SCIENCE BEHIND CHOCOLATE BY ALEksandr nenoglyadov

Cocoa butter as triglycerides

Have you ever wondered what cocoa butter in chocolate actually is? What is it made of? You notice that it can be both liquid and firm, but what makes that possible? How is it that its physical properties can be controlled through tempering? Sounds like magic, right?
The main idea of this post is that once you have a better understanding of what happens on a molecular level, you’ll develop a stronger intuition about what’s happening when you work with chocolate. This knowledge helps to avoid many common mistakes.

I’ve spent quite some time studying various scientific research papers to explain the science behind cocoa butter for a wider audience. So, here we are.
First, we need to define cocoa butter from a chemical perspective. Cocoa butter is a fat. I’m sure you already know that, as it doesn’t dissolve in water, is hard to wash off without soap, and so on. Due to its chemical composition, cocoa butter is solid at room temperature. Natural fats like cocoa butter are made up of triglycerides. Don’t worry about the term—triglyceride is simply an organic compound consisting of three fatty acids. You’ve probably heard of unsaturated and saturated fats. Cocoa butter is a relatively simple fat, primarily composed of stearic acid (saturated), palmitic acid, and oleic acid (unsaturated).

Polarized light microscopy pictures of crystals obtained cocoa butter
So now we know: cocoa butter = triglyceride = three fatty acids. That should be enough to continue.
Triglycerides are believed to exist in "tuning fork" configurations in both liquid and crystalline states. In the liquid state, triglycerides laterally interlock to form lamellar structures, as shown in Figure 4. When the temperature of the liquid decreases and approaches the crystallization point, the lamellar units become more organized and grow in size. The disordered triglyceride hydrocarbon chains arrange themselves into more ordered, rigid structures, forming crystal nuclei. Eventually, at crystallization temperature, these nuclei reach a critical size. Crystallization involves the rapid growth of these nuclei, a stage referred to as crystal growth.

Triglycerides
You can see that each triglyceride looks like "tuning fork". They become more organized as reaching crystalline state.

Schematic representation of cocoa butter crystals
On the right is what we call "form V crystals"
The time required for a certain proportion of the liquid cocoa butter to solidify depends on the number of nuclei present and how quickly they grow. This is essentially what we aim to achieve during tempering: encouraging the growth of crystals.

In the next stage, the individual fat crystals come into contact, and bridges may form between them. From a manufacturer's viewpoint, this is called the point of apparent solidification. Take a look at the schematic representation (Figures 9 and 10) of densely packed crystals. Figure 10 shows form V crystals—the ones we aim to create during tempering.
Now that we understand what happens at the molecular level, it’s easier to visualize when working with chocolate. Although our eyes can’t see this deeply into the substance, having strong theoretical knowledge will help us better "feel" the process. In upcoming posts, I’ll cover the topic of polymorphism to explain what it means and how it impacts the daily work of a chocolatier.
Bibliography:

Paul S. Dimick, Ph.D., "Principles of Cocoa Butter Crystallization"

Thais Lomonaco Teodoro da Silva, Renato Grimaldi, Lireny Aparecida Guaraldo Gonçalves, "Effect of Cocoa Butter Equivalent on Cocoa Butter Crystallization Behavior and on Dark Chocolate"
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