Analysis of saffron volatile fraction by TD–GC–MS and e-nose

Saffron spice is valuable for its colour, taste and aroma. All these properties depend on the different postharvesting treatments that Crocus sativus L. stigmas received to convert it into a spice. No previous scientific data relate the volatile content with its postharvesting process or origin. In this paper, two different analytical methods are used, CG-MS to determine volatile markers and an electronic nose based on metal oxides to determine the volatile profile of the samples from different geographic origins. It is demonstrated by means of CG-MS that 3,5,5-trimethyl-2-cyclohexenone, 2,6,6-trimethylcyclohexane-1,4-dione and acetic acid are capable to differentiate saffron from its origin. The content of acetic acid is very high in samples from Iran or Morocco, while low or undetectable content was observed in Greek and Spanish samples. In turn, using an e-nose (specifically optimised for this particular application), samples from different countries could be discriminated using Principal Component Analysis with a 90% of confidence.     

Biogenic amines and fish freshness assessment using a multisensor system based on voltammetric electrodes. Comparison between CPE and screen-printed electrodes

The present work relates to a method for determining the degree of freshness of fish by monitoring the production of spoilage products. This method comprises the global detection of the spoilage products including biogenic amines resulting from the degradation of fish by using arrays of voltammetric sensors chemically modified with phthalocyanines. The performance of an array of screen-printed electrodes (SPE) has been compared with that of an array formed by classic carbon paste electrodes (CPE). The sensors have shown good sensitivity towards model solutions of biogenic amines (ammonia, dimethylamine, trimethylamine, cadaverine and histamine). It has been evidenced that the electroactivity and basic character of amines influences considerably the electrochemical behaviour of the electrodic material.The pattern of responses provided by the array has been successfully used to evaluate fish freshness and to determine the post-mortem period. An increase of the signals associated to biogenic amines and other spoilage products is observed with increasing storage days. Signals provided by classical CPE are better resolved and show better sensor-to-sensor reproducibility than SPE. However, the modification of SPE enables simple mass-production of low-cost and miniaturised sensing units with good sensibility and repeatability. The capability of discrimination demonstrated by Principal Component Analysis (PCA) and the capability of prediction of fish freshness calculated by Partial Least Squares-Discriminant Analysis (PLS-DA) is similar in both cases.     

Alleviation of diabetic nephropathy by zinc oxide nanoparticles in streptozotocin‐induced type 1 diabetes in rats

This study examines the effect of nanoparticles with zinc oxides (ZnONPs) on diabetic nephropathy, which is the primary cause of mortality for diabetic patients with end‐stage renal disease. Diabetes in adult male rats was induced via intraperitoneal injection of streptozotocin. ZnONPs were intraperitoneally administered to diabetic rats daily for 7 weeks. Diabetes was associated with increases in blood glucose level, 24‐h urinary albumin excretion rate, glomerular basement membrane thickness, renal oxidative stress markers, and renal mRNA or protein expression of transforming growth factor‐β1, fibronectin, collagen‐IV, tumour necrosis factor‐α and vascular endothelial growth factor‐A. Moreover, the expression of nephrin and podocin, and the mRNA expression of matrix metalloproteinase‐9 were decreased in the diabetic group. These changes were not detected in the control group and were significantly prevented by ZnONP treatment. These results provide evidence that ZnONPs ameliorate the renal damage induced in a diabetic rat model of nephropathy through improving renal functionality; inhibiting renal fibrosis, oxidative stress, inflammation and abnormal angiogenesis; and delaying the development of podocyte injury. The present findings may help design the clinical application of ZnONPs for protection against the development of diabetic nephropathy.     

Anomalous thickness increase in crosslinked closed cell polyolefin foams during heat treatments

When crosslinked closed cell polyolefin foams are under a temperature above the melting point of the base polymer, a reduction of their size is expected due to the gas diffusion out of the foam. However, some kinds of crosslinked closed cell polyolefin foams present one direction (thickness direction) in which the foam size increases during the first minutes of the thermal treatment. The thickness of the foams after the thermal treatment can be higher than the thickness of the original foams. An experimental study is presented on the thickness increase, as well as on the changes in the dimensions and the properties of foams with different densities, which were obtained from different foaming processes and made of different base polymers, as a function of the treatment temperature and the treatment time. This investigation sought to discover the physics mechanisms that control the anomalous thickness increase. The experimental results show that the thickness increase of these materials is related to the anisotropic cellular structure of the original foams. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2825–2835, 1999     

Foaming behaviour and cellular structure of LDPE/hectorite nanocomposites

This paper presents the compared analysis of the foaming behaviour and cellular structure of LDPE/hectorite nanocomposites and respective neat LDPE foams. To assess the influence of hectorite on the foaming behaviour and final foam morphology, nanocomposites containing 3 and 7 wt.% of a modified hectorite were first melt-compounded in a twin-screw extruder. Variables such as temperature, pressure and time were optimized to prepare foams in a second stage by a two-step compression-molding process. Crystallinity and crystal structure of the polymer matrix were determined using X-ray scattering (WAXS) and differential scanning calorimetry (DSC). Clay intercalation/exfoliation was analyzed by WAXS and transmission electron microscopy (TEM), with the results indicating that partial exfoliation of the particles was only reached with foaming but not during melt mixing. A quantitative characterization of the cellular structure and morphology of the foamed nanocomposites was done using both scanning (SEM) and transmission electron microscopies. The nanocomposite foams exhibited differences in the crosslinking degree, showing lower gel content values (from 35% of the neat LDPE to as low as 28% for the 7 wt.% hectorite foam), expansion behaviour, cell aspect ratio, with the foamed nanocomposites showing more isometric type of cells, and cell wall texture with regard to the neat LDPE foams. All these differences, analyzed and compared for the three composites, directly affect both the thermal and mechanical responses of the foams and due to that fact are of extreme importance.     

