Molecular Origins of Cocoa Butter Triclinic Polymorphism

Date and Time


Food Science building - lecture room 128


Final Examination for the Degree of PhD


Examining Committee
Dr. Paul Spagnuolo, Chair
Dr. Alejandro Marangoni, Advisor
Dr. Amanda Wright, Student Advisory Committee Member
Dr. Loong-Tak Lim, Department Member
Dr. Kiyotaka Sato, External Examiner (Skype)


ABSTRACT: This thesis is a comprehensive study of the solid-state properties of the main triglyceride molecular species in cocoa butter, namely 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1-palmitoyl-2-oleoyl-3-stearoyl-glycerol (POS) and 1,3-stearoyl-2-oleoyl-glycerol (SOS). Two new triclinic crystal polymorphic forms (β₃ and β₂) of POS were discovered. Small and wide-angle powder x-ray diffraction patterns of these β₃ and β₁ crystal polymorphs of POS were identical to those of crystal forms V and VI in cocoa butter, while those of SOS and POP were not. Moreover, we also discovered that the crystal structure of CB in its meta-stable form IV and its transformation to form V was controlled by POS. The ternary phase behavior between POP, POS and SOS in their triclinic crystal polymorphic form was determined herein. POP:POS mixtures displayed a strong eutectic region. Also, POP addition always led to a decrease in the melting point of mixtures, while the opposite was true for SOS. A novel molecular compound was also identified with a melting point of 40 ºC at 40:40:20 (w/w/w) POP:POS:SOS. In this work we showed that a novel algal butter was compatible with cocoa butter and could be used as an alternative for high SOS exotic butters in the design of CBEs. Additionally, we showed the potential for synthesizing a CBM, a coco butter mimetic, for full replacement of CB in chocolate. The CBM was synthesized from natural fat fractions using a simple single step enzymatic conversion method. Since POS showed critical functionality in crystal polymorphism and melting behavior in ternary mixtures with POP and SOS, we recommend the inclusion of POS in the design of CBEs.

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