The binary phase behavior of 1,3-dimyristoyl-2-stearoyl-sn-glycerol and 1,2-dimyristoyl-3-stearoyl-sn-glycerol.
The binary phase behavior of pure 1,3-dimyristoyl-2-stearoyl-sn-glycerol (MSM) and 1,2-dimyristoyl-3-stearoyl-sn-glycerol (MMS) was investigated in terms of polymorphism, melting and crystallization behavior, SFC, hardness and microstructure. Samples were crystallized at cooling rates of 3.0 and 0.1 degrees C/min. The asymmetric TAG demonstrated lower melting and crystallization points at both cooling rates. All samples crystallized in the beta' polymorph when cooled at 0.1 degrees C/min and in the alpha polymorph when cooled at 3.0 degrees C/min. The experimentally determined kinetic phase diagram of MSM-MMS was monotectic for both cooling rates. This data was well described by a thermodynamic model using the Bragg-Williams approximation for non-ideality of mixing and suggested that in both the solid and liquid states, like pair interactions (MSM-MSM and MMS-MMS) were favored over MSM-MMS interaction. A strong tendency to phase separation in the solid phase was also observed. For both cooling rates, the fit of the SFC (%)-time curves to a modified form of the Avrami model indicated that crystallization occurred in two distinct kinetic steps. Depressions seen in SFC did not correspond to depressions in hardness or melting temperatures.
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Alberta Lipid Utilization Program, Department of Agriculture Forestry and Food Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
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D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D005989:Glycerides / Q000737:chemistry*; D005990:Glycerol / Q000031:analogs & derivatives* / Q000737:chemistry; D008853:Microscopy; D044367:Phase Transition; D013228:Stearates / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014961:X-Ray Diffraction
C532945:1,2-dimyristoyl-3-stearoyl-sn-glycerol; C532946:1,3-dimyristoyl-2-stearoyl-sn-glycerol; D005989:Glycerides; D013228:Stearates; D005990:Glycerol