Thermally stimulated depolarization currents in PVDF-α: a dipolar interaction approach toβ andγ transitions

The analyst of the thermally stimulated depolarization current (TSDC) spectrum of the phase of polyvinilide fluoride (PVDF-) by means of the thermal sampling technique permits a series of elementary peaks to b8 obtained. The relaxation associated with and transitions is usually assumed to be due to dipolar motions; however, the relaxation time of these processes when represented as a function of the temperature does not follow an Arrhenius law. The definition of a relaxation time describing the experimental relaxation process requires, in addition to the frequency factor 1/₀ and the activation energyE, a third parameter,q, which we call the interaction parameter. These considerations lead to defining a relaxation time, which accounts for the dipolar interaction during the relaxation. This relaxation time has successfully described thedipo!orrelaxation in other materials. The evolution ofq, obtained from the elementary peaks of the TSDC spectrum of PVDF-, leads to the assignment of three relaxation zones, which are in agreement with those reported by other authors, as being associated with the molecular motion in the different phases of PVDF-.     

Foaming of EVA/starch blends: Characterization of the structure,physical properties,and biodegradability

Foams produced from blends of an ethylene‐vinyl acetate copolymer (EVA) with high VA (vinyl acetate) content (28%) and corn starch have been successfully fabricated using an improved compression molding technique. A detailed characterization of the structure and physical properties has been carried out. The results showed that the corn starch acts as filler for EVA, showing a good compatibility with the polyolefin. Different types of cellular structure (closed, partially interconnected, and fully interconnected) and cell sizes were obtained depending on the relative density and the amount of starch included in the composition. Besides, the addition of starch allows tailoring the physical properties of the composite foams. An increase in the starch content leads to an increase of the density, compressive strength, hardness, and thermal conductivity and a decrease of the elasticity. Finally, biodegradability tests showed how increases the biodegradation with the amount of starch in the foam, which reaches 60% at 100 days for the foam with 70% of starch. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Application of instrumented falling dart impact to the mechanical characterization of thermoplastic foams

The applicability of instrumented falling weight impact techniques in characterizing mechanically thermoplastic foams at relatively high strain rates is presented in this paper. In order to try simulating impact loading of foams against sharp elements, an instrumented dart having a hemispherical headstock was employed in the tests. Failure strength and toughness values were obtained from high-energy impact experiments, and the elastic modulus could be measured from both flexed plate and indentation low-energy impact tests. The results indicate a dependence of the failure strength, toughness, and the elastic modulus on the foam density, the foaming process, and the chemical composition. This influence was found to be similar to that of pure nonfoamed materials and also to that observed from low-rate compression tests. The results also indicate that the indentation low-energy impact tests were more accurate in obtaining right values of the elastic modulus than the flexed plate low-energy impact tests usually used to characterize rigid plastics. The foam indentation observed with this test configuration contributes to obtaining erroneous values of the elastic modulus if only a simple flexural analysis of plates is applied.     

Analysis of the longitudinal acoustic mode (LAM) of poly(3,3-dipropyl oxetane)

Summary The analysis of the Raman low frequencies region of the Poly(3, 3-Dipropyl oxetane) allows to separate the torsional motions from the Longitudinal Acoustic Mode (LAM). Shift frequencies of this last band are observed with different annealing temperatures, which result in an increase of the crystallinity.     

Structure and properties of polypropylene/hydrotalcite nanocomposites

This article presents the study of the modification of the particle/matrix interface region and its effects on the structure and dynamic mechanical behavior of polypropylene (PP)/hydrotalcite nanocomposites prepared by melt extrusion. The interface modification was promoted by combinying the organophillization of the hydrotalcite particles with blending the PP with a maleic anhydride‐grafted‐PP (PP‐g‐MAH) or a maleic anhydride‐grafted‐poly(styrene‐co‐ethylenebutylene‐co‐styrene) (SEBS‐g‐MAH). Sodium dodecyl sulphate was used to promote the organophillization of the hydrotalcite particles. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) showed a partially exfoliated hydrotalcite structure, with an increasing exfoliation being achieved by adding a compatibilizer and organo‐modifying the particles. Values of the Young's modulus (E), storage modulus (E′), maximum tensile strength (σ_max), neck propagation strength (σ_neck), and elongation at break (ε_b) were found to depend both on the nature of the particle matrix interface as well as on the type of compatibilizer. Also, nanocomposites prepared with the organophillized particles showed lower T_g and loss factor values. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers