Cocoa powder surface composition during aging: A focus on fat

International audience; The surface of 11 wt.% fat cocoa particles was thoroughly investigated during a 2-month storage at 20 and 40 degrees C and at a(w) = 0.2. Surface fat migration was evidenced only for powders stored at 40 degrees C by X-ray Photoelectron Spectroscopy. This was confirmed by ToF-SIMS, which allowed visualizing bigger fat patches at the surface of 40 degrees C-stored powders. These observations emphasize that fat need to be under a melted form to move toward the surface during storage. However, an increase in the free fat content was observed at both 20 degrees C and 40 degrees C. These results suggest rearrangements of particle structure during storage; free fat being more accessible to solvents at both temperatures. Confirmation was done by Scanning and Transmission Electron Microscopy images. Free and encapsulated fat were also extracted and analyzed during storage and no significant difference in fatty acids distribution (C16, C18, C18:1, C18:2) was observed by gas chromatography.