ABTS•+ scavenging activity of polypyrrole,polyaniline and poly(3,4‐ethylenedioxythiophene)

Although many methods are available for the evaluation of the antioxidant capacity of samples presented in the liquid state, typically food and beverages, to date only the 2,2′‐diphenyl‐1‐picrylhydrazyl (DPPH) assay has been applied to the measurement of the antioxidant capacity of solid samples such as active packaging materials. A modified 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS) assay has been successfully developed for the measurement of the antioxidant capacity of conducting polymer powders. The ABTS^?+ radical scavenging activity of polypyrrole (PPy), polyaniline (PANI) and poly(3,4‐ethylenedioxythiophene) (PEDOT) powders was compared. The ranking order for greatest antioxidant capacity among the conducing polymer powders was PANI > PPy > PEDOT. The reduced forms of all the three conducting polymer samples were found to show greater radical scavenging activity than their as‐prepared partially oxidized forms. The modified ABTS assay is a simple, rapid and sensitive method for evaluating the antioxidant capacity of conducting polymer powders. The method is also suitable for composite antioxidant materials comprising a conducting polymer and a conventional packaging polymer. Copyright © 2010 Society of Chemical Industry     

Influence of thyme and clove essential oils on cottonseed oil oxidation

Simple model systems composed of refined cottonseed oil and thyme oil or clove oil, without additives, were designed to approximate conditions in natural oils in order to study their oxidation behavior. Three methods were used to follow cottonseed oil oxidation, i.e., coupled oxidation withβ-carotene, the TBA test and hydroperoxide number. The results illustrate that clove and thyme oils at various concentrations exhibit antioxidant activity and this phenomenon for clove oil is superior to that of thyme oil. Sensory evaluation tests indicate that the addition of thyme oil or clove oil to cottonseed oil at concentrations ranging from 50 to 1200 ppm do not affect the odor note of cottonseed oil. Therefore, thyme and clove essential oils are recommended for use as natural antioxidants to suppress lipid oxidation.     

Preparation of viscoelastic gel‐like halloysite hybrids and their application in halloysite/polystyrene composites

Self‐reinforcement gel‐like halloysite nanotube (g ‐HNT ) hybrids with various viscoelastic behaviors were fabricated by firstly treating with various concentrations of sodium hydroxide (NaOH ) solution and then grafting tertiary amine and ion‐exchange reacting with sulfonate anions. The morphology, composition, thermal stability and rheological behavior of the g ‐HNT hybrids were systematically characterized and analyzed using various methods. It is found that the viscoelasticity of g ‐HNT hybrids can be easily regulated by using different NaOH solution‐treated HNTs as inorganic core and temperatures. In addition, the g ‐HNT hybrids treated with medium concentration of NaOH (0.06 mol L^?1) have the lowest viscosity and highest level of dispersion compared with those treated with other concentrations of NaOH solution. Due to the amphiphilic nature of g ‐HNT hybrids and their lower viscosity than HNT powder, as novel hybrid fillers, they were utilized to prepare polystyrene composites by direct melt blending for achieving simultaneous reinforcement and plasticization effects. Besides the above mentioned advantages, the thermal conductivity of polystyrene composites is also surprisingly improved by reducing the interfacial mismatch between the filler and polymer matrix. The solvent‐free and self‐reinforcement hybrids provide a convenient and green path for fabricating high‐performance polymer composites. © 2017 Society of Chemical Industry     

Electrospun poly(vinyl alcohol) composite nanofibers with halloysite nanotubes for the sustained release of sodium d‐pantothenate

