Nucleation kinetics of emulsified triglyceride mixtures

The purpose of this study is to determine characteristic nucleation paramet ers such as the surface free energy for nucleus formation in mixtures of fu lly hydrogenated palm oil (HP) in sunflower oil (SF). These parameters will be used to model the bulk crystallization kinetics of the same mixtures. T his was achieved by determining the crystallization kinetics in emulsified triglyceride mixtures using differential scanning calorimetry, proton nucle ar magnetic resonance, and ultrasound velocity measurements. The latter tec hnique appeared to be very sensitive for monitoring the crystallization kin etics of fat dispersions containing triglycerides with a simple phase behav ior. Isothermal crystallization of emulsified HP stabilized by sodium casei nate started at 7 K below the alpha clear point, and the kinetics were best fitted assuming heterogeneous nucleation. Isothermal crystallization of em ulsified 10% HP in SF stabilized by caseinate started at 14 K below the alp ha melting point, and the kinetics were best fitted assuming homogeneous nu cleation. If the same dispersion was stabilized by Tween 20, crystallizatio n started at 11 K below the alpha melting point, and the kinetics were fitt ed best using heterogeneous nucleation. Analysis of the temperature depende ncy of the fit parameters yielded a surface free energy of a nucleus of abo ut 4 mJ.m(-2) in the case of homogeneous nucleation. Pre-exponential nuclea tion frequencies indicated that a large proportion of the triglyceride mole cule should be in the right conformation to be incorporated ina nucleus.