What has occurred is that the chocolate has undergone a process called "bloom." There are two main types of chocolate bloom. The first is sugar bloom and the second fat bloom. Each has different causes. However, no matter the type of bloom, the surface of the chocolate will become unappealing and will have a mottled or hazy look. If fat bloom is present, it is likely that the texture of the chocolate may have changed from when it was originally molded.
Sugar Bloom
Sugar bloom is caused by moisture coming into contact with the chocolate. Chocolate is composed of ground cocoa beans and sugar, and sometimes vanilla and lecithin. While you may not see the sugar crystals present in chocolate, they are there. They simply are too small to see. Water when it comes in contact with the chocolate, dissolves the sugar on the surface of the chocolate. As the water dries, the dissolved sugar crystallizes and precipitates onto the surface of the chocolate. The resulting small sugar crystals give the chocolate a dusty appearance.
The sugar bloom may have occurred in a number of ways. The most obvious of is that water was inadvertently spilled on the chocolate, or the chocolate came in contact with or was placed on something wet. Sugar bloom may occur in other not so obvious ways. For example, if the chocolate was placed in the refrigerator where it became cold and then removed and placed in open air, the cold chocolate will condense moisture from the air, and the condensation will cause the sugar bloom. Sugar bloom may also occur if the chocolate has been in an environment with too high a humidity.
The best way to avoid sugar bloom is to store your chocolate in an area of low humidity and stable temperature so as to avoid condensation. If the chocolate is cold, such as when it has been stored in the refrigerator, it should be covered (perhaps with a towel) so that it will warm slowly and air circulation is minimized.
A Simple Test
One way you can easily check to see if a piece of chocolate has undergone sugar bloom or fat bloom is to lick your finger and touch it to the chocolate. If the dusty appearance disappears, then it is sugar bloom. (The moisture on your finger dissolved the sugar crystals on the chocolate.) If the bloom remains, then it is fat bloom.
Fat Bloom
Fat bloom, unlike sugar bloom, is not always caused by a simple set of circumstances, such as the chocolate becoming wet. Fat bloom is more complicated, and oftentimes it may be more difficult to discover the actual source of the problem.
Fat bloom typically appears as lighter color spots on the chocolate. As the name implies, the bloom is composed of fat, in this case the naturally occurring fat that comes from the cacao bean -- cocoa butter.
When discussing the reasons for fat bloom, it is important to note that when
cocoa butter hardens, it forms crystals. Some of the crystals are stable, but other crystals are not and will actually change form over time. During chocolate manufacturing, a process called tempering is used to ensure that only stable crystals form, while the chocolate hardens. Fat bloom is caused by the interaction of the various types of crystals or the tempering process (or lack thereof).
An example of severe fat bloom in completely untempered chocolate
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.
An example of fat bloom on a chocolate bar
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.
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