The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Paul Ainsworth - One of the best experts on this subject based on the ideXlab platform.
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Preparation of modified fats from vegetable oil and fully hydrogenated vegetable oil by randomization with alkali catalysts
Food Chemistry, 1996Co-Authors: Štefan Schmidt, Silvia Hurtová, Jaroslav Zemanovic, Stanislav Sekretár, Peter Šimon, Paul AinsworthAbstract:Randomization of fat blends, formulated by mixing vegetable oil with fully hydrogenated vegetable oil in various ratios, using alkali catalysts, have been investigated. The relationship between the structure and physical properties was examined. The fatty acid and triacylglycerol composition of each original fat blend and the randomization products together with the physical properties such as melting, crystallization characteristics and solid fat content were correlated. The differences in the exothermic and Endothermic Peak temperatures, melting points and solid fat content among the fat blends showed the effects of the composition on the physical properties.
Keiji Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Thermal behavior of ursodeoxycholic acid in urea: identification of anomalous Peak in the thermal analysis.
Drug development and industrial pharmacy, 2001Co-Authors: Siriporn Okonogi, Satit Puttipipatkhachorn, Keiji YamamotoAbstract:The objective of this study was to clarify the thermal behavior of ursodeoxycholic acid (UDCA) in mixtures with urea. Physical mixtures of UDCA and urea in various ratios were prepared, and the thermal analysis of these sample mixtures was investigated using conventional differential scanning calorimetry (DSC) and variable-temperature powder X-ray diffractometry (VTXRD). The hot-stage microscopy (HSM) and powder X-ray diffractometry (PXRD) were used as complementary techniques. From the DSC results of all sample mixtures, it was found that there was no Endothermic Peak at the melting temperature of intact UDCA crystals. The DSC thermograms of each ratio showed only the Endothermic Peak at about 136°C due to the melt of urea and the anomalous Endothermic Peak at about 155°C–157°C. The VTXRD study revealed that the crystals of urea completely disappeared at a temperature of 140°C. At this temperature, it was identified that the VTXRD pattern obtained was of UDCA crystals. The crystalline Peaks gradually dec...
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Thermal Behavior of Methyl p-hydroxybenzoate in Controlled-Pore Glass Solid Dispersion
Journal of Colloid and Interface Science, 1995Co-Authors: Etsuo Yonemochi, Masazumi Kojima, Akiko Nakatsuji, Siriporn Okonogi, Toshio Oguchi, Yoshinobu Nakai, Keiji YamamotoAbstract:Abstract Physicochemical properties of methyl p-hydroxybenzoate (MPHB) in a mixture with controlled-pore glass of 120 A (CPG120) were investigated by differential scanning calorimetry (DSC), powder X-ray diffraction measurement, and IR spectroscopy. In the DSC thermogram of a mixture of 40% MPHB and 60% CPG120, a broad Endothermic Peak (108-112°C) and a sharp Endothermic Peak due to the fusion of MPHB were observed. In the following DSC run, the temperature of the Endothermic Peak (108-112°C) was shifted to a lower temperature (80-100°C). The effects of grinding and atmospheric gas pressure on the DSC thermograms were also studied. Increase of the grinding time caused a decrease in the DSC Peak area of fusion, and the adsorption of MPHB into the CPG pores was enhanced with grinding. The Peak at 108-112°C moved to higher temperatures in the condition of increased gas pressure. In the second DSC run, the temperature of the Endothermic Peak depended upon the pore size of the mixed CPG. These results indicated that MPHB in the mixture adsorbed into the pores of the CPG during the first DSC run and that the adsorbed and crystallized MPHB fused in the pores in the second run.
A.m. Abdel-rehim - One of the best experts on this subject based on the ideXlab platform.
