Addition Of Tea Polyphenols Research Articles

Electrospun gelatin/tea polyphenol@pullulan nanofibers for fast-dissolving antibacterial and antioxidant applications.

Bio-based active food packaging materials have a high market demand. We use coaxial electrospinning technology to prepare core-shell structured nanofibers with sustained antibacterial and antioxidant properties. The fiber core layer was composed of gelatin and tea polyphenols, whereas tea polyphenols provide antibacterial and antioxidant properties; the fiber sheath was composed of pullulan polysaccharides with antioxidant properties. By using a scanning electron microscope, it can be seen that the diameter distribution of the prepared nanofibers was uniform and the surface is smooth; using a transmission electron microscope, it can be clearly seen that the nanofibers have a core-shell structure; Fourier Transform Infrared and X-ray diffraction analysis indicate that the nanofibers have an amorphous structure; the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging shows that nanofibers have higher antioxidant properties with the addition of tea polyphenols; antibacterial test showed that nanofibers had obvious inhibitory effect on the growth of Staphylococcus aureus and Escherichia coli; and the nanofiber film dissolution test shows that nanofibers can be used as fast soluble active packaging. Finally, core-sheath-structured nanofibers can serve as active packaging for instant food, possessing both rapid water solubility and excellent antibacterial and antioxidant activity, making water-soluble nanofibers interesting applications in the field of food packaging.

Establishing a biodegradable film with gluten and tea polyphenols: Structure, properties, and function

Film packaging is a common method to extend the shelf life of food during storage. But the non degradability and potential toxicity of some synthetic films are gradually limiting their usage in food packaging. In present study, gluten and tea polyphenols were utilized to prepare a packaging film, and the properties of this film were determined. With addition of tea polyphenols, thickness and tensile properties of film were improved. By using scanning electron microscope, fourier transform infrared spectra and molecular docking, this film showed a dense network structure, which was due to the strong interactions between tea polyphenols and gluten. Hydrogen bonds and hydrophobic interactions were the main molecular forces during the interactions. Meanwhile, the film showed the good thermal stability and barrier properties. In addition, this film exhibited the remarkable capability to scavenge free radicals and inhibited the increase of peroxide value of oil during storage. Moreover, this film had the slow-release properties of tea polyphenols, and could be biodegradable in nature. All present results suggested that tea polyphenols improved the properties and functions of gluten film effectively, and this complex film showed the potential for food preservation in food industry.

Intelligent active films of sodium alginate and konjac glucomannan mixed by Lycium ruthenicum anthocyanins and tea polyphenols for milk preservation and freshness monitoring

To achieve real-time monitoring of food freshness, a pH-responsive film based on sodium alginate-konjac glucomannan loaded with Lycium ruthenicum anthocyanins (LRA) was prepared, with the addition of tea polyphenols (TP) to enhance the stability of LRA. The surface structure of the films was observed by AFM. The results of FTIR and molecular docking simulation showed that LRA and TP were bound to polysaccharide by hydrogen bonds. The mechanical properties, barrier properties, and antioxidant/antibacterial properties of the films were significantly improved and the films showed obvious color response to pH. Notably, the AFM images showed TP and LRA could lead to more severe damage to the bacterial structure. The results of molecular docking simulation suggested that TP and LRA could act on different components of the bacterial cell wall, indicating their synergistic mechanism in antimicrobial activity. Moreover, the stability of LRA was improved due to the interactions of TP and polysaccharides with LRA. The aggregates formed by TP and LRA were clearly observed by AFM. Finally, the film showed excellent preservation and freshness monitoring effect in milk. In conclusion, TP-LRA-SA-KGM intelligent film exhibited excellent performance and represented a promising novel food packaging material with potential applications.

Reaction kinetics and shelf-life prediction of Maillard reaction products in milk simulated system with tea polyphenols

To better monitor and reduce the generation of Maillard reaction products (MRPs) during the heat treatment and storage of dairy products, a reaction kinetic model was established to evaluate the inhibitory effects of tea polyphenols on MRPs in the milk simulation system. The inhibition of MRPs by tea polyphenols followed first order kinetics, while the inhibition of 5-hydroxymethyl-2-furfural (5-HMF) was most pronounced at 95 °C with the reaction rate constant of −0.0683 d−1. Arrhenius model showed that the conversion rate of 5-HMF (35.672 d−1) was higher than Nε-carboxyethyllysine (2.585 d−1) and Nε-carboxymethyllysine (0.53 d−1) after the addition of tea polyphenols, which indicated that 5-HMF was the main intermediate product of Maillard reaction. Moreover, the shelf life of the two-stage sterilised milk containing tea polyphenols was 141 d, which was 2.1 times longer than that of the control sample (67 d), which provided reference for consumers during the drinking period.

Exploring the quality change mechanism of tea polyphenol-assisted cured grass carp from perspectives of physicochemical and flavor

ABSTRACT In this study, the quality changes of grass carp during tea polyphenol-assisted curing were studied from physicochemical and flavor perspectives. The addition of tea polyphenols has a positive effect on maintaining the water content of fish as the curing time increases (p < 0.05). The tea polyphenol-assisted treatment maintains the brightness of grass carp meat. The addition of tea polyphenols also slowed down the rate of pH growth and enhances the texture of grass carp (p < 0.05). The addition of tea polyphenols reduced His content, which had a positive effect on the taste of the cured grass carp products. When the pickling time reached 60 min, the inosine monophosphate content of tea polyphenol-treated groups was higher than that of the group soaked in salt only. Combined with equivalent umami concentration and taste activity values, it was found that the addition of 0.1% TP could improve freshness of grass carp cured products.

Effect of Tea Polyphenols on the Melt Grafting of Glycidyl Methacrylate onto Polypropylene.

It is considered to be one of the most effective strategies to prepare functionalized polypropylene (PP) materials via the melt grafting of polar monomers onto PP chains. However, the grafting efficiency of functional monomers is generally low. To achieve a high grafting efficiency, we explored the effect of tea polyphenols (C), which are good free radical scavengers, on the melt grafting of glycidyl methacrylate (GMA) onto PP chains initiated by dicumyl peroxide (DCP). Specifically, 0.5~3 wt% of tea polyphenols (C) were introduced to the PP/DCP/GMA melt blending system. The morphology, melt flow rate (MFR), thermal and mechanical properties of tea polyphenols (C) incorporated PP/DCP/GMA blends were investigated systematically. The results showed that the proper amount of tea polyphenols (C) (0.5~2 wt%) promoted the grafting of GMA. Unexpectedly, the PP backbone suffered from more severe degradation with the addition of tea polyphenols (C). The phenomena were ascribed to the reaction between phenolic hydroxyl groups of tea polyphenols (C) and epoxy groups of grafted GMA, which was revealed by the FTIR results. In addition, according to DSC and the tensile test, the co-grafting of GMA and tea polyphenols (C) improved the crystallization ability, yield strength and Young's modulus of the PP matrix.

Effect of tea polyphenols on the fermentation quality, protein preservation, antioxidant capacity and bacterial community of stylo silage.

The present study was aimed to evaluate the improvement potential of tea polyphenols (TPP) on silage characteristics and bacterial community. Stylo ensiled with TPP (0, 0.2 or 0.4%, on a fresh basis) were analyzed for fermentation parameter, protein fraction, antioxidant activity and bacterial community after 7, 14, 30 and 60 days fermentation. The addition of TPP resulted in the decrease (P < 0.05) of pH values (5.09 vs. 4.91), dry matter loss (11.77 vs. 8.02% DM), butyric acid concentration (1.64 vs. 1.02% DM) and ammonia-N proportion (13.69 vs. 8.98% CP, on Day 30) of stylo silage as well as the increase (P < 0.01) of lactic acid bacteria population (6.17 vs. 7.54 cfu/g FM) and true protein content (6.03 vs. 7.44% DM), particularly at the first 30 days of ensiling. It somewhat enhanced the antioxidant capacity of style silage at the early stage, and altered the bacterial community of stylo silage, with Clostridium_sensu_stricto_1 and Lachnoclostridium_5 much decreased but Enterobacter and Clostridium still being the dominant genera. It is suggested that TPP could help improve fermentation quality and nutrient preservation of stylo silage, and delay proteolysis process and antioxidant decay.

