Abstract:Differential scanning calorimetry is used to obtain specific heats of the α, β′2, β′1 and β phases of trimargarin and tristearin in the temperature range from 190–350 K. Unequal specific heats are observed for β′ phases of the 2 lipids in contrast to nearly coincident values for their respective α and β phases. These results are discussed on the basis of odd vs even chain length triglycerides.
“… 9 Experimental relative enthalpy curves: ▴, α-phase; ·, β-phase; ▾, the solid formed by annealing the melt at 328 K for 4 h. The curves are shifted so that they coincide in the liquid phase. 10 Comparing the experimental heat capacity curves of tristearin with literature data: α-phase: - -, this work; □, Simpson; ▿, Hampson and Rothbart; ▪, Charbonnet and Singleton +, Hampson and Rothbart; ·, Charbonnet and Singleton . β‘-phase: - · -, this work; ▵, (β 1 ‘) Simpson; ▴, (β 2 ‘) Simpson; □, Hampson and Rothbart .…”
Section: Resultsmentioning
confidence: 86%
“…Comparing the experimental heat capacity curves of tristearin with literature data: α-phase: - -, this work; □, Simpson; ▿, Hampson and Rothbart; ▪, Charbonnet and Singleton +, Hampson and Rothbart; ·, Charbonnet and Singleton .…”
Section: Resultsmentioning
confidence: 87%
“…From the plot of the equilibrium temperatures in the melt against the reciprocal of the melted fraction, the purity of the sample was calculated to be (97.9 ± 0.1) mol %. 9 Experimental relative enthalpy curves: ▴, α-phase; ·, β-phase; ▾, the solid formed by annealing the melt at 328 K for 4 h. The curves are shifted so that they coincide in the liquid phase. 10 Comparing the experimental heat capacity curves of tristearin with literature data: α-phase: - -, this work; □, Simpson; ▿, Hampson and Rothbart; ▪, Charbonnet and Singleton +, Hampson and Rothbart; ·, Charbonnet and Singleton .…”
Section: Resultsmentioning
confidence: 90%
“…β-phase: , this work; ○, Simpson; +, Hampson and Rothbart; ·, Charbonnet and Singleton . β‘-phase: - · -, this work; ▵, (β 1 ‘) Simpson; ▴, (β 2 ‘) Simpson; □, Hampson and Rothbart . Liquid phase: , this work; ◇, Morad et al; ◆, Phillips and Mattamal; + , Charbonnet and Singleton 20 . …”
Section: Resultsmentioning
confidence: 92%
“…Moreover, the use of adiabatic calorimetry made it possible to start the measurements at such a low temperature that the absolute entropy of the stable phase could be calculated. Tristearin exhibits four polymorphic forms (α, β 2 ‘, β 1 ‘, and β), which have been identified by different techniques, like X-ray studies, − DSC, − Raman spectroscopy, calorimetry, − and microscopy . In this work, we observed the existence of two β‘-forms by DSC, but the small temperature range in which the β 2 ‘-phase occurred prevented detailed measurements on this form.…”
The thermal behavior of tristearin was studied by adiabatic calorimetry and differential scanning calorimetry (DSC). Specific heat capacities of two polymorphic forms were measured in the adiabatic calorimeter, where the -form was measured from 10 K to 370 K and the R-form was measured from 175 K to 370 K. The start of the measurement of the stable -form from 10 K allowed the calculation of its entropy, so we report the derived values of absolute entropy for the two forms of tristearin at 298.15 K. The enthalpies of fusion and melting temperatures for each polymorph were calculated from both the adiabatic and the DSC experimental data and are compared to the literature values. The values for the enthalpies of fusion of the stable -form are in excellent agreement, being (221.6 ( 1) J‚g -1 and (219.6 ( 2) J‚g -1 according to the adiabatic and DSC measurements, respectively. The data for the R-form are not in so good agreement, which we attribute to the difficulty to crystallize this phase in its pure form. Moreover, we examined the fleeting existence of the ′-form and its transformation to the -phase under isothermal conditions.
IntroductionGlycerides form an important class of natural products, as they are constituents of oils and fats. A very detailed review of the thermal properties of the acylglycerides is found in the chapter written by Hagemann in the Surfactant Science Series. 1 Glycerol trioctadecanoate (C 57 H 110 O 6 ), or tristearin for short, often indicated as SSS, is one of the saturated monoacid triglycerides and is probably the best researched triglyceride concerning thermal behavior. Despite this fact, we undertook this research as we feel that the combination of adiabatic calorimetry and DSC can give more precise data and a better insight in the crystallization processes. Moreover, the use of adiabatic calorimetry made it possible to start the measurements at such a low temperature that the absolute entropy of the stable phase could be calculated. Tristearin exhibits four polymorphic forms (R, 2 ′, 1 ′, and ), which have been identified by different techniques, like X-ray studies, 2-12 DSC, 7-18 Raman spectroscopy, 11 calorimetry, 20-22 and microscopy. 23 In this work, we observed the existence of two ′-forms by DSC, but the small temperature range in which the 2 ′-phase occurred prevented detailed measurements on this form. In previous publications, we reported on the thermal properties of trielaidin 25 (or EEE) and tripalmitin 26 (or PPP). This work is part of a research project aimed at the study of metastable crystallization of binary mixtures, tristearin being one of the possible constituents.
“… 9 Experimental relative enthalpy curves: ▴, α-phase; ·, β-phase; ▾, the solid formed by annealing the melt at 328 K for 4 h. The curves are shifted so that they coincide in the liquid phase. 10 Comparing the experimental heat capacity curves of tristearin with literature data: α-phase: - -, this work; □, Simpson; ▿, Hampson and Rothbart; ▪, Charbonnet and Singleton +, Hampson and Rothbart; ·, Charbonnet and Singleton . β‘-phase: - · -, this work; ▵, (β 1 ‘) Simpson; ▴, (β 2 ‘) Simpson; □, Hampson and Rothbart .…”
Section: Resultsmentioning
confidence: 86%
“…Comparing the experimental heat capacity curves of tristearin with literature data: α-phase: - -, this work; □, Simpson; ▿, Hampson and Rothbart; ▪, Charbonnet and Singleton +, Hampson and Rothbart; ·, Charbonnet and Singleton .…”
Section: Resultsmentioning
confidence: 87%
“…From the plot of the equilibrium temperatures in the melt against the reciprocal of the melted fraction, the purity of the sample was calculated to be (97.9 ± 0.1) mol %. 9 Experimental relative enthalpy curves: ▴, α-phase; ·, β-phase; ▾, the solid formed by annealing the melt at 328 K for 4 h. The curves are shifted so that they coincide in the liquid phase. 10 Comparing the experimental heat capacity curves of tristearin with literature data: α-phase: - -, this work; □, Simpson; ▿, Hampson and Rothbart; ▪, Charbonnet and Singleton +, Hampson and Rothbart; ·, Charbonnet and Singleton .…”
Section: Resultsmentioning
confidence: 90%
“…β-phase: , this work; ○, Simpson; +, Hampson and Rothbart; ·, Charbonnet and Singleton . β‘-phase: - · -, this work; ▵, (β 1 ‘) Simpson; ▴, (β 2 ‘) Simpson; □, Hampson and Rothbart . Liquid phase: , this work; ◇, Morad et al; ◆, Phillips and Mattamal; + , Charbonnet and Singleton 20 . …”
Section: Resultsmentioning
confidence: 92%
“…Moreover, the use of adiabatic calorimetry made it possible to start the measurements at such a low temperature that the absolute entropy of the stable phase could be calculated. Tristearin exhibits four polymorphic forms (α, β 2 ‘, β 1 ‘, and β), which have been identified by different techniques, like X-ray studies, − DSC, − Raman spectroscopy, calorimetry, − and microscopy . In this work, we observed the existence of two β‘-forms by DSC, but the small temperature range in which the β 2 ‘-phase occurred prevented detailed measurements on this form.…”
The thermal behavior of tristearin was studied by adiabatic calorimetry and differential scanning calorimetry (DSC). Specific heat capacities of two polymorphic forms were measured in the adiabatic calorimeter, where the -form was measured from 10 K to 370 K and the R-form was measured from 175 K to 370 K. The start of the measurement of the stable -form from 10 K allowed the calculation of its entropy, so we report the derived values of absolute entropy for the two forms of tristearin at 298.15 K. The enthalpies of fusion and melting temperatures for each polymorph were calculated from both the adiabatic and the DSC experimental data and are compared to the literature values. The values for the enthalpies of fusion of the stable -form are in excellent agreement, being (221.6 ( 1) J‚g -1 and (219.6 ( 2) J‚g -1 according to the adiabatic and DSC measurements, respectively. The data for the R-form are not in so good agreement, which we attribute to the difficulty to crystallize this phase in its pure form. Moreover, we examined the fleeting existence of the ′-form and its transformation to the -phase under isothermal conditions.
IntroductionGlycerides form an important class of natural products, as they are constituents of oils and fats. A very detailed review of the thermal properties of the acylglycerides is found in the chapter written by Hagemann in the Surfactant Science Series. 1 Glycerol trioctadecanoate (C 57 H 110 O 6 ), or tristearin for short, often indicated as SSS, is one of the saturated monoacid triglycerides and is probably the best researched triglyceride concerning thermal behavior. Despite this fact, we undertook this research as we feel that the combination of adiabatic calorimetry and DSC can give more precise data and a better insight in the crystallization processes. Moreover, the use of adiabatic calorimetry made it possible to start the measurements at such a low temperature that the absolute entropy of the stable phase could be calculated. Tristearin exhibits four polymorphic forms (R, 2 ′, 1 ′, and ), which have been identified by different techniques, like X-ray studies, 2-12 DSC, 7-18 Raman spectroscopy, 11 calorimetry, 20-22 and microscopy. 23 In this work, we observed the existence of two ′-forms by DSC, but the small temperature range in which the 2 ′-phase occurred prevented detailed measurements on this form. In previous publications, we reported on the thermal properties of trielaidin 25 (or EEE) and tripalmitin 26 (or PPP). This work is part of a research project aimed at the study of metastable crystallization of binary mixtures, tristearin being one of the possible constituents.
Fat polymorphs influence the quality of some food and cosmetic products. Emulsifiers traditionally have been added in order to retard undesired polymorphic transformations. The present study is an attempt to understand the role of selected emulsifiers on such transformations. Tristearin was heated or aged under controlled conditions using differential scanning calorimetry (DSC) and X‐ray techniques, and the extent of transformation was evaluated in view of the possible pathways of α transforming into β. The temperature regime controls the extent of mobility of fat molecules, the local crystal imperfections and the degree of liquefaction. As a result, it dictates the kinetics of the polymorphic transformation.The surfactant added as an impurity does not have a straightforward effect, as thought previously, but rather varies with the kinetic conditions. During aging some selected solid emulsifiers will retard the α‐β transformation while others still enhance it (during heating, all of them will inhibit β form crystallization). Their effect probably is related to different crystalline organizations and the creation of imperfections. Liquid emulsifiers in any case will enhance the α‐β transformation, due probably to their weak structure compatibility with tristearin, which causes a higher mobility of triglyceride molecules.
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