October 28, 2020

Temper in Chocolate - What it is and why it matters

by Amy Coronado, Senior Chocolate Engineer

Any chocolatier worth their cocoa butter will tell you, real chocolate needs to be “tempered.” But what is temper and why is it important? To answer these questions, we should start by understanding a little more about the composition of chocolate, and how the various ingredients interact.

What IS chocolate?

“Real” chocolate is made primarily of four main ingredients: 

  • Cocoa Butter   
  • Cocoa Solids (think cocoa powder used for cooking)
  • Sugar  
  • Milk/Cream Powder (in milk chocolate and some white chocolates)

For any bar of dark chocolate sitting on the shelf, the ingredients list will include the above (and likely some complex-sounding ingredients such as soy lecithin to help make the chocolate shelf-stable/easier to process). You will often see these bars say something on their packaging like “72% cacao” or “60% cacao,” which refers to the percentage of cocoa solids in the bar. As you probably know if you’ve tasted one of these bars, higher cacao percentages usually translates to complex, darker, sometimes bitter flavors, and correspondingly lowers sugar content.

How do these ingredients interact?

The magic ingredient that gives chocolate its shine and snap is cocoa butter— when chocolate solidifies, the fat molecules in cocoa butter line up into ordered “crystals”. As the chocolate cools, these invisibly small crystals grow until they touch each other. “Tempering” chocolate is the process of controlling the size and type of crystals that are formed in the chocolate. The image below shows what one of these crystals looks like.

This large cocoa butter crystal is roughly as wide as a few human hairs are thick (scale bar in um). Source

But there are other things in chocolate besides just cocoa butter; the cocoa solids give chocolate most of its signature taste, the sugar appeals to our sweet tooth, and the milk/cream gives chocolate a creamy, smooth texture. If we think about crystal structure as a jenga tower with some open spaces, the cocoa solids, sugar, and dairy powder in the chocolate are like different size blocks that we poke into the spaces in the cocoa butter jenga tower. These different blocks interrupt the crystal structure, sometimes making it more stable, sometimes less. If the agglomerate crystals of all the ingredients are stable and well-formed, you get well-mixed, shiny, hard chocolate (a very stable jenga tower that doesn’t want to fall). However, if your crystal isn’t well-formed (meaning your jenga tower is unbalanced), then ingredients will start to slip out of the crystal and come to the surface of the chocolate (like jenga blocks falling out of your unstable tower). When ingredients in your chocolate separate out like this and come to the surface, they can form a whitish film on the surface of the chocolate called “bloom”. Even if you have perfectly tempered chocolate, bloom can happen over time, especially when stored at higher humidities or when put through temperature fluctuations.

This is why you should never put your chocolate in the refrigerator— when you put chocolate in the refrigerator, the temperature of the chocolate changes rapidly, which (like giving your jenga tower a shove) can cause the cocoa butter in the chocolate to separate out and come to the surface, causing fat bloom. Additionally, the high humidity of most refrigerators will cause the sugar in the chocolate to separate out and come to the surface as well, causing sugar bloom (because sugar wants to dissolve into the water in the air). 

Sugar bloom (caused by exposure to moisture/humidity) is dusty to the touch and often looks like ice frost. The sugar molecules form very small sugar crystals on the surface of the chocolate, which can give them an almost-ordered appearance. Source

Fat bloom (caused by temperature fluctuations) is waxy to the touch and usually looks less ordered than sugar bloom. The image to the right shows an electron microscope image of the surface of fat-bloomed chocolate (scale bar 5um). You’ll notice, the spikes of cocoa butter fat look similar to the spiky cocoa butter crystal from earlier. Source 1, source 2

Fun fact: You may have heard that bloomed chocolate has “gone bad” but actually, bloomed chocolate is still perfectly edible and safe, it's just not quite as pretty to look at, and may have a strange texture in your mouth!

Why does crystal ‘type’ matter?

