Blooming of chocolate is the major problem of the confectionery industry. It is the formation of visible white spots or a greyish haze on the chocolate surface, which leads to rejection by the consumer. Blooming of chocolate is due to large sugar or fat crystals on the chocolate surface, denoted as sugar or fat blooming, respectively.
The formation of chocolate blooming is often related to migration of sugar or lipid molecules to the surface with subsequent uncontrolled recrystallization.
The aim of the project is to understand the migration pathway and driving forces of lipid migration in chocolate. Chocolate is composed of particles, which are embedded in a continuous fat matrix. Thus, migration can take place through the matrix material, through the particle phase or at the interface between particles and matrix (Figures).
Therefore, migration is observed on a macroscopic and microscopic level. Furthermore, the structure of cocoa butter composites and chocolates is analyzed with X-ray tomography and synchrotron micro small angle X-ray scattering (µSAXS, Figure above). Additionally, wetting behavior and surface changes are observed with contact angle by the sessile drop protocol (Figure below).
The Figure below shows that the wetting behavior is dependent on the composition of the material. For a better understanding of the wetting behavior, the influence of roughness, contact angles of different test liquids and the of temperature are analyzed in addition. Finally, structural changes during storage are investigated with contact angle measurements with the sessile drop protocol.
Reinke S. K., Roth S. V., Santoro G., Vieira J., Heinrich S., Palzer S. (2015). Tracking Structural Changes in Lipid-based Multicomponent Food Materials due to Oil Migration by Microfocus Small-Angle X-ray Scattering, ACS Applied Materials & Interfaces.
Reinke S.K., Roth S.V., Santoro G., Vieira J., Palzer S., Heinrich S. (2014). Lipid migration in multicomponent food products such as chocolate, Presentation at the DPG 2015, Berlin, Germany.
Reinke S.K., Roth S.V., Santoro G., Rasburn J., Palzer S., Heinrich S. (2014). Molecular migration in multicomponent food products, Presentation at the DPG 2014, Dresden, Germany.
Project started 2013
Funded by Nestec Ltd, Switzerland; Nestlé PTC York, United Kingdom