT FROM AUTHOR]

In this study, quantitative taste evaluation based on sense and electronic tongue (ET) combined with chemical composition analysis reveals the taste quality difference of Keemun black tea (KBT) with natural withering, sun withering and warm-air withering treatments. The results showed that there were significant differences between the taste of the three finished teas, both in sensory and ET evaluation, indicating a stronger bitterness and astringency in the sun withering and a weaker bitterness and astringency in the warm-air withering. The quantitative results of LC-MS and HPLC on the taste compounds indicated that the total amount of catechins in sun withering was 20.85 mg/g, which was 1.90 mg/g and 5.06 mg/g higher than that in natural withering and warm air withering, respectively. This may be because sunlight promotes the conversion of theanine to catechins. The correlation results indicated that there was a quantitative and effective relationship between taste and tasting compounds and that there was a synergistic effect (R ≥ 0.8) between sweet and astringent compounds. This study emphasised a comparative evaluation in methods and in the taste effect of different withering methods, especially providing a theoretical basis for the quality control and flavour improvement of KBT. • Withering methods played a vital role in taste quality of KBT. • Sun withering improved the catechins content. • Warm-air withering enhanced the umami and sweetness of tea infusion. • Catechins and flavonoid glycosides were the main astringency contributors to KBT. [ABSTRACT FROM AUTHOR]

This study aimed to optimize the dark tea pile-fermentation conditions through single factor and orthogonal experiments. The optimal conditions consisted of 38 g/100g moisture content of wet green tea, 45 °C of temperature, and 85 g/100g humidity. On this basis, the dynamic changes of flavor components during pile-fermentation were systematically explored by chromatography, mass spectrometry and other methods. During pile-fermentation, changes were observed in the internal ratio of the following various substances, with a decrease in the content of tea polyphenols (especially ester catechins), amino acids, and soluble sugars, as well as the formation of new substances of theaflavin, thearubigin, and theabrownin, thereby affecting the brew color, flavor, and taste of dark tea. After pile-fermentation, a gradual decrease was detected in the floral aroma components, such as phenethyl alcohol, linalool oxides, and linalool, in contrast to a gradual increase in the content of aged fragrance components, including methoxy aromatic compounds like 1,2,3- and 1,2,4-trimethoxybenzene. During pile-fermentation, the important aroma substances such as benzaldehyde, β-ionone, and dihydroactinidiolide showed an uptrend first and then a downtrend. The changes in the ratio of these substances contributed jointly to the aroma quality formation of dark tea. • Dark tea pile-fermentation conditions are optimized by different experiments. • Dynamic changes of quality components during pile-fermentation are explored. • Aged fragrance formation conditions in pile-fermentation are revealed. • Different flavor types of dark tea are obtained by controlling the time point. [ABSTRACT FROM AUTHOR]

To explore the impact of harvest season in white tea, high-performance liquid chromatography (HPLC) and amino acid analyzer were developed for the determinations of 17 phenolic compounds, 3 purine alkaloids, 19 amino acids, γ-aminobutyric acid (GABA) and 4 main quality components in 18 Bai mudan sub-type of Xinyang white teas harvested in spring, summer and autumn seasons, respectively. Additionally, the in vitro antioxidant capacity was evaluated by 5 various assays. Principal component analysis (PCA), hierarchical cluster analysis (HCA) and partial least squares-discriminant analysis (PLS-DA) could completely classify these white teas by the harvest season, and indicated its profound impact on chemical composition in white tea. 14 Characteristic compounds (VIP ≥1.0), such as (−)-epigallocatechin (EGC), gallic acid, caffeine, l -theanine, conduced to identify the harvest season of white tea. Through comparison, the spring tea was observed to possess the highest amino acids, catechins contents and in vitro antioxidant capacity. (−)-Epicatechin (EC), EGC, (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG) were considered as the major antioxidants in white tea due to their highly significantly (p < 0.01) positive correlations. Overall, the research results provided support for the identification of harvest season in white tea. • Xinyang white teas were classified by harvest season through multivariate statistical analysis. • Spring and autumn teas possessed relatively higher amino acids, catechins and gallic acid. • 14 Characteristic compounds (VIP ≥1.0) conduced to identify the harvest season of white tea. • Spring tea had the highest antioxidant capacity of FRAP, ABTS, HSA and SSA. • EC, EGC, ECG and EGCG were confirmed as major antioxidants in the white tea. [ABSTRACT FROM AUTHOR]

