Effect of limonene on the crystallization kinetics and polymorphic behavior of cocoa butter

Effect of limonene on the crystallization kinetics and polymorphic behavior of cocoa butter Annelien Rigolle1, Bart Goderis², Imogen Foubert1, KU Leuven KULAK, Kortrijk, Belgium1; KU Leuven, Leuven, Belgium² The fat content of chocolate is usually from about 30% to 34% by weight based on the total weight of the chocolate. Because of the high calorific value of fats, consumers are interested in a reduced fat chocolate. However, the amount of cocoa butter in chocolate is important for the flow properties of the liquid chocolate and an incorrect viscosity may cause a poor quality product, by influencing the shape of chocolate products or the perception of texture by the consumer. A US Patent by Beckett (2001), claims that adding limonene (in a concentration of up to 5% by weight) to a reduced-fat chocolate, results in a lower viscosity and softer chocolate, that melts more easily in the mouth, when compared with the original reduced-fat chocolate which does not contain limonene. Limonene is a diterpene, which is naturally present in the D-form in ethereal oils of lemon and orange. Do et al. (2008) indeed found a lower viscosity, but also a lower solid fat content with addition of limonene to cocoa butter. Ray et al. (2011) however observed that with the addition of 5% limonene the crystallization induction time of cocoa butter was also altered as well as the polymorphic behavior. The aim of this research was to investigate the effect of limonene on the crystallization behavior of cocoa butter in more detail. Limonene was added in concentrations from 1 to 7.5% by weight and the isothermal crystallization behavior was examined at different temperatures using DSC. The crystallization kinetics was studied by fitting the Foubert model to the crystallization curves. Information about the polymorphs formed during crystallization was obtained by DSC stop-and-return experiments and confirmed with synchrotron X-ray diffraction analyses. The microstructure development during crystallization was followed using polarized light microscopy. The crystallization kinetics was dependent on the degree of supercooling and a concentration effect could be observed. Furthermore, the polymorphic behavior was altered with addition of limonene. Initially, less unstable polymorphs were formed with addition of limonene in comparison with the pure cocoa butter. However, the transition to the stable  polymorph was accelerated by addition of higher concentrations limonene. References Beckett, S.T. (2001). Preparation of chocolate with limonene to reduce fat content. US Patent 6,200,625. Do, T.-A.L., Vieira, J., Hargreaves, J.M., Wolf, B. and Mitchell, J.R. (2008). Impact of limonene on the physical properties of reduced fat chocolate. Journal of the American Oil Chemists' Society 85, 911-920. Ray, J., MacNaughtan, W., Chong, P.S., Vieira, J. and Wolf, B. (2011). The Effect of Limonene on the Crystallization of Cocoa Butter. Journal of the American Oil Chemists' Society 89, 437-445.status: publishe