There are moments in life in which time itself comes to a halt, as the body pumps with adrenalin and all the senses work in concert. Many say that this is exactly what happens the moment a delicious chunk of chocolate makes contact with their tongue. In my opinion, fine chocolate is indeed a pure pleasure and a celebration of the palate – who would dare disagree with me?
Chocolate, in its final form, is a colloid (suspension) made of several components, each playing a different and important role in its creation. Numerous factors influence chocolate quality, taste, texture, and color, all of which are strongly affected by the chemical character and physical properties of the various components. How exactly did this wonderful delicacy gain such popularity all over the world, and what are the factors we should consider if we want to make the perfect chocolate?
Cocoa beans| Shutterstock
How it all began – a taste of chocolate history
The story of chocolate begins in the rainforests of Central and South America and West Africa – the home of the Cocoa tree (Theobroma cacao). Its pods grow for some four months, until they reach their maximum size – similar to that of a melon. About one month later, they are considered ripe. But what interests most people is not the spectacular pod but rather the 40 cocoa beans it contains.
Cocoa beans taste very bitter, a fact that raises the question of who was the first to consider using them – and how did it even occur to them? Experts believe that it was the Olmecs, an ancient nation that lived in Mexico between 1500 and 200 BC, who dried, crushed, and mixed the cocoa beans with hot or cold water to create the first chocolate drink. This drink was probably very bitter (the translation of chocolate is actually “bitter water”) and also in high demand, so much so that cocoa beans were used by the Olmecs, Mayans, and Aztecs, all hailing from Central America, as a substitute for money.
The cocoa bean made its European debut in 1502, after Christopher Columbus returned from the Americas. In those times in Europe, the cocoa drink was consumed only by the upper classes; but unlike the Olmecs, the Europeans were not fond of its bitterness and therefore, added sugar. It was not long before the cocoa drink spread throughout Europe and migrated with the European settlers to North America as well.
The industrial revolution led to a sharp decline in the production costs of chocolate, which soon became everybody’s drink. From then on, the chocolate industry prospered – new factories opened and novel, varied, and more savory chocolates appeared. Today, there are countless types and forms of chocolate and cocoa products, consumed almost everywhere in the world, and by all ages.
Most chocolate lovers treat it as a delectable sweet, but in fact, chocolate is a fascinating chemical system that consists of many ingredients affecting its taste, color, and texture. To understand how to make truly good chocolate, we must first consider the chemical properties of the various molecules it contains.
The science behind chocolate
Who is not familiar with this scenario: Full of pleasant anticipation, you are about to put a piece of chocolate in your mouth – only to discover it has already melted over your entire hand. Such chocolate will not be considered as high quality, nor would granular chocolate, or one that does not melt on your tongue as soon as you put it in your mouth.
Simply put, high-quality chocolate has a defined and particular texture, i.e., it is not granular and only melts at ‘mouth temperature’ (36.7 degrees Celsius). To make high-quality chocolate, we need to know its chemical composition and the various stages of its preparation. Only by breaking down the chocolate into its constituents and recognizing each and every one of their chemical properties, can one really understand chocolate, and how its ultimate taste and texture can be controlled during its preparation process.
The chemical composition of chocolate
The process of preparing chocolate includes several stages, each contributing separately to taste, texture and color. But the story of chocolate actually begins in the rainforest, at the moment the cocoa beans are formed in the cocoa pod. They grow for about five months, and this is also the period when their chemical composition is determined.
Cocoa beans are made up of cocoa butter (54%) and cocoa solids (46%).
Cocoa butter is a collection of fat molecules called triglycerides. While they do not give chocolate its familiar bitter taste, these molecules are responsible for its texture so we cannot make it without them.
Cocoa solids include all the ingredients found in cocoa beans which are not cocoa butter, i.e., proteins, vitamins, antioxidants, caffeine, theobromine, fiber, a small percentage of sugars (sucrose and fructose), minerals like potassium and magnesium, and more. These ingredients are responsible for the bitter taste of chocolate (caffeine and theobromine) and its nutritional value (antioxidants, vitamins, minerals, etc.).
During the preparation process, the cocoa butter is mixed with the cocoa solids until a uniform distribution of the cocoa particles in the liquid cocoa butter is achieved, creating a colloidal system otherwise known as a suspension. As the suspension cools, the cocoa butter hardens and traps the cocoa particles inside it, creating the chocolate we know.
Sounds simple? Not quite. While making chocolate is not a complicated matter, making chocolate that is both delicious and has a precise, high-quality texture, is much more complex.
Making the perfect chocolate
1. Preliminary phase – Determining the chocolate’s chemical composition
The first stop en route to making the perfect chocolate are the thick rain forests, where the right cocoa pods are handpicked. Three main steps are required to extract the cocoa beans from the pods and prepare them for use as the raw material for chocolate.
Fermentation is the primary and critical stage in making chocolate. In this process, the cocoa beans are placed in a bucket and covered, usually with banana tree leaves. The leaves maintain the heat generated during fermentation. Fermentation occurs as microorganisms, especially yeast, naturally develop on the external case of the beans and begin to dissolve sugars into ethanol and eventually to carbon dioxide through oxidation reactions. As part of this process, the beans peel open and the microorganisms enter inside. At this stage, many chemical processes take place that lead, among other things, to creating the taste and aroma of the chocolate along with its brown color. At the end of the fermentation process, the beans are dehydrated in the sun to reduce moisture levels.
Once completely peeled, the beans are roasted at a temperature ranging between 90-170 degrees Celsius. During the roasting process, the beans’ water content falls to below 3%, while other chemical reactions take place between amino acids and sugars (the Maillard reaction). These heat-driven reactions produce odor and taste molecules that contribute to the final product. Thus, changing the roasting temperature and duration would lead to chocolate of slightly varying flavors and aromas.
