Has this ever happened to you: you opened up a pack of chocolate only to find a whitish coating on the surface? Unappetizing, right? Well, some people wonder if chocolate in this state is still edible. Well, we cannot really blame them though. Besides, this change in appearance is considered a major quality defect in the confectionery industry. It leads to loss of gloss, bright color and smooth appearance in chocolate products. Obviously, these may affect consumer preference. Luckily, the white coating is not some work of spoilage microorganisms—it is not moldy. So, yes, chocolate with whitish coating is safe to eat. But how does it form though?

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That whitish coating form is chocolate blooming. Chocolate blooming is either fat or sugar bloom. Let’s see what causes both types of chocolate blooming to form.

FAT BLOOM

Fat bloom is most common. This usually happens when the chocolate is stored in an area where the temperature fluctuates constantly. The temperature changes encourage the cocoa butter to melt and resolidify. Here’s what exactly happens here. As the fat melts, it moves and migrates through capillary action. Then, it recrystallizes as it settles to the surface as what looks like whitish coating.

Fat bloom is what forms when you leave a chocolate candy in the car. When the chocolate melts and cools, the fat separates from the rest of the ingredients and rises to the surface.

However, fat bloom can be prevented by storing chocolate at a temperature of 59–64°F (15–18°C). It is a must that the temperature must be held steady in this range to prevent melting and resolidification.

Aside from fluctuating storage temperature, poor tempering is also a reason for fat bloom. Tempering is careful heating and cooling chocolate to stabilize it and create a glossy and smooth finish. This is achieved if there are sufficient number of stable polymorphic form V. Cocoa butter has six crystal forms or polymorphs (form I-VI). Form VI is the most stable. If tempering is poorly done, the cocoa butter crystallizes uncontrollably, forming white moldy finish on the surface of the chocolate.

When tempering dark chocolate, melt it at 115-120°F (46-49°C) and then cool with constant stirring to 82-84°F (28-29°C) to form nuclei for growth of predominantly stable crystals. After that, reheat the chocolate at 88-90°F (31-32°C) to melt the unstable crystals. The subsequent cooling must be controlled—not too rapid to produce only stable crystals and prevent fat bloom.

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In some chocolates, higher ratios of cocoa butter are used to make thinner chocolate. In such cases, a small amount of lecithin (up to 0.5%) is added to prevent bloom.

SUGAR BLOOM

The less common type of chocolate bloom. Sugar bloom can be distinguished by the rough, grainy coating on the surface. If you touch it and it does not disappear, that confirms it. Otherwise, it is fat bloom. Storing chocolate in a humid environment, like your refrigerator at home, mainly causes sugar bloom.

When the area is humid, the chocolate absorbs moisture from the atmosphere. And this also draws out the sugar. The condensation on the surface of the chocolate causes the sugar to absorb the moisture. When the moisture evaporates, the sugar dries and recrystallizes leaving behind whitish grainy texture on the surface.

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Sugar bloom is even more likely if the ingredient used in making chocolate is more hygroscopic (such as brown sugar), substances that absorb moisture from the air.

The best way to prevent sugar bloom is placing chocolate in an air-tight container and then storing it in a cool, dry place. Chocolate that has bloomed may not be fixed, but it can still be used in recipes that call for melted chocolate.

So that’s about it.

This post focuses on what causes chocolate bloom and how it forms. If you are someone from the manufacturing industry, and want to know further, this review on the formation process of bloom and its influencing factors will definitely help.

References:

M. Wallert, K. Colabroy, B. Kelly, J. Provost (2016). The Science of Cooking: Understanding the Biology and Chemistry Behind Food and Cooking. John Wiley & Sons, Inc.

M. Gibson (2018). Food Science and the Culinary Arts. Academic Press.

E. Afoakwa (2016). Chocolate Science and Technology. John Wiley & Sons, Ltd.

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