Chocolate composition and its crystallization process: A multidisciplinary analysis.

In this work, the composition of different types of chocolate was studied by using microscopy (optical and confocal fluorescence) and vibrational spectroscopy (Raman) aimed at obtaining more chemical information about this important food. By combining these techniques, it is possible to distinguish different components of chocolate. It was not possible to obtain Raman spectra of dark chocolate due to the presence of fluorescent flavonoids in cocoa particles. However, silver nanoparticles quench this fluorescent signal, and thus it is possible to obtain a surface-enhanced Raman spectroscopy spectrum of dark chocolate. The effect of ultrasound on the crystallization process of cocoa butter was also studied. These samples were also analysed by X-ray diffraction and differential scanning calorimetry. Furthermore, the combination of all these techniques was very useful in the specific analysis of different components of chocolate and could have a high impact in the chocolate industry.

The impact of dihydrogen phosphate anions on the excited-state proton transfer of harmane. Effect of ß-cyclodextrin on these photoreactions.

Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the presence of a proton donor/acceptor such as dihydrogen phosphate anions in aqueous solution have been studied by stationary and time-resolved fluorescence spectroscopy. The presence of high amounts of dihydrogen phosphate ions modifies the acid/base properties of this alkaloid. Thus, by keeping the pH constant at pH 8.8 and by increasing the amount of NaH(2)PO(4) in the solution, it is possible to reproduce the same spectral profiles as those obtained in high alkaline solutions (pH >12) in the absence of NaH(2)PO(4). Under these conditions, a new fluorescence profile appears at around 520 nm. This result could be related to the results of a recent investigation which suggests that a high intake of phosphates may promote skin tumorigenesis. The presence of ß-cyclodextrin (ß-CD) avoids the proton transfer reactions in this alkaloid by means the formation of an inclusion complex between ß-CD and HAR. The formation of this complex originates a remarkable enhancement of the emission intensity from the neutral form in contrast to the cationic and zwitterionic forms. A new lifetime was obtained at 360 nm (2.5 ns), which was associated with the emission of this inclusion complex. At this wavelength, the fluorescence intensity decay of HAR can be described by a linear combination of two exponentials. From the ratio between the pre-exponential factors, we have obtained a value of K = 501 M for the equilibrium of formation of this complex.