Poly(vinyl alcohol) (PVA) nanofibers containing halloysite nanotubes (HNTs) loaded with sodium d ‐pantothenate (SDP) were successfully fabricated via simple blend‐electrospinning. SDP was efficiently loaded into the innate HNT lumen with an SDP/HNT mass ratio of 1.5:1 via vacuum treatment. The SDP‐loaded HNT‐inclusion complex was evaluated with drug‐loading efficiency testing, Fourier transform infrared (FTIR) spectroscopy, and X‐ray diffraction. The morphologies of the nanofibers were observed by scanning electron microscopy, which revealed uniform and smooth surfaces of the nanofibers. The addition of HNTs to the composite nanofibers increased the viscosity of the polymer solution, and this suggested shorter fiber diameters. FTIR spectroscopy verified the good compatibility of the SDP and HNTs with PVA. Moreover, the swelling properties were found to quantitatively correlate with weight loss. In vitro drug‐release testing revealed that the HNTs and crosslinking reaction most dramatically affected the sustained release of SDP from the PVA and SDP‐loaded HNT complex. In the drug‐release kinetics model, SDP release depended on the diffusion caused by the deformation of the polymer‐based structures in the medium; it followed Fickian diffusion with acceptable coefficient of determination (r²) values between 0.88 and 0.94. Most importantly, the HNTs as natural biocontainers effectively modulated the release profile by loading the active compound in harmony with the electrospun nanofibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42900.     

Development of new,nonabsorbable polymeric antioxidants for use in foods

The metabolic fate of a new, oil soluble antioxidant, selected from a series representing a unique class of phenolic polymers, is discussed together with its activity in unsaturated vegetable oils as compared to butylated hydroxytoluene, butylated hydroxyanisole, and tertiary butylhydroquinone (TBHQ). Using gel permeation chromatography,¹⁴C-radiolabeled polymer was isolated into discrete mol wt fractions and these administered as single oral doses to rats. Results indicate that while monomeric¹⁴C-TBHQ with a mol wt of 166 shows a total absorption of 88.3% of the administered dose, the absorption of polymeric antioxidant is vastly reduced with increasing mol wt; i.e., mol wt 760: 1.5%, mol wt 7300:0.44%, and mol wt 67,000: 0.34%. Functionality tests using the active oxygen method indicate that by increasing the phenolic constituents in the polymer composition the antioxidant activity can surpass that of certain traditional, monomeric food grade antioxidants. Stability tests using thermogravimetric analysis indicate the polymeric antioxidants are not depolymerized in the presence of air at temperatures up to 300 C. Further, the polymers are nonvolatile and under deep frying conditions result in nearly quantitative carry-through of antioxidant in that portion of oil absorbed by the food; a monomeric food grade antioxidant (TBHQ) shows losses due to volatilization. Presented at the AOCS Meeting, Dallas, April 1975.     

Emblicanin Rich Emblica officinalis Encapsulated Double Emulsion and its Antioxidant Stability during Storage

Emblicanin rich water‐soluble extract of Emblica officinalis (EEO) is encapsulated in the inner phase of double emulsion (DE) by using emulsifiers in different phases at different concentrations. The effects of other variables like homogenization speed, salt and herbal concentration are also investigated on various phases of DE to obtain a stable matrix. Finally, optimized EEO encapsulated DE has 2% w/w NaCl and 50% w/w EEO in inner (W₁) phase, 4% w/w polyglycerol polyricinoleate (PGPR) in middle oil‐phase and 2% w/w low‐methoxy‐pectin and reverse osmosis water in outer (W₂) phase. Ultra‐Turrax high shear homogenizer is employed to prepare primary emulsion (W₁/O) at 20 000 rpm and DE (W₁/O in W₂) at 12 000 rpm. The EEO encapsulated DE has been characterized for encapsulation efficiency (>90%), viscosity (0.715 ± 0.18 Pa s), sedimentation stability, zeta potential (?32.17 ±1.17 mV), and particle size. Light and confocal laser microscopy are used for elaborating the microscopic structure of EEO encapsulated DEs. DE has shown storage stability up to 42 days and protect antioxidant activities as compared to control (herbal extract was not encapsulated in the inner phase). The present study demonstrates that the optimized DE matrix can be used to protect the bioactive properties of EEO for its use in functional food formulation.     

