Phase Equilibria and Phase Properties in Systems Containing Lecithins, Triglycerides, and Water.

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Abstract
The phase behavior and molecular interaction in systems of lecithins (egg lecithin, dipalmitoyl lecithin) and triglycerides (triolein, tristearin) with and without water were studied with differential thermal analysis, X-ray diffraction, IR spectrometry and polarizing microscopy. A maximum of 15% (wt/wt) triolein can be incorporated into the lamellar liquid crystalline phase of hydrated lecithin. Low-angle X-ray diffraction measurements of this phase indicate that the triolein is mostly located at the lipid water interface; a minor part is dissolved in the apolar region. Triolein induced a broadening of the gel-liquid crystalline transition of dipalmitoyl lecithin, but no change in the transition temperature. The solubilities of the lecithins in triolein were found to be less than 1%. No pronounced molecular interaction between tristearin and the lecithins was recorded, neither with differential thermal analysis nor X-ray diffraction. On heating, pure tristearin shows a complex phase behavior which is preserved also in mixtures with lecithins, but the .alpha.L form is less stable. IR spectrometry appears to be a convenient method to recognize different polymorphic forms of triglycerides also in mixtures with other lipids.