Chocolate bloom
Encyclopedia
Chocolate bloom is a moldy-looking white coating that can appear on the surface of chocolate
. This effect is one of the main concerns in the production of chocolate. There are two types of bloom: fat bloom, arising from changes in the fat in the chocolate; and sugar bloom, formed by the action of moisture on the sugar ingredients. The unsightly crystals of fat and sugar bloom limit the shelf life of many chocolates. Chocolate that has "bloomed" is still safe to eat, but may have an unappetizing appearance and surface texture.
that has separated toward the surface. It is caused by:
There is no single universally accepted theory that describes fat bloom in chocolate. Current theories about fat bloom fall into two categories: polymorphic transformation and phase separation theory.
. At higher temperatures, the lower melting point triglycerides in cocoa butter will melt and this liquid phase occupies a greater volume than the solid. The liquid phase will then be squeezed out to the surface through fissures or pores in the chocolate. After the liquid phase reaches the surface, the triglycerides will recrystallize into the most stable form, with bloom occurring.
, there are six essential polymorphic forms
. The polymorphic transformation theory is based on the fact that bloomed chocolates are always found to contain the most stable VI polymorph of cocoa butter. According to this theory, bloom occurs through the uncontrolled polymorphic transformation of cocoa butter from a less stable form (form IV or V) to the most stable form (form VI). The technology of good chocolate production depends on ensuring that only the stable form of the cocoa butter
ingredient exists in the final product. In poorly tempered chocolate, form IV will transform to V and eventually form VI, resulting in bloom, while in well-tempered chocolate, form V will transform to form VI and bloom may also occur. Elevated and/or fluctuating temperatures promote the transformation rate and thus also promote the rate of bloom formation. However, it is found that the production of form VI from form V does not always lead to bloom; a direct relationship cannot be established between fat bloom and the evolution of the crystalline forms. The onset of transformation from form V to form VI crystals is not the cause of visual bloom; rather, this transition should be considered as an aspect of cocoa butter recrystallization
that may result in bloom.
bloom also occurs and is not necessarily distinguishable from the fat bloom by appearance. In freshly sugar bloomed samples, it is often easy to feel the surface difference; sugar bloom feels dry and does not melt to the touch, while fat bloom feels slick and melts. One can often see the difference by touching a small droplet of water to the surface. With fat bloom, the droplet simply beads up. With sugar bloom, the droplet quickly flattens and spreads, as the water dissolves the microscopic sugar particles on the surface (Seguine, 2001). Alternatively, gentle warming of the surface (with a hairdryer, for example) will cause the crystals of fat bloom to melt, removing the appearance of bloom, while leaving sugar bloom unchanged.
Sugar bloom is caused by moisture. Condensation
on to the surface of the chocolate or moisture in the chocolate coating causes the sugar to absorb the moisture and dissolve. When the moisture evaporates, the sugar forms larger crystals, leaving a dusty layer. It is caused by:
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...
. This effect is one of the main concerns in the production of chocolate. There are two types of bloom: fat bloom, arising from changes in the fat in the chocolate; and sugar bloom, formed by the action of moisture on the sugar ingredients. The unsightly crystals of fat and sugar bloom limit the shelf life of many chocolates. Chocolate that has "bloomed" is still safe to eat, but may have an unappetizing appearance and surface texture.
Fat bloom
A great deal has been written about chocolate fat bloom. To date, it is generally accepted that visual fat bloom in chocolate is the cocoa butterCocoa butter
Cocoa butter, also called theobroma oil, is a pale-yellow, pure edible vegetable fat extracted from the cocoa bean. It is used to make chocolate, biscuits, and baked goods, as well as some pharmaceuticals, ointments, and toiletries...
that has separated toward the surface. It is caused by:
- Poor (incorrect or incomplete) tempering of the chocolate
- Incorrect cooling methods, including covering cold centers
- The presence of soft fats in the centers of chocolate-covered units
- Warm storage conditions
- The addition to chocolate of fats incompatible with cocoa butter
- Abrasion and finger marking
There is no single universally accepted theory that describes fat bloom in chocolate. Current theories about fat bloom fall into two categories: polymorphic transformation and phase separation theory.
