Food antioxidants and phytochemicals: present and future perspectives

The relatively high concentration of phenolic flavonoids in wines, grapes, green tea, and berry extracts contributes powerful antioxidant properties that may be beneficial by reducing oxidative reactions deleterious to health. Our data showed that polyphenolic compounds in red wine and grapes strongly inhibit the oxidation of human low-density lipoproteins (LDL), a reaction that initiates atherosclerosis and heart diseases. Marked variations were found in antioxidant activity of rosemary, green tea, and berry extracts in different lipid systems. These variations are attributed to differences in partition between phases in various lipid systems. The activities of natural antioxidants are thus very system dependent and their effectiveness in different real food systems is difficult to predict. In addition to preventing LDL oxidation, plant flavonoids may reduce the thrombotic tendencies and inflammatory reactions in the body. The antioxidant activity of phenolic compounds in wine, grapes, green tea, and berry extracts supports the epidemiological evidence that fruits and vegetables may have a cardioprotective effect. More research is needed however to relate the extensive in vitro studies showing the potent antioxidant activities of flavonoids to their potential health effects in the diet.     

肉桂原花青素的片段化研究

采用食物来源的茶多酚为亲核试剂对肉桂中原花青素多聚体(PPC)进行片段化反应,采用大孔吸附树脂HP-20对片段化反应产物进行分级处理,使低聚体从片段化反应产物中分离出来。以反应后低聚体含量和低聚体中原花青素含量为考察指标,通过单因素试验、正交试验考察了片段化反应时间、反应温度、盐酸体积分数和多聚体与茶多酚物料比对反应的影响。结果表明,各因素对反应的影响次序为:盐酸体积分数 > 多聚体与茶多酚物料比 > 反应温度 > 反应时间,片段化反应最佳条件为:反应温度为50 ℃、反应时间为60 min、盐酸体积分数为1%、多聚体与茶多酚物料比为1:1,在此条件下,得到片段化反应后低聚体含量为65.26%,低聚体中原花青素含量为75.28%。     

Modification of maillard browning in a microwaved glucose/glycine model system by water-soluble natural antioxidants and foods containing them

Inhibition of pyrazine formation by natural antioxidants and the foods containing them was measured in a microwaved glucose/glycine model system. Inhibition of lipid oxidation by the same materials was assayed in both bulk and emulsion systems. Pyrazines were determined by solid-phase micro extraction followed by GC. Lipid oxidation volatiles were assayed by polyamide fluorescence produced by either a bulk oil display or a hematin- or 2,2′-azobis-(2-amidino=propane) dihydrochloride-accelerated lecithin or fish oil emulsion. It was shown that (i) the inhibition of pyrazine formation depends on high concentrations of water-soluble antioxidants; (ii) such antioxidants occur naturally in some foods and are usually polyphenols; (iii) during pyrazine inhibition, oxidized polyphenols show enhanced nonfluorescing browning similar to enzymic browning products; (iv) monophenols, which structurally cannot form quinone polymers on oxidation, inhibit pyrazines with less browning; (v) during the final pyrazine-forming phase of the Maillard reaction, polyphenolics and reducing agents such as glutathione and ascorbic acid are partially consumed with some nutritional loss; (vi) fruit powders of grape seed, grape skin, and red wine are highly pyrazine-inhibitory, steeped blueberry strongly so, but plum purees are moderately pro-pyrazine, and freeze-dried vegetables strongly pro-pyrazine; and (vii) black and green tea infusions are highly inhibitory, whereas spices have mixed effects.     

