Stabilization of refined olive oil by enrichment with chlorophyll pigments extracted from Chemlali olive leaves

This paper presents the first investigation on the effect of enrichment refined olive oil by chlorophyll pigment extracted from Chemlali olive leaves during storage (6 months). The changes that occurred in the quality indices, fatty acids, sterol, and phenolic content were investigated during the storage of refined olive oil under RT (20°C) and accelerated conditions (50°C) in the dark. Additionally, the pigments (chlorophyll and carotene) changes during 6 months of oil storage were evaluated. At the end of the storage, more than 90% of chlorophyll pigments decomposed in all samples, while, carotene pigment loss was lower showing up to 60 and 85% loss for oil stored at 20 and 50°C, respectively, at the end of storage. The reduction of total phenolic compounds exhibited similar degradation profiles, being reduced by 5% and up to 60% for the enriched refined olive oil stored at 20 and 50°C in 6 months, respectively. In the fatty acid composition, an increase in oleic acid and a decrease in linoleic and linolenic acids were less significant in enriched than non‐enriched refined olive oil. On the other hand, sterol composition was less affected by storage in enriched oil samples. However, the sterol concentration of the oil samples showed an increase in β‐sitosterol, 24‐methylene cholesterol, stigmasterol, and a decrease in cholesterol, Δ5, 24‐stigmastadienol percentage at the end of storage. Based on the Rancimat method, the oils with added leaf pigment extract had the lowest peroxide value and the highest stability. After 6 months of storage, the oxidative resistance of refined olive oil fell to 0.2 and to zero for enriched refined olive oil stored at 20 and 50°C, respectively.     

Effects of peroxide crosslinking on the mechanical and morphological properties of poly(ethylene‐co‐vinyl acetate)/zeolite composites

Uncrosslinked and chemically crosslinked ethylene‐vinyl acetate copolymers (EVAs) with 5–25 volume percentages of zeolite were prepared in a melt‐mixing process and then compression‐molded on a hot‐press machine according to standard test specifications. The mechanical properties measured by tensile test showed a reduction in tensile strength and elongation at break with increasing zeolite content. However, an increasing trend was observed for tensile modulus with addition of zeolite. Experimental results for ultimate stress were compared with those from Pukanszky equation. The experimental data showed a good fit to the Pukanszky model. The improvement in the interfacial interaction for crosslinked composites was also confirmed by this model. Morphological changes of EVA/zeolite composites were analyzed by scanning electron microscopy (SEM). The fractured surface of the composites indicated more complex morphology at higher zeolite loading. The influence of crosslinking induced by 2 wt% of dicumyl peroxide on the properties of EVA/zeolite composites was also investigated. The crosslinked composites showed better tensile properties than the uncrosslinked ones, a result which might be an indication of enhanced interaction between the EVA and zeolite. Density measurements, gel content determinations, and Fourier transform infrared analyses were also performed to evaluate the crosslink content of the composites. The changes in the properties of chemically crosslinked EVA/zeolite composites were observed. Meanwhile, SEM micrographs of the crosslinked EVA/zeolite composites showed better interfacial strength between zeolite and the EVA matrix as compared to that of the uncrosslinked composites. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Thermal,structural, and optical properties of γ‐irradiated poly(vinyl alcohol)/poly(ethylene glycol) thin film

Poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) copolymer was prepared using casting technique. The obtained PVA/PEG thin films have been irradiated with gamma rays with doses ranging from 1.5 to 20 Gy. The resultant effect of gamma irradiation on the thermal properties of PVA/PEG has been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The onset temperature of decomposition T_o and activation energy of thermal decomposition E_a were calculated, results indicating that the PVA/PEG thin film decomposes in one main weight loss stage. Also, the gamma irradiation in dose range 4–12 Gy led to a more compact structure of PVA/PEG copolymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with gamma dose has been determined using DTA. The PVA/PEG thermograms were characterized by the appearance of an endothermic peak due to melting of crystalline phase. In addition, structural property studies using X‐ray diffraction and infrared spectroscopy were performed on both nonirradiated and irradiated samples. Furthermore, the transmission of the PVA/PEG samples and any color changes were studied. The color intensity (E was greatly increased with increasing the gamma dose and was accompanied by a significant increase in the blue and green color components. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Comparative study on natural antioxidant as an aging retardant for natural rubber vulcanizates