Biodegradable polypropylene/thermoplastic starch nanocomposites incorporating halloysite nanotubes

In this work, polypropylene/thermoplastic starch (PP/TPS) with and without halloysite nanotubes (HNTs) was prepared via melt mixing in order to obtain environmentally friendly plastics. PP‐grafted maleic anhydride (PP‐g‐MA) was used to improve the compatibility among the highly incompatible polymers. The mechanical characterization showed a reduction in the tensile properties of the polymer when TPS increased; however, HNT successfully compensated for some of the observed losses. The results from the thermogravimetric analysis (TGA) indicated that HNT is an efficient reinforcement for the thermal stability improvement. TPS caused an increase in the storage modulus (G′) and the complex viscosity (η*) which marks a change in the viscoelastic properties of the system. The scanning electron microscope (SEM) images showed the effective plasticization of starch and better dispersion of TPS in the presence of HNT. Some samples were also buried in the soil to measure their sustainability after their lifetime lapse. The results indicated that TPS improves the biodegradability of the PP/TPS system. PP considerably lowered the moisture uptake of TPS; nevertheless, HNT caused a slight increase in the moisture absorption. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45740.     

Antioxidant activity of some spice essential oils on linoleic acid oxidation in aqueous media

Some spice essential oils (caraway, clove, cumin, rosemary, sage and thyme) and their major constituents were added to emulsified linoleic acid in aqueous media to examine their antioxidant activity. The methods used for measuring linoleic acid oxidation were coupled oxidation ofβ-carotene, conjugated diene formation and thiobarbituric acid test. The essential oils under study possess an antioxidant effect and this phenomenon was increased by increasing their concentration. Generally, the effectiveness of the various essential oils on linoleic acid oxidation was in the following descending order: caraway >sage>cumin>rosemary>thyme>clove. It appears that there was a relationship between the antioxidant effect and the chemical composition of the oils.     

A non‐extractable condensed‐tannins fiber reduces thermal oxidation in oils at frying temperature

Several compounds presenting antioxidant properties have been tested in frying oils to delay thermal oxidation of the triglycerides containing unsaturated fatty acids. The present study was designed to evaluate, for the first time, the antioxidant and antipolymerizing effects of addition of Exxenterol®, a denatured carob fiber very rich in non‐extractable tannins, on olive oil (OO), sunflower oil (SO) and a homogeneous blend of both oils. Exxenterol was added to the three oils in amounts of 50, 250, 500 and 1000 mg/kg oil before heating. After 36 h of heating at 180 °C, there was a large and relevant increase of the polar material and the polymer contents, but tocopherol decreased to non‐detectable levels in all three oils. Polar content, polymer and thermal oxidation formation (p ≤0.004) and tocopherol degradation (p ≤0.022) were significantly and dose‐dependently inhibited by Exxenterol. Both polar material and polymer formation were inhibited (at least by 44%) in OO and SO and at least by 27% in the oil blend when 1000 mg/kg oil of this product was added. Small but detectable amounts of tocopherol were found in the oil blend containing 50 mg Exxenterol/kg. The results clearly show that this non‐extractable tannin‐rich fiber can be successfully employed as an additive to prolong oil shelf life at frying temperature.     

Review on Polymer/Halloysite Nanotube Nanocomposite

Halloysite nanotube (HNT) is a unique type of nanofiller, i.e., structurally much similar to nanoclay, whereas geometrically analogous to carbon nanotube. Due to nanosize, surface area, low cost, and natural availability, HNT offers up to date latent for polymeric nanocomposite. Polymer/HNT nanocomposites have been prepared using different techniques; however, melt mixing technique was widely used. Thermal stability, mechanical robustness, and nonflammability of polymer nanocomposite have been found to increase by HNT addition. Application areas discovered so far include materials for flame retardancy, stimuli-response, anticorrosion, dye removal, and drug delivery. Future research is desired to expand the potential of polymer/HNT nanocomposite.     

