Discovering the taste of molecules in chocolate: More than just sweet or bitter, chocolate hides a wide world of flavors

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Flower of the Lobatera Criollo cocoa, Táchira - Venezuela.

Photo. Darwin Márquez, farmer Leopoldo Guerra.



By Alexis J. Zambrano G.

I'm a chemist. And you generally don't think about chemistry when you have a delicious cup of chocolate. But I have studied the chemical composition of chocolate for 20 years and I would like to share what I have learned with you.

For more than three decades, the properties of chocolate have been discussed and chocolate is increasingly being said to be an excellent product to control anxiety or stress or simply to relax and improve mood. This feeling of well-being has been achieved due to the release of endorphins from the consumption of cocoa and chocolate. In addition, several countries have already listed chocolate as a food, due to its nutritional properties and health benefits. This is undoubtedly the product of the chemical compounds it contains.

The chemical composition of cocoa beans and their by-products is very complex, changing throughout the development and biochemical and physicochemical transformation of the bean. Where, the different varieties of cocoa, due to their genetics, can contribute a wide range of chemical compounds, in addition to environmental conditions such as microclimate and soil, agronomic management and post-harvest and storage benefits, substantially influence the development of compounds of aroma and flavor.


Cocoa beans

Cocoa beans are the seeds of the tree Theobroma cacao L. named after Carl von Linneo in 1753. Theobroma from the Greek θεός/teos/god and βρώμα/joke/food) “food of the gods”. While the epithet cacao is a term that comes from Nahuatl and is considered Latinized. Cocoa belongs to the Malvaceae family, native to South America.

Fundamentally, there are three types of cocoa, the Criollos, Forasteros and Trinitarios. Initially, the seed stores part of the chemical elements and molecules necessary for its germination and initial development. However, if the seed is not germinated, it will undergo a post-harvest process of benefit — fermentation and drying—, where a series of compounds such as sugars, polyphenols, aldehydes, alcohols, esters, ketones, among others, suffer a series of chemical reactions that finally complement each other when roasting the cocoa, giving it very particular flavors and smells. Delighting in this way the most developed and demanding palates of all cultures. Drawing a smile of satisfaction like that of a child, that girlfriend in love or that adult who remembers some scene of his life through the delicacy that he now enjoys.



Criollo Porcelana Cocoa, Sur del Lago de Maracaibo Venezuela.

One of the ancestral cocoas, most exquisite in the world for its particular nutty flavor.


The cocoa bean is composed of approximately half of fat or butter, in which there are a significant number of triglycerides, phospholipids and free fatty acids, mainly oleic, palmitic and stearic acids, our contents and types of acids depending on the maturity of the fruit, environmental conditions of the crop and on a smaller scale of the cocoa variety. These characteristics determine its properties, namely, the melting point and hardness. Very important variables for the chocolate industry.

The mature cocoa has been harvested, the cocoa beans are fermented and dried, producing numerous chemical and biochemical changes both in and around the pulp or mucilage that surrounds them. The fermentation time depends on the type of cocoa; the Criollo cocoas are fermented for three and four days, the Trinitario for five to six days and the Forasteros for seven to eight days, in all cases under the control of the temperature of the fermenting mass and the aeration. In this stage of fermentation and drying, changes occur that allow the development of the chocolate flavor as well as the color change of the seeds.

The pulp, or mucilage, is rich in sugars — mainly fructose, glucose, maltose, and sucrose — that are metabolized by yeasts, forming acetic acid and ethanol. The latter activates some bacteria, for example acetic bacteria and lactic acid bacteria, which transform it into their respective acids. Ethanol and acids are able to pass into the cotyledon through the scale. This change in acidity (pH) can remain until the final product such as natural cocoa powder or chocolate, a product of acids such as acetic, citric and malic acid, among others. In the case of cocoa powder, under industrial chemical treatments with potassium carbonate, the pH is increased to reduce acidity and increase the solubility of cocoa powder and change the color.

Once the cocoa beans are fermented, the embryo dies due to the increase in acidity, increased temperature and loss of oxygen. From this moment on, the seeds are called cocoa beans.



Cocoa fermentation in wooden crates.

Cocoa in mesh is a microfermentation for research.

Photo of Satfel Dugarte, Somos Cacao, Norte de Santander, Colombia.


During fermentation, many of the proteins degrade providing their constituent amino acids, among which valine and glycine stand out, which are very important in the formation of the taste and smell of chocolate. Similarly, sulfur compounds, polyphenols — such as coumarin, gallic acid, caffeic acid, catechin, epicatechin, anthocyanins, cyanidine, and catechol — are produced, acetophenone, benzaldehyde, terpenes, and linalol. In addition, there are cyanogenetic compounds, dopamine, sterols (campesterol, ergosterol), phenylethylamine, furfural, furfurol, isoleucine, lecithin, lysine, luteolin, serine, pectins, methylxanthines — theobromine, caffeine and theophylline—, vitamins B1 and B2, C and E. You also get minerals like calcium, magnesium, phosphorus, potassium, copper, iron and zinc. Research indicates that cocoa has more than 400 volatile compounds including esters, aldehydes, ketones, alcohols, acids, pyroles, and pyrazines.



Cocoa beans during fermentation.

Photo by María Forero, Grupo La Palma Sur del Lago, Venezuela.


Transformation of cocoa beans

Research indicates that during the first stages of drying, enzymatic activity, typical of fermentation, is still achieved, which ends with the loss of moisture and temperature reduction. After fermentation, the cocoa beans are dried by different mechanisms (natural drying in the sun, with wooden drawers, drying patios or guardiolas) and then stored with a maximum of 8 % moisture and then transported to the chocolate industry. There the cocoa paste or cocoa liquor, cocoa powder, cocoa butter and the much desired product such as chocolate are made.