The research aim is mainly to investigate the effectiveness of natural antioxidant (NA) obtained from oil palm leaves (Elaeis guineensis) as an aging retardant in natural rubber (NR) vulcanizates. Comparison of NA with other commercial antioxidants, trimethyl quinoline (TMQ) and butylated hydroxy toluene (BHT), is investigated. The effect of natural and commercial antioxidants on NR vulcanizates was explored before and after aging. Aging test was carried out at 70°C for three different periods, 4, 7, and 14 days to determine aging property by performing the tensile and tear tests. NA shows lower tensile properties, crosslink density, tack strength but high tear strength compared to the commercial antioxidants, BHT and TMQ. However, upon aging NR vulcanizates with NA retains its properties equivalent to that of commercial antioxidants, BHT and TMQ. Thus, NA can be used as an aging retardant for short‐term protection in application requiring moderate tensile properties and can be used as alternative source for commercial antioxidant. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of MnO2 additive on the dielectric and electromagnetic interference shielding properties of sintered cement-based ceramics

Cement-based ceramic pellets were prepared and their properties were studied for electromagnetic interference (EMI) shielding applications. The shielding materials were made of Portland cement with the addition of different concentrations of manganese oxide (MnO₂) up to 10 wt%. The pellets were sintered at 850 °C for 5 h and then polished prior to characterizations of density, porosity, microstructures, dielectric properties, and EMI shielding effectiveness (SE). Results show that the MnO₂-cement pellets have good dielectric properties, i.e. high dielectric constant (∼300) and low dielectric loss (<0.3). The dielectric constant increased with increasing MnO₂ content in the cement matrix. The SE values of the MnO₂-cements fluctuated between 2 dB and 9 dB in the frequency range of 8-13 GHz. The sample with 10 wt% MnO₂ additive had SE values of up to 9 dB. Most of the samples with high additive concentrations produced SE exceeding 7 dB.     

Synthesis and physicochemical investigation of chitosan-built hydrogel with induced glucose sensitivity

There is an urgent need to treat diabetes, and therefore, this work reports on a chitosan-built hydrogel functionalized by a glucose sensing moiety, which simulates pancreatic activity. The effect of external stimuli on various internal properties was investigated to establish the action of the hydrogel. The model drugs, fluorescein (D1) and rhodamine (D2), with a diol architecture, were investigated spectroscopically with 75.94% loading and 65.63% release. Consequently, a ligand to glucose ratio of 2:1 in comparison with a ligand to model drug ratio of 1:1 was addressed. The system was expected to lead to findings on applications for the self-controlled release of insulin in response to blood glucose levels.     

Dynamic Modeling and a Parametric Study of an Indirect Solar Cabinet Dryer

A dynamic mathematical model for drying of agricultural products in an indirect cabinet solar dryer is presented. This model describes the heat and mass transfer in the drying chamber and also considers the heat transfer and temperature distribution in a solar collector under transient conditions. For this purpose, using conservation laws of heat and mass transfer and considering the physical phenomena occurring in a solar dryer, the governing equations are derived and solved numerically. The model solution provides an effective tool to study the variation of temperature and humidity of the drying air, drying material temperature, and its moisture content on each tray. The predicted results are compared with available experimental data. It is shown that the model can predict the performance of the cabinet solar dryer in unsteady-state operating conditions well. Furthermore, the effect of some operating parameters on the performance and efficiency of dryer is investigated and compared with selected published data.     

