Formation of glucose and fructose acetates during maturation and ageing of balsamic vinegars

We report for the first time the detection of glucose acetates in balsamic vinegars. It is well known that during traditional balsamic vinegar (TBV) ageing several modifications occur. In this paper it was experimentally determined that some modifications take also place during the short maturation time of balsamic vinegar of Modena (BVM), with an increase of the esters content due to the reaction between acetic acid and sugars, in particular glucose. The formation of esters was observed both on reference solutions containing glucose and acetic acid, subjected to an accelerated ageing by heating at 50 °C, and on real balsamic vinegar samples. Glucose esters were mainly detected as α- and β-glucopyranose acetates. The formation of fructose acetates in reference solutions, was also studied, recording a more complex pattern of products. The structures of the esters were determined by GC/MS analyses and NMR spectroscopy.     

Swelling Kinetics of HPMC Tablets

Hydroxypropyl methylcellulose (HPMC) is a cellulosic polymer widely employed in tablets formulation. In contact with biological fluids, it undergoes a glassy–rubbery transition and drug release is strongly influenced by swelling. We study the kinetic parameters of a classical phenomenological model (Astarita and Sarti), which describes the velocity of a glassy–rubbery interface as a function of the local solvent concentration. One-dimensional mass transport equations with moving boundaries are numerically solved by finite elements method in order to fit Astarita–Sarti parameters k and n on experimental swelling fronts and concentration profiles taken from literature for HPMC K4M, HPMC K15M, and HPMC K100M.     

Drying kinetics of cork planks in a cork pile in the field

Moisture content is one important parameter in the trading of raw cork planks after harvesting. This study presents a mathematical modeling of the drying curve of raw cork planks in a cork pile in the field, under natural sun drying conditions. Experimental data were obtained by following the water loss (i.e. by daily weighing) of 97 cork planks positioned in nine points within a cork pile. Immediately after harvesting, the raw cork planks had a mean moisture content in a dry basis of 40.4% and after 20-day drying 16.6%. The drying process of the cork planks showed three phases: drying was very fast in the first 2 days; in the next 2–15 days there was a decreasing drying rate; and a final phase, after 15 days in the cork pile, with a slightly decreasing drying rate. Mathematical modeling provided a direct relation between moisture content and drying time. After comparing sixteen empirical drying models, the Modified Henderson and Pabis model showed the best fit. According to this model, the cork planks are commercial dry (14% moisture content in a wet basis) 15 days after harvest.     

Determination of aloe emodin in Aloe vera extracts and commercial formulations by HPLC with tandem UV absorption and fluorescence detection

Aloe emodin is an anthraquinone compound found in Aloe vera and other species of the Asphodelaceae and the Polygonaceae families, which has recently attracted much attention as a prospective antineoplastic agent. A HPLC method with tandem UV absorption and fluorimetric detection, was developed and validated for the analysis of aloe emodin in products obtained from Aloe leaves, such as capsules, tablets, dried extracts and mother tinctures. The stationary phase was a C18 reversed-phase column and the mobile phase was composed of water and methanol (30/70, v/v). Satisfactory linearity was obtained over the 10.0–1000.0 ng/mL range for photodiode array detection (limit of detection: 3 ng/mL) and over the 2.5–1000.0 ng/mL range for fluorimetric detection (limit of detection: 0.8 ng/mL). Aloe emodin levels were determined in A. vera extracts and commercial formulations by both detection means, with good precision (R.S.D. < 9%) and accuracy (recovery > 85%) and consistent results. Thus, the method seems to be suitable for the analysis of aloe emodin in different herbal and commercial products; it could also be useful for the identity confirmation of formulations and extracts.     

Sensitivity analysis of flexible multibody systems using composite materials components

In this paper, a general formulation for the computation of the first‐order analytical sensitivities based on the direct method using automatic differentiation of flexible multibody systems is presented. The direct method for sensitivity calculation is obtained by differentiating the equations that define the response of the flexible multibody systems of composite materials with respect to the design variables, which are the ply orientations of the laminated. In order to appraise the benefits of the approach suggested and to highlight the risks of the procedure, the analytical sensitivities are compared with the numerical results obtained by using the finite difference method. For the beam composite material elements, the section properties and their sensitivities are found using an asymptotic procedure that involves a two‐dimensional (2‐D) finite element analysis of their cross section. The equations of the sensitivities are obtained by automatic differentiation and integrated in time simultaneously with the equations of motion of the multibody systems. The equations of motion and the sensitivities of the flexible multibody system are solved and the accelerations, velocities and the sensitivities of accelerations and velocities are integrated in time using a multi‐step multi‐order integration algorithm. Through the application of the methodology to two simple flexible multibody systems the difficulties and benefits of the procedure, with respect to finite difference approaches or to the direct implementation of the analytic sensitivities, are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Characterization of creep and creep damage by in-situ microtomography

Application of in-situ microtomography to characterization of power law creep and creep damage in structural materials is presented. It is shown first that the successively reconstructed volumes are adequately monitoring the macroscopic sample shape and that microtomography is an optimal tool to characterize inhomogeneous specimen deformation. Based on a two-step image correlation technique the evolution of single voids is revealed and the basis of a pioneering approach to creep damage studies is presented. The method allows the unequivocal separation of three concurrent damage mechanisms: nucleation, growth, and coalescence of voids. The results indicate that growth rate of voids with equivalent diameters in the range of 2–5 mm is of about one order of magnitude higher than the prediction of continuum solid mechanics. Analysis of void coalescence points out the presence of two stable growth regimes related to coalescence between primary and secondary voids, respectively.     

Sustainable Process for Production of Azelaic Acid Through Oxidative Cleavage of Oleic Acid

This work describes two sustainable methods for production and purification of azelaic acid (AA) to replace the current process of ozonolysis of oleic acid (OA). The first proceeds in two steps, coupling smooth oxidation of OA to 9,10‐dihydroxystearic acid (DSA) with subsequent oxidative cleavage by sodium hypochlorite. An alternative methodology is also proposed, using a chemocatalytic system consisting of H₂O₂/H₂WO₄ for direct oxidative cleavage of the double bond of OA at 373 K. A convenient technique for separation and purification of azelaic acid is also proposed.     

The species-specific ratios of 2,3-butanediol and acetoin isomers as a tool to evaluate wine yeast performance

The isomers of 2,3-butanediol [R,R; S,S; R,S (meso-form)] and of acetoin (R,S) were determined in laboratory wine fermentations carried out by 50 yeast strains, 10 for each of the following species, Saccharomyces cerevisiae, Kloeckera apiculata, Candida stellata, Metschnikowia pulcherrima and Brettanomyces bruxellensis, in order to evaluate if such parameters might be used to differentiate wines obtained with different yeast species. According to analysis of variance (ANOVA), the strains of the same species behaved similarly, whereas the five yeast species behaved differently so that species-specific profiles were recognized. Moreover, the discriminant analysis grouped the wines into five groups, each including the 10 wines obtained by the 10 yeast strains of the same species. Trials were also included where musts partially fermented by non-Saccharomyces species were inoculated with a selected strain of S. cerevisiae to complete fermentation, and the content in 2,3-butanediol and acetoin isomers was again determined and statistical analysis was performed. Although the final values of these parameters resembled those obtained in pure fermentation with S. cerevisiae, statistical analysis discriminated wines according to the yeast species performing the first fermentation phase.