Both in drying and roasting reactions occur, where, for example, proteins and peptides interact with polyphenols to give the brown color associated with cocoa, in polyphenols they also end their oxidation process, as well as the loss of volatile acids .



Drying of the cocoa beans, in wooden drawers.

Photo of Avelino Barillas, La Palma Sur del Lago Group, Venezuela.


Once the cocoa has been cleaned and selected in the industry, the process begins with roasting the beans, which establishes the time and temperature of roasting according to criteria such as: origin, type of cocoa, percentage of fermentation, size of grain and even end product and customer. Once roasted, the cocoa bean is fragmented and the shell or testa is removed. From this moment on, the broken bean is called cocoa nibs. During these last two stages there are no chemical reactions, however, the cocoa is exposed to contamination if there are no proper sanitary controls.

During roasting, other flavor and aroma precursors are formed through reactions between sucrose and protein to produce pyrazines through the Maillard reaction. In the same way, depending on the type of cocoa and roasting conditions, part of the content of the low boiling point volatile compounds is lost. This is why the master chocolatier must maintain a balance, for example, between the loss of acetic acid and aldehydes or esters that give attributes to cocoa and chocolate.


The magic of chocolate

Cocoa and chocolate, keep innumerable chemical reactions, which — like coffee — affect our mood. In this sense, according to the type of chocolate, for example theobromine, reaches values ​​slightly higher than 1.5 %, with dark chocolate being the one with the highest concentration. Similar effects have another compound from the same family as caffeine, which acts as a stimulant of the nervous system but with less intensity. About 0.2 % caffeine has been found in chocolate. It should be noted that the contents of these compounds vary according to the type of cocoa, therefore, the Criollo cocoas have a higher concentration of caffeine than the Forasteros cocoas, while the Foreign cocoas have a higher theobromine content than the Criollo cocoas and in the Trinitarian cocoas. , will depend on your tendency towards Criollo or Forasteros.

Another important alkaloid in chocolate is phenylethylamine, which is an aromatic amine, a neurotransmitter that has stimulant and antidepressant effects. Also known as the love molecule, for its properties and sensations generated when consuming chocolate.

Other compounds that are present in chocolate and that are maintained and transformed in cocoa in all its stages of development and transformation are polyphenols. These are antioxidant substances that react with free radicals through their -OH groups, preventing other compounds present in the body from oxidizing, which would be modified and stop exercising their function. The antioxidants in chocolate are flavonoids (epicatechin and catechin are present in greater quantity). A 30 gram dark chocolate bar is said to contain similar amounts of antioxidants as a glass of red wine.

Similarly, anandamide has been obtained in chocolate, a substance that affects the central nervous system, relieving pain, the feeling of hunger, improving memory by facilitating the creation of new neural connections. However, anandamide levels are estimated to be very low in chocolate, so a healthy person should eat large amounts of chocolate in order to substantially impact normal levels.

In addition to all this, chocolate has very important nutritional properties given its carbohydrates, which mainly provide sugars, which provide almost half of the total energy. It also contains starch and fiber, which is found in appreciable amounts in cocoa powder, but not in chocolate. The high fat content provides the other half of the energy of the chocolate. Except cocoa powder, which usually only provides between 10 and 12 % fat. On the other hand, since the proteins have reacted with the amino acids during roasting, the chocolate does not present an important contribution of these, except in the milk and white chocolate, product of the incorporation of milk in the formulation. Basically the same thing happens with vitamins, in this case only the contribution of folic acid is highlighted. However, white and milk chocolates have higher amounts of vitamin A than the rest of the cocoa derivatives due to the dairy they contain.

Normally, chocolate has no greater ingredients than sugar (sucrose) and milk, except for white chocolate that does not have cocoa solids, only cocoa fat. Vanillin is often added, regularly in its synthetic version that mimics the properties of the compound extracted from the vanilla plant, to enhance its flavor. Another ingredient incorporated into chocolate is lecithin, which is applied at the end of the conching process so that it does not interfere with the elimination of moisture. Its presence considerably reduces the viscosity of the mass due to the decrease in the interfacial tension between the cocoa butter and the sugar particles, thus avoiding the use of additional amounts of cocoa butter.



Unique moments, full of joy and beautiful smiles at an excellent chocolate.


Actually, cocoa and chocolate have a series of chemical interactions, which not only depend on the genetics of the cocoa, but also on the environmental conditions of the crop, the handling and, even more, the post-harvest treatment and transformation processes to which has been subdued. Behind every chocolate there are infinite flavors and smells given by simple molecules and others more complex such as polyphenols, which not only delight when consumed, but also activate and lead to a large number of biochemical reactions in the body. Without a doubt the Aztecs were not wrong in saying that cocoa is the food of the gods. It only remains for us to preserve this iconic tree with particular characteristics and to appreciate the patience, dedication and art that is hidden in every chocolate we taste.


Alexis J. Zambrano G., is a professor in the Department of Chemistry at the Faculty of Sciences of the Universidad de Los Andes in Venezuela. It belongs to the area of ​​analytical chemistry. Coordinator of the Research Laboratory in Industrial and Agricultural Chemical Analysis (LIAQIA). He has a degree in chemistry, MSc. in Soil Sciences, PhD in Biotechnology of Microorganisms. Researcher in the area of ​​analytical chemistry, quality control, soil organic matter and post-harvest benefit of cocoa. Coordinator of the LIAQIA sensory analysis panel. E-mail:;