Grinding the peeled beans releases the cocoa butter and creates smaller particles of cocoa solids. During grinding, the cocoa butter becomes liquid, allowing the particles of cocoa solids to disperse evenly, creating a suspension. These two ingredients are often needed separately – as cocoa butter and cocoa solids. The main separation process, in which about 85% of the cocoa butter is collected, is achieved by compressing the suspension under high pressure while heating it. In this process, the cocoa butter drips out, leaving only the cocoa solids.
Roasted cocoa beans| Shutterstock
Now that we have all the raw materials, we can delve into the actual chocolate preparation.
2. Making the chocolate
The process of preparing chocolate consists of three main stages: mixing the ingredients, grinding (conching), and crystallizing the cocoa butter in a process called tempering.
Mixing the ingredients is the stage that determines the type of chocolate we end up with: Dark, milk, or white.
Dark chocolate consists mainly of cocoa butter, cocoa solids, and sugar, so its color is dark and its taste is relatively bitter, but it is the most “genuine” chocolate you can get, as it is closest to the raw composition of the cocoa beans.
In comparison, milk chocolate requires adding sugar and milk (usually milk powder) to the cocoa butter and solids. Adding milk reduces the concentration of the cocoa solids and therefore produces a less bitter taste of a lighter color, greatly increasing its demand among both children and adults.
White chocolate is the stepbrother, or if you will, the “black sheep” in the chocolate family, as it contains no cocoa solids – only cocoa butter, milk, and sugar. The cocoa solids give chocolate its unique taste, color, and health benefits. So despite the appeal of white chocolate, I myself and many others do not consider it real chocolate.
After mixing the various ingredients your chocolate is now ready. But that’s not the end of the story, since perfect chocolate is more than just chocolate, and to prepare it, its physical properties, such as viscosity, texture, and melting temperature must be controlled.
The secret to perfect chocolate – controlling its physical properties
The grinding process is responsible for determining the viscosity and final texture of the chocolate. In this process, the mixture is ground to reduce the size of the cocoa particles that are stirred in with the liquid cocoa butter. The smaller the particles are, the less granular the final chocolate product. It also decreases the viscosity meaning less of a “bubble gum” sensation while chewing.
The process of crystallization is the final stage in which the chocolate’s melting temperature is determined – whether it would melt in your hands or not until you put it in your mouth. In fact, the only ingredient that determines the melting temperature of chocolate is cocoa butter, which is made up of fat molecules called triglycerides. One interesting chemical property of triglycerides is their ability to be packed into several different crystalline structures as the cocoa butter solidifies. This phenomenon is called polymorphism (many shapes).
Triglycerides can be packed into six different crystalline structures, each with a different melting temperature. The cocoa butter's hardening temperature, which determines the main crystalline structure of the triglycerides, dictates the chocolate’s melting temperature.
The average temperature in our mouth is about 36.8°C. In order to produce the perfect chocolate, it is important that it fully melts immediately after it is placed in the mouth, so that its texture will be uniform and its flavors will merge into one strong and dominant taste. The melting temperatures of structures I-IV are fairly low, so that the best-case scenario is their melting in our hands and the worst case they would melt still in their wrapping, leaving a sticky, dirty chocolaty liquid.
Structure VI has a different problem. Its melting temperature is 36°, so it won’t get your hands dirty, but will take a relatively long time to fully melt in your mouth, thus requiring the assistance of our teeth or tongue. The drill affects our eating experience, making this crystalline form not particularly desirable. That leaves us with the fifth crystal structure. Its melting temperature is 34-35°, ensuring rapid melting in the mouth, but not in our hands. Perfect!
To ensure the cocoa butter crystallizes and forms the desired crystalline structure (structure V), a controlled process called tempering is needed. The two main parameters of this process are the chocolate temperature and the mixing rate.
The following steps will ensure a chocolate product with crystal structure V:
A. Heat the chocolate to 50°C. This guarantees all the chocolate’s crystalline structures will be melted.
B. After melting, re-cool the chocolate to 32°C. Higher than the melting temperature of crystal structures I-IV, this temperature enables only crystals of structures V and VI to form. At this temperature, mostly small crystals are formed, mainly in structure V, and are called “seed crystals”.
C. Lower the temperature to 27°C to increase the crystal growth rate.
D. Re-heat to 30°C. This stage ensures that if crystals structures I-IV formed, they will melt and disappear.
Controlled application of the tempering process will ultimately yield chocolate with the desired melting point. Combined with the accurate grinding of cocoa solids, it results in a smooth, non-granular textured chocolate that would melt as soon as we put it in our mouths, producing a delightful celebration of flavors – this is the perfect chocolate!
Undoubtedly, you have come across chocolate with a kind of fatty, white layer that looked like something had grown on it. Before getting rid of such chocolate, stop – your chocolate is not spoiled! At worst, it is just not tasty.
This white layer is actually the cocoa butter. If the chocolate is exposed to significant temperature changes, for example, when moved from a shady place to a warmer spot, some of the cocoa butter crystals temporarily liquefy and then re-solidify. If the process is repeated a few times, the cocoa butter slowly seeps away from the cocoa solids to the chocolate surface, creating the white spots, in a process called blooming.
To minimize the risk of blooming, it is important to ensure that during the chocolate’s production process, the cocoa butter crystallizes in structure V – the most stable of them all. It is also advisable to store the chocolate in a shady place, away from the sun – thus preventing exposure to temperature changes.
Now you can understand that chocolate is not just a simple and delicious sweet. Creating the perfect chocolate is fraught with obstacles, and requires an understanding of its chemical and physical properties. So next time you eat chocolate, remember to appreciate every bite!
Chocolate after "blooming"| photo by Narisa