There is an urgent need for the development of a protein emulsifier with antioxidant and emulsifying properties. In this study, caffeic acid (CF), chlorogenic acid (CA) with a C3–C6 structure, epigallocatechin gallate (EGCG), catechin (CT), and quercetin (QE) with a C6–C3–C6 structure were conjugated to egg white protein (EWP) by using an ultrasound-assisted free radical method to create a dual-function emulsifier. Results indicated that ultrasound accelerated the interaction between EWP and CA, CT, CF, EGCG, or QE by strengthening the generation of hydroxyl free radicals and dispersion of EWP and polyphenols. The antioxidant activities of EWP were significantly improved after being induced by ultrasound-assisted CA, CF, EGCG, CT, or QE conjugation (p < 0.05), particularly modified by EGCG and QE with a C6–C3–C6 structure. The emulsifying properties of EWP were significantly improved after being induced by ultrasound-assisted CA, CF, EGCG, CT, or QE conjugation (p < 0.05), particularly modified by CF with a C6–C3 structure, it might be due to an increase in surface hydrophobicity, and this structural transformation has further improved the in vitro digestion efficiency of EWP. Therefore, the dual-function EWP emulsifier can be fabricated by the conjugation of polyphenols to EWP using an ultrasound-assisted free radical method. • Ultrasound accelerated the interaction between EWP and CA, CT, CF, EGCG, or QE. • Sonochemical of ultrasound can strengthen the generation of hydroxyl free radicals. • The antioxidant activities of EWP were improved, particularly modified by EGCG and QE. • The emulsifying properties of EWP were improved, particularly modified by CF. • Ultrasound-assisted free radical method was efficient for production of dual-function EWP. [ABSTRACT FROM AUTHOR]

Frying is an important process in cooking a wide spectrum of food products in homes, restaurants and the food industry due to the unique sensory characteristics of fried foods combined with a relatively low-cost operation. Due to health and nutritional concerns however, novel approaches are being sought to reduce oil uptake and minimize deleterious oil degradation. This study investigated the potential of utilizing water injection and as a vehicle for continuous delivery of one or a combination of antioxidants at different pH values. Selected antioxidants were tested during simulated frying at 180 °C by monitoring commercial canola oil quality indices. Water injection increased free fatty acids (FFA) during frying, while simultaneously enhancing oil stability as indicated by conjugated diene value, radical-scavenging activity and p -anisidine value. It was demonstrated as an effective carrier for continuous incorporation of antioxidant, which maintained a low concentration of FFA during deep-fat frying. Selection of buffer and/or neutralizing chemical and antioxidant is of high importance. Catechin had both antioxidant and pro-oxidant activities, highlighting the need for system optimization. The protective role of water injection could be significant for foodservice and restaurants where the frying oil is maintained idle at high temperatures for relatively long periods. [ABSTRACT FROM AUTHOR]

Reducing powers, scavenging DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical activities and anti-lipid-oxidation capabilities of synthetic antioxidants, BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), PG (propyl gallate), and TBHQ (tert-butylhydroquinone) and natural phenolics α-T (α-tocopherol), CA (chlorogenic acid), GA (gallic acid), QCT (quercetin), RSV (resveratrol), and SA (syringic acid) were determined to examine their correlations. The results demonstrated that the reducing power of CA and GA were over 200 (μmol/L of catechin equiv.), however, their anti-lipid-oxidation capability was only 13.8 and 4.2%, respectively. Oppositely, BHA and RSV had the lowest scavenging DPPH activity, but performed well in anti-lipid-oxidation. Although the EC 50 values of PG and GA in DPPH assay were at a similar level of 35.8 and 36.3 μmol/L, the anti-lipid-oxidation capability of PG was five times higher than GA. Only QCT and PG had better performance in all the three measurements. It indicated that the reducing power, scavenging DPPH activity, and anti-lipid-oxidation capability of an antioxidant were not always positively correlated with each other. The result of anti-lipid-oxidation capability may closely reflect the activity of an antioxidant in protecting food and body lipid against undesirable oxidation. [ABSTRACT FROM AUTHOR]

