After chocolate has been stored for a while or moved through changing temperatures, pale grey streaks or patches may appear on its surface. This is usually called bloom, but it is not a single process.
Fat bloom involves the crystal structure of cocoa butter. When chocolate warms, some fat can soften and migrate. As it cools again, that fat may rearrange into larger or less desirable crystals at the surface. The formerly glossy, dark surface then looks grey, and the chocolate may lose some of its clean snap. Repeated temperature fluctuations make this process more likely.
Sugar bloom requires moisture. If cold chocolate is suddenly exposed to warm, humid air, tiny droplets may condense on it. The water dissolves surface sugar; when it evaporates, larger sugar crystals remain, often producing a rougher, powderier feel than fat bloom. Both forms are changes in the distribution and crystallisation of ingredients, so a pale coating alone does not establish that the chocolate is mouldy. Whether food is still suitable to eat should also be judged from its use-by guidance, smell, storage history, and any unusual dampness or actual mould. Stable, cool and dry storage, without abrupt temperature changes, is the practical way to reduce bloom.
https://arxiv.org/abs/1612.00741
https://www.callebaut.ru/en-AE/callebaut-chocolate-academy/tutorials/storing/prevent-sugarbloom
Discover more from Geoffrey Chen
Subscribe to get the latest posts sent to your email.