Quantitative determination of volatile organic compounds (VOC) in milk by multiple dynamic headspace extraction and GC-MS

A method for the accurate determination of volatile organic compounds (VOC) in milk samples has been developed and tested. It combines multiple dynamic headspace extraction with GC-MS. Absolute amounts of VOC in the liquid phase are obtained by determining the first order kinetic dependence of the stepwise extraction of the analytes and internal standards from the liquid matrix. Compounds released from milk were collected on a train of traps filled with different solid sorbents to cover all components having a number of carbon atoms ranging from 4 to 15. They were analysed by GC-MS after thermal desorption of VOC from the collecting traps. Quantification of VOC in milk was performed using deuterated compounds as internal standards. The method was used to follow seasonal variations of monoterpenes in goat milk and to detect the impact of air pollution on the quality of milk.     

Guidelines for buckwheat enriched bread

Thermal analysis was used to check the role of the main components of buckwheat flour (polysaccharides and proteins) to assess guidelines for novel recipes for bread from wheat and buckwheat flour blends with improved nutritional properties. The structure-related poor protein quality, namely, the lack of network-forming links, severely limits the use of buckwheat flours in bread-making. Data from TG and DSC analysis indicate that the introduction of a de-hulling step in the buckwheat milling diagram and the addition of some buckwheat polysaccharide fractions, isolated from the buckwheat husk, that contribute to the formation of the crumb structure thanks to their effect on the phase separation driven by the thermodynamic incompatibility with wheat gluten proteins, allows one to tune opposite effects and obtain bread from de-hulled buckweat/wheat flour blends with alveolar distribution much close that of the wheat bread.     

Thermal analysis on parchments I: DSC and TGA combined approach for heat damage assessment

Ancient, new and artificially aged parchments were investigated with both differential scanning calorimetry (DSC) and thermogravimetry (TGA). Criteria to define a quantitative ranking of the damage experienced by the bulk collagen of historical parchments were assessed. A damage-related correlation was found between the collagen denaturation temperature and the moisture content of the parchment. Qualitative rules for the evaluation of the damage at the nano-and mesoscopic level were achieved on the basis of peculiarities of the shape and width of the DSC signals and confirmed by small angle X-ray scattering patterns.     

New limit on the lepton-flavor-violating decay μ+→e+γ

We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton-flavor-violating decay μ(+)e(+)γ. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the μ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.     

Interaction induced light scattering in orientationally disordered crystals: the translational phonon region

We have derived an expression for the light scattering spectrum of a crystal in which the mechanically regular sites are occupied by point polarizable orientationally disordered molecules when the polarizabilities are assumed to depend on the positions of the surrounding atoms (interaction induced polarizability fluctuations).

Owing to the ‘electrical’ disorder properties of the system all phonons can contribute to the anisotropic scattering measured in all polarization configuration with wavevector, branch index and polarization dependent coefficients. Assuming short range interaction induced polarizabilities we show that the temperature reduced intensity I(ω)/[n(ω) + 1] is given by a superposition of the Brillouin zone centre symmetry ‘projected’ density of states with polarization dependent coefficients. These coefficients are found to be essentially frequency independent for all the projections, exception made for those corresponding to the acoustic phonons. For the acoustic branches the coefficients vanish in a first approximation. They can however be treated on more rigorous grounds and, as already found by other authors, their contribution is proportional to the density of states multiplied by ω².

In addition zone centre (k?0) totally symmetric phonons can also be present in the ‘isotropic’ term (which appears only in the polarized VV configuration).

A procedure is suggested to obtain the total density of states from the spectra measured in different polarization configurations.     

Isothermal calorimetry protocols to monitor the shelf life and aftermarket follow-up of fresh cut vegetables

Journal of Thermal Analysis and Calorimetry - Protocols and guidelines were assessed in order to apply isothermal calorimetry as a complementary/alternative method to monitoring, during the shelf...     

Study of a drawing-quality sheet steel. II: Forming-limit curves by experiments and micromechanical simulations

In Part I of the current paper, we showed the results of uniaxial-tension tests, through-thickness and plane-strain compression experiments, quantitative texture – orientation distribution function – evaluations and Lankford coefficient measurements. These data were used for calibration and verification of a visco-plastic self-consistent (VPSC) polycrystal-plasticity simulation code for predicting a steel sheet’s ability to be stretched and deep drawn. Lankford coefficients are one, although incomplete, measure of a steel’s drawing quality. In order to obtain a deeper insight and better verification of the simulation code, we measured the forming-limit curve, FLC, for the same steel sheet. To make these measurements we stretched circle-gridded sheets of material with a punch and die. Samples had both a flat-sided and hourglass geometry and ranged from 20 to 80 mm in width. The 80 mm wide sample completely filled the die. With this range of sample sizes, we spanned all of the stress states applicable to a FLC, from uniaxial to biaxial tension. Our FLC curve had the classic “V” shape typical of drawing-quality steel, with a minimum safe forming strain of about 0.35 in plane-strain deformation and a safe forming strain of nearly 0.45 in balanced biaxial stretching. To model the FLC behavior, we used the same VPSC model and calibration employed in Part I. In order to obtain a necking instability in the calculation, a Marciniak defect was implemented into the VPSC model. The severity of the defect was adjusted to match the measured instability strain, 0.35, in plane-strain deformation. Both hardening laws fit in Part I were used to calculate the FLC. In the positive biaxial quadrant of the FLC, the limit strains predicted by the power law closely follow the measured uniform deformations, while the saturation law appears to over predict the limit strains. In uniaxial-tension, it was the opposite. The power-law hardening predictions seemed excessive. However, if we consider the FLC curve to be a band of finite width, both hardening laws and the VPSC formulation capture the essence of the FLC data.