Autoclave treatment (AT) modified the dietary fiber composition of brewers' spent grain (BSG), impacting its techno-processing properties. However, its impact on antioxidant properties and stability of polyphenolic compounds remain unclear. This study aimed to evaluate the influence of AT on several antioxidant activities and polyphenolic composition. The results showed that AT increased ORAC (oxygen radical absorbance capacity), ABTS (2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulfonic acid), and FRAP (ferric-reducing antioxidant power) value upto 7 folds compared to the untreated BSG. The lower temperature degraded the amount of flavan-3-ols and phenolic acids. However, AT at 110 °C and 130 °C upgraded the phenolic acids upto 4 and 11 folds respectively. Higher temperature also induced the formation of benzoic acid and (+)-catechin. UPLC-MS/MS identified several phenolic acids including syringic acid, benzoic acid, coumaric acid, ferulic acid and its derivatives, and flavan-3-ols such as (+)-catechin and (−)-epicatechin. In conclusion, AT improved the bioactivity of BSG, enhanced the amount of certains phenolic compounds and released the bioactive compounds from BSG matrices thus offering a higher benefit for industry to utilise autoclaved BSG. • Autoclave improved the antioxidant activities of spent grain upto 7 folds. • Higher temperature upgraded the amount of phenolic acids upto 11 folds. • Lower temperature decreased the amount of flavan-3-ols and phenolic acids. • Higher temperature induced the formation of benzoic acid and (+)-catechin. [ABSTRACT FROM AUTHOR]

This study investigated the changes of main quality components and the effect of bioactivities of black tea during a manufacturing process that adds to enzymatic treatment. It used black tea harvests in summer and autumn for manufacturing and analyzed the number of main quality components and bioactivities of the black tea produced by treating cellulase during rolling and polyphenol oxidase (PPO) and peroxidase (POD) during fermentation. The results found that the contents of total catechins (TC), total polyphenols (TP), reducing sugars (ReS), and individual catechins in the tea infusions of summer and autumn black tea that were obtained during enzymatic treatments decreased significantly (p < 0.05). However, the content of free amino acid (FAA), the tea quality parameter such as the total liquor color (TLC), the briskness index (BI), and the tea pigments including total theaflavin (TF), thearubigens (TR), TRSI, and TRSII all increased significantly (p < 0.05). Moreover, the biological activity enhanced black tea's antioxidant and metabolic capacity with enzymatic treatments were proved by in vitro experiments. The results of this study contribute to gaining further knowledge on how black tea's quality and potential health benefits are maximized by using exogenous enzyme addition methods in the manufacturing process preparation. • The quality is significantly enhanced by enzymatic treatment in the manufacturing process of black tea. • TF and TR improved bioactivities more than total polyphenol, free amino acids, and catechin. • Enzymatic treatment of black tea may effectively increase TLC levels in tea liquor and improve the quality of black tea brew. [ABSTRACT FROM AUTHOR]

Green, white and black teas showed different degrees in enzymatic fermentation through relevant processing procedures. To reveal the impact of enzymatic fermentation in tea-leaves, 44 chemical components including 17 phenolic compounds, 3 purine alkaloids, 19 free amino acids and γ-aminobutyric acid (GABA) in 27 various tea samples were determined by HPLC and amino acid analyzer, respectively. Additionally, E-tongue and 5 various assays were developed for taste evaluation and in vitro antioxidant activities analysis. Multivariate statistical analyses, such as PCA, HCA and PLS-DA (R2X = 1.000, R2Y = 0.932, Q2 = 0.908, respectively) divided theses teas into green, white and black tea categories, indicating the profound impact of enzymatic fermentation on tastes and chemical compositions. The enzymatic fermentation highly significantly (p < 0.001) promoted the decreases of 5 catechins (i.e. C, EC, GC, ECG and EGCG), gallic acid, rutin and 6 free amino acids, and the accumulations of 4 flavonoids (i.e. taxifolin, myricetin, queretin and luteolin), ellagic acid and 4 free amino acids in tea-leaves. The bivariate correlation analysis confirmed that 7 catechins, GG and 7 free amino acids might impress bitterness, umami and astringency, which also contributed to the antioxidant activities in tea-leaves. This study advanced the knowledge about enzymatic fermentation in tea-leaves processing. • Enzymatic fermentation caused the chemical differences among green, white and black teas. • Enzymatic fermentation significantly impact 5 catechins,5 flavonoids, 6 free amino acids. • Slight enzymatic fermentation might improve the in vitro antioxidant activities in tea-leaves. • Catechins, free amino acids contributed to antioxidant activities, bitterness, umami, astringency. [ABSTRACT FROM AUTHOR]