Drying with Chemical Reaction in Cocoa Beans

Desirable flavor qualities of cocoa are dependent on how the cocoa beans are fermented, dried, and roasted. During fermentation and drying, polyphenols such as leucocyanidin and apecatechin are oxidized by polyphenols oxidase to form o-quinone, which later react nonenzymatically with a hydroquinone in a condensation reaction to form browning products and moisture. The objective of this article is to model the cocoa beans drying together with the browning reaction. A Luikov drying model for the moisture and a simple Fick's law diffusion model combined with first-order reactions for both the enzymatic oxidation and nonenzymatic condensation reactions were constructed. Both models were used to identify moisture diffusivity coefficient and total polyphenols diffusivity in cocoa beans from experimental drying and polyphenols degradation data and published kinetic data of the reactions. The theoretical drying model fitted the experimental cocoa bean drying curves with low mean square of residuals. The polyphenols diffusion and reaction model also fitted the experimental polyphenols degradation curves with minimum mean residual squares. The rate of polyphenols degradation in the cocoa beans increases at higher temperature and higher relative humidity. This is because the increasing reaction rate of polyphenols oxidation reaction as well as higher moisture diffusion at higher relative humidity and temperature. The effective moisture diffusivity in cocoa beans is estimated to be between 8.194 × 10^?9 and 8.542 × 10^?9 m²·s^?1, which is of the same order of magnitude as published data. The effective total polyphenols diffusivity is estimated to be between 8.333 × 10^?12 to 1.000 × 10^?11 m²·s^?1 with minimum mean residual squares. It is three orders of magnitude less than the estimated moisture diffusivity because of the larger polyphenols molecules. The estimated polyphenols diffusivity is very close to those published in the literature for sorption and ultrafiltration processes.     

Drying with Chemical Reaction in Cocoa Beans

Desirable flavor qualities of cocoa are dependent on how the cocoa beans are fermented, dried, and roasted. During fermentation and drying, polyphenols such as leucocyanidin and apecatechin are oxidized by polyphenols oxidase to form o-quinone, which later react nonenzymatically with a hydroquinone in a condensation reaction to form browning products and moisture. The objective of this article is to model the cocoa beans drying together with the browning reaction. A Luikov drying model for the moisture and a simple Fick's law diffusion model combined with first-order reactions for both the enzymatic oxidation and nonenzymatic condensation reactions were constructed. Both models were used to identify moisture diffusivity coefficient and total polyphenols diffusivity in cocoa beans from experimental drying and polyphenols degradation data and published kinetic data of the reactions. The theoretical drying model fitted the experimental cocoa bean drying curves with low mean square of residuals. The polyphenols diffusion and reaction model also fitted the experimental polyphenols degradation curves with minimum mean residual squares. The rate of polyphenols degradation in the cocoa beans increases at higher temperature and higher relative humidity. This is because the increasing reaction rate of polyphenols oxidation reaction as well as higher moisture diffusion at higher relative humidity and temperature. The effective moisture diffusivity in cocoa beans is estimated to be between 8.194 × 10^-9 and 8.542 × 10^-9 m²·s^-1, which is of the same order of magnitude as published data. The effective total polyphenols diffusivity is estimated to be between 8.333 × 10^-12 to 1.000 × 10^-11 m²·s^-1 with minimum mean residual squares. It is three orders of magnitude less than the estimated moisture diffusivity because of the larger polyphenols molecules. The estimated polyphenols diffusivity is very close to those published in the literature for sorption and ultrafiltration processes.     

自分散纳米炭黑色浆的制备和研究

为了获得一种具有良好自分散性能的纳米炭黑色浆.利用硝酸对炭黑表面进行氧化改性处理,通过FT-IR,XPS,元素分析仪对原始炭黑及氧化炭黑的表面官能团结构、表面含氧量进行了表征;将氧化炭黑与去离子水按30%的固含量混合,并在小磨介磨设备中研磨45 min,得到自分散的纳米炭黑色浆,通过粒度分析仪,分光光度计对色浆中的颗粒尺寸分布、炭黑在体系中的分散稳定性进行了表征.研究结果表明,利用硝酸氧化改性可以大大增加炭黑表面的亲水性官能团,如C=O,O-C=O,O-H, 炭黑表面的含氧量比原始炭黑提高近6倍,色浆中的炭黑颗粒尺寸在200 nm以内,并且分布均匀、稳定.     

Changes of constituents and activity to apoptosis and cell cycle during fermentation of tea

Tea is believed to be beneficial for health, and the effects of the fermentation process on its contributions to apoptosis and cell cycle arrest of gastric cancer cells have not been completely investigated. In this study, the chemical components in green tea, black tea and pu-erh tea aqueous extracts were analyzed and compared. The polysaccharide and caffeine levels were substantially higher in the fermented black tea and pu-erh tea, while the polyphenol level was higher in the unfermented green tea. Hence, a treatment of tea aqueous extract and the components, which are emerging as promising anticancer agents, were pursued to determine whether this treatment could lead to enhance apoptosis and cell cycle arrest. In the human gastric cancer cell line SGC-7901, the cell viability and flow cytometry analysis for apoptotic cells indicated effects in a dose-dependent inhibition manner for the three tea treatment groups. The apoptosis rates were found to be elevated after 48 h of treatment with 31.2, 125, and 500 μg/mL of green tea extract, the higher catechins content may be involved in the mechanism. Cell cycle was arrested in S phase in the fermented black tea and pu-erh tea, and the populations were significantly decreased in G2/M phases, possibly due to the oxidation of tea polyphenols, which causes an increase of theabrownins. CCC-HEL-1 normal cells were not sensitive to tea extract. These findings suggest that the fermentation process causes changes of the compounds which might be involved in the changes of cell proliferation inhibition, apoptosis induction and cell cycle arrest.     

Partially oxidized potassium intercalate of ultradispersed diamond: A cautionary note

Direct reaction of gray ultradispersed diamond (UDD) powder with molten potassium metal gives K/UDD intercalate as a black powder. Upon prolonged storage in glass vials, presumed partial oxidation of this black powder by diffused air occurs giving a partially oxidized K/UDD gray powder. Powder XRD data indicate likely formation of undetermined amounts of KO₂ and stage-3 potassium graphite intercalate. Exposure of this gray powder to ambient atmosphere initiates a violent detonation (or rapid oxidation) having sufficient force to pulverize glass vial containers. It is recommended that handling of any partially oxidized carbonaceous potassium intercalate material should be conducted with extreme caution. Partially oxidized K/UDD powder appears to be stable to mild mechanical shock and could possibly be of interest as a secondary explosive activated by direct exposure to ambient atmosphere.     

Oxidation of cellulose in pressurized carbon dioxide

This work presents first results upon oxidation of type II cellulose by nitrogen dioxide dissolved in carbon dioxide at high pressure. This reaction leads to oxidized cellulose, a natural-based bioresorbable fabric used for biomedical applications. The oxidation reaction takes place in a heterogeneous fluid-solid system. Kinetics of oxidation is presented here and effects of operating conditions such as pressure, temperature and initial moisture content of cellulose are investigated. Results are presented in terms of degree of oxidation of cellulose and quality of the final oxidized cellulose, which has been characterized using liquid-state and solid-state ¹³C NMR. The experimental results show the existence of possible secondary reactions which may lead to oxidized cellulose with insufficient mechanical strength. An attempt is made to evidence and understand the role of CO₂ as a solvent in this system. Indeed, although supercritical CO₂ appears to be a suitable candidate as a solvent for oxidation reactions, some inhibiting effect on nitrogen dioxide activity are observed in this case.     

Electrochemical oxidation of glucose on silver nanoparticle-modified composite electrodes

Silver nanoparticle-modified composite electrodes were prepared by electroless forming silver nanoparticles in carbon black dispersed electroless silver plating solution, and then incorporating the silver nanoparticle/carbon black mixture in a polystyrene matrix. The electrooxidation of glucose in 0.1 M NaOH was studied by using cyclic voltammetry. The electrode has surface-confined nanoparicles showing effective catalytic behavior in the studies of glucose oxidation. It showed stepwise electrocatalytic oxidation behavior clearly without suppression by high background redox current caused by inner layer silver of disk-type silver electrodes. Initially the glucose was catalytically oxidized by AgO, and then the reaction glucose oxidation intermediates with Ag₂O were followed stepwisely. Based on the cyclic voltammetric results, pulsed amperometric detection parameters for flow injection analysis were optimized for sensitive detection of glucose.     

