Why Does Chocolate Sometimes Turn White?

A forgotten chocolate bar may develop pale streaks or a dusty white surface. It can look moldy, but the change is usually something called chocolate bloom.

Chocolate contains cocoa solids, sugar, and cocoa butter. Cocoa butter can solidify into several different crystal arrangements. Manufacturers carefully control heating and cooling through a process called tempering so that the most desirable crystals dominate. These give finished chocolate its shine, firm snap, and smooth melting behavior.

If chocolate becomes too warm, some cocoa butter melts and moves toward the surface. When it cools again, the fat forms larger or less orderly crystals that scatter light and appear gray or white. This is known as fat bloom.

A second form, sugar bloom, occurs when moisture collects on the chocolate. Water dissolves some sugar at the surface. After the moisture evaporates, the sugar remains as a rough layer of tiny crystals.

Rapid temperature changes encourage both problems. Moving cold chocolate into warm, humid air can cause condensation, while repeatedly warming and cooling it can disturb the cocoa butter crystals. Poor tempering or incompatible fats in a filling can also produce bloom.

Bloomed chocolate is generally safe to eat if it has been stored properly and shows no sign of actual spoilage. Its texture, appearance, and flavor release may be less pleasant, but it can still be melted into baking recipes.

The white coating is therefore not normally chocolate becoming old or losing its color. It is material that was already inside the bar, rearranged into crystals large enough to become visible.