Phase separation theory
According to this theory, storage bloom is due to phase separation of the triglycerides within the crystalline structure of cocoa butter. This theory is based on the fact that cocoa butter is a mixture of diverse triglycerides and each type of triglyceride has a unique melting temperatureMelting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
. At higher temperatures, the lower melting point triglycerides in cocoa butter will melt and this liquid phase occupies a greater volume than the solid. The liquid phase will then be squeezed out to the surface through fissures or pores in the chocolate. After the liquid phase reaches the surface, the triglycerides will recrystallize into the most stable form, with bloom occurring.
Polymorphic transformation
In cocoa butterCocoa butter
Cocoa butter, also called theobroma oil, is a pale-yellow, pure edible vegetable fat extracted from the cocoa bean. It is used to make chocolate, biscuits, and baked goods, as well as some pharmaceuticals, ointments, and toiletries...
, there are six essential polymorphic forms
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
. The polymorphic transformation theory is based on the fact that bloomed chocolates are always found to contain the most stable VI polymorph of cocoa butter. According to this theory, bloom occurs through the uncontrolled polymorphic transformation of cocoa butter from a less stable form (form IV or V) to the most stable form (form VI). The technology of good chocolate production depends on ensuring that only the stable form of the cocoa butter
Cocoa butter
Cocoa butter, also called theobroma oil, is a pale-yellow, pure edible vegetable fat extracted from the cocoa bean. It is used to make chocolate, biscuits, and baked goods, as well as some pharmaceuticals, ointments, and toiletries...
ingredient exists in the final product. In poorly tempered chocolate, form IV will transform to V and eventually form VI, resulting in bloom, while in well-tempered chocolate, form V will transform to form VI and bloom may also occur. Elevated and/or fluctuating temperatures promote the transformation rate and thus also promote the rate of bloom formation. However, it is found that the production of form VI from form V does not always lead to bloom; a direct relationship cannot be established between fat bloom and the evolution of the crystalline forms. The onset of transformation from form V to form VI crystals is not the cause of visual bloom; rather, this transition should be considered as an aspect of cocoa butter recrystallization
Recrystallization (chemistry)
-Chemistry:In chemistry, recrystallization is a procedure for purifying compounds. The most typical situation is that a desired "compound A" is contaminated by a small amount of "impurity B". There are various methods of purification that may be attempted , which includes recrystallization...
that may result in bloom.
Methods to minimize fat bloom
- Maintain an appropriate storage temperature for chocolate products
- Use an appropriate recipe for the fat
- Use a fat–based barrier coating between two domains of differing fat content and composition
- Add a bloom inhibitorReaction inhibitorA reaction inhibitor is a substance that decreases the rate of, or prevents, a chemical reaction.-Inhibition of a catalyst:An inhibitor can reduce the effectiveness of a catalyst in a catalysed reaction...
- Add seeding crystalsSeed crystalA seed crystal is a small piece of single crystal/polycrystal material from which a large crystal of the same material typically is to be grown...
Sugar bloom
While the most common is fat bloom, sugarSugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
bloom also occurs and is not necessarily distinguishable from the fat bloom by appearance. In freshly sugar bloomed samples, it is often easy to feel the surface difference; sugar bloom feels dry and does not melt to the touch, while fat bloom feels slick and melts. One can often see the difference by touching a small droplet of water to the surface. With fat bloom, the droplet simply beads up. With sugar bloom, the droplet quickly flattens and spreads, as the water dissolves the microscopic sugar particles on the surface (Seguine, 2001). Alternatively, gentle warming of the surface (with a hairdryer, for example) will cause the crystals of fat bloom to melt, removing the appearance of bloom, while leaving sugar bloom unchanged.
Sugar bloom is caused by moisture. Condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
on to the surface of the chocolate or moisture in the chocolate coating causes the sugar to absorb the moisture and dissolve. When the moisture evaporates, the sugar forms larger crystals, leaving a dusty layer. It is caused by:
- Storage of chocolates in damp conditions
- Deposit of "dew" during manufacture from damp cooler air or allowing chocolates to enter a packing room at a temperature below the dew point of that room
- Use of hygroscopicHygroscopyHygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment. This is achieved through either absorption or adsorption with the absorbing or adsorbing material becoming physically 'changed,' somewhat, by an increase in volume, stickiness, or other...
ingredients (low grade or brown sugars) - High-temperature storage conditions of chocolate-covered confectionary, where the centers have a high relative humidity and the water vapor given off is trapped in the wrappings
Method to minimize sugar bloom
- Maintain an appropriate storage temperature for chocolate products. A psychrometric chart is a valuable tool in determining the temperature above which food must be maintained in order to avoid condensation.