In the production of fat containing food products, insight in the crystallization behavior of fats is of utmost importance to obtain the desired product functionality and product quality. Several methodologies exist to follow the crystallization. In particular non-destructive techniques, such as ultrasonic waves, are interesting in a production environment since these allow for in-line measurements. The aim of the research is to study the potential of advanced ultrasonic techniques to monitor fat crystallization. Most research up to now deals with longitudinal transmission measurements of the solid fat content. In this research however reflection experiments are carried out with shear waves. A sample holder was custom build with a Plexiglas delay line and a temperature control unit. The main advantages of this experimental set-up are that no problems with excessive attenuation of the fat arise and that shear ultrasonic reflectance, unlike longitudinal measurements, seems sensitive to changes in microstructure. Measurements were performed within a centre frequency range of 500kHz to 5 MHz. We conjecture that several particular effects observed in the evolution of the reflection coefficient are due to the various crystallization phases of the cocoa butter.