The discoloration or "bloom" you see is nothing more than the cocoa butter which has separated due to either age or improper storage (most likely in a too warm area). The fact that you are going to melt the chocolate means that this bloom will no longer exist because the cocoa butter will be re-incorporated.
It's actually just a scientific process called “chocolate bloom”. There are two types of this bloom: sugar bloom and fat bloom. Sugar bloom happens when moisture comes in contact with the chocolate - it dissolves the sugar crystals on the chocolate's surface, leaving a white, powdery look.
The good news is that whatever type of bloom is affecting your chocolate, it's still completely safe to eat. Ultimately, chocolate bloom doesn't affect the taste or shelf life of your chocolate, you just have to accept a slightly different appearance — which can still be frustrating if you're giving it as a gift!
Fat Bloom. When a fat bloom occurs, you will see lighter brown streaks on your chocolate. The streaks are actually visible fat particles that have separated from the rest of the chocolate and settled on its surface.
That white discoloration that sometimes forms on old chocolate turns the stomachs of chocolate lovers everywhere. For years, researchers have known that the harmless change, known as a fat bloom, is caused by liquid fat such as cocoa butter migrating through the chocolate and crystalizing on the candy's surface.
The white coating that forms on the surface of chocolate is called bloom, and—here's the good news—it's perfectly safe to eat.
If you see a white or grey hue to your chocolate then it's probably had a fat bloom – whilst it takes away from the glossy shine of your chocolate, it doesn't affect the taste. If your chocolate has a grainy and bitty texture then it will have experienced a sugar bloom.
The usual brown hues of chocolate can become discoloured with a hazy white coating. This coating is called "chocolate bloom" and appears naturally. Although it can make the product taste a bit different, it's not harmful.
Chocolate that has "bloomed" is still safe to eat (as it is a non-perishable food due to its sugar content), but may have an unappetizing appearance and surface texture.
Moldy chocolate has white fuzz growing above its surface and will feel fuzzy to the touch. Bloomed chocolate has a chalky layer or grey/white streaks on its surface and will feel slick to the touch.
You should try to not eat any chocolate after around 4 or 5 pm to give your body time to metabolize its caffeine. Generally, it's also a good idea to stop eating at least 2 hours before turning in for the night to give your food time to digest.
Moisture in the fridge can also lead to “sugar bloom,” meaning the sugar rises to the surface and discolors the chocolate (which has no effect on flavor, but doesn't look too appealing). So instead of the fridge: Store it in a cool, dry place.
Chocolate bloom can be repaired by melting the chocolate down, stirring it, then pouring it into a mold and allowing it to cool, bringing the fat back into the solution. You can also re-temper the chocolate to regain its glory: all the shine, snap, and stability that you expect from tempered chocolate.
Oxidation: When chocolate comes into contact with air and light then a process known as oxidation occurs, and this means that the fat contained in the chocolate changes into other substances leading to marked impairment of the flavour and to an unappealing smell.
The grey streaks that sometimes appear on chocolate are caused by two different factors: fat bloom and sugar bloom. Fat bloom occurs when cocoa butter, which is a polymorphic fat (which means it can take various forms), crystallises.
The only way it can get moldy is if it was exposed to water/humidity. If your milk chocolate bar is wrapped well, this likely won't happen. So long story short, solid chocolate bars rarely ever go moldy, especially if still sealed in their original packaging. That's also what makes chocolate excellent for prepping.
Chocolate can last a long time, she adds, but it often develops a white coating, known as the "bloom", when it's exposed to the air. This happens when some of the crystalline fat melts and rises to the top. It's not mould, she says, and it's fine to eat.
Chocolate bloom might look unappetizing, but it's completely safe to eat. That doesn't mean you'll want to eat it, though, as flavor and texture can both be compromised. “Bloom usually strips the chocolate of some of its most pleasing qualities,” says Laiskonis.
Chocolate never truly “expires,” so nothing will happen if you eat it past the expiration date. As long as it's stored properly and not exhibiting any other signs of spoilage, most chocolate will remain edible and yummy up to two or three years past the listed date.
Dark chocolate contains 50-90% cocoa solids, cocoa butter, and sugar, whereas milk chocolate contains anywhere from 10-50% cocoa solids, cocoa butter, milk in some form, and sugar.
If the chocolate has seized because it has been overheated, try stirring in a couple of pieces of solid chocolate (this will not work if the chocolate has seized from moisture). Or adding fat to the chocolate can bring it back – the ideal fat to use is cocoa butter however if you don't have any, try vegetable oil.
Dark chocolate, with its higher cacao content, can be good to eat for as long as three years past the best before. Due to their high milk contents, milk and white chocolates might not last as long as dark, but their longevity is still nothing to sniff at — you can expect to get another 8 months or so out of it.
Taste of other non-chocolate flavours such as onion or garlic or even overpowering bitterness are signs of spoiled chocolate. Cocoa powder can last a long time if stored properly in a sealed container, but can quickly take on a funky taste and scent if exposed to a pantry full of spices.
Chocolate, like many other products, degrades in quality over time. A 10-year-old bar won't be nearly as good as a fresh one. If your chocolate seems to be perfectly okay but is somewhat flavorless, it's past its prime, and you should toss it out.
While fat bloom and sugar bloom have a negative effect on appearance, the product remains perfectly safe to eat and can be remelted to remove discoloration.