The impact of the concentration of casein micelles and whey protein-stabilized fat globules on the rennet-induced gelation of milk

The rennet-induced aggregation of skim milk recombined with whey protein-stabilized emulsion droplets was studied using diffusing wave spectroscopy (DSW) and small deformation rheology. The effect of different volume fractions of casein micelles and fat globules was investigated by observing changes in turbidity (1/l*), apparent radius, elastic modulus and mean square displacement (MSD), in addition to confocal imaging of the gels.Skim milk containing different concentration of casein micelles showed comparable light-scattering profiles; a higher volume fraction of caseins led to the development of more elastic gels.By following the development of 1/l* in recombined milks, it was possible to describe the behaviour of the fat globules during the initial stages of rennet coagulation. Increasing the volume fraction of fat globules showed a significant increase in gel elasticity, caused by flocculation of the oil droplets. The presence of flocculated oil globules within the gel structure was confirmed by confocal microscopy observations. Moreover, a lower degree of κ-casein hydrolysis was needed to initiate casein micelles aggregation in milk containing whey protein-stabilized oil droplets compared to skim milk.This study for the first time clearly describes the impact of a mixture of casein micelles and whey protein-stabilized fat globules on the pre-gelation stages of rennet coagulation, and further highlights the importance of the flocculation state of the emulsion droplets in affecting the structure formation of the gel.     

Lagrangians adapted to submersions and foliations

Lagrangians related to submersions and foliations, which are analogous to Riemannian submersions and Riemannian foliations respectively are studied in the paper. One prove that a bundle-like Lagrangian, a transverse hyperregular Lagrangian, a hyperregular Lagrangian foliated cocycle or a geodesic orthogonal property are equivalent data for a foliation. A conjecture of E. Ghys is proved in a more general setting than that of Finslerian foliations: a foliation that has a transverse positively definite Lagrangian is a Riemannian foliation. One extend also a result of Miernowski and Mozgawa on Finslerian foliations, proving that the natural lift to the normal bundle of a Lagrangian foliation that has a transverse positively definite Lagrangian is a Riemannian foliation.     

Improved tuning and calibration in liquid chromatography/thermospray mass spectrometry using acetic acid cluster ions

Tuning and calibration of a thermospray ion source can cause rapid contamination of the source, and can have the disadvantage of introducing substances or solvents that are not used in the subsequent analytical work on the mass spectrometer. The use of aqueous 0.05 M ammonium acetate alone to produce acetic acid clusters for calibration in the mass range up to m/z 800 is reported. A low temperature of the vaporizer and the source block is used in order to maintain the clusters formed. The low temperature makes possible a very good signal-to-noise ratio, since the only ions formed are clusters of the general formula [(CH₃COOH)_m(NH₃)_n(H₂O)_pNH₄]⁺. Owing to the use of the ammonium acetate mobile phase, no interference from other sources was observed, e.g. clusters of solvents with ammonium acetate or impurities.     

Determination of cadmium in urine specimens by graphite furnace atomic absorption spectrometry using a fast atomization program

A simple, fast, and reliable method was developed for the determination of cadmium in urine specimens by graphite furnace atomic absorption spectrometry (GFAAS). The method involved dilution (1:1) of the specimens with a 4.0% HNO₃, direct injection of a 10 μl aliquot of the corresponding solution into a hot transversely-heated graphite atomizer (110 °C), and application of a fast atomization program (42 s) in which the conventional dry-pyrolysis sequence was substituted by a high-temperature (300 °C) drying step. The effect of the injection temperature (A), injection rate (B), pyrolysis’ ramp (C) and hold (D) times over the analyte’s integrated absorbance, peak-shape and repeatability of the measurements was evaluated by means of a 2^4-1 fractional factorial design. All those individual variables, as well as their first-order interactions (AB-, AC- and AD-type interactions) were found to exert a statistically significant effect (P<0.05). The lack of a chemical modifier other than the nitric acid itself benefited the overall methodology by allowing low-temperature atomization (1200 °C), enhanced atomic and background signals separation, and reduced blank values. A detection limit (3s, n=20) of 0.06 μg l⁻¹ Cd, corresponding to 0.12 μg l⁻¹ Cd in the urine specimen, and a characteristic mass of 1.78 pg/0.0044 s were obtained under the optimized conditions. The standard calibration technique (SCT) was used for quantitation. The successful determination of cadmium in Seronorm™ Trace Elements Urine Batch No. 115 (Nycomed Pharma AS) and in four urine specimens from volunteer donors (recoveries: 91.3-103.4%) attested to the robustness of the proposed method.     

Affine Hamiltonians in Higher Order Geometry

Affine Hamiltonians are defined in the paper and their study is based especially on the fact that in the hyperregular case they are dual objects of Lagrangians defined on affine bundles, by mean of natural Legendre maps. The variational problems for affine Hamiltonians and Lagrangians of order k≥2 are studied, relating them to a Hamilton equation. An Ostrogradski type theorem is proved: the Hamilton equation of an affine Hamiltonian h is equivalent with Euler–Lagrange equation of its dual Lagrangian L. Zermelo condition is also studied and some non-trivial examples are given. The authors were partially supported by the CNCSIS grant A No. 81/2005.     

Liquid crystal biomimetic nanosystems loaded with vegetal extracts

Abstract

This article is aimed to design new antioxidant phyto-nanosystems based on liposomes and vegetal extracts of sage (Salvia officinalis L.) and mint (Mentha piperita L.). The lipid vesicles were obtained by thin film hydration method, and vegetal extracts of sage or mint were incorporated both in hydrophobic and in aqueous compartments of these lipid systems. The obtained phyto-containing liposomes were characterized by UV–Vis absorption and dynamic light scattering (DLS) measurements, and their antioxidant activity was assessed through chemiluminescence technique. The obtained artificial lipid bilayers loaded with phyto-extracts exhibited impressive antioxidant properties.     

Nitrogen assay in winter wheat by short-time instrumental photon activation analysis and its comparison with the Kjeldahl method

The nitrogen content in winter wheat from various crops grown organically or conventionally was determined by instrumental photon activation analysis. The method utilizes measurement of the annihilation gamma line at 511 keV from the short-lived photoactivation product ¹³N, corrected for interference contributions from other positron emitting nuclides. Results compared well to those obtained by the Kjeldahl method. A positive impact of conventional agriculture on higher crude protein content in grain was found. Analysis of whole kernels and their germination and growth after irradiation were also tested.

     

Novel anion receptors based on thiacalix[4]arene derivatives

Starting from the thiacalix[4]arene tetraacetate, novel derivatives bearing four ureido or thioureido functions on the lower rim have been prepared. As proven by NMR titrations, these compounds can bind anions via hydrogen bonding interactions and represent the first example of anion receptors in the thiacalixarene series.     

Determination of organotin compounds in environmental samples by supercritical fluid extraction and gas chromatography with atomic emission detection

The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n-pentylmagnesium bromide prior to gas chromatographic analysis). A 2³ factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride.