Microstructure of fat bloom development in plain and filled chocolate confections

Temperature-controlled environmental scanning electron microscopy was used to examine the microstructural changes in plain solid chocolate and its counterpart stored against a tricaprylin-based filling cream. Sample storage at 26 °C for 40 days led to significant changes in microstructure as a function of time. Surface imperfections (pores, pits, etc.) initially present on the filled confection disappeared within two days whereas those on the control did not throughout the storage period. Morphological changes on the surface of the control were dominated by the growth of needle-like crystals whereas spherulites appeared on the filled chocolate, with large crystals (upwards of 100 microns in length, in some cases) observed in both cases. From a microstructural perspective, both diffusion and capillarity appear to have a part in fat bloom initiation and propagation, though temperature and the presence of a filling fat strongly dictate which mechanism will dominate.