Showing 6 results for Differential Scanning Calorimetry
Volume 1, Issue 1 (12-2017)
Abstract
In this research,nanocomposite coatings based on epoxy containing pristine graphene oxide and starch-modified graphene oxide are prepared and characterized by Fourier transfer infrared spectroscopy, andtheir crosslinking behavior is studied using nonisothermal differential scanning calorimetry.These nanocomposites, because of having platelet-like nanomaterials inside and their organic origin, can be applied as coating on metal surface in diverse industries.The reason behind using starch was its natural basis and abundance of hydroxyl groups in its structure which can take part in crosslinking reaction with epoxide. Neat epoxy systems having amine curing agent, and nanocomposites containing epoxy, amine curing agent, andpristine or starch-modified graphene oxide nanosheets were cure at different heating rates to assess their curing behavior. Change in hearing rate of test caused change in onset and peak temperature of the exotherm curves and consequently heat of reaction changed. It was observed that the presence of the graphene oxide nanosheets hindered the crosslinking reactions, while surface modification of them with starch natural polymer compensated for such a hindrance via catalytic role of starch, and increased crosslink density of system.
Volume 9, Issue 3 (9-2018)
Abstract
Aims: The probability of establishing electrostatic interactions due to the abundance of charged hydrophilic residues and especially arginine is considered the most important thermal stabilizing factor of thermophilic enzymes. The current study was conducted with the aim of comparing thermodynamic stability and kinetic refolding of Lampyris turkestanicus and some of its mutants.
Materials and Methods: In the present experimental thermal stability and the way of refolding Lampyris turkestanicus and 3 mutations, including ERR, ERR/I232R, ERR/Q35R/I182R/I232R were investigated by various spectroscopic techniques. In order to high expression of proteins, a single clone of each sample was selected and inoculated into 10ml of LB culture medium, containing Kanamycin at a concentration of 50μg/mg and incubated at 37°C with an ideal aeration for 12-15 hours. The culture medium was centrifuged for 5 minutes at 5000g at 4°C to provide the cellular contents of the bacteria. The results were obtained through spectroscopic methods of remote and near circular dichroism, intrinsic fluorescence, differential scanning calorimetry, and kinetics experiments, using fluorescence-stopped flow technique.
Findings: Along with the increase in the number of arginine residues at the protein level, the stability and structural compression of the mutated enzymes in comparison with the wild enzyme were increased and the thermograms obtained from differential scanning calorimetry showed a slight increase in Tm and calorimetric enthalpy of mutated proteins in comparison with wild protein.
Conclusion: The rate constant of refolding mutated enzymes has increased compared with the wild type. The improvement of thermodynamic and kinetic parameters results from the improvement of electrostatic interactions, which results in a higher degree of compression and structural density.
Volume 13, Issue 55 (9-2015)
Abstract
Food adulteration is done in various forms. The most common adulteration in sesame oil is done with adding by sunflower oil, corn oil and hazelnut oil. This study examines the pure sesame oil using Differential Scanning Calorimetry (DSC) analysis deals. Samples of pure sesame oil, 5%, 10% and 15% corn oil and sunflower oil was mixed with sesame oil. With the increase of corn oil and sunflower oil, sesame oil, peak displaced towards lower temperatures and the temperatures start, maximum and end of both large and small melting peak was reduced. According to the triglycerides of saturated fatty acids at higher temperatures than triglycerides with unsaturated fatty acids are melted. The peak shift toward lower temperatures can be increased by addition of unsaturated lipid components of corn and sunflower oils.
A. Sankhon, I. Amadou, W. Yao, H. Wang, H. Qian, E. Mlyuka,
Volume 16, Issue 2 (3-2014)
Abstract
Parkia biglobosa starch was subjected to different heat-moisture treatment (HMT) at different moisture contents (15, 20, 25, and 30%) at 110oC for 16 hours. The content of resistant starch (RS) was the lowest (33.38%) in the untreated native Parkia and increased in the samples with HMT-15 (37.79%), HMT-30 (39.64%), HMT-25 (46.63%), and HMT-20 (50.14%), showing significant increase (P < 0.05) in RS following the HMT. There was a reduction in the swelling power and pasting properties of HMT starches, but the solubility of the HMT starches was higher than that of untreated native starch. Differential scanning calorimetry and the changes in the X-ray diffraction (XRD) patterns confirmed the effect of HMT on Parkia starch. Therefore, replacing native Parkia with heat-moisture treated Parkia starch leads to the development of new products from RS-rich powder with high RS levels and functional properties.
F. Baghdadi, M. Aminifar, M. Farhoodi, S. Shojaee,
Volume 20, Issue 4 (10-2018)
Abstract
Poor organoleptic and physicalproperties of Low Fat Cheese (LFC) suggest the use of some hydrocolloids in its production. In this study, the effect of addition of Basil Seed Gum (BSG (into the structure of low-fat white brined cheese was investigated. To obtain a good view about the protein and polysaccharide interactions in cheese, Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared (FTIR) spectroscopy were also used. The results indicated that the incorporation of BSG into the cheese matrix and the creation of new interactions caused some changes in the cheese properties. There was considerable slump in the hardness value of the cheese samples containing BSG throughout ripening. The addition of BSG in the cheese matrix weakened its microstructure due to a decrease in the electrostatic attraction between the macromolecules, which was mainly a result of high salt concentration. Thermal properties and FTIR spectra of cheese samples were altered with polysaccharide incorporation as well as the ripening period.
B. Abbastabar, M. H. Azizi, S. R. Nabavi,
Volume 22, Issue 3 (4-2020)
Abstract
In this research, the potential of the electrospraying technique was used for encapsulation of curcumin in natural polymers such as Whey Protein Isolate (WPI) and mixture of WPI/β-CycloDextrin (β-CD). The encapsulated particles were physicochemically characterized and curcumin release profile was evaluated. At WPI concentration of 25%, more uniform particles were formed and most of them were smaller than 0.7 µm in diameter. The encapsulation efficiency of curcumin in WPI and WPI/β-CD solutions was determined as 45.4% and 53.6%, respectively. Differential Scanning Calorimetry (DSC) and ThermoGravimetric Analysis (TGA) of the obtained encapsulated curcumin revealed that WPI and WPI/β-CD polymers could not increase thermal stability of curcumin. Encapsulated curcumin had a better stability than pure curcumin at acidic and alkaline conditions, and the release of curcumin after 7 hours was lower than 40% with the sustained mode in buffer solution conditions (pH= 7.4).
