Thermal Relaxation of Gelatin and Date Flesh Measured by Isothermal Condition in Differential Scanning Calorimetry (DSC) and its Relation to the Structural and Mechanical Glass Transition

Abstract

A new innovative method was developed to measure the thermal-relaxation by maintaining isothermal condition in a Differential Scanning Calorimetry (DSC). The DSC thermalrelaxation characteristics of gelatin and date flesh were found to be related with the structural-and mechanical-glass transition measured by conventional DSC linear-heating and thermal-mechanical analysis (i.e, Differential Thermal Mechanical Analysis, DMTA). Initial slope of the thermal relaxation curve (i.e., heat flow versus relaxation time) was determined and it was plotted as a function of relaxation temperature (i.e., isothermal condition). The initial slope-temperature graph showed three thermal relaxation characteristics: limited mobile, freely mobile and restricted mobile regions. The region 1 showed limited molecular mobility with increasing temperature, while region 2 showed free mobility with increasing temperature sensitivity. The intersection of the regions 1 and 2 was related to the structuralglass transition measured by conventional linear-heating in a DSC. The region 3 showed restricted mobility due to enhanced interactions of the phases at higher temperature. This region 3 was related to the entangled flow region measured by thermal-mechanical analysis in a DMTA.

Effect of Spray Drying Conditions on the Physicochemical Properties and Enthalpy Relaxation of α-Lactose

“…Physical aging of various food ingredients have been investigated, including gelatin, [29,30] lactose, [31] sucrose, [32] maltose, [17,24] the mixtures of glucose and fructose [33,34] and starch, [3,35−42] and foods themselves. [20] Other studies have been conducted to examine, explain, and model the enthalpic aging process in polymer glasses.…”

Glass transition of pomegranate skin, as analyzed by thermal, mechanical, and nuclear magnetic resonance methods

“…[3,4] Measurement of glass transition is not straightforward, especially for non-homogeneous complex biomaterials. [5] Thermal analysis, such as differential scanning calorimetry (DSC) is commonly used to measure glass transition, and this technique is most suitable for sugar based and other simple biomaterials. Recent studies showed the difficulty in using DSC for complex biomaterials.…”

“…Recent studies showed the difficulty in using DSC for complex biomaterials. [5,6] In this case modulated DSC and differential mechanical thermal analysis (DMTA) are commonly used. [5,7] DMTA measures the effect of longitudinal and sinusoidal varying stress on dynamic moduli and modulated DSC measures the reversible and non-reversible components of total heat flow.…”

“…[5,6] In this case modulated DSC and differential mechanical thermal analysis (DMTA) are commonly used. [5,7] DMTA measures the effect of longitudinal and sinusoidal varying stress on dynamic moduli and modulated DSC measures the reversible and non-reversible components of total heat flow. In some instances, the glass transition measured by DSC are related with the measured values from DMTA [5,8,9] and time domain nuclear magnetic resonance (TD-NMR) relaxation.…”

“…[5,7] DMTA measures the effect of longitudinal and sinusoidal varying stress on dynamic moduli and modulated DSC measures the reversible and non-reversible components of total heat flow. In some instances, the glass transition measured by DSC are related with the measured values from DMTA [5,8,9] and time domain nuclear magnetic resonance (TD-NMR) relaxation. [6] In order to understand different relaxation processes in the biomaterials, the use of combinations of instruments, such as DMTA and DSC could be necessary.…”