Storage temperature plays a very important role in the flavor development of fermented beverages. In this study, fermented persimmon beverage was stored for one year to study the changes in flavor-related compounds during storage at different temperatures. Fresh persimmon beverage and fermented beverages stored at 10, 20, and 30 °C had different tastes, distinguished by electronic tongue (ET). The fermented beverage was sweet when stored at 10 °C and salty when stored at 20 °C or above. A total of 658 nonvolatile metabolites were identified, among which quercetin and epicatechin were detected by a liquid chromatography-mass spectrometry (LC-MS) based metabolomics approach from four fermented beverage samples. The volatile compounds in the beverages were determined by headspace solid phase microextraction, combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and gas phase-ion migration spectroscopy (GC-IMS), respectively showing totals of 47 and 69 compounds in the four beverage samples. As detected by both methods, ethyl acetate, ethyl hexanoate, ethyl octanoate, ethanol, and acetic acid were all found in beverages stored at different temperatures and the results showed that a higher storage temperature resulted an increase in the number of volatile compounds in the beverage. However, fermented persimmon beverage stored at low temperatures had a better taste and flavor characteristics. • Volatile flavor components, analyzed by GC-MS and GC-IMS showed different composition. • Higher storage temperature promoted the release of esters and alcohols like flavor components. • Non-volatile components, identified by LC-MS mainly included phenol, propane, and polyketones • The storage temperature of 10 °C enhanced sweetness, while that of 20 °C enhanced saltiness. • Lower storage temperature was beneficial for stability of sensory qualities. [ABSTRACT FROM AUTHOR]

This study investigated the effect of wall material types and concentrations on hygroscopicity, solubility, encapsulation efficiency (EE), flavonoid recovery (FR), and antioxidant activity of catechin nanoemulsion (CaNE) powder produced by foam mat freeze-drying. CaNE containing 0.4 g/100 g green tea catechins was ultrasonically fabricated and foamed with hydroxypropyl methylcellulose, as a foaming agent, and three different types of wall materials (maltodextrin [MD], gum arabic [GA], or a mixture of MD and GA [M + G]), at two concentration levels (5 and 10 g/100 g), before being freeze-dried at −50 °C for 48 h. The wall materials increased the hygroscopicity of CaNE powder while improving its water solubility by up to 92%. CaNE containing GA and M + G had higher EE and FR values than that containing MD. MD and M + G samples had higher antioxidant activity than GA. The antioxidant activity of the powder decreased as the concentration of wall material increased. CaNE powder with high EE and FR values, good solubility, and high antioxidant activity can be obtained when using M + G at 5 g/100 g. The findings are significant in providing an efficient method for developing CaNE powder as an effective ingredient for functional foods or beverages. [Display omitted] • High encapsulation efficiency of catechin nanoemulsion (CaNE) powder was achieved. • Wall material types and concentrations highly affected CaNE powder characteristics. • The CANE powder had high flavonoids and antioxidant activity, and better stability. • Maltodextrin combined with gum arabic was optimal as a wall material for CaNE powder. [ABSTRACT FROM AUTHOR]

In the French West Indies, to cope with the yam disease anthracnose, new hybrids were selected for their resistance to this disease. However, some of them have quality flaws. The new hybrids of Dioscorea alata exhibited contrasted susceptibility to browning in relation to their total phenolic content (r = 0.91). The detailed polyphenol profiles of "INRA15", highly susceptible to browning, and of "Kabusah", with moderate susceptibility to this flaw, were achieved by HPLC coupled to UV–Visible and mass spectrometry. For the first time, total procyanidins of yam were finely characterized and quantified using HPLC after phloroglucinolysis , revealing that those compounds are by far the main polyphenols in the two cultivars. Differences in terms of browning susceptibilities of the two cultivars are clearly explained by their contrasted polyphenol profiles: (i) absence versus presence of catechin which is a substrate of polyphenol oxidase (PPO). - (ii) significant differences in procyanidin levels and in their average degree of polymerization potentially involved in PPO inhibition. • New hybrids of yam exhibit susceptibility to browning after cutting. • This susceptibility depends on the total phenolic content of the pulp and its phenolic profile. • For the first time, total procyanidins of yam were finely characterized and quantified. • Higher browning susceptibility is due the presence versus absence of catechin. • It is also linked to differences in procyanidin levels and in their average degree of polymerization. [ABSTRACT FROM AUTHOR]