Two in One: Modified Polyurethane Foams by Dip‐Coating of Halloysite Nanotubes with Acceptable Flame Retardancy and Absorbency

Poor flame retardancy of polyurethane foam (PUF) limits its practical application in many fields. Here, flame‐retardant performance of PUF is improved by a simple dip‐coating method. Halloysite nanotube (HNT) coating can be uniformly bonded to PUF surfaces via hydrogen‐bonding interactions, which is confirmed by element mapping and X‐ray photoelectron spectra. Density and mechanical properties of PUF increase with the concentration of HNT suspension, while porosity of the foam decreases with HNT loading. Weight ratio of HNTs to PUF in the composite can be achieved as high as 65.2%. Surfaces of PUF transfer from hydrophobic to super‐hydrophilic after HNT coating, and the water contact angle decreases from 116° to 0° after HNT coating. As a result, methylene blue adsorption capacity of HNTs‐coated PUF increases from 0.02 to 0.15 mg g^?1, and adsorption efficiency can reach 98% after 10 s. HNT coating can prevent PUF from burning and dripping, which suggests that flame‐retardant performance of PUF is significantly improved by HNTs. This work establishes a general procedure for improving flame retardancy and dye absorbency of polymer materials by simple dip‐coating of environmental‐friendly clay nanotubes, which shows great potential in high‐performance polymer and functional composite materials.     

Controlled release mechanisms of sodium benzoate from a biodegradable polymer and halloysite nanotube composite

Multiscale polymeric composites combining a biodegradable matrix with low cost and biocompatible hybrid nanocarriers promise to supply a new generation of multipurpose devices for drug delivery. The aim of this work was to investigate the release mechanisms of sodium benzoate (NaBz ) from halloysite nanotubes (HNTs ) embedded in a biodegradable polymer matrix (poly(?‐caprolactone)). To that purpose, different amounts of NaBz molecules were successfully incorporated into HNTs using a simple environmentally friendly procedure. The resulting HNT‐NaBz nano‐hybrids were then incorporated into a poly(?‐caprolactone) matrix by high energy ball milling at ambient temperature and in dry conditions. Analysis of the resulting composites showed important effects of the HNT‐NaBz nano‐hybrids on the thermal and mechanical properties. Controlled drug release, followed by UV spectrophotometry, was also found to be dependent on the HNT‐NaBz relative fractions. Experimental data were thus analyzed using a modified Gallagher ? Corrigan model and correlated with the nano‐hybrid morphologies. © 2016 Society of Chemical Industry     

Microwave‐assisted hydrodistillation of essential oil from Zataria multiflora Boiss

Microwave‐assisted hydrodistillation (MAHD) has recently gained attention for the extraction of essential oils. A concern with the use of MAHD is the possibility of sample deterioration during the extended exposure to microwave irradiation. In this study, MAHD was applied as a new and green technology for the extraction of essential oil from Zataria multiflora Boiss. (Shirazi thyme) aerial parts. Superior results were obtained with the proposed method in terms of extraction time [1 h vs. 4 h in hydrodistillation (HD)] for an essential oil recovery of 3.66 and 3.44%, respectively. Images obtained from thyme leaves using scanning electron microscopy indicated a sudden eruption of essential oil glands undergoing MAHD. GC‐MS analysis of the essential oils did not indicate any new or missing compounds in the essential oil obtained by MAHD in comparison with that by HD. Therefore, a microwave oven can be safely used for the extraction of essential oil from Shirazi thyme.     

Antioxidant Properties of Three Aromatic Herbs (Rosemary, Thyme and Lavender) in Oil-in-Water Emulsions

Lipid oxidation is the major form of deterioration in foods because it decreases food quality and nutritional value, and may have negative health implications. Selected aromatic plant extracts from leaves, flowers and stems of rosemary, thyme and lavender were investigated for their antioxidant activity. The total polyphenol content was determined by the Folin–Ciocalteu assay and the antioxidant capacity was determined by the Trolox equivalent antioxidant capacity, 1,1-diphenyl-2-picrylhydrazyl, oxygen radical absorbance capacity and ferric-reducing antioxidant power assays. For all four antioxidant assays, the extracts from thyme flowers, lavender leaves and thyme leaves had the highest antioxidant activity, followed by rosemary stems, rosemary leaves, and lavender stems, and the lavender flowers and thyme stems had the lowest antioxidant activity. The antioxidant activity was correlated with the polyphenol content, although minor deviations were observed. In oil-in-water emulsion, extracts from rosemary leaves and thyme leaves were most effective at retarding oxidation followed by the rosemary stems and thyme flowers. Extracts from thyme flowers and lavender leaves were less effective in the emulsion than predicted by the homogeneous antioxidant assays. This study demonstrated the potential use of plants extract as substitutes for synthetic antioxidants.     

