Crystallization behavior and kinetics of blends of cocoa butter and milk fat or milk fat fractions

The crystallization behavior and kinetics of mixtures of cocoa butter (CB) with milk fat (MF) and milk fat fractions (MFF) were studied by evaluating changes in thermal and solid fat profiles with composition, temperature and time. Isothermal and nonisothermal kinetics of the fat blends were evaluated using the empirical Avrami, Ozawa and Kissinger equations.;The addition of greater than 10% MFF inhibited crystallization of CB. Faster cooling rates resulted in a decrease in the amount of fat crystallized in the fat blends. Effects of additives on the crystallization behavior of CB were significantly dependent on their chemical and physical properties. Tempering greatly influenced thermal profile of CB in the fat blends, but not that of MF or MFFs. Isosolid diagrams of fat blends confirmed eutectic and diluent interactions. In general, MF and high-melting MFFs were more compatible with CB than very high-melting MFFs.;MF and MFFs had shorter induction time for nucleation than CB during isothermal crystallization at 15, 20 and 25;The Avrami equation (isothermal crystallization) revealed different nucleation and growth mechanisms for component fats and fat blends. The suggested mechanism for crystallization of CB was heterogeneous nucleation and spherulitic growth from sporadic nuclei. For MF, the mechanism was instantaneous heterogeneous nucleation followed by spherulitic growth. For MFFs, the mechanism was high nucleation rate at the beginning of crystallization and decreasing with time, and plate-like growth. The additives did not change the nucleation and growth mechanism of CB crystals.;Nonisothermal crystallization (Ozawa equation) suggested different nucleation and growth mechanisms for component fats and fat blends as compared to isothermal crystallization. The suggested mechanism was lineal growth with decreasing nucleation rate. Apparent activation energy for crystallization (Kissinger equation) of CB and fat blends did not show significant differences.