Predicting Cocoa Butter Melting from Pairwise TAG Phase Behavior and Boundary Mismatch Free Energy

Abstract

A pairwise boundary mismatch framework reconstructed polymorph-dependent cocoa butter melting from multicomponent triacylglycerol (TAG) composition and structural organization. Melting was represented as the collective thermal response of local POP−POS, POP−SOS, and POS−SOS pair environments. Conditional mixed-channel weights were calculated from composition, while historical apparent-β binary solidus−liquidus envelopes defined their reference phase behavior. An entropy-of-dilution correction accounted for embedding each pair within the multicomponent mixture, and a six-mode distribution of boundary mismatch free energies generated melting-temperature depressions. Crucially, this approach bypassed the Wesdorp isomorphism classification and Margules activity-coefficient construction; pair nonideality was supplied directly by experimental phase envelopes. Using mean boundary mismatch free energy as the only fitted curve-shape parameter and fixing the low-temperature solid amplitude from the 5 °C experimental anchor, the model reconstructed Form V (β) and Form IV (β′) solid fat content−temperature profiles with root-mean-square errors of 2.93 and 1.38 SFC percentage points and mean energies of 2.54 and 2.43 kJ mol−1, respectively. Because β′ binary diagrams were unavailable, apparent-β envelopes were transformed using polymorph-specific pure-TAG melting temperatures and fusion enthalpies. Exploratory transfer to aged Form VI exposed limitations arising from historical β data lacking polymorphic resolution. The framework connects binary TAG phase behavior, local structural accommodation, and macroscopic cocoa butter melting.