The Truth Behind That Powdery Film on Your Chocolate Bar

There's nothing worse than unwrapping a pricey chocolate bar, only to find it covered in a dull, chalky coating instead of the smooth, shiny finish you expected. This harmless but unsightly phenomenon is called chocolate bloom. So what causes it, and does it mean your chocolate experience is ruined? We spoke with Michael Laiskonis, former pastry chef at Le Bernardin and now a culinary instructor at New York City's Institute of Culinary Education, to uncover the science behind chocolate bloom and how you can prevent or fix it.

To understand chocolate bloom, let's start with a bit of chocolate 101. Real chocolate consists of just two key ingredients: sugar and cocoa beans. The cocoa beans are made up of cocoa solids (the roasted, fermented mass of cacao seeds) and cocoa butter (which is essentially the fat in cocoa).

"Cocoa butter is solid at room temperature, which is unusual for a plant-based fat," explains Laiskonis. "It can actually take on several solid forms depending on how it cools."

What Is Fat Bloom and How Does It Affect Your Chocolate?

With this knowledge, we can better understand one of the main reasons chocolate can turn chalky: fat bloom. When cocoa butter transitions from liquid to solid, it forms crystals—something often discussed when it comes to chocolate tempering. "During tempering, we aim to isolate a specific crystal [the fifth of six solid forms cocoa butter can take], which is key to achieving the shine, snap, and resistance to melting that make chocolate look and feel perfect," explains Laiskonis.

Improperly tempered chocolate or chocolate exposed to heat—like being left in a hot car or stored near a stove—can melt and then re-solidify in a less stable form, resulting in a dull, streaky, or blotchy appearance. This process, known as fat bloom, can also affect the texture of chocolate, causing it to melt unevenly. However, Laiskonis clarifies that while it may feel uneven, fat bloom doesn't typically create the grainy texture associated with sugar bloom, the second form of bloom.

What Is Sugar Bloom and How Does It Damage Chocolate?

Chocolate is free of any measurable water content, and the sugar inside is finely ground, not dissolved. This is because fat and water don't mix well, says Laiskonis. When chocolate is exposed to water—whether from spills or humidity—its finely ground sugar crystals dissolve and re-crystallize into larger, coarser ones. This can lead to a gritty, sandpapery texture on the surface. Though sugar bloom can be tough to tell apart from fat bloom, it tends to have a more grayish hue than the typical white of fat bloom, notes Laiskonis.

Good News: It Can Be Fixed!

Sugar bloom can't be fixed, unless you're lucky enough to have professional chocolate equipment at home to re-grind it," he jokes. However, fat bloom is another story. To restore your chocolate to its glossy, crisp glory, simply melt it down and re-temper it on the stovetop, in the microwave, or even in a slow cooker.

If the idea of tempering chocolate sends you into a panic and you happen to have some heavy cream nearby, you can transform your bloomed chocolate into a silky ganache. Just break the chocolate into pieces, stir it into freshly boiled cream, and voila—use the smooth glaze to top off cakes, drizzle over profiteroles or cookies, or dip fresh strawberries.

For the true chocolate enthusiasts out there, Laiskonis adds a final, gentler form of bloom that affects chocolate when it sits around for a long time. Over time, all type-five cocoa butter crystals eventually change into type-six crystals. This transformation can take months, or even a year or more. "It's like that forgotten bar of chocolate you discover in the back of your pantry—when you open it, you might find it's lost its shine and looks a little dull and gray," he explains.

Since this type-six crystal has a higher melting point, it melts more slowly and has a more brittle texture than freshly made chocolate. So, while it may not feel quite as satisfying as a fresh bar, the main impact is more mental than anything else, as it's just not the experience you expect from a piece of chocolate.

"In truth, chocolate never really goes bad," Laiskonis explains. "There's not enough moisture in it for mold or bacteria to grow. While dark chocolate may not last forever—the cocoa butter will eventually go rancid—it takes years for that to happen."

Next time you find yourself staring at chocolate with a chalky surface, don’t worry. Simply melt it with some cream, and you’ll be enjoying a delicious treat in no time.