The total phenolic content (TPC) and antioxidant activity (AA) of a low-fat hard cheese fortified with different concentrations of catechin was examined over 90 days of ripening after in vitro digestion of cheese samples. TPC and AA increased in cheese after manufacturing and over the ripening period at 8 °C. Prior to analysis, the cheese samples were subjected to a two-stage in vitro digestion with gastric and intestinal phases to simulate human digestive conditions. The AA, measured as both ferric reducing antioxidant power and oxygen radical absorbance capacity, showed a high degree of correlation (R 2 > 0.89) with the TPC results. The in vitro recovery fraction of catechin after 90 days of ripening was 0.607, 0.628 and 0.752 for the cheeses fortified with catechin at 125, 250 and 500 mg kg −1 , respectively. This study shows the feasibility of incorporating phenolic antioxidants into a protein-rich food, such as cheese, and maintaining antioxidant activity after digestion. [ABSTRACT FROM AUTHOR]

The minimum loss of processed fruit nutritional quality must been guaranteed during storage and the atmosphere can be a limiting step. Strawberry purées flushed with gas mixtures: 10 kPa O 2 + 90 kPa N 2 , 100 kPa N 2 and air (78 kPa N 2 + 21 kPa O 2 + 0.03 kPa CO 2 ) were stored for 90 days at 4 and 23 °C and revealed no effect in total antioxidant activity and in total phenolic content. The compounds (+)-catechin, (−)-epicatechin and quercetin-3-rutinoside were not affected by the atmospheres for both temperatures and ellagic acid was the exception within strawberry phytochemicals, where its concentration was higher for samples stored in air. Total anthocyanin content was better preserved when strawberry purée was stored in 100 kPa N 2 at 4 and 23 °C, at which temperatures their levels decreased 24 and 77%, respectively. At 4 °C cyanidin-3-glucoside presented no significant differences between atmospheres. Pelargonidin-3-glucoside and pelargonidin-3-rutinoside decreased both 27% for 100 kPa N 2 and 45% for 10 kPa O 2 and air. All the individual anthocyanins were not affected by the atmospheres when stored at 23 °C. [ABSTRACT FROM AUTHOR]

A mass balance approach was used quantify select polyphenols in pre- and post-fermentation products resulting from the fermentation of Vitis vinifera cv. Grenache noir and Airén. For Grenache noir, the overall mass recovery was 102.7%. The main products were wine (78.3%), pomace (8.5%), lees (4.2%), and rachises (3.4%). Pomace was a rich source of all identified polyphenols. Lees sorbed significant amounts of gallic acid, catechin, epicatechin, malvidin-3-O-glucoside, malvidin-3-acetylglucoside, quercetin-3-O-glucoside, and quercetin. An approximately 200% increase in the total amount of gallic acid occurred during fermentation. For the Airén grapes, the overall mass recovery was >90%. The pomace, rachises, juice solids after settling, and lees constituted ∼50% of the total mass of products obtained; pomace alone accounted for 40% of the total product mass. Over 90% of the total amount of gallic acid, catechin and epicatechin and ∼50% of the quercetin-3-O-glucoside were found in the pomace. [ABSTRACT FROM AUTHOR]

“Normal-season” (bud plus first two leaves processed as commercial tea between Apr–Sep), “unused” (remaining leaves collected in Sep and Apr) and “off-season” (all leaves collected between Sep–Apr) green tea leaves samples from Camellia sinensis were extracted by water infusion followed by solvent–solvent partition to recover catechins, that were separated and quantified by HPLC methods. Total catechins content ranged between 23.72 and 73.61 mg/g of the dry weight (DW) leaves for the off-season samples and was 97.51, 115.12 and 184.62 mg/g DW for Apr, Sep and normal-season samples, respectively. The free radical scavenging activity of the off-season samples ranged between 45 and 80%, 79–90% and 90–92% for the 25, 50 and 100 ppm concentrations, respectively, after 20-min reaction time. The other samples presented values of 87%, 91% and 94% (Sep), 88%, 92% and 93% (Apr) and 89%, 93% and 95% (normal-season), using the same conditions. Total phenolics content ranged between 43.21 and 139.02 mg of gallic acid equivalents (GAE)/g DW for the off-season samples and was 182.23, 216.05 and 221.32 mg of GAE/g DW for Apr, Sep and normal-season samples, respectively. Results revealed that the unused and off-season Azorean green tea leaves (catechins-rich waste products) have potential antiradical activity that can be used for food and cosmetics preservation. [ABSTRACT FROM AUTHOR]

