Phospholipid Self-Assembly in Cocoa Butter Provides a Crystallizing Surface for Seeding the Form V Polymorph in Chocolate

The addition of specific phospholipids to chocolate was recently shown to direct the crystallization of cocoa butter to the desirable triclinic form V polymorph, thus achieving the most desirable crystal structure in chocolate without the need for shear or complex temperature gradients. However, the mechanism of action of these phospholipids remains unknown. Herein, we determined the structure of self-assembled 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in chocolate and its fat phase, cocoa butter, to better understand its effects on the crystallization behavior and polymorphism of cocoa butter. Small-angle neutron scattering studies suggested that DMPC forms a variety of micelles in cocoa butter. A strong interaction between the DMPC micelles and the triglyceride palmitoyl-oleoyl-stearoyl glycerol (POS), the most abundant triglyceride in cocoa butter, which also directs the triclinic crystallization of the cocoa butter, was also observed by small-angle X-ray scattering (SAXS), interfacial tension measurements, and attenuated total reflectance-fourier transform infrared spectroscopy. This suggested that DMPC micelles serve as a seeding surface, templating form V crystal growth via its effects on POS. We propose a mechanism that involves a solid-state polymorphic transition form IV to V POS in the seeding crystals. Crystal strain and defects were observed in the templated nano- and microstructure observed by synchrotron microcomputed tomography and SAXS. These could affect the product's properties, suggesting that a simple tempering step may still be required.