Mangrove Oyster (Crassostrea belcheri) as a Biomonitor Species for Bioavailability of Polycyclic Aromatic Hydrocarbons (PAHs) from Sediment of the West Coast of Peninsular Malaysia

ABSTRACT

Rapid industrialization and urbanization in the west coast of Peninsular Malaysia has caused increasing pollution particularly of petroleum and petroleum by-products. Surface sediment and mangrove oyster (Crassostrea belcheri) were collected from five mangrove ecosystems in the west coast of Peninsular Malaysia and investigated for bioavailability of polycyclic aromatic hydrocarbons (PAHs). Sampling locations were selected from both remote areas with few or no previous records of petroleum pollution such as Pulau Merambong and polluted areas that are under international attention such as Klang mangrove ecosystem. PAH fractions were obtained through soxhlet extraction and two-step column chromatography and the fractions were injected to gas chromatography-mass spectrometry (GC-MS) for analysis. The concentrations of PAHs ranged from 151 to 4973 ng g^?1 dw in the sediments, while from 309 to 2225 ng g^?1 dw in the oysters. When tested for diagnostic ratios, a predominance of pyrogenic source PAHs was detected in the sediments, whereas PAHs in the oysters had mixed petrogenic and pyrogenic sources. A significant correlation (p < 0.05) was found between high molecular weight (HMW) PAHs in the sediments and oysters and biota accumulation factors (BAFs) of PAHs were approaching or exceeding unity indicating the ability of mangrove oyster in bioaccumulation of PAHs. Overall, this study indicates that mangrove oyster (C. belcheri) can be used as a biomonitor species for PAHs in an aquatic environment.     

On-Line Characterization of Morphology and Water Adsorption on Fumed Silica Nanoparticles

The first wetting layer on solid nanoparticles has direct implications on the roles these particles play in industrial processes and technological applications as well as in the atmosphere. We present a technique for online measurements of the adsorption of the first few water layers onto insoluble aerosol nanoparticles. Atomized fumed silica nanoparticles were dispersed from aqueous suspension and their hygroscopic growth factors (HGF) and number of the adsorbed water layers at subsaturated conditions were measured using a nanometer hygroscopic tandem differential mobility analyzer (HTDMA). Particle morphology was characterized by electron microscopy and particle density was determined by mobility analysis. The HGFs of the size-selected particles at mobility diameters from 10 to 50 nm at 90% relative humidity (RH) varied from 1.05 to 1.24, corresponding to 2–6 layers of adsorbed water. The morphology of the generated fumed silica nanoparticles varied from spheres at 8–10 nm to agglomerates at larger diameters with effective density from 1.7 to 0.8 g/cm³ and fractal dimension of 2.6. The smallest spheres and agglomerates had the highest HGFs. The smallest particles with diameters of 8 and 10 nm adsorbed two to three water layers in subsaturated conditions, which agreed well with the Frenkel, Halsey, and Hill (FHH) isotherm fitting. In comparison to the small spheres or large agglomerates, the compact agglomerate structure containing a few primary particles increased the number of adsorbed water layers by a factor of ～1.5. This was probably caused by the capillary effect on the small cavities between the primary particles in the agglomerate.     

Investigation of the phase separation of PNIPAM using infrared spectroscopy together with multivariate data analysis

The use of vibrational spectroscopy to investigate complex structural changes in polymers yields chemically rich data, but interpretation can be challenging and subtle but meaningful spectral changes may be missed through visual inspection alone. Multivariate analysis is an efficient approach to gain an oversight of small but systematic spectral differences anywhere within the spectra, providing further insight into structural changes and associated transformation mechanisms. In this study, the novel analytical approach of infrared spectroscopy combined with principal component analysis and Gaussian peak fitting was used to investigate the structural changes in aqueous solutions of a polymer, using poly(N-isopropyl acrylamide) (PNIPAM) in the atactic form and with controlled tacticity as a model system. Subtle spectral changes associated with the dehydration and phase separation upon heating included peak shifts, an area ratio change of the amide I band to the amide II band and formation of a new peak in the amide I band were efficiently detected. Dehydration and phase separation of PNIPAM occurred in two temperature ranges, one for the atactic and one for isotactic rich part, both involving a complex re-organization of the hydrogen bonds and change of the hydration layer. The changes agreed with existing results from other techniques, and new insights were gained into the effect of controlled tacticity on phase transformation behaviour. The study demonstrates that infrared spectroscopy combined with the multivariate analytical method principal component analysis and Gaussian peak fitting is an efficient approach to probing structural change in polymers during heating. The simplicity of the presented approach could find excellent use in analysing and understanding the molecular environment of a range of stimuli-responsive polymers, for instance block or grafted types of polymers, as well as those with controlled tacticity.