Another good question from reader Alicia. Sugar bloom is a different phenomenon, familiar to anyone who’s refrigerated or frozen chocolate for any period of time. Sugar bloom happens when moisture contacts the surface of solid chocolate. When that happens the sugar near the surface of the chocolate dissolves into the water and becomes syrup. In time the water evaporates leaving sugar crystals behind.
The problem is exacerbated when chocolate is repeatedly chilled and warmed. So for instance if you have a large chocolate bar in the refrigerator or freezer and you occasionally take it out to chip a bit off, you get condensation on the chocolate bar when it meets the warm air. When you put the chocolate back in the chill chest the syrup-evaporation thing happens, and the cycle is repeated with every removal. Pretty soon a large proportion of the sugar is drawn out, and because long-term freezing also exacerbates fat bloom, shortly your expensive chocolate bar has the mouthfeel of sidewalk chalk. The same thing happens if you have a habit of leaving the refrigerator or freezer door open for a long period of time.
Thanks for a great question, Alicia!