Demystifying Chocolate Bloom: The Science Behind the White Stuff
When you open a bag of M&Ms and find a hazy, white film, your first thought might be that the candy has gone bad. Fortunately, this is not the case. The phenomenon, known as "chocolate bloom," is a natural process that affects the appearance of chocolate without impacting its safety. Chocolate bloom can be broken down into two distinct types: fat bloom and sugar bloom. Both are triggered by improper storage, but their underlying causes and effects on texture differ slightly.
Fat Bloom: When Cocoa Butter Gets Out of Place
Fat bloom is the more common type of chocolate bloom and is the result of temperature fluctuations. Chocolate, including the kind used in M&Ms, contains cocoa butter, a type of fat. When the chocolate is exposed to warm temperatures—for example, sitting in a hot car or a warm pantry—the cocoa butter begins to melt and separate from the other ingredients. As the chocolate cools and re-solidifies, the cocoa butter reforms into larger, less stable crystals that rise to the surface. These surface crystals create the tell-tale grayish-white, streaky, and sometimes greasy-looking film. The candy may also feel crumbly or soft to the touch. For M&Ms, the colorful candy shell provides some protection, but prolonged exposure to heat can still affect the chocolate inside and cause fat bloom to appear on the surface of the shell.
Sugar Bloom: The Effects of Moisture
Less common than fat bloom but equally harmless, sugar bloom occurs when the chocolate is exposed to moisture. This can happen if the M&Ms are stored in a humid environment or if they are moved too quickly from a cold place (like a refrigerator) to a warmer room, causing condensation to form on the surface. The moisture dissolves the sugar in the candy shell and chocolate, and as the water evaporates, the sugar recrystallizes into larger, coarser particles on the surface. This results in a gritty, dusty-white coating. The feel of sugar-bloomed chocolate is different from fat bloom; instead of greasy, it will feel dry and rough. This type of bloom is more prevalent in milk and white chocolates, which have a higher sugar content.
Can You Eat Bloomed M&Ms?
Yes, bloomed M&Ms are completely safe to eat, though the change in texture may be less than ideal. The flavor is generally unaffected, but the mouthfeel can change. Fat bloom can result in a soft or crumbly texture, while sugar bloom leads to a grainy, gritty sensation. The good news is that for many applications, like baking or making hot chocolate, these texture differences are unnoticeable once melted.
How to Prevent Chocolate Bloom
Proper storage is the most effective way to prevent chocolate bloom. The key is to keep the candy in a cool, dry place with a consistent temperature. Avoid temperature extremes and humidity to maintain the candy's perfect shine and texture.
- Maintain an ideal storage temperature: For chocolate, the best storage temperature is between 60–68°F (16–20°C). A pantry or a cool cupboard is often ideal. Avoid storing chocolate near heat sources like ovens or stovetops.
- Avoid refrigeration: Despite the common practice of storing chocolate in the fridge, it's actually not recommended by M&M's and chocolate experts. Refrigerators are typically too cold and humid, which can cause condensation and lead to sugar bloom.
- Use airtight containers: If you have an opened bag of M&Ms, transfer them to an airtight container. This protects the candy from absorbing moisture and odors from other foods, which cocoa butter is prone to.
- Handle temperature transitions carefully: If you must refrigerate your M&Ms, allow them to come back to room temperature slowly while still sealed in their airtight container. This prevents condensation from forming on the surface as the candy warms up.
Comparison of Fat Bloom and Sugar Bloom
| Feature | Fat Bloom | Sugar Bloom |
|---|---|---|
| Appearance | Grayish-white streaks, hazy film, or a greasy sheen. | Dull, chalky, dusty-white coating or speckled dots. |
| Texture | Soft, crumbly, or slightly greasy. | Grainy, gritty, or sandy. |
| Primary Cause | Temperature fluctuations, causing cocoa butter to melt and recrystallize. | Moisture and high humidity, causing surface sugar to dissolve and recrystallize. |
| Trigger | Exposure to warm temperatures. | Moving from a cold to a warm environment (condensation) or humid storage. |
| How to Fix | Can be reversed by melting and properly re-tempering. | Irreversible, but can be used in recipes where the chocolate is melted. |
Can a Manufacturing Issue Cause Bloom?
While improper storage is the most common culprit, bloom can sometimes be traced back to manufacturing issues. If chocolate is not tempered correctly during production—a process of heating and cooling to stabilize cocoa butter crystals—it can be more susceptible to blooming. Reputable manufacturers like Mars, Inc. (the makers of M&Ms) have rigorous processes in place to ensure proper tempering and minimize the risk of bloom. However, factors like using recycled chocolate with higher fat content can also contribute to bloom during the manufacturing process.
Is That Other Stuff Mold?
Some people may wonder if the white stuff on M&Ms could be something other than bloom, such as mold. It's highly unlikely. Mold requires moisture to grow, and chocolate has a very low water activity, making it an inhospitable environment for most types of mold. The white film from bloom is not microbial growth. If you do encounter a chocolate product with an off odor or visible fuzzy mold, it should be discarded, but chocolate bloom is not a safety issue. The ingredients used in M&Ms, including various sugars, milk solids, and cocoa butter, are the components involved in bloom, not any type of spoilage.
Conclusion
So, the next time you find a white film on your M&Ms, don't worry. It's simply a sign that your chocolate has undergone a natural process called blooming. Whether it's fat bloom from heat exposure or sugar bloom from moisture, the candy is still perfectly safe to eat. While the appearance and texture may be slightly altered, the fix is easy for many applications: simply melt the chocolate down and incorporate it into a recipe like cookies or hot chocolate. The best way to avoid this is to store your candy properly in a cool, dry place and avoid placing it in the refrigerator. With proper care, your M&Ms will stay shiny, snappy, and delicious for as long as possible.
Use Bloomed Chocolate in Baking
As mentioned, bloomed chocolate is perfectly fine for use in baking. When melted, the fat or sugar crystals re-incorporate into the chocolate, and the final product is unaffected. It’s an excellent way to avoid food waste while still enjoying the full chocolate flavor.
- Hot Chocolate: Melt the bloomed M&Ms into hot milk for a delicious and rich beverage.
- Cookies or Brownies: Chop the bloomed M&Ms and mix them into your favorite baked goods batter.
- Chocolate Sauce or Ganache: Melt the chocolate down to create a silky sauce or rich ganache.