Antioxidant activity and free radical‐scavenging capacity of ethanolic extracts of thyme,oregano, and marjoram

Phenolic compounds were extracted from thyme (Thymus vulgaris L.), oregano (Origanum vulgare L.) and marjoram (Origanum majorana L.) with 95% ethanol. A number of antioxidant and radical‐scavenging capacity tests were performed on the prepared extracts using colorimetric assays and model system studies. Specifically, these included determining the content of total phenolics, antioxidant efficacy in a linoleic acid‐ferric thiocyanate model system, reducing power, scavenging effect on 2,2'‐diphenyl‐1‐picrylhydrazyl radical, and hydroxyl radical‐scavenging activity by electron paramagnetic resonance spectroscopy. Moreover, the efficacies of the prepared herb extracts were investigated in a real‐life food product: the stabilization of butter against oxidation.     

The Antioxidant Functions of Tocopherol and Tocotrienol Homologues in Oils,Fats, and Food Systems

This review paper is focused on the relative antioxidant activities of tocopherols and tocotrienols in oils and fats and certain food systems. α-Tocopherol generally showed better antioxidant activity than γ-tocopherol in fats and oils, but at higher concentrations γ-tocopherol was found to be a more active antioxidant. The results of studies on the optimum antioxidant concentrations of tocopherols in oils and fats indicated that the optimal level for α-tocopherol is usually lower than other tocopherols, meaning less α-tocopherol is needed for maximum antioxidant protection. There are comparatively very few studies related to the antioxidant activities of tocotrienols in oils and fats. It has been stated that generally γ-tocotrienol has higher antioxidant effect than α-tocotrienol, and tocotrienols may be better antioxidants than their corresponding tocopherols in certain oils and fats systems. Studies on the antioxidant activity of various tocopherols in food systems are varied and cannot be uniformly evaluated because experiments have generally focused on different foods and used various methods for the detection of antioxidant activities. Depending on the food system, in certain cases tocopherols were better antioxidants than synthetic antioxidants such as butylhydroxy toluene (BHT) or butylhydroxy anisole (BHA). However, in certain other food systems the synthetic antioxidants were more effective to increase the shelf life and the stability of foods than those containing tocopherols.     

The effect of polyethylene crystallinity and polarity on thermal stability and controlled release of essential oils in antimicrobial films

Antimicrobial packaging can preserve and increase shelf life of free preservatives food products. Active materials present in the packaging material can migrate, in a controlled manner, to the food surface, avoiding bacterial and fungal proliferation and keeping the food product edible for longer periods of time. Essential oils (EO) are natural antimicrobial agents that can be released to the headspace with no direct contact between the package and the food. To minimize loses of EO during high heat melt processing, a three stages process was implemented and tested. Antimicrobial films were prepared by melt mixing a variety of polyethylene copolymers in the presence of organo‐modified montmorillonite nano clay (NC) and thymol, an EO present in oregano and thyme. A controlled EO desorption from films can be achieved by changing the polymer crystallinity and polarity. As the crystallinity increased, the thermal stability of the EO during the extrusion process improved. The addition of NC affects the structure and homogeneity of the crystals. The combination of high polymer crystallinity and chemical affinity between EO and NC increased the thermal stability of the EO during film processing, enabling to control the desorption rate. The effect of multilayer structure based on varied densities and polarities was also studied. Increasing the polarity of the outer layers in multilayered film reduced the EO desorption rate as a result of chemical interactions between the polymer and the EO. The final antimicrobial activity of the films was also found to be dependent on the EO partitioning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40309.     

