Pre-nucleation structuring of TAG melts revealed by fluorescence polarization spectroscopy and molecular mechanics simulations Article uri icon

abstract

  • We have studied the pre-nucleation behavior of tripalmitin (TP) and tristearin (TS) in blends with triolein (TO), high oleic safflower oil (HOSfO) and soybean oil (SBO) by means of fluorescence polarization spectroscopy (FPS) and molecular mechanics simulations (MM). The FPS measurements at different temperatures showed that there is an increase in the anisotropy of the TP:HOSfO and TP:SBO blends as opposed to the TP:TO sample. This increase is directly related to an increase in the microviscosity of the blend which is interpreted as a structuring step prior to the nucleation and growth of the crystals. A similar but less pronounced effect was also observed in the TS:SBO blends. We performed MM simulations in an attempt to understand the molecular interactions responsible for this behavior. The simulation results have shown that short range van der Waals (vdW) interactions are the ones responsible for the increase in the microviscosity of the blends prior to crystallization. Our results also indicate that the presence of molecules that contain at least one chain of palmitic acid in their triglyceride (TAG) composition will induce a pre-nucleation increase in the microviscosity of the blend in both TP and TS containing systems. Lastly, we studied the applicability of these conclusions to longer chain TAG analogues. Our MM results show that hypothetical blends of TS and TAGs containing stearic acid in their structure, will not have a low enough vdW energy to account for an increase in the microviscosity. Hence, there seems to be a specific interaction particularly favorable when the oil contains TAGs with at least one palmitic acid chain. © AOCS 2010.

publication date

  • 2010-01-01