Chocolate Bloom Explained: What It Is, Why Chocolate Turns White, and How to Prevent Fat and Sugar Bloom

Chocolate sometimes develops a white, grey, or cloudy layer on its surface. This is called chocolate bloom. It looks like mold, but in most cases it is not. Bloom is a physical change in the way fat or sugar crystals arrange themselves on the surface of chocolate, affecting how it looks and feels rather than its safety (Afoakwa et al., 2009; Stortz & Marangoni, 2011).

Understanding bloom is important for consumers, chocolatiers, and premium brands because it reduces unnecessary food waste and helps explain why high-quality chocolate sometimes looks imperfect.

What exactly is chocolate bloom?

Chocolate bloom happens when either fat or sugar moves out of the chocolate and recrystallizes on the surface. Food scientists classify bloom into two main types:

• Fat bloom – caused by cocoa butter or other fats migrating and crystallizing on the surface.
• Sugar bloom – caused by moisture dissolving sugar, which later recrystallizes when the water evaporates.

These processes are driven by temperature changes, humidity, and the natural instability of fat crystals in chocolate (Afoakwa et al., 2009).

Fat bloom vs sugar bloom

Fat bloom usually appears as smooth grey or white streaks or cloudy patches. The surface still feels relatively smooth or slightly waxy. It forms when cocoa butter melts slightly and then re-solidifies in a different crystal structure on the surface. This process is closely linked to cocoa butter polymorphism, meaning that fat molecules can arrange themselves in multiple crystal forms, some of which are less stable over time (Declerck et al., 2021).

Sugar bloom, on the other hand, looks chalky and feels gritty. It happens when condensation forms on chocolate, dissolving surface sugar. When the moisture evaporates, sugar crystals remain on the surface. This often occurs when cold chocolate is moved into warm, humid air (Stortz & Marangoni, 2011).

Why does chocolate bloom happen?

The main trigger for bloom is temperature instability. When chocolate warms and cools repeatedly, cocoa butter crystals partially melt and then reform in less desirable structures. Over time, these fats migrate to the surface, creating fat bloom (Afoakwa et al., 2009).

Manufacturing also plays a role. Chocolate must be tempered correctly so that most cocoa butter solidifies in a stable crystal form (commonly called Form V or βV). Improper tempering or later exposure to heat can disrupt this structure and increase bloom risk (Stobbs et al., 2025).

Moisture is the main driver of sugar bloom. Water droplets dissolve sugar on the chocolate surface, and when the water dries, sugar recrystallizes as a white, powdery layer (Stortz & Marangoni, 2011).

Filled chocolates, such as pralines or nut-based centers, are more prone to bloom because fats from the filling can migrate into the chocolate shell, accelerating fat crystallization on the surface (Hřivna et al., 2021).

Is bloomed chocolate safe to eat?

In most cases, yes. Bloom is not mold. It is a physical rearrangement of fat or sugar crystals and does not mean the chocolate is spoiled or dangerous (Stortz & Marangoni, 2011).

However, chocolate should be discarded if it shows fuzzy growth, strong off-odors, or signs of contamination. Bloom affects quality, not food safety.

How to prevent chocolate bloom

The best way to prevent bloom is to keep chocolate in a stable, cool, and dry environment. Avoid frequent temperature changes. Chocolate should not be repeatedly moved between hot and cold places (Afoakwa et al., 2009).

Humidity control is equally important. Chocolate should be protected from moisture and condensation. If refrigeration is necessary in hot climates, the chocolate must be sealed in airtight packaging and allowed to return to room temperature before opening, so moisture forms on the packaging instead of on the chocolate surface (Stortz & Marangoni, 2011).

For manufacturers, proper tempering and fat-compatible fillings are critical. Correct crystal formation and barrier layers between fillings and shells significantly reduce bloom risk (Stobbs et al., 2025; Hřivna et al., 2021).

Can bloomed chocolate be fixed?

Bloomed chocolate can still be used for baking, melting, and hot chocolate. Melting removes visible bloom, but unless the chocolate is properly re-tempered, bloom may return. Professional re-tempering restores the correct cocoa butter crystal structure (Stobbs et al., 2025).

Why chocolate bloom matters

Chocolate bloom is one of the most misunderstood quality issues in food. It does not mean poor ingredients or unsafe chocolate. It reflects how sensitive cocoa butter and sugar are to temperature, moisture, and time. Understanding bloom helps consumers trust premium chocolate and helps brands reduce waste and unnecessary returns.

References (APA, with DOI)

Afoakwa, E. O., Paterson, A., Fowler, M., & Vieira, J. (2009). Fat bloom development and structure–appearance relationships during storage of under-tempered dark chocolates. Journal of Food Engineering, 92(4), 383–390. https://doi.org/10.1016/j.jfoodeng.2008.12.019

Declerck, A., Nelis, V., Danthine, S., Dewettinck, K., & Van der Meeren, P. (2021). Characterisation of fat crystal polymorphism in cocoa butter by time-domain NMR and DSC deconvolution. Foods, 10(3), 520. https://doi.org/10.3390/foods10030520

Hřivna, L., Machálková, L., Burešová, I., Nedomová, Š., & Gregor, T. (2021). Texture, color, and sensory changes occurring in chocolate bars with filling during storage. Food Science & Nutrition, 9(9), 4863–4873. https://doi.org/10.1002/fsn3.2434

Stobbs, J. A., Ghazani, S. M., Donnelly, M.-E., & Marangoni, A. G. (2025). Chocolate tempering: A perspective. Crystal Growth & Design, 25(9), 2764–2783. https://doi.org/10.1021/acs.cgd.5c00269

Stortz, T. A., & Marangoni, A. G. (2011). Heat resistant chocolate. Trends in Food Science & Technology, 22(6), 304–312. https://doi.org/10.1016/j.tifs.2011.02.001