Lipid thermal behavior

Differential scanning calorimetry is a well known technique in the study of the thermal behavior of lipids and can be used to assess purity and stability of lipids, perturbation of aggregate structures, phase transition temperatures, lipid mixing behavior, and influence of other molecules and ions on structure. ... 

Ollivon, M., Simultaneous Examination of Structural and Thermal Behaviors of Fats by Coupled X-Ray Diffraction and DSC Techniques Application to Cocoa Butter Polymorphism, Conference on Crystallization and Solidification Properties of Lipids, American Oil Chemists Society, Toronto, Canada, 2000. 

In a similar study using differential thermal analysis (DTA), the perturbation effects of fatty acids on the SC were studied (Tanojo et al., 1994). Thermal behavior of the SC revealed that saturated fatty adds easily mix with the skin lipids and monounsaturated fatty acids to form a separate domain containing mostly pure fatty acids within the SC lipids. Polyunsaturated fatty acids also formed separate domains, but the extent of thermal transition was more than that showed by saturated fatty acids and less than monounsaturated fatty acids. In a recent investigation, SEMs of the skin treated with 10% oleic acid in ethanolic solution showed generation of pores on the surface of epidermal comeocytes (Touitou et al., 2002). 

The Thermal Behavior of Lipid Systems and Biological Membranes... 

A condensed soft matter system like the phospholipid bilayer exhibits complex dynamic behavior that is strongly dependent upon composition and temperature. The thermal behavior of phosphohpid bilayers can be understood using simplified phase diagrams that correlate temperature and membrane composition. For typical mixtures of phosphatidylcholines with cholesterol three important phases exist over physiologically relevant temperatures (Figure 2a).Pure phosphatidylcholine bilayers will form a gel phase at low temperatures, which is often called the solid ordered (So) or phase. It is characterized by low lateral mobility of the lipids and strong interactions between lipids in the bilayer (diffusion rates of cm s ). ... 

In Fig. 22, three typical types of DSC curves are shown for the DMPE-water system at the same water content. A distinct difference in the thermal behavior is observed not only for the phase transition of the Upid but also for the melting of the ice. Figure 23 shows a schematic diagram of relative enthalpy (AH) versus temperature (t) curves that was constructed on the basis of the transition enthalpies and temperatures associated with the lipid phase transitions shown in Fig. 22. By reference to the diagram, it becomes apparent that the DMPE-water system can be present in two phases, designated the L- and //-subgel phases, other than the gel phase at temperatures where the hydrocarbon chains of the lipids are in a solid-like state and the thermodynamic stability of these phases increases... 

To introduce the subject, we first present some general aspects of food constitution and of the most useful calorimetric techniques in this context. Because the thermal behavior of foods depends strongly on their composition, we concentrate at first on the thermal characteristics of food constituents—of water, lipids, glu-cides, proteins, and minor constituents—and then consider composite and reconstituted foods. Aspects of process safety are also considered. 

Studies focused on oxidative and thermal behavior of oils have been performed to investigate quality and stability patterns of oils in foods to investigate lipid and biological oxidation in foods [5-9]. Other authors [10] conducted comparative studies on the oxidative stability of linseed oils. 

The effect of 5th generation polyamidoamine (PAMAM G5) dendrimers on multilamellar dipalmitoylphosphocholine (DPPC) vesicles was investigated. PAMAM was added in 2 different concentrations to the lipids (10 and 10 dendrimer/lipid molar ratios). The thermal behavior of the evolved systems was characterized by DSC while the structure and the morphology were investigated with small- and wide-angle X-ray scattering (SWAXS), freeze-fracture electron microscopy (FFTEM) and P NMR spectroscopy, respectively. The obtained results show that the dendrimers added in 10 molar ratio to the lipids generate minor perturbations in the multilamellar structure and thermal character of... 

BUiaderis CG, Page CM, Slade L, Sirett RR. Thermal behavior of amylose-lipid complexes. Car-bohydrPolym 1985 5(5) 367-389. 

The interest in vesicles as models for cell biomembranes has led to much work on the interactions within and between lipid layers. The primary contributions to vesicle stability and curvature include those familiar to us already, the electrostatic interactions between charged head groups (Chapter V) and the van der Waals interaction between layers (Chapter VI). An additional force due to thermal fluctuations in membranes produces a steric repulsion between membranes known as the Helfrich or undulation interaction. This force has been quantified by Sackmann and co-workers using reflection interference contrast microscopy to monitor vesicles weakly adhering to a solid substrate [78]. Membrane fluctuation forces may influence the interactions between proteins embedded in them [79]. Finally, in balance with these forces, bending elasticity helps determine shape transitions [80], interactions between inclusions [81], aggregation of membrane junctions [82], and unbinding of pinched membranes [83]. Specific interactions between membrane embedded receptors add an additional complication to biomembrane behavior. These have been stud-... 

Contrary to the accumulated knowledge on the static or quasi-static characteristics of thin lipid films at air/water interface, less attention has been paid to the dynamical or nonequilibrium behavior of the film. Studies on the dynamical characteristics of thin lipid films may be quite important, because the life phenomena are maintained under nonequilibrium conditions. According to the modern biochemistry [11,12], thin lipid membrane in living cells is not a rigid wall but a thermally fluctuating barrier with high fluidity. In the present section, we will show that thin lipid film exhibits the various interesting dynamical tc-A characteristics, such as the "overshoot hump", the "zero surface pressure", and the "flat plateau". 

This chapter focuses on some aspects of phase transition behavior and other material properties of starch, particularly as they pertain to the structural order and interactions of the starch polysaccharides with water, lipids and other solutes. Understanding the thermally induced structural transitions of starch is helpful in controlling its physical properties and processing behaviors (e.g. plasticization, viscosity), as well as in designing products with improved properties (e.g. texture, stability). 

In summary, the dimeric lipids (29a-29h) with low m-value (3-4) and high m-value (20-22) showed exceptional thermal, lipid-packing and cholesterol-association properties. Obviously the introduction of a polymethylene spacer chain at the level of headgroup brought about dramatic effect on the aggregation behavior, membrane organization and lipid packing of 29. 

Michalski, M.C., Ollivon, M., Briard, V., Leconte, N., and Lopez, C. (2004). Native fat globules of different sizes selected from raw milk thermal and structural behavior. Chem. Phys. Lipids. 132,247 261. 

Figure 5 shows the thermally induced (10-60°C) changes in the CHj stretching frequency of intact human SC plotted as a function of hydration and reheating. Corresponding data for the extracted lipid samples are depicted in Fig. 6. For SC, the frequency increased with temperature and showed a small, but definite, inflection point between 35 and 45°C. Under dry conditions, the midpoint was estimated to be 45°C, decreasing to a constant value of 35°C as the hydration level was increased. This behavior closely mimicked the calorimetric results described, suggesting that the 35°C inflection observed by IR corresponded to the same endothermic process measured by DSC. However, no evidence of a thermal transition at 35°C was observed by IR in the...

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