CRYSTALLIZATION KINETICS OF EMULSIFIED TRIGLYCERIDES

Nucleation and crystal growth process of triglycerides in water emulsions composed of trimyristin (c14:0) admixed with 0, 40, and 80 ml litre-1 trilaurin (c12:0) (expressed v per total v emulsion) were followed with NMR (nuclear magnetic resonance) and DSC (differential scanning calorimetry). Mathematical analysis of the time dependence of the phase changes and thermal data distinguished two distinct 'apparent' kinetic phases. These phases were tentatively referred to as nucleation and crystal growth. With 40 and 80 ml litre-1 trilaurin (NMR data at 293 K) nucleation and crystal growth phases of trimyristin were simulated with zero order and second order rate expressions, respectively. Relative to these mixtures, pure trimyristin nucleation was delayed in the initial phase, but crystal growth occurred with fast homogeneous nucleation and slower growth in the second phase. Statistical analyses indicated that homogeneous nucleation similarly occurred when 40 or 80 ml litre-1 trilaurin was admixed with trimyristin. NMR resolution made it possible to follow the crystallization phenomena in different locations of the crystallization vessel effectively in situ and undisturbed. Statistical analyses in this case revealed a significant trilaurin-location interaction confirming that the rate of nucleation processes was affected both by the concentration of trilaurin and the heat transfer properties of the sample and vessel. The time-location interactions were not significant, confirming the hypothesis that in the absence of tilaurin, zero order nucleation did not occur in the first phase.