Chocolate is some pretty magical stuff. It’s right up there with eggs on my list of all-time favorite food science ingredients. I’m not talking magical like the movie Chocolat which is not, in fact, magical at all. I’m talking about the scientific properties of chocolate’s makeup that allows it to be a liquid, a solid and just about all of the phases in between (a phase is a state of matter: solid, liquid, gas, etc.).
Ready to nerd out? Good.
So first off, the term “tempering” refers to the process of altering chocolate’s fat composition so that it hardens at room temperature with all of the characteristics of a fancy shmancy chocolate bar; an attractive sheen, a hard “snap” when it’s broken and a proper melt point (…not in your hand kind of melting). For my techniques on how to actually temper chocolate, don’t fret, that post is coming up next!
Tempering is all possible thanks to the fat found in chocolate: cocoa butter. Cocoa butter is almost always in a crystal form, and what’s really special is that as a crystal, it has the ability to exist in many different shapes and sizes depending on its temperature. This characteristic is called polymorphous crystallization, and without it we’d live in a world without chocolate bars – or at least good ones.
The major crystal formations are generally defined by the temperature range they exist in. The way I think of crystal formation in chocolate is like plants in an ecosystem. Only certain plants can exist in the heat of the dessert, certain ones in the cold tundra, etc. and the same goes for cocoa butter crystals. For example, any temperature over 63F/17C is too hot for a Form I crystal to exist. Above that temperature it loses its form and either reforms as a different crystal or turns to liquid if the chocolate is too hot to support anything.
Here are the temperature limits of the six cocoa butter crystal forms:
Form I – 63F/17C
Form II – 74F/23C
Form III – 78F/25.5C
Form IV – 81F/27C
Form V – 93F/34C
Form VI – 98F/36C
Almost all of the crystal forms are unstable due to their shape. They lack the ability to efficiently interlock with each other and at best create a loose, weak, uneven network of fat throughout the chocolate. This translates into a crumbly texture, a dull finish and at worst a complete lack of solidification, melting on contact with anything warmer than room temperature. But one form – Form V – is perfect for getting all of the right qualities we want in chocolate. The structure of a Form V interlocks nicely with itself forming tight, ordered rows that give the chocolate strength and stability. The foundation of tempering chocolate, then, is “growing” just the right amount of Form V crystals by managing the temperature range that supports them.
To start, you need to heat your chocolate to a temperature that is too hot for any major crystals to form. This gives you a sort of blank canvas or fresh patch of dirt to start growing your crystals. For dark chocolate (anything over 58% cocoa content) a temperature of 113F/45C is hot enough. For milk and white chocolate, 104C/40C is fine. Why the difference? Well for one thing, milk and white chocolate contain much more milk solids than dark chocolate, and those are easier to burn or split at higher temperature.
Once your chocolate is hot, you want to cool it slowly. Staying above a temperature where Form I-IV crystals can grow and spending the majority of your time in that Form V zone to ensure you have the right environment to grow the right type of crystal.
After you’ve bottomed out in the Form V zone at around 85F/29.5C, it’s time to warm the chocolate back up a little. The extra heat eliminates some of the less stable crystals that may have formed and settles you in the prime temperature for maintaining Form V: 90.5F/32.5C. Done? Not quite.
Cooling and warming the chocolate isn’t enough. You could technically leave hot chocolate out in a cool room and it would hit the correct temperature eventually, but it wouldn’t be tempered properly.
The other piece of the puzzle is agitation. By agitating the chocolate you stir the crystals together. This causes chain reactions that forms similar crystals and starts to interlock them. So throughout the entire cooling and warming process you have to keep your chocolate moving, stirring up the Form V crystals to enlist their buddies to join the party.
As the chocolate continues to set, the cocoa butter crystals continue to grow and interlock, forming a tight network that not only creates stability and texture, but contracts, allowing the chocolate to release from a mold it may be casted in.
But what happens if your chocolate isn’t at 90.5F/32.5C when you’re done? What if it’s too cold? Or too hot? Good questions, but I have no idea.
…Psyche! You should see your face, I totally fooled you. Anyway, in terms of a temperature range that is still workable, anything over 93F/34C is too warm and realistically anything under 79F/26C is too cold. Chocolate that’s too warm is pretty obviously not going to work. We know any temperature above 93F/34C is too hot for Form V to exist and so your precious crystals will melt away leaving you with untempered chocolate and a lifetime of shame. If your chocolate ever gets that warm while you’re working with it, there’s nothing to do but heat it back up to 113F/45C and start the tempering process over again.