The antimicrobial effect of gallic acid and catechin on Escherichia coli cultures was investigated. The antimicrobial activity was evaluated by measuring the absorbance of liquid culture media at 600 nm, by an agar-well diffusion method and by scoring colony forming units. Then, the OD 600 and CFU/mL values decreased when the medium was supplemented with gallic. Besides, the CFU/mL values decreased continuously with the time of exposure to gallic acid in a range of 360 min. Likewise, the diameters of the growth inhibition zones around the wells increased gradually with the content of gallic acid or catechin. In summary, both polyphenols displayed growth inhibitory effects on the bacterium. Further, the antibacterial effects were dependent on dose, time of exposure and type of polyphenol. Gallic acid showed a higher anti- E. coli effect compared to catechin. Mixtures of subeffective doses of gallic acid and an effective dose of catechin produced growth inhibition halos similar to those produced by catechin alone. [ABSTRACT FROM AUTHOR]

Pu-erh tea is a Chinese dark tea produced by sun-dried green tea-leaves. In this study, 17 phenolic compounds and 3 purine alkaloids in 36 Pu-erh teas were determined by high-performance liquid chromatography. Additionally, the in vitro antioxidant activities were evaluated by 5 various assays, respectively. PCA, HCA and OPLS-DA (R2X = 0.639, R2Y = 0.945 and Q2 = 0.940, respectively) could divide into fermented Pu-erh tea (FPT) and non-fermented Pu-erh tea (NFPT) groups absolutely. Compared with NFPT, solid-state fermentation caused the extremely significant (p < 0.001) decreases of 8 catechins, 3 other flavonoids (i.e. taxifolin, rutin and luteolin), gallic acid (GA), hydrolyzed tannin and theophylline, and enhanced ellagic acid, kaempferol and quercetin contents significantly (p < 0.05, <0.01 or <0.001) in FPT. Bivariate correlation analysis confirmed that 8 catechins, 3 flavonoids, theophylline and GA promoted the antioxidant activities of Pu-erh teas, while queretin showed extremely significantly (p < 0.001) negative correlation to the results of DPPH, ABTS and HSA assays. Furthermore, multivariate linear regression equations efficiently evaluated the results of FRAP, DPPH, ABTS and HSA assays in Pu-erh tea with a R2 value over 0.95. This study elaborating the interrelation between phenolic compounds and in vitro antioxidant activities advanced the knowledge about Pu-erh tea. • 5 Various assays were developed for in vitro antioxidant activities analysis in Pu-erh teas. • Multivariate statistical analyses revealed impact of solid-state fermentation in Pu-erh tea. • 8 Catechins, 3 flavonoids, gallic acid decreased, ellagic acid, kaempferol, quercetin increased. • Most of phenolic compounds, like catechins, promoted the antioxidant activities. • Multivariate linear regression equations evaluate variation of antioxidant activities. [ABSTRACT FROM AUTHOR]

Shaken black tea (SBT) is a new type of black tea that combines the traditional black tea processing technology with the shaking process of oolong tea. In this study, non-targeted metabolomics analysis based on ultra-high-pressure liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) was applied to comprehensively analyze the non-volatile metabolites of SBT during the manufacturing process. Using multivariate statistical analysis, 93 compounds were screened as differential compounds. During the whole process of SBT, amino acids, dipeptides, theaflavins and lipids contents showed significant increases, while that of catechins and procyanidin C1 significantly decreased. Compared with fresh leaves, the content of proteinaceous amino acids (PAAs) in the dried black tea increased 1.61-fold, and total catechins decreased to 7.25%. The results of hierarchical clustering analysis (HCA) showed that fermentation is the key process that causes the variations of these metabolites, followed by drying and shaking. The biosynthesis metabolism of amino acids, flavonoids and linoleic acid are abundant, mainly due to the stress response of fresh tea leaves to dehydration and mechanical damage during shaking processing. It is beneficial to explore the quality formation during the production of SBT through comprehensive analysis of the changes in metabolites. • Fermentation led to significant changes in metabolites, followed by drying, shaking. • Shaking process promoted the accumulation of amino acids, dipeptides and theaflavins. • Remarkable increase of dipeptides is mainly in the fermentation and drying process. • Variation of taste compounds, amino acids, flavonoids, and dipeptides, were studied. • Metabolic pathway of key compounds like amino acids, flavonoids, lipids, were revealed. [ABSTRACT FROM AUTHOR]