INTRODUCING TEA POLYPHENOLS AND VITAMIN C TO IMPROVE THE IN SITU HYDROGENATION AND REDUCTION PROCESS OF NBR AND NBR/GO LATEX

ABSTRACTTea polyphenols and vitamin C are used as reducing agents that are introduced into nitrile–butadiene rubber (NBR) and NBR/graphene oxide (GO) latex systems, and the double bonds in the NBR and the GO sheet in NBR/GO are simultaneously hydrogenated and reduced through the synergistic hydrazine hydrate/hydrogen peroxide/copper sulfate catalytic system to prepare hydrogenated NBR (HNBR) and HNBR/reduced GO (RGO) nanocomposites. The degree of hydrogenation of the product is improved and the gel content of the product is reduced, which effectively solves the problems of the low degree of hydrogenation and high gel content in the diimide catalytic hydrogenation system. At the same time, the HNBR and HNBR/RGO nanocomposites, which are co-reduced by tea polyphenols and vitamin C, have good thermal stability and mechanical properties. Tea polyphenols are more likely to participate in the hydrogenation reaction. The degree of hydrogenation of the NBR double bonds is higher than the amount of reduction occurring within the GO sheet with the addition of tea polyphenols.

Characterization of chitosan/zein composite film combined with tea polyphenol and its application on postharvest quality improvement of mushroom (Lyophyllum decastes Sing.)

In this study, chitosan/zein composite film combined with tea polyphenol was fabricated, and the effect of tea polyphenol on the structure and physical properties of chitosan/zein film was investigated. Low-field nuclear magnetic resonance spectroscopy indicated that the distribution and content of water molecules in chitosan/zein film were changed with the addition of tea polyphenol. The results of fluorescence measurement and secondary structure analysis proved the enhanced physical and structural properties of tea polyphenol composite film. And the film showed favorable stretching resistance and flexibility. Furthermore, the effect of composite film on quality and physiological indexes of mushroom (Lyophyllum decastes Sing.) stored at 4 °C for 15 d were systematically evaluated. The results indicated that the tea polyphenol composite film showed the effectiveness of maintaining color, texture as well as integrity of cell membrane evidenced by relatively lower membrane permeability and malondialdehyde content of mushrooms. Besides, weight loss and respiration rate were efficiently retarded. In comparison with control and chitosan/zein film, the tea polyphenol composite film inhibited the activity of polyphenol oxidase and peroxidase, while enhanced the activity of antioxidant enzymes (superoxide dismutase and catalase). In a word, the chitosan/zein composite film incorporated with tea polyphenol showed the potential as an effective technology for maintaining the postharvest quality of mushroom (Lyophyllum decastes Sing.).

Formation and Inhibition of Lipid Alkyl Radicals in Roasted Meat

Free radicals are ubiquitous in roasted foods. In this work, lipid-derived carbon-centered alkyl radical formation was first studied in roasted meat by electron spin resonance (ESR). The influence of antioxidants on the inhibition of free radicals was investigated. The results showed that the high temperature, high heat transfer rate, and high polyunsaturated fatty acid (PUFA) content resulted in high radical content in roasted meat, while the high water content in meat retarded radical formation. The 0.03% addition of tea polyphenols (TPP) significantly reduced radical formation during roasting (p < 0.05), whereas the 0.03% rosemary extract (RE) had no significant inhibitory effect (p > 0.05). These results suggested that water retention and the addition of TPP would decrease radical generation during the roasting of meat.

Application of Tea Polyphenols to Edible Oil as Antioxidant by W/O Microemulsion

The lipophilic properties of tea polyphenols have restricted their application as a natural antioxidant in oils. In order to increase the weight percentage of tea polyphenols in edible oil, a water-in-oil (W/O) microemulsion (ME) of Tween 80/Span 80/ethanol/soybean oil/H2O for envelopment of tea polyphenols was prepared. The ternary phase diagram, electrical conductivity, particle size, viscosity, rheological behavior, and oxidation resistance potential of the ME were investigated. The results showed that (1) the W/O ME formed when water content was below 30%; (2) the mean particle size of the ME system was about 8.40 nm and basically remained stable for 45 days; (3) the ME was characterized as pseudoplastic at low shear rate and as Newtonian viscous fluid at high shear rate; moreover, it had acceptable salinity and pH tolerance; and (4) peroxide value determination indicated the antioxidant effect of the ME was enhanced by the addition of tea polyphenols.

