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2025 AOCS Annual Meeting & Expo.

Edible Applications Technology

Lipid Crystallization I

Effect of alkyl chain length on the clustering of molten triacylglycerols

Monday, April 28, 2025
1:55 PM – 2:15 PM PST
Room: A106
Abstract: The clustering of molecules in the liquid state is a recent discovery. The alkyl chain length of triacylglycerols affects the average number of molecules per cluster (N_C) in the molten state. These numbers are estimated for the homologous series trilaurin (C12), trimyristin (C14), tripalmitin (C16), and tristearin (C18). N_C values are estimated from experimental results of in-house and synchrotron x-ray scattering and small angle neutron scattering. The temperatures are between 473 K (200 °C) and 5 K below the melting point of each polymorph. Numerical simulations are performed as well for a subset of these conditions.

As for tripalmitin, a reduction of N_C  with increase in temperature is observed in the other materials. This confirms that this temperature dependence is a general behaviour of liquid triacylglycerols. For trilaurin (C12), N_C  is between 6 at 473 K and 7.5 at 313K. For tristearin (C18) this number ranges from 8 at 473 K to 10 at 335 K. For trimyristin (C12) and tripalmitin (C16) the values of   are in between. Thus, N_C increases with alkyl chain length.

This trend arises from the competition of the attractive forces between the glycerol cores and the alkyl chains against the mobility of the molecules due to their kinetic energy. Although the relative glycerol-glycerol attraction in the small molecules is larger than in the bigger molecules, the bigger molecules have less mobility. This reduction in mobility predominates in the determination of N_C. The understanding of the non-ideality of the liquid state can now be used for the development of new thermodynamic and kinetic models for crystallization.