Detailed observation of crystal phase transition of fats occurring over a narrow temperature range

Crystalline fat, which is raw material of cocoa butter, margarine, etc., has a number of crystal polymorphs and shows complex phase transitions around room temperature. Controlling crystal phase and phase transition process is important for manufacturing process management and quality assurance. 

It is necessary to find the heat treatment conditions to obtain appropriate crystal forms as easily as possible. Using a high-speed two-dimensional X-ray detector and simultaneous measurement of XRD and DSC, it is possible to investigate the crystal forms deposited and the influence of heating, cooling and other temperature conditions. 

The figure on the right is a schematic of the phase transition of cocoa butter in a tempering process. Tripalmitin, one of triglycerides contained in cocoa butter, experiences three phase transitions in a temperature range of only several degrees.

The figure below shows the results of simultaneous measurement of XRD and DSC. XRD scanning was performed at 160°/min using a Rigaku Ultima IV multipurpose diffraction system equipped with a DTEX high-speed two-dimensional X-ray detector. The temperature was increased at a rate of 1°/min. A series of phase transition was observed between 46°C to 51°C.