Search results for "calorimetry"
showing 10 items of 504 documents
Comparative Study of Different Methods for the Prediction of Drug–Polymer Solubility
2015
In this study, a comparison of different methods to predict drug-polymer solubility was carried out on binary systems consisting of five model drugs (paracetamol, chloramphenicol, celecoxib, indomethacin, and felodipine) and polyvinylpyrrolidone/vinyl acetate copolymers (PVP/VA) of different monomer weight ratios. The drug-polymer solubility at 25 °C was predicted using the Flory-Huggins model, from data obtained at elevated temperature using thermal analysis methods based on the recrystallization of a supersaturated amorphous solid dispersion and two variations of the melting point depression method. These predictions were compared with the solubility in the low molecular weight liquid ana…
The impact of whey protein preheating on the properties of emulsion gel bead
2014
Thermal treatment effect (70 or 80 °C for 5 or 30 min) was evaluated on functional properties of whey protein isolate (WPI) dispersions used for the development of novel vitamin A delivery systems based on emulsion gel beads. This process combines an (O/W) emulsion diluted by a polysaccharide solution and a cold-set gelation induced by salt addition. Pre-heated WPI had a significant impact on the denaturation degree and on the surface hydrophobicity, respectively studied by differential scanning calorimetry and fluorescence. Stronger heating conditions (i.e. duration or temperature) induced complete denaturation, an increase of surface hydrophobicity and of viscosity. Under these conditions…
Liquid and vapour water transfer through whey protein/lipid emulsion films
2010
BACKGROUND: Edible films and coatings based on protein/lipid combinations are among the new products being developed in order to reduce the use of plastic packaging polymers for food applications. This study was conducted to determine the effect of rapeseed oil on selected physicochemical properties of cast whey protein films. RESULTS: Films were cast from heated (80 °C for 30 min) aqueous solutions of whey protein isolate (WPI, 100 g kg−1 of water) containing glycerol (50 g kg−1 of WPI) as a plasticiser and different levels of added rapeseed oil (0, 1, 2, 3 and 4% w/w of WPI). Measurements of film microstructure, laser light-scattering granulometry, differential scanning calorimetry, wetti…
Determination of water intrusion heat in hydrophobic microporous materials by high pressure calorimetry
2010
International audience; The understanding of interactions between a solid surface and a non-wetting liquid still remains of fundamental interest in numerous research fields, from chemistry to biology. This work focuses on the mechanisms of water intrusion in hydrophobic microporous materials through the thermal analysis of the phenomenon. A specific calorimetric technique coupled to high pressure equipment has been developed to investigate equilibrium thermal effects in such thermodynamic systems from 0 to 400 MPa under isothermal conditions. First validation tests of this method were carried out by compressing degassed water in a constant volume V with successive small pressure increments …
Microporous volume and external surface of Y zeolites accessible to p-xylene and m-xylene
1997
Abstract Isothermal adsorption of p-xylene and m-xylene on NaY, KY and BaY zeolites was studied by thermogravimetry at 25°C. Adsorption isotherms showed type H4 hysteresis associated with a xylenes adsorption process activated by the pressure. Experimental data were analysed with the t-method to distinguish the amounts of xylene adsorbed in the α-cages and on the external surface of crystallites. Results were compared with those previously achieved by calorimetry. Whatever may be the isomer and the Y zeolite, the adsorption capacity of α-cages at 25 °C is equal to 3.5 molecule α−1. At saturation, the amount of xylenes adsorbed on the external surface represents 13% of the total amount adsor…
Rapid odorant release in mammalian odour binding proteins facilitates their temporal coupling to odorant signals.
2010
; We have measured the effect of rat odorant-binding protein 1 on the rates of ligand uptake and liquid-to-air transfer rates with a set of defined odorous compounds. Comparison of observed rate constants (k(obs)) with data simulated over a wide range of different kinetic and thermodynamic regimes shows that the data do not agree with the previously held view of a slow off-rate regime (k(off) <0.0004 s(-1)). We propose that a rapid koff would be a necessary requirement for such a system, since slow odorant-release rates would result in significant decorrelation between the olfactory world and odour perception. (c) 2010 Elsevier Ltd. All rights reserved.
Alkylated Aromatic Thioethers with Aggregation‐Induced Emission Properties—Assembly and Photophysics
2019
In this contribution, we present the synthesis and self-assembly of alkylated thioethers with interesting photophysical properties. To this end, the emission, absorption and excitation spectra in organic solvents and as aggregates in water were measured as well as the corresponding photoluminescence quantum yields and lifetimes. The aggregates in aqueous media were visualized and measured using transmission electron microscopy. Besides that, crystal structures of selected compounds allowed a detailed discussion of the structure–property relationship. Furthermore, the mesomorphic behavior was investigated using polarized optical microscopy (POM) as well as differential scanning calorimetry (…
The complementary structural studies of the double metal cyanide type catalysts for the ring opening polymerization of the oxiranes
2016
Przeprowadzono badania strukturalne katalizatorów dimetalocyjankowych (DMC) z dwoma rodzajami ligandów organicznych. Zaproponowano wyjaśnienie etapów przebiegu krzywych otrzymanych metodą analizy termograwimetrycznej i różnicowej kalorymetrii skaningowej (TG/DSC) badanych katalizatorów. Wykazano obecność kilku stopni związania ligandów w kompleksach DMC. Na podstawie wyników badań z wykorzystaniem absorpcji rentgenowskiej (XAS) stwierdzono, że centrum aktywne katalizatora stanowi atom cynku. W bezpośrednim sąsiedztwie atomów Zn wykryto obecność atomów Cl, natomiast w najbliższych sferach koordynacyjnych atomu Zn nie wykryto atomów tlenu.
Protein and glycerol contents affect physico-chemical properties of soy protein isolate-based edible films
2010
Abstract This study was conducted to determine the effect of both soy protein and glycerol contents on physico-chemical properties of soy protein isolate-based edible (SPI) films. The aim of this study was to better understand the influence of SPI and GLY contents on the behavior of the physico-chemical properties of soy protein isolate-based films. Films were casted from heated (70 °C for 20 min) alkaline (pH 10) aqueous solutions of SPI at 6, 7, 8, and 9 (w/w %), glycerol (50%, w/w, of SPI) and SPI at 7 (w/w %), glycerol (40, 60, 70 %, w/w of SPI). Water vapor permeability (WVP), was measured at 25 °C and for four different relative humidities (30–100%, 30–84%, 30–75%, 30–53%). Surface pr…
A contribution to the study of staling of white bread: effect of water and hydrocolloid
1996
Abstract Staling of white bread at ambient temperature was studied using differential scanning calorimetry and dynamic mechanical thermal analysis. During storage, sample hydration varied slightly, from 0 to 0.4% per day, depending on packaging conditions. An increase in rigidity was observed, which was attributed both to starch retrogradation and to changes in the organization of the amorphous part of crumb. The glass transition temperature of crumb was not significantly modified by these structural changes. Hydrocolloids did not affect the overall shape of the viscoelastic behavior of crumb in the temperature range from −40°C to 80°C, and had a limited influence on the kinetics of starch …