Testing the Antioxidant Effect of Essential Oils and BHT on Corn Oil at Frying Temperatures: a Response Surface Methodology

Food habits worldwide have increased the demand for oxidative-resistant oils that can be used for deep-frying. Oxidative stability in oils can be improved by changing the fatty acid composition of the oil or by adding natural antioxidants to the oil. In this study, the effect of essential oils of seven plants; cinnamon, rosemary, sage, turmeric, clove, thyme and oregano enriched with carvacrol on the oxidative stability of corn oil at frying temperatures were studied. Experiments were conducted by using a PetroOxy device, a rapid small scale oxidation stability test. A central composite design was used to evaluate the effects of concentration of essential oil (X1: 1,500–5,000 ppm) and temperature (X2: 150–180 °C), on the induction time of corn oil. In order to compare the results with the synthetic antioxidant, butylated hydroxy toluene (BHT), another design was made with a concentration range (60–350 ppm) containing the legal upper limit of BHT, 200 ppm. Induction periods obtained from the accelerated oxidation test revealed that increasing temperature decreased the induction time of all the samples. However, the essential oils except for oregano oil had no significant antioxidative effect on corn oil, probably due to a lower content of their active components. The antioxidative effect of oregano oil was also found to be higher compared to BHT. At very high temperatures (e.g., 180 °C), the concentration of antioxidants had no effect on the induction periods.     

Evaluation of the Antioxidant Properties of Micronutrients in Different Vegetable Oils

Micronutrients (tocols, sterols, and total phenolic) and antioxidant activities of 15 varieties of common vegetable oil samples obtained from different countries are investigated. All methanol extracts are assayed for total antioxidant ability and cellular antioxidant activity (CAA) using oxygen radical absorbance capacity (ORAC) method and CAA assay. CAA has been widely used in the evaluation of food antioxidants recently. It quantifies antioxidant capacity utilizing a HepG2 cell model, which is more biologically representative. Linseed and sesame oils show much higher CAA values than the others tested; however, levels of walnut, sunflower, and coconut oils are extremely low, which are hard to be quantified. A significant correlation between the ORAC and CAA values and total phenolic content (p < 0.05) is observed. High‐phenolic olive oil has the highest level of phenolics and the highest ORAC, while linseed oil has the highest CAA value. Based on this, choosing proper edible oil consumption may reduce oxidative damage of human body and promote the precision processing of edible oil such as retaining beneficial ingredients moderately. Practical Application: This study demonstrates the evaluation of the universality of vegetable oils by the cellular antioxidant model and provides a data reference for the selection of edible oils with excellent antioxidant properties.     

Halloysite nanotube reinforced polylactic acid composite

Polylactic acid (PLA) has a long history in medical applications. Reinforced PLA has the potential to be used in the medical applications that require high mechanical strength such as coronary stents and bone fixation devices. Halloysite nanotube (HNT) has received considerable attention recently due to its tubular structure, high aspect ratio, high mechanical strength, thermal stability, biocompatibility and sustained drug releasing properties. Halloysite has been investigated in compounding with many polymers. However, the research in compounding halloysite with biodegradable materials for use in biological applications is sparse. In this study various weight fractions of HNT was compounded with the biodegradable polymer PLA using a melt compounding method. Tensile test, Fourier infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), contact angle test, scanning electron microscopy (SEM), void content and thermogravimetric analysis (TGA) were carried out to study the PLA/HNT composite. Tensile test results indicated that Young's modulus and stiffness of PLA were enhanced with the addition of HNT; FTIR spectra showed the interaction between the PLA and HNT; whereas contact angle measurements indicated that the wettability of the PLA/HNT composite was not affected by the addition of HNT. However, the thermal stability of PLA was adversely effected by the addition of HNT which may be related to the presence of voids between the polymer and matrix. Nevertheless, the reinforced PLA/HNT composite, which maintains the surface characteristics, may prove beneficial for use in biological applications. POLYM. COMPOS., 38:2166–2173, 2017. © 2015 Society of Plastics Engineers