The low stability and loss of antimicrobial activity of catechins limited their application in food preservation. In this study, four kinds of catechins including (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG), and (−)-epigallocatechin-3-gallate (EGCG) were selected as model compounds. Natural deep eutectic solvents (NADES) are a new generation of green solvents that have attracted much attention due to their unique characteristics. The effects of NADES on the stability and antimicrobial activity of catechins were investigated in the present study. Eight typical NADES, especially choline chloride/glycerol (ChG), were found to significantly enhance the thermal and storage stability of catechins. This finding accounted for by hydrogen bonding network formation between ChG and catechins, confirmed by FT-IR and 2D NMR analysis. Additionally, ChG decreased the minimum inhibitory concentration of catechins on Gram-positive and Gram-negative bacteria, which may be associated with its stabilizing property. The stability of catechins combined with NADES revealed their potential of applications in the food industry. Therefore, this study aimed to investigate the effects of the NADES on the stability of catechins at different temperatures and explore the stabilizing mechanism of NADES on catechins by NMR and FT-IR. Finally, the antimicrobial activity of catechins dissolved in NADES and water were comparatively studied. This work represented a novel approach substantiating the role of NADES as green additive to enhance the stability of bioactive compounds. • NADES significantly enhanced the thermal and storage stability of catechins. • The strong hydrogen bonding network was formed between ChG and catechins. • Catechins dissolved in NADES showed better antimicrobial activity than in water.. • Agar diffusion method was unsuitable for evaluation antimicrobial activity of sample in NADES.. [ABSTRACT FROM AUTHOR]

Nanoscale catechin/β-cyclodextrin inclusion complex (CA/β-CD IC) particles were prepared by nanoprecipitation method (absolute ethanol as precipitant). The effects of β-CD concentration, ethanol amount used for precipitating and ethanol dropping rate during precipitation on size of CA/β-CD IC particles were studied. Dynamic light scattering results indicated the above operating conditions have a significant effect on size of CA/β-CD IC nanoparticles. Nanoparticles can be further reduced to about 90 nm by adjusting operating parameters, such as reducing β-CD concentration, increasing amount of ethanol and decreasing ethanol drop rate. Inclusion ratio of CA/β-CD IC nanoparticles was about 71%. Fourier transform infrared spectroscopy results indicated that intermolecular hydrogen bond interactions maintain CA in cavity of β-CD. X-ray diffraction results showed the crystalline structure in nanoscale CA/β-CD IC was different from that in micro-size CA/β-CD IC. Differential scanning calorimetry and scanning electron microscopy results confirmed the formation of CA/β-CD IC nanoparticles. CA/β-CD IC nanoparticles displayed great storage stability and ionic strength stability, and exhibited excellent stability at pH 4–9. Release behavior of CA from CA/β-CD IC nanoparticles was controlled. The CA/β-CD IC nanoparticles have potential applications in nano-functional foods. • Catechin/β-cyclodextrin inclusion complex nanoparticles were successfully prepared. • The size of nanoparticles can be controlled by adjusting the operating parameters. • The inclusion complex nanoparticles presented new solid crystalline phase. • The antioxidant stability of catechin was improved after encapsulation. • Inclusion complex have potential applications in nano-functional foods. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated interactions of six type catechins monomers with human pancreatic α-amylase and the structural requirements for inhibitory activity. The in vitro and in silico results showed that inhibitory effects of catechins followed the order: (+)-gallocatechin-3-O-gallate > (−)-epicatechin-3-O-gallate > (−)-epigallocatechin-3-O-gallate > (−)-epicatechin > (−)-epigallocatechin > (+)-catechin. The A, B and C rings of catechins affected the activity by interact with the catalytic residues of the active site of α-amylase forming a phenols–protein complex, including hydroxyl on the 3-position or 5-position of A–C rings, number of hydroxyl substation on the B-ring or C ring, or 2,3-cis/trans isomerism. The galloylated catechins has higher binding affinity with α-amylase than non-galloylated catechins. The results showed that biological activity of catechins against α-amylase, which supported catechins monomer is a promising ingredient as a development strategy of health food for regulation of energy balance and reduction of related diseases risk. [Copyright &y& Elsevier]