Figure 1. Untempred dark chocolate. The reason the chocolate colour is mottled and blotchy is due to the way the fat in this chocolate crystalized. Not in the way we wanted it to.

You have a brand new chocolate bar, with the wrapper intact. You’re excited to open it up and take a bite, only to notice that once you tear open the wrapper, the bar looks a bit strange. Instead of a nice dark smooth shiny bar, you see something more similar to what you see in the picture here. Is it mold? Is something wrong? But the most important question is, can I eat it?

If it looks like this piece of chocolate here, then it is not moldy. It is untempred chocolate, or chocolate not in temper. And yes, it is perfectly fine to eat it!

What is tempering?

To make chocolate bars you can’t just take liquid chocolate, pour it in a mold, and cool it. There is more involved. This is why we have chocolatiers!

Figure 3. Tempering dark chocolate on a slab of granite.

When we temper chocolate, we cool down liquid molten chocolate in a certain way that allows the proper fat crystals to form. If you’ve ever seen a chef pour chocolate on a granite surface and move it around like a toddler playing with paint (and it is that fun), then you’ve watched someone temper chocolate. The key points to tempering molten chocolate is, one, to melt it to around 50 degrees Celsius, and then cool it down quickly via granite or in a machine that does the cooling. This will create the crystal “seeds” we need for which all the fat will build onto and form a nice shiny dark bar. The second key point is that the liquid chocolate needs to be stirred continuously so that we disperse these seeds throughout the liquid chocolate as it cools. This is one reason why tempering machines are constantly spinning the bowl or drum of chocolate around and around. Unless you want me to bore you, I wont’ go into more detail about tempering here. Just know that this is what it is, and the reason it is done is to make the chocolate look like the Figure 2 (right side of course).

The fat of cacao, coined “cocoa butter”, is very unique.

Figure 2. Untempered chocolate on the left, and tempered chocolate on the right. Ignore some of the little flecks you see on the tempered piece, as that is due to cutting the bar in half. Notice how difference the colour, texture, and overall appearance is. The only difference between these two dark chocolates is the way the cocoa butter fat crystalized.

It melts below body temperature, but stays hard at room temperature. Perfect for us to store/sell chocolate as a solid, and consume as a liquid. It also has a very pleasant texture to it when it is in liquid form. It’s not too greasy or waxy, like some other fats are. Another unique aspect of this fat is that when it solidifies, it doesn’t just harden into a solid. The fat molecules actually crystalize, very similar to how a gemstone is formed. A cocoa butter molecule will build onto another cocoa butter molecule in a very specific way, sort of how we stack chairs or put Lego blocks together. Not only does the fat crystalize as it cools, but there are 6 possible ways the cocoa butter fat can crystalize. Of those 6 forms, it is the 5th form of crystallization we try to achieve when we temper.

In order to temper chocolate properly, that is, to get the fat to crystalize into the 5th form we want (also termed Beta 5 crystals) we need to constantly move and stir it while it cools down relatively quickly (as mentioned above). This will allow our chocolate to look as it does in Figure 2, on the right. The only difference between the two dark chocolates here is that the one on the left is not tempered properly. The fat has not all crystalized into the Beta 5 form. The dark chocolate on the right has. There is no other difference between them.

So why did my chocolate turn this way?

Figure 4. Fresh chocolate in a refiner (top and bottom right) and some images of cocoa beans (bottom left). The chocolate you see here is just ground up liquified cocoa beans, and some sugar.

If you were to pull fresh molten chocolate out of a refiner/melanger, and just let it set on its own, it would look like the chocolate on the left of Figure 2. It wasn’t tempered. If you purchased a bar, then it should have been properly tempered. Let’s assume it was. Therefore, at some point between when it was packaged and when you opened it, the bar either melted completely, or heated up enough that most of the crystalized solid cocoa butter molecules liquified. Eventually, the bar cooled again and re-solidified. However, it solidified in a similar way as when you just pull the fresh molten chocolate from a refiner. It didn’t temper itself in the packaging! Therefore, the crystals within it changed. They changed because they were heated up, broke apart, and set not in the Beta 5 form, but in another form.