柿叶挥发油的提取及抗菌活性的研究进展

柿叶具有较高的营养价值和医疗保健作用,能制作保健茶、抗菌药物、食品香料等应用;通过水蒸气蒸馏、有机溶剂提取、超临界CO2萃取等方法对柿叶挥发油提取研究作了较为详细的综述,展望酶解辅助提取、亚临界水萃取等现代植物有效成分提取方法在柿叶有效成分提取研究;综述了柿叶提取物的抗菌作用及抗菌成分分析,表明柿叶提取物对金黄色葡萄球菌、枯草芽孢杆菌等细菌具有不同程度的拮抗作用。     

Antioxidant activity of tea extracts in lipids and correlation with polyphenol content

The present study examined the antioxidative activity of water and ethanol extracts of green and black tea leaves against the oxidation of heated sunflower oil and lard. Oxidation was conducted at 110 °C in the Rancimat test. Total polyphenols and catechin contents in tea extracts were measured. The research showed that the total polyphenol content in green and black tea leaves was 205.2 and 148.7 mg/g, respectively. In tea leaves extracts, it ranged between 245.9 mg/g and 837.7 mg/g and depended on the extraction solvent and the kind of tea used (p <0.001). The highest polyphenol content was observed in samples extracted with 95% ethanol, lower contents were found with the use of water. Results showed that the highest antioxidant activity, measured as an induction period, with 1000 ppm green tea ethanol extract, was comparable to á‐tocopherol activity in sunflower oil. In lard, the longest induction period was measured with 500 and 1000 ppm of green tea ethanol extract. Other tea extract concentrations were significantly less active. Statistical analysis of the tea extract antioxidant activity in lipids in the Rancimat test showed an essential influence of the catechin contents. Further statistical analysis also showed an influence of (?)‐epicatechin gallate (ECG), (?)‐epicatechin (EC), and (+)‐catechin (C) contents in the tea extracts on the antioxidant activity in lipids. It was stated that the antioxidant activity was higher in tea extracts containing high levels of ECG, EC, and C.     

Synthesis and characterization of the polyols by air oxidation of soybean oil and its effect on the morphology and dynamic mechanical properties of poly(vinyl chloride) blends

The use of natural additives, with low toxicity and good compatibility, for PVC is becoming increasingly attractive. In this study, soybean oil additives were prepared by air oxidation reactions and blending with PVC. The oxidation reaction produced a significant increase in the number of hydroxyl groups in soybean oil; however, this kind of reaction results in the formation of a heterogeneous structure due to free radical reactions in the medium. The oxidized soybean oil improved the compatibility with PVC due to an increase in the number of polar groups, such as hydroxyls, and thus a reduction in the amount of atactic polymer was observed. Furthermore, an increase in the molecular weight of the oxidized oil, as well as large amounts of polar groups contributes to reducing the migration of oil in the PVC. Regarding the crystallinity of PVC, the use of pure and oxidized soybean oil causes small changes in the crystalline phase of the polymer. Oxidized soybean oil has great potential for usage as a secondary plasticizer for PVC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42102.     

天然抗氧化剂——茶多酚的应用

介绍茶多酚在国内外食品工业、医药保健、日用化学品等方面的应用现状,展望了茶多酚在国际市场上的广阔前景。     

Antioxidant Effects of Berry Phenolics Incorporated in Oil-in-Water Emulsions with Continuous Phase β-Lactoglobulin

The purpose of this study was to evaluate the effects of berry phenolics, in this case, black currant (Ribes nigrum) anthocyanins and raspberry (Rubus idaeus) ellagitannins, in the presence of continuous phase β-lactoglobulin (β-Lg), on the oxidative stability of Brij 35-stabilized corn oil-in-water emulsions. The extent of lipid oxidation in emulsions was measured by determining the formation of lipid hydroperoxides and hexanal, and extent of protein oxidation by monitoring the loss of tryptophan and cysteine residues in the continuous phase β-Lg. Berry phenolics at concentration levels of 20 and 50 μM were able to prevent lipid oxidation with and without β-Lg in the aqueous phase. The results show that a combination of β-Lg and berry phenolics was more efficient in inhibiting hexanal formation than either component alone. Synergistic effects on antioxidant activity toward hexanal were observed only at the 20 μM levels of berry phenolics in combination with continuous phase β-Lg. The berry phenolics were also able to inhibit the oxidation of tryptophan and cysteine residues of β-Lg. The results show that the amino acid residues were oxidized prior to the propagation of lipid oxidation. This suggests that these amino acids were able to inhibit fatty acid scission. The information gained from this study would be useful in protecting emulsion-based food products from oxidative deterioration.     

