Chocolate bloom refers to the formation of crystals on the exterior of chocolate which makes the surface appear gray, swirled, or gritty. This typically occurs due to poor or improper storage, or as part of preparing chocolate for use in making candy without properly tempering the chocolate. There are two basic types of blooming that can occur in chocolate: fat blooming occurs when the fat solids in cocoa butter melt and come to the exterior of the chocolate, before reforming as crystals; sugar blooming occurs when sugars crystallize on the chocolate exterior. Chocolate bloom results in an unpleasant appearance and potentially a gritty texture, but does not alter the taste of the chocolate. Bloomed chocolate can still be safely consumed.
Though there are two basic ways in which chocolate bloom can occur, they both tend to create similar results. The surface of the chocolate will often appear gray or swirled, and it may also take on a gritty appearance and texture. Both types of chocolate bloom often occur due to improper storage or handling of chocolate, usually resulting in exposure to moisture or extreme changes in temperature.
Fat blooming is one of the major causes of chocolate bloom and often produces the gray exterior commonly perceived as a bloom. There are a few different theories as to why this type of blooming occurs, but it is attributed to the fats in cocoa butter used to produce chocolate. The interior fats typically melt or separate from the rest of the chocolate, and emerge through pores to the exterior of the chocolate. Once at the outside, these fats solidify once more and create a gray coloration.
Sugar blooming is the other major cause of chocolate bloom and produces a gritty texture and appearance. This type of blooming occurs when sugars in the chocolate, often on the exterior, are exposed to water or moisture and dissolve. Once the moisture evaporates, the sugars are left behind and form crystals. This creates an appearance and texture that is gritty, since the sugar crystals coat the exterior of the chocolate.
Chocolate bloom does not typically affect the flavor of the chocolate, and it can be eaten safely, though it may be unsightly. Melting chocolate that has bloomed will often remove the discoloration or gritty texture, though it should be tempered before returning to a solid form to prevent future chocolate bloom. Tempering involves a process of alternately heating and cooling chocolate to control how the fats in the cocoa butter behave, preventing fat blooming. As long as the chocolate is tempered and not exposed to moisture or high humidity, blooming should not occur.