Bhaskar, A. R., Rizvi, S. S. H. & Bertoli, C. (1996): Cocoabutter fractionation with supercritical carbon dioxide, -in: Von Rohr, R. Ph. & Trepp, Ch. (Eds) Proceedings of the 3rd Inernational Symposium on High Pressure Chemical Engineering , October 7
Authors:D. Fessas, M. Signorelli, and A. Schiraldi
Large experimental evidence was collected on polymorphous transitions of triacyl glycerols (TAG) in cocoa butter by means
of DSC investigations. The cooling treatment (in conditions close to those of the industrial practice) and the annealing temperature
significantly affect the overall crystal fraction and the distribution of the various polymorphs. These data allowed a quantitative,
although purely phenomenological, kinetic parameterization of polymorphous transitions of cocoa butter. The evaluation of
the relevant kinetic constants and their dependence on the temperature allowed prediction of the yield in every polymorph
after a given thermal history. Similar evidences were attained for cocoa liquor and dark chocolate where TAG are sided by
other ingredients. These results can be the basis for an industrial exploitation.</o:p>
In the article thermal behaviours of cocoa butter and representatives of the 3 classes of cocoa butter alternative fats were investigated using isothermal DSC-method. Besides traditional parameters, Avrami transformation and polar qualification system (adapted from NIR-technique) were used for data evaluations.Using a new parameter, tmax*, the influence of the temperature change could be avoided. This parameter gave 100% success in classification of the investigated confectionery fats (p<0.05).In comparison with traditional Avrami parameters such as n and lgk measured at different temperatures, a new parameter (t*) gave the best result in distinguishing confectionery fats (approx. 71% correctly classified). The classification improved using lgk and n together (79%).Better classification could be achieved using polar qualification system. The percentage of correctly classified cases was 87.5% using either the point or the surface method (p<0.05). In every case there was a clear borderline between cocoa butter-CBE fat and CBR-CBS fats.Comparing Avrami method and PQS, it can be concluded that the latter is a more successful method in classification of unknown fat samples (pure cocoa butter alternative fats only). However PQS does not give any information about thermal behaviour of the sample.
Mixtures of milk fat or milk fat fractions, produced by melt crystallization, and cocoa butter were studied using isothermal calorimetry. Crystallization of cocoa butter (at 15, 20 and 25‡C) was observed, and induction time for nucleation, peak time and amount of heat produced were recorded. Melting profiles and X-ray spectra were also obtained, yielding information about extent of crystallization and type of polymorph obtained. Induction time for nucleation generally increased with increasing temperature. Peak time increased at 15‡C, but decreased at 20‡C. Amount of crystallized fat decreased with increasing level of milk fat.
Thermal stability of pharmaceutical ingredients is an important aspect. In this study, we adopted differential scanning calorimetry
(DSC) to investigate thermal stability of suppository bases, theobroma oil (cocoa butter) and a palm kernel oil (PKO) blend.
The study shows theobroma oil possesses six polymorphic forms whilst the palm kernel oil blend has three. Upon rescanning,
the PKO blend does not show changes in the enthalpy of fusion and the melting point with time, whilst the theobroma oil shows
significant reduction, and only regained its thermal stable state after 10 days. This indicates that PKO blend possesses better
Authors:G. Keller, F. Lavigne, C. Loisel, M. Ollivon, and C. Bourgaux
The thermal behavior of three ural fats (displaying very different composition), cocoa butter (CB)2, lard, and a stearin obtained from anhydrous milk-fat (AMF) fractionation, were studied by both DSC and X-ray diffraction as a function of temperature (XRDT). To perform temperature explorations between −30‡C and +80‡C, at rates identical to those used for DSC and ranging from 0.1 K min−1 to 10 K min−1, a new set of X-ray sample-holders, temperature-controlled by Peltier effect, has been developed. It is shown that the three more stable polymorphic forms of CB were easily characterized by either X-ray diffraction or DSC, and existence of two Β-3L forms was confirmed. On the contrary, the more complex polymorphism of lard and AMF required combined examination by DSC and XRDT and the brightness of the synchrotron source for studies at the highest heating rates. Quantitative analysis of the long spacings of XRDT recordings is invaluable for interpretation of thermal events. For instance, it was found that the simultaneous formation of two polymorphic forms, of apparent long spacing of 34 and 42 å, at the onset of lard crystallization might explain the difficulty of its fractionation.
The crystallisation properties of a mixture of triacylglycerols (TG), cocoa butter (CB) 75%/miglyol 25%, were investigated
on cooling at 0.5 °C/min using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The influence of (i) the
dispersion of TG within nanoparticles stabilised by proteins, and of (ii) the presence of polar lipids were characterised.
In bulk, crystallisation of TG successively occurred with a α 2L (49.3 Å) structure, then the formation of longitudinal stackings
of 44.5 and 34.5 Å of β′ form was interpreted as co-crystallisation of TG from CB and miglyol. The dispersion of TG in nanoparticles
of about 400 nm induced a higher supercooling and changed their crystallisation properties. The formation of α 49.2 Å and
β′ 45 Å structures corresponded to the segregation of TG from CB in solid phases while TG from miglyol remained liquid. Phospholipids
with saturated fatty acid chains affected the thermal properties of TG, which demonstrated their localisation at the surface
of the nanoparticles. DSC and XRD revealed to be very sensitive and adapted methods to increase the knowledge about the mechanisms
of crystallisation in emulsion.
Authors:Tímea Kaszab, Lídia Bornemisza, and Katalin Badak-Kerti
Introduction Chocolate is an important product of the confectionery industry. The fat in chocolate, the cocoabutter, has quite a few interesting properties, but there are some factors that make it not always suitable. The first is its extremely