Crystal structure, fats cocoa butter

Ollivon, M., Loisel, C., Lopez, C., Lesieur, P., Artzner, F., Keller, G. 2001. Simultaneous examination of structural and thermal behaviours of fats by coupled X-ray diffraction and differential scanning calorimetry techniques application to cocoa butter polymorphism. In, Crystallization and Solidification Properties of Lipids (N. Widlak, R. Hartel, S. Narine, eds.), pp. 34-41, AOCS Press, Champaign, IL. 

Ollivon, M., Simultaneous Examination of Structural and Thermal Behaviors of Fats by Coupled X-Ray Diffraction and DSC Techniques Application to Cocoa Butter Polymorphism, Conference on Crystallization and Solidification Properties of Lipids, American Oil Chemists Society, Toronto, Canada, 2000. 

In products containing lipids, control of the crystal polymorphic form is also necessary. Lipids form different crystalline structures, or polymorphs, depending on the nature of the fat and the processing conditions. Transitions from less stable to more stable polymorphs are also dependent on composition and processing conditions. For example, tempering (or precrystallization) of chocolate is a process through which the chocolate is sequentially cooled and warmed to promote crystallization of cocoa butter into the desired polymorphic form. Controlling crystallization to produce the proper size distribution of this polymorph provides ... 

Similarly, cocoa butter (CB) will develop a texture of good consistency and uniform matrix in chocolate if the fats solidify from the melt into a crystalline IV or V polymorphic modification of the cocoa butter. Severe fat migration (fat bloom) will take place after prolonged storage or temperature fluctuations if the CB modification is crystallized or transformed in situ into the VI form. Several additional products suffer from similar problems. It is well documented that the formation of crystal structure and the solution- or solid-mediated transformations can be delayed, slowed, or enhanced by small amounts of specific amphiphiles dissolved or dispersed in the fat during the crystallization stages. 

---