Isotropic liquid state of cocoa butter

Abstract: The complex crystal structure of coca butter (CB) is responsible for the unique melting behavior, surface gloss, and mechanical properties of chocolate. While most of the studies concentrated on the crystalline state or the crystallization process of CB, the isotropic liquid state, which has a major impact on fat crystallization and the resulting crystal, was not explored. At the last AOCS conference, I presented the initial work focusing on the molecular organization of pure tristearin and triolein as model triacylglycerols (TAGs). The current research employed molecular dynamics simulation to study the molecular organizations of a ternary mixture of the main three CB TAGs, i.e. palmitoyl-oleoyl-stearoylglycerol (POS), 1,3-distearoyl-2-oleoylglycerol (SOS), and 1,3-dipalmitoyl-2-oleoylglycerol (POP), at liquid state while the findings were correlated with the crystallization process. Based on the calculated scattering factor, it seems that the scattering of the CB at the isotropic liquid state is similar to the arrangements of pure SOS. Clustering analysis showed that, on average, every molecule has two neighbor molecules, suggesting that the clusters have elongated shape rather than spherical or bulky. Such elongated shape has different characteristics than the crystalline lamellar structure, formed at solid state, suggesting that during the crystallization process they must rearrange to allow a crystal formation. In-depth analysis of the molecules inside the clusters demonstrated that the probability of the formation of a POS nucleus is higher than the probability of the formation of POP and SOS nuclei which is later resulting in a crystal structure similar to POS crystal pattern. Overall, the current research provided new insights into a complex lipidic food system using the toolbox developed in our previous study. The results shed a light on the behavior of CB TAGs at liquid state prior to crystallization, providing knowledge that can be exploited to manipulate and control CB crystallization.