A model for primary and heterogeneous secondary reactions of wood pyrolysis

A chain growth model for heterogeneous secondary reactions is developed for the pyrolysis of large wood particles and the parameters determined by nonlinear optimization. The model takes both the volatile retention time and cracking and repolymerization reactions of the vapours with the decomposing solid as well as sutocatalysis into consideration. The extent of the secondary reactions is strongly influenced by the time and the ratio of the autocatalytic (propagation) reaction rate to noncatalytic (initiation) reaction rate. The wood which has a higher value of the autocatalytic/noncatalytic ratio also has a higher exothermic heat of reaction and yields a higher amount of final char residue. This fact confirms the heterogeneous secondary reactions lead to carbon enrichment of the final residue and are accompanied with an exothermic heat of reaction. The lower activation energies of the initiation and propagation reactions as compared to primary reactions (competitive reaction model consisting of weight loss and char forming reactions) confirm autocatalysis in large particles. The sealed reactor studies of small quantities of fine wood samples show that heterogeneous secondary reactions and not lower heating rates in large particles are the main source of char formed during the thermal decomposition of large wood particles. The model predictions are in agreement with the weight loss and temperature versus time curves over a wide range of particle size and furnace temperatures.     

茶多酚提取工艺影响因素探究

茶多酚是茶叶的主要活性化合物,有效提取茶多酚,实现其综合利用具有十分重要的现实意义。初步探讨浸提次数、提取温度、不同浓度的提取液、不同的反应时间和茶叶的粉碎情况对茶多酚提取结果的影响。结果表明:70℃水浴为最佳提取温度,70%的甲醇水为最佳提取浓度,60min为最佳放置时间。     

Selective Degradation of Lignin Polymer by Chlorine Dioxide During Chemical Pulp Delignification in Flow Through Reactor

The delignification of pulp in a conventional batch reactor provides convenient conditions for inutile secondary reactions in which ClO₂ reacts with oxidized aromatic units of lignin. In this study the flow-through reactor was applied to minimize secondary reactions. The obtained results showed that the removal of oxidized lignin from the reaction zone significantly enhanced the ClO₂ reaction toward non-oxidized units of lignin. Application of an organic solvent-water solution, bleaching liquor, significantly increased the removal of oxidized lignin and decreased considerably the secondary reactions. Although this technique considerably improved ClO₂ effective efficiency, large amounts of chlorate formation decreased the overall effect of improved ClO₂ global efficiency.     

Behavior of polyphenoloxidases in food

One of the problems in the handling and processing of various kinds of fruits, is the enzymatic and nonenzymatic browning. The polyphenoloxidases are strictly related with the first aspect, needing therefore, more attention from the scientists and food industries. These enzymes oxidize mono, di and polyphenols in the presence of molecular oxygen, producing dopachromes which are polymerized to melanins as a final product. Their mechanism of action, however, is still unknown. The purpose of this article is to provide specific information as to the nature and behavior of the polyphenoloxidases found in different kinds of fruits and foods.     

Antioxidant Efficacy of a New Synergistic,Multicomponent Formulation for Fish Oil Omega-3 Concentrates

Today, tocopherols serve as the industrial standard antioxidant protection for fish oil omega-3 concentrates. Synergistic interactions between tocopherols, ascorbyl palmitate and natural polyphenols extracted from plant sources have been demonstrated in model systems. The main goal for this work was to develop a mix of such antioxidants with improved efficacy in the context of preserving industrial marine oil concentrates. The antioxidant formulation comprises tocopherols, ascorbyl palmitate, rosemary extract and green tea catechins. Part of the scope was to develop a method for dissolving green tea catechins in oil. The key element of the method is to introduce green tea on a lipid insoluble carrier when dissolving the extract in the oil, and thereafter remove the carrier by filtration. The antioxidant mix was tested against tocopherol in omega-3 concentrates of minimum 300 mg/g eicosapentaenoic acid (EPA) plus 200 mg/g docosahexaenoic acid (DHA) in the form of triacylglycerides and ethyl esters. The mix was superior compared to tocopherols in suppressing both primary- and secondary oxidation. Weight increase measurements of oil in contact with air correlated well with standard oxidation tests within individual samples and the method was considered simple and useful for monitoring oxidation in omega-3 concentrates.