The lesser of two evils in temperature is leaving it on the cooler side, but it’s a little more complicated as to why. Let’s be clear, chocolate that’s too cold is no fun, but at least it maintains an environment where beta prime crystals can live. So why should you avoid it? Well, we know at low temperatures Form I – IV crystals will grow, and that will contaminate the Form V you worked to develop. Also, at low temperatures the chocolate just generally sets too quickly. Beta prime crystals interlock tightly with lots of strength and stability, but ideally they like to take their time doing it.
Here’s an illustration of the concept I love to use: Picture a room full of chairs – the metal and plastic variety that stack onto one another. If I gave you a full day to stack those chairs as uniformly as possible, it would be a piece of cake. At the end of the day the chairs would be in nice, even rows, all snug and happy. Now let’s say I gave you 5 minutes instead. Could you stack all of them? Maybe, maybe not, but for sure they’d be a mess of rows and heights with maybe some stragglers left lying around.
This is exactly what’s happening to cocoa butter crystals setting up at too low a temperature. They don’t have the proper time to align evenly and compactly. So while your chocolate may set up quickly when it’s at a low temperature, it’s likely to be weak and crumbly. This wonderful analogy illustrates the fact that your tempered chocolate should not just be in a nice 86F/30C – 90F/32C range while you work with it, but given as much time as possible to set after you’ve casted your chocolate bar or made your candies or whatever. And yet….
….not too much time. At least not at a warm temperature. Too much time will allow unstable crystals to grow and congregate until they can be seen with the naked eye (known as bloom, which we’ll get into in just a second).
The best environment for your chocolate to set in is 55F/12C – 60F/15.5C with moderate to low humidity. Think wine cellar. Notice I didn’t say the refrigerator? A terrible myth is that chocolate should be kept in the fridge, when in fact it’s about the worst place to keep it. Yes, you should keep chocolate in a cool, dark environment and yes, a fridge is both of those, but it still isn’t the best option. Chocolate is incredibly shelf stable thanks to the fact that if contains virtually no water. A refrigerator is a very humid environment, so placing chocolate in the fridge introduces it to more bacteria growth potential, not less. The moisture that condenses on the surface of the chocolate can also cause discoloration and ruin its texture. This is of course only when you’re dealing with solid chocolate. If you’ve made a ganache or any product with dairy, eggs, etc. then duh, keep it in the fridge.
In the right environment it’s never a bad idea to give your chocolate 24hrs to fully set, no matter what you might be doing with it (decorations, bon bons, ganache). But as I mentioned before, in a warm temperature, too much setting time will cause fat bloom.*
*Sometimes this bloom is caused by sugar, but we’ll talk about that in a different post.
You’ve almost certainly seen fat bloom on chocolate before. Most of us have our first encounter with bloom after buying a candy bar from the drugstore. We unwrap our little treat only to see a light brownish-grey texture all over the outside of the bar that kind of looks like mold. Sure, we eat the candy anyway, but we’re left with questions.
Fat bloom is not mold. It’s the physical evidence of Form VI cocoa butter crystals that have gathered on the surface of the chocolate and recrystallized in such large quantities that they can be seen with the naked eye. For a drugstore candy bar fat bloom is almost always the result of age or poor temperature control. If the candy bar is old, then the Form V crystals have simply had enough time and leftover energy to create Form VI crystals (which only happens after several weeks or months) and bloom results. In terms of temperature, the candy bar sits somewhere cold, then somewhere warm, then back again; moving in and out of temper and setting the neat little rows of Form V crystals into pandemonium. Most of the Form V crystals stay alive and reorganize. But other crystals form too, and when the Form Vs tighten their ranks, the other crystals are pushed out of the club, gathering and forming on the surface of the chocolate to scare us all into thinking we secretly eat moldy candy bars. While Fat bloom won’t make you sick, it creates a waxy or fatty texture and taste that isn’t pleasant. Get down on those candy bars, guilt free!
Whew, we’ve covered a lot in a short amount time. Hopefully this little chat has not only given you a better sense of how cocoa butter acts and reacts, but how you can manipulate it to create beautifully tempered chocolate. If nothing else you’ve likely picked up a little ammo for your next trivia night. You’re welcome!
Cheers – Chef Scott