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Thermal analysis of topaz synthesis from kaolinite
Thermochimica Acta, 1999Co-Authors: A.m. Abdel-rehimAbstract:Abstract The present work represents a thermal analysis study of topaz synthesis from kaolinite by its sintering with aluminium fluoride using a derivatograph. Also, it includes the study of the influence of aluminium fluoride on the thermal behaviour of kaolinite. The products of sintering were identified microscopically and by using a Siemens Crystalloflex diffractometer. The DTA and X-ray powder diffraction data show the beginning of the appearance of both topaz and mullite at 600°C and indicate that the reaction of kaolinite and aluminium fluoride of different amounts takes place in two distinct steps. The first is marked by a medium Endothermic Peak at 750–790°C, representing the intensive formation of topaz, and the second by a large and sharp or wide Endothermic Peak at 930–950°C, representing its subsequent dissociation with the formation of either mullite or (corundum and mullite) or corundum, depending on the amount of aluminium fluoride. This process is accompanied by a sharp decrease in weight, (TG curve), due to the volatilization of silicon tetrafluoride, water vapour and other gases. The synthesized topaz is colourless in thin sections and crystallizes in orthorhombic system in the form of elongated prismatic crystals, with perfect basal (0 0 1) cleavage; it is optically positive.
Katsuyoshi Nishinari - One of the best experts on this subject based on the ideXlab platform.
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Thermal measurements of curdlan in aqueous suspension during gelation
Food Hydrocolloids, 2000Co-Authors: H. Zhang, L Huang, Mineo Watase, Katsuyoshi Nishinari, Akira KonnoAbstract:Abstract Differential scanning calorimetry (DSC) measurements of curdlan in aqueous suspension were carried out in a temperature range of 40–200°C by using silver pans with and without heat treatment, respectively. Silver pans with heat treatment were heated at 200°C and then cooled. Heating DSC curves of curdlan in aqueous suspension showed an Endothermic Peak around 60°C and were identical below 120°C, but quite different above 120°C. A large exothermic Peak was observed at 140–190°C in a heating DSC curve when a non-heated pan was used, whereas a small Endothermic Peak was observed at 140–160°C and no exothermic Peak was observed at higher temperatures when a heated pan was used. It was suggested that the large exothermic Peak was attributed to an interaction between the non-heated silver pan and water above 120°C. Only the Endothermic Peak at 140–160°C reflected the reality of the thermal property of curdlan in aqueous suspension, which was caused by the melting of the curdlan gel formed.
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DSC and rheological studies on aqueous dispersions of curdlan
Thermochimica Acta, 1997Co-Authors: Madoka Hirashima, Tomohisa Takaya, Katsuyoshi NishinariAbstract:Abstract Differential scanning calorimetry (DSC) and dynamic viscoelastic measurements of aqueous dispersions of curdlan were performed to clarify the gelation mechanism. Second run DSC heating curves for aqueous dispersions of curdlan showed a single Endothermic Peak for dispersions heated to temperatures lower than 53°C, and splits into two Peaks for dispersions heated to temperatures higher than 53°C, indicating that the structural disorders of at least two different energies are involved. Dispersions heated at temperatures higher than 120°C did not show any Endothermic Peak in the second run DSC heating curves indicating that structures formed at temperatures higher than 120°C are stable and thermo-irreversible. Mechanical spectra of the aqueous dispersions of curdlan showed solid-like behaviour both at 40 and 70°C although the mechanical loss tangent for the dispersion heated to a higher temperature was much smaller. All these results are consistent with previous findings that gels formed at higher temperatures are thermo-irreversible, and that gels formed at lower temperatures are thermo-reversible.