How did it melt? Who knows. Perhaps it melted or warmed up too much at the manufacturer and they didn’t realize because it was already wrapped. Perhaps it heated up while it was being shipped to the store or to you. Often times this is the case. It could also be you didn’t store it in a cool dark area below 24 Celsius, and so it went out of temper (warmed up enough or melted completely which caused it to look like Figure 1 when it re-solidified).

Fat bloom

This essentially is what happens when your bar was kept too warm for too long, and some of the fat molecules (not all) began to melt. The bar itself may still keep its shape, but it may be a bit soft. If or when it cools down, those loose molecules of fat solidify, but not in the way we want obviously (since they were not tempered as mentioned earlier). This liquid fat can even wiggle around and move, often via capillary action) to the surfaces of the chocolate, and when they solidify they leave behind a whitish appearance. Cocoa butter is an off-white fat when it is in solid form (Figure 5). There is also sugar bloom, when the surface of the chocolate becomes wet (often from humidity) and the water dissolves the sugar, which then solidifies into a whitish layer on the bar as well.

So, is it okay to eat?

Figure 5. Some solid cocoa butter. You can see why bloomed chocolate can go whitish if this fat makes its way to the surface of your chocolate and solidifies.

If this is what happened to your bar, it is not moldy or gone bad, and yes, it is okay to eat. The texture may be off - more crumbly and less smooth as it melts, but it is perfectly fine. It’s not ideal. If you paid $13 for a fine chocolate bar, and it looked like Figure 1 when you opened it (or something similar) then you won’t experience the same smooth texture. It won’t quite melt the same. And since texture is very closely tied to our perception of flavour, then the overall flavour may be somewhat altered. It’s not that the aroma molecules have changed per se, but our impression of the flavour due to a different texture and the way it melts may make us perceive the flavour slightly different.

That said, it can still be enjoyed! If you’re not crazy about this new texture, you can melt it and enjoy it this way. You can place it in a small teacup, placed over another teacup of hot water, and allow the chocolate to melt before eating it. The melted form will heighten or mute some of the aromas, and also give you a new perspective on the overall flavour of the chocolate. It’s a wonderful way to eat fine chocolate, especially in the cooler months!

How do I know if it is moldy or not?

Chocolate bars (dark, or milk chocolate) that is not filled with any creams or perishable ingredients (like chocolate truffles or bonbons), doesn’t really mold if kept well. Especially if it is in its original package. I don’t even have an image of moldy chocolate because it’s so rare! The only time I have seen moldy chocolate was on an old milk chocolate showpiece I left out for over a year in a damp cold basement. Since milk chocolate has lots of sugar, and milk proteins, it has more food for mold to grow on. Also, it was exposed, not wrapped. It was in a damp area where the humidity allowed the sugar/milk to dissolve slightly and created the perfect habitat for mold to grow. I have never seen this happen to my dark chocolate showpieces, even ones left out for years exposed to the elements.

This is because dark chocolate has high amounts of what mold and such organisms can’t thrive in: fat and tannins. The reason chocolate is dark (and sometimes bitter) is the high level of tannins within it. This is also what makes tea dark, or red-wine dark. Most organisms can’t live in an environment with high amounts of tannins. Puddles or small lakes that fill with leaves in the fall can become very dark due to the tannins from the leaves. This makes the water very inhospitable to many organisms. Fat acts as a preserving agent, such as vinegar or salt. This is why we can jar some vegetables and have them keep for years if kept in oil. Dark chocolate has high amounts of both of these.

Milk chocolate also has these, and also has high levels of sugar. 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. It can last for years. The flavour may change over time slightly, especially if exposed to air, but if kept in an air-tight and moisture free environment, it will last for ages.

I can’t say for sure that your chocolate isn’t moldy, as I would have to see it. However, mold has a much different look and feel than what you see in Figure 1.

Recap

The chocolate in Figure 1 is untempered chocolate. The crystals in the fat are not in the ideal
This chocolate is perfectly fine to eat, and is not moldy
The texture is different, and you may or may not enjoy it. You can eat it in its melted state instead if you wish.

FAQs & Myths Home

Why does my chocolate look whitish or moldy?