Lead phytoavailability change driven by its speciation transformation after the addition of tea polyphenols (TPs): Combined selective sequential extraction (SSE) and XANES analysis

Metal species in rhizosphere soil profoundly influence their mobility and phytoavailability. Clarifying the speciation transformation of heavy metals helps understand their translocation and accumulation in plants. Single extraction, selective sequential extraction (SSE) and X-ray absorption near-edge structure (XANES) spectroscopy were employed to investigate the speciation transformation of lead (Pb) and its influence on metal accumulation in tea plants after the addition of tea polyphenols (TPs). Pb content was decreased in young leaves and stems, whereas increased in roots, after TPs were amended to soil. Both SSE and XANES analysis suggested bioavailable Pb was transformed to organically bound Pb after the addition of TPs. The increased percentage of organically bound Pb might be fixed in the cell wall of plant root through a ternary complex formed between the Pb-organic matter complex and cell wall components. Therefore, Pb translocation from roots to young tissues was decreased. Pb phytoavailability change was driven by its speciation transformation after the addition of TPs. Combined SSE and XANES spectroscopy represent powerful tools to study metal speciation transformation in plant and soil systems.

Preparation and characterization of active films based on chitosan incorporated tea polyphenols

Active films based on chitosan incorporated tea polyphenols with different concentrations were developed. Attenuated total reflectance Fourier transform infrared spectrometry was used to investigate the potential interactions between chitosan and tea polyphenols in the films. Physical properties of the chitosan films incorporated tea polyphenols, including density, moisture content, opacity, color, water solubility and water vapor permeability, were measured. Antioxidant activity of the films was characterized in terms of total phenolic content and 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging activity. The results indicated that the incorporation of tea polyphenols caused interactions between chitosan and tea polyphenols and gave rise to the films darker appearance. After the addition of tea polyphenols, the films showed increased water solubility and decreased water vapor permeability. Meanwhile, the incorporation of tea polyphenols enhanced the total phenolic content and 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging activity of the films, i.e., increased the antioxidant activity of the films. But the antioxidant activity of the chitosan films incorporated tea polyphenols declined with time.

Green synthesis of Au nanoparticles immobilized on halloysite nanotubes for surface-enhanced Raman scattering substrates

A facile and green route was introduced to synthesize Au nanoparticles immobilized on halloysite nanotubes (AuNPs/HNTs) used for surface-enhanced Raman scattering substrates. The naturally occurring HNTs were firstly functionalized with a large amount of -NH(2) groups by N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (AEAPTES), which possesses one lone electron pair and will "anchor" Au ions to form a chelate complex. Then, with the addition of tea polyphenols (TP), the Au ions were reduced on the surface of the previously formed Au-NH(2) chelate complex to form AuNPs. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) observations indicate that a large amount of AuNPs were synthesized on HNTs. The AuNPs are irregularly spherical and densely dispersed on HNTs and the diameter of the nanoparticles varies from 20 to 40 nm. The interactions between AuNPs and -NH(2) groups were verified by X-ray photoelectron spectroscopy (XPS) and the results showed that the functional groups can "anchor" AuNPs through the chelating effect. The as-prepared AuNPs/HNTs nanomaterials with several nanometers gaps among nanoparticles were used as a unique surface-enhanced Raman scattering substrate, which possessed strong and distinctive Raman signals for R6G, indicating the remarkable enhancement effect of the AuNPs/HNTs.

Effect of irradiation and storage time on lipid oxidation of chilled pork

The effects of γ-irradiation with different doses (0, 2, 4, 6, 8 and 10 kGy) and storage time (0–30 days) on the lipid oxidation of chilled pork and the combined effect of irradiation and antioxidant on the lipid oxidative stability during storage at 4 °C were investigated. The results indicated that irradiation treatment increased lipid oxidation, measured as peroxide (PV) and thiobarbituric acid reactive substance (TBARS) values. Lipid oxidation was increased with the increase in storage time. The addition of tea polyphenol (TP) was effective in controlling the lipid oxidation of chilled pork after irradiation during cold storage.

Antimicrobial effects of green tea polyphenols on thermophilic spore-forming bacteria

The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. Among the tested Bacillus bacteria, tea polyphenols showed antibacterial effects towards Bacillus stearothermophilus, which is a thermophilic spore-forming bacterium. The heat resistance of B. stearothermophilus spores was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. (−)-Epigallocatechin gallate, which is the main component of tea polyphenols, showed strong activity against both B. stearothermophilus and C. thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.