There are 6 different types of chocolate crystals that can form, and only one of them yields the kind of shiny, hard chocolate we love to eat: beta type V crystals. Beta V crystals are highly ordered, stable, and dense, which gives them the finish and snap of good chocolate and locks the ingredients securely in place to help prevent them from blooming. The stability of beta-V crystals also gives them a slightly higher melting temperature. This higher melting temperature means that well-tempered beta-V chocolate will, as M&Ms famously put it “melt in your mouth, not in your hand.” The graphic below describes the properties of chocolates with each of the different crystal types.

The different possible crystal structures of chocolate and their properties. “Polymorphs” means different types of structures (“poly”=many, “morph”=shape/structure). Each crystal type listed corresponds to a different arrangement of ingredients in the crystal structure. Temperatures listed vary between chocolate types (white/milk/dark) and sometimes between brands. Source

How to get ‘perfectly tempered’ chocolate

To get these elusive, jenga-perfect beta-V crystals that snap, shine, and resist blooming, you must put chocolate through a “tempering process” where we carefully control the temperature of the chocolate and introduce ‘starter’ crystals of the type we want. The basic steps of tempering are:

  1. Heat up your bulk chocolate to melt it
  2. Stop heating and add solid chocolate with beta-V crystals to the melted chocolate to “seed” correct crystal growth
  3. Cool your chocolate down at a controlled rate to a temperature below the “temper point” (the temperature at which beta-V crystals start to form)
  4. Remove any unmelted seed chunks
  5. Gently heat your chocolate back up to a temperature just below the temper point to melt away undesirable type IV crystals and make it pour-/extrude-able
  6. Pour (or 3D print!) your chocolate
  7. Allow chocolate to cool in a low-humidity environment, ideally 15-18°C

This graph shows the general heating and cooling steps of the tempering process. Physically adding in seed chunks of chocolate is not technically necessary, which is why it isn’t shown here. However, the seed chunks act like a good example for the melted chocolate, helping to encourage formation of correct beta-V type crystals, which is why chocolatiers often use seed crystals. Temperatures shown (in Fahrenheit) are approximate and differ by chocolate source. Source

Tempering can be done by hand, or using an automatic tempering machine. We use a Chocovision V tempering machine to create small batches of a new chocolate for testing, and the chocolate refills we sell on our website are tempered by a large, production-scale tempering machine. When the steps for tempering are carried out properly, you should end up with hard, shiny beta-V crystals, giving you chocolate that look like this:

This is a 3D-printed dark chocolate vase (Scripted Vase - Gear), made using Cocoa Press professionally-tempered chocolate refills.

The genius of the Cocoa Press 3D chocolate printer is in precise heating of our chocolate to just under the temper point. Before you get them, our chocolate refills go through the entire tempering process, ensuring they have the perfect beta-V crystal structure. Then, when these refills go into the printer, the chocolate is not melted, it is softened. This subtle but important distinction means that the chocolate is heated just enough so it can flow through the nozzle, but not so much that it destroys (melts) all the tiny crystals in the chocolate. After extrusion, these remaining tiny crystals “seed” growth of more beta-V crystals in your printed part, resulting in perfectly-tempered prints. Essentially, the printing process simply takes the chocolate through steps 5, 6, and 7 of the tempering process, preserving your perfect temper.

Good chocolate should be delicious, shiny, snap when broken, and melt only in your mouth. While the taste comes from other ingredients in your chocolate, the shine, snap, and melting behavior of chocolate all depend on that perfect beta-V cocoa butter crystal structure. If you choose to use the chocolate refills we sell for Cocoa Press, you can skip right past the time-consuming and complicated tempering process and get right to printing while avoiding bloom. However, as long as you temper your chocolate and carefully preserve your temper by gentle heating, you can use whatever chocolate you want! See our blog post on “Using your own chocolate with Cocoa Press” for more tips on how. With proper tempering and temperature management, any cocoa butter chocolate can be coaxed into and maintain ideal crystal structure to achieve confection perfection!

Want to learn more about Cocoa Press 3D Chocolate printers? Click here