Comparative structural and vibrational investigations between cocoa butter (CB) and cocoa butter equivalent (CBE) by ESI/MALDI-HRMS, XRD, DSC, MIR and Raman spectroscopy.

A high quality chocolate requires not only a shiny surface, a crunchy and pleasant texture, but also a proper resistance to blooming. All these characteristics are influenced by the physical and chemical properties of the components, which are directly related to their crystalline structure. Some works found that the proportion of cocoa butter (CB), cocoa butter equivalent (CBE) and milk fatty acid (AMF) tend to strongly delay the blooming when mixing them. The goal of our research is to determine how the choice of adding CBE to the mixture delays chocolate blooming. ESI/MALDI-HRMS, X-ray, DSC, MIR and Raman investigations were used to analyze the structure features and the vibrational modes of CB and CBE. The comparison of these experimental results between CB and CBE made it possible to highlight markers of differentiation between CB and CBE which seems to explain the impact of CBE in the chocolate blooming. Part of these triglycerides remains in form IV instead. The presence of the latter seems to be a key parameter that favors the transformation deceleration to the form VI, which is responsible for the fat bloom development.

Temperature dependent Raman and X-ray diffraction studies of anhydrous milk fat.

Raman spectroscopy was used to characterize the polymorphs and liquid state of anhydrous milk fat, with emphasis placed on the thermal evolution of the ester carbonyl stretching modes (1800-1700cm-1) and the comparative study of the Raman-active CC (1660cm-1) and CH (3000-2700cm-1) vibrational modes. Specific Raman signatures in the crystalline phase were found and attributed to the coexistence of two groups of triglycerides. This was confirmed using differential scanning calorimetry and X-ray diffraction methods. In the ester carbonyl band, the effect of changing temperature on both the number of modes and new defined intensity ratios was studied and enabled polymorph discrimination. CH stretching signals increased with polymorph stability, indicating the dominance of antisymmetric CH methylene vibrations as the anhydrous milk fats crystal lattice became more ordered. The change in intensity of the CH stretching bands as a function of temperature was used to probe the order-disorder transition.

Dielectric properties of twist grain boundary phases: influence of the anchoring and the distance between grain boundaries.

The dielectric properties of the twist grain boundaries TGB(A) and TGB(C) of liquid crystal phases differ from the smectic-A and smectic-C phase ones: a theoretical model confirmed by experimental results shows that the Goldstone mode of the TGB(C) phase and the soft mode of the TGB(A) phase are strongly reduced. This behavior is due to elastic strain, which is connected to two parameters: the anchoring at the grain boundaries and the distance between the grain boundaries. It is shown quantitatively that a relatively flexible anchoring in the TGB(A) phase becomes rigid in the TGB(C) one. The relaxation frequencies of these modes allow analysis of the rotational viscosity variations.