Fat bloom in chocolate and compound coatingsAlthough bloom in chocolates and compound coatings has been studied for many decades, the specific mechanisms of fat bloom still remain largely unknown. Furthermore, it is generally considered that the mechanisms for fat bloom formation in chocolate are different than those for compound coatings.After a brief review of chocolates and compound coatings, we summarize past studies on fat bloom formation in both products. A comparison of the effects of various parameters on bloom formation, either as accelerators or inhibitors, provides insight into the similarities and differences in these phenomena.Based on this analysis, a global view of the mechanisms of bloom formation in both chocolates and compound coatings is suggested.

Surface bloom on improperly tempered chocolateThe surface composition, in terms of sugar and fat content, on untempered and overtempered chocolates was estimated by carefully scraping the surface layer and analyzing fat and sugar melting enthalpies by differential scanning calorimetry. The dull surface of over-tempered chocolate had a fat and sugar composition similar to the initial chocolate mass, whereas the surface bloom formed on untempered chocolate was nearly depleted of fat, containing primarily sugar and cocoa solids. This was confirmed qualitatively by using polarized light microscopy, where no fat crystals could be observed in the bloom spots. Bloom on untempered chocolate corresponded to a phase separation between fat, sugar and cocoa solids. In contrast, the grey, dull aspect of the surface of over-tempered chocolate had essentially the same sugar-tofat ratio as the intact chocolate and was due to a diffuse reflection of light on a rough surface, most likely induced by large cocoa butter crystals. Bloom on untempered chocolate developed regardless of the relative humidity of storage (between 0 and 75%). However, bloom developed more quickly and to a greater extent at lower relative humidity. Whiteness was directly related to the number, diameter and growth speed of the white bloom spots.