It is proposed that “crystal memory”, observed in the solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystals and liquid TAG molecules, in a superheated metastable regime. In the superheated regime of a system exhibiting a single phase transition, solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered after the system has been heated. This process is interpreted as a “crystal memory” effect. We outline a mathematical model, with a single phase transition, that shows how the observations can be explained, makes predictions and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. The “holding time” is associated with the lifetime of a metastable state and a plot of lifetime versus temperature, using the modified VFT equation, is in agreement with recent data. The model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime.
