Polymorphic Phases of Natural Fat from Cupuassu (Theobroma grandiflorum) Beans: A WAXS/SAXS/DSC Study
Résumé
The polymorphic phases of natural fat extracted from cupuassu beans were studied by performing in situ temperature-dependent X-ray scattering experiments and differential scanning calorimetry (DSC) using synchrotron radiation. Cupuassu (Theobroma grandiflorum) is a native plant of the Theobroma species originally found in Brazil's Amazon region, with a great potential for utilization in the chocolate industry. The experiments and data analysis were performed using as a reference the known polymorphic phase behavior of cocoa butter. The results led to the identification of cupuassu fat polymorphic crystalline phases. Using the nomenclature generally found in the literature for triaceylclycerols (TAGs) systems, these phases were labeled γ, R, β 0 , and β in increasing order of melting temperature and stability. Differential scanning calorimetry measurements of fusion temperatures indicated the existence of two β states in cupuassu fat. These phases were labeled β 2 and β 1 , following the aforementioned nomenclature. In spite of the different melting points, the existence of a β 2 f β 1 transition could not be proven, due to the great deal of structural similarity of the corresponding X-ray patterns obtained in our experiments. A comparison of our results with those reported for several pure compounds and ternary mixtures of TAGs indicated that these components are mainly responsible for the cupuassu fat phase behavior. This study provided the first experimental results of an in-situ follow-up of the polymorphic phase transitions and crystallization of fat from Brazilian cupuassu beans, an industrially important natural product.