If chocolate is not tempered, the unstable forms of cocoa butter crystal will form, most notability the Beta Prime and Alpha forms. After the cocoa butter hardens, these unstable forms will slowly change their forms to the stable Beta form. The Beta crystals are slightly smaller than the Beta Prime or Alpha forms, so that when this transition occurs, the chocolate contracts. The new stable Beta crystals then form, projecting above the surface of the chocolate, visible as bloom.
If the chocolate is stored in a room where the temperature fluctuates near the melting temperature of the stable Beta crystals, two additional types of fat bloom may form. In the first, some of the Beta crystals melt. When they recrystalize, they recrystalize slowly, since the ambient temperature is close to that of the chocolate. This allows the crystals to grow much larger than the original small, compact crystals. In addition to projecting above the surface of the chocolate, these larger crystals may displace cocoa butter, forcing it to the surface.
The second type of bloom is created when the crystals have softened instead of melted. It is during this period that cocoa butter that has slightly melted migrates toward the surface. When it breaks the surface, it pools ever so slightly, and when it cools the cocoa butter appears as spots.
Many people are surprised to learn that fat bloom also occurs in cocoa powder. Cocoa powder contains between 12-20% cocoa butter. Since some cocoa butter is present, it must be tempered during manufacturing, just as chocolate is. Cocoa powder that has been improperly tempered or undergone temperature fluctuations may cause bleaching of the cocoa powder and may cause clumping as the cocoa butter helps the particles of the cocoa powder adhere to each other. As with chocolate, when bloom occurs it does not affect the edibility of the cocoa powder but may have an aesthetic impact.
Studies on fat bloom indicate that the bloom consists of large, single cocoa butter crystals or collections of crystals of the stable Beta form of cocoa butter. Other forms of cocoa butter crystals are not present in fat bloom.
Fat blooming actually occurs in a third process. This case affects not so much the chocolate industry directly but the ancillary confectionary industry. When chocolate is used to coat nuts or fillings that contain oils or fats (such as nut butters) that are incompatible with chocolate, the oils may actually seep into or through the chocolate over time. This is called fat migration. As the oils displace the cocoa butter, cocoa butter may seep onto the surface of the piece of confectionary and recrystalize as bloom. When this occurs, the manufacturing process needs to be examined or the confectionary reformulated.
If fat bloom is present and the chocolate is not newly cast, then temperature fluctuations should be the first thing looked at. If an air conditioner is in use, the outlet may be too close to the chocolate (causing temperature fluctuations as the air conditioner turns on and off), or it may simply be undersized for the room to be cooled. If the chocolate was recently molded, the temper of the chocolate is suspect, and adjustments to the temper procedure may be required.
Fat Bloom as Quality Indicator
Fat Bloom is a good indicator that the chocolate may not be in good condition. It is not uncommon for chocolate that has bloomed to undergo other changes. For example, it may have lost its temper. When chocolate has properly crystallized, it will have a shiny finish, have a nice snap when broken, and will melt at approximately 95 degrees Fahrenheit (35 C). If chocolate is stored in a room where the temperature has fluctuated or has become too hot, the chocolate will recrystallize. When this happens, the cocoa butter crystals will regrow in an uncontrolled fashion and will likely result in fat bloom. While fat bloom may be only an aesthetic problem, chocolate where fat bloom is present should be examined to ensure that its temper remains intact. If the chocolate will be melted and then remolded or used in baking, neither sugar nor fat bloom will appreciably affect the quality of the final product. The one exception to this is where fat migration has occurred, such as may happen in the confectionary industry.
In an effort to eliminate bloom, some manufacturers will add a variety of fats and their derivatives (most notably stearins) to the chocolate prior to molding. This provides only a limited amount of protection from bloom, though as of yet, there is no bloom-free chocolate. Of course, at Amano Chocolate, we do not use additives to prevent bloom, nor do we encourage their use. Instead, at Amano we choose to watch our manufacturing practices with added diligence. Chocolate simply means too much to us to adulterate it.