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Effects of salts on the gel-sol transition of gellan gum by differential scanning calorimetry and thermal scanning rheology☆
Thermochimica Acta, 1995Co-Authors: Emako Miyoshi, Tomohisa Takaya, Katsuyoshi NishinariAbstract:Abstract The rheological and thermal properties of sodium form gellan gum solutions with and without sodium chloride, potassium chloride, calcium chloride and magnesium chloride were studied by dynamic viscoelastic measurement and differential scanning calorimetry. Temperature dependence of the loss modulus for gellan gum solutions of lower concentrations without salt showed a one step-like change at a certain temperature, however that for concentrated gellan gum solutions (>2.0%) showed two step-like changes. The higher temperature process Thc may be attributed to the helix-coil transition and found in between the exothermic and Endothermic Peak temperatures Ts and Tm observed in cooling and heating DSC curves, while the lower temperature process Tsg may be attributed to the sol-gel transition. Temperature dependence for gellan gum solutions of higher concentrations (>3.2%) showed a large hysteresis, moreover, the temperature at which the loss shear modulus G″ showed the second step decrease shifted to higher temperatures with increasing concentration of gellan gum. The cooling or heating DSC curves for gellan gum solutions of lower concentrations showed a single exothermic or Endothermic Peak, and both exothermic Peak temperature Ts and Endothermic Peak temperature Tm shifted to higher temperatures, and both exothermic and Endothermic enthalpies increased with increasing concentration of gellan gum. However, for a gellan gum solution of a concentration higher than 3.2%, the Endothermic Peak in the heating DSC curve split into two Peaks, while the cooling curve showed only one Endothermic Peak. The lower temperature Endothermic Peak in the heating DSC curve corresponds with the first step decrease of G″ in the heating process of rheological measurement, and the higher temperature Endothermic Peak corresponds with the second step decrease of G″. The viscoelastic change of gellan gum solutions was more remarkable by the addition of K+ than Na+, and by Ca2+ than by Mg2+. The viscoelastic behavior of gellan gum solutions was influenced much more strongly by divalent cations than by monovalent cations. DSC cooling curves of gellan gum solutions showed a single exothermic Peak shifting to progressively higher temperatures with increasing concentration of monovalent cations. At low concentration of monovalent cations, the DSC heating curves showed a single Endothermic Peak, however, with more progressive addition of salt, the Endothermic Peak gradually developed bimodal character and eventually split into multiple Peaks. With increasing concentration of divalent cations, the exothermic and Endothermic enthalpies estimated for a main Peak increased up to a certain concentration and then decreased. Moreover, the Endothermic Peaks in the presence of sufficient salts were too broad to be resolved from the baseline, and many other Peaks were observed at higher temperatures. Gellan gum solutions with sufficient divalent cations form firm gels on cooling to below the setting temperature, and then it was difficult to remelt them, which was quite different from the behavior of thermoreversible gels formed in the presence of monovalent cations.
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dynamic viscoelastic study on the gelation of 7s globulin from soybeans
Journal of Agricultural and Food Chemistry, 1992Co-Authors: Takao Nagano, Motohiko Hirotsuka, Hiroyuki Mori, Kaoru Kohyama, Katsuyoshi NishinariAbstract:7S globulin was isolated according to a new method from soybeans. Its physicochemical properties were studied by differential scanning calorimetry (DSC) and by dynamic viscoelastic measurements. Heating DSC curves for 7S globulin showed only one Endothermic Peak. Extrapolation of the incipient temperature (T i ) and the Endothermic Peak temperature (T p ) observed at slow heating rates in DSC curves to 0 o C/min led to the result T i0 =64 o C and T p0 =70 o C
Shelly J. Schmidt - One of the best experts on this subject based on the ideXlab platform.
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Comparison of the kinetic behavior of crystalline cane and beet sucrose thermal decomposition
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: Ben Averill, Leonard C. Thomas, Kiran Subedi, Shelly J. SchmidtAbstract:Although crystalline cane and beet sucrose are > 99.8% pure, they exhibit different thermal behavior. In general, the cane sucrose DSC curve contains a small Endothermic Peak before the main Endothermic Peak, which is not present in the beet DSC curve, leading to a lower onset temperature for thermal decomposition in cane. To compare their thermal behavior, the thermal decomposition kinetic parameters for analytical and commercial cane sucrose and commercial beet sucrose were determined. Beet sucrose had a higher activation energy than either cane source, indicating that thermal decomposition is inhibited in beet sucrose. However, the k values from isothermal experiments at a single temperature did not match the nonisothermally predicted k values, suggesting that, while useful for comparison, the nonisothermal kinetic parameters cannot be used to predict the behavior of sucrose thermal decomposition under isothermal conditions.