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Science of Chocolate

Crystal Risko
Product Developer

Many people enjoy the taste of chocolate, but taste isn't all there is to know about the well-loved flavor. There is also the engaging science of chocolate that you can share with your students. One place to start the discussion is with the cacao tree. Theobroma cacao produces yellow-green pods that contain fruit embedded with dark colored seeds (beans). Chocolate production starts with these seeds. The cacao tree grows in the tropical belt, a very narrow geographic range approximately 20° north and south of the equator.

Cacao trees begin producing fruit at 4 to 5 years of age, after which each tree annually produces approximately 30 fruits that yield between 30 and 50 seeds each. The production of a pound of chocolate takes approximately 500 seeds, therefore each tree can produce approximately enough seeds per year for about 2 lb of chocolate.

How is chocolate produced?

Grades 3–5

Each fruit ripens at a different rate and requires harvesting by hand when ready. Opening the pods requires more hands-on work, as does simultaneously removing the pulp (the flesh of the fruit) and seeds. Then the seeds and pulp undergo fermentation for 2 to 8 days, during which yeasts convert the sugars into alcohol and carbon dioxide. Mycoderma aceti, a type of bacteria, then converts the alcohol into acetic acid. This process produces large amounts of heat, reaching temperatures of 45° C (122° F). The germ (seed embryo) dies due to the production of the alcohol, acid, and heat. This process also releases enzymes and develops flavors. Following fermentation the seeds are dried, often in a single layer spread in the sun. The dried cacao beans are shipped to manufacturing plants for further processing.

Beans arrive at the manufacturing facilities for sorting and roasting. How the beans are roasted varies greatly from manufacturer to manufacturer and depends on the planned use of the beans. Roasting the beans further develops flavor and allows an easier separation of the nib (what was the seed embryo) from the hull. The roasted beans undergo winnowing (a mechanical separation), in which the husk of the bean is broken apart, leaving husk fragments and cocoa nibs. The husk fragments and nibs are separated from one another. Then the nibs are sorted based on their size and weight. The husks are discarded or sometimes given away as garden mulch.

In some manufacturing plants, the nibs are packaged and sold at this point. However, making traditional chocolate requires more steps. The nibs must be crushed or ground, which melts the cocoa butter and allows the components of the nib—the interior of the seed—to form a homogenous mixture called chocolate liquor. This chocolate liquor is not alcoholic; the term refers only to the liquid property of the mixture. Chocolate liquor is chocolate solids suspended in cocoa butter. If the chocolate liquor is allowed to harden, it forms bittersweet or baker’s chocolate. If the liquor is pressed, it separates into the components cocoa butter and cocoa powder. Cocoa butter consists of a triglyceride made of steric, palmitic, and oleic acids. Chocolate liquor mixed with other ingredients, including sugar and often more cocoa butter, results in other chocolate products, such as chocolate candy.

The conching process combines chocolate liquor with extra cocoa butter, sugar, lectin, and milk solids. The ingredients are melted and mixed continuously until the appropriate viscosity is achieved. This mixing may take a few hours or as long as several days. 

After conching the chocolate requires tempering, heating the chocolate to specific temperatures and then cooling it to specific temperatures, allowing crystals to form. The temperatures at which the crystals form determine the size and evenness of the crystals in the chocolate. These crystals determine the properties of the finished product, including hardness (snap), melting temperature, and texture.

What chemicals are in chocolate?

Chocolate contains over 300 compounds; however, not all of them have been extensively studied.

  • Caffeine, a stimulant, is 1 of the most well-known chemicals found in chocolate. However, it is only present in small amounts, equivalent to the amount of caffeine in decaffeinated coffee.
  • Theobromine, a methylxanthine alkaloid, is specific to plants in the genus Theobroma. It is a known vasodilator, diuretic, and heart stimulant. Its chemical structure is similar to caffeine, differing by only 1 methyl group.
  • Flavanoids, such as polyphenols, have been shown to reduce blood pressure and increase blood flow to the brain. They are also thought to protect the circulatory system and improve insulin sensitivity.
  • Anandamide, often referred to as the bliss molecule, is a cannabinoid neurotransmitter. Since it activates some of the same receptors as THC (tetrahydrocannabinol), it may produce a feeling of well-being. However, it does not activate all of the same receptors, so approaching the level of "high" that THC produces would require very large quantities of chocolate. The human body naturally produces anandamide; when this occurs the compound is broken down rapidly. There is speculation that when anandamide is eaten in chocolate, some of the other chemicals found in the chocolate may inhibit the rapid breakdown.
  • Phenylethylamine, a biogenic amine, is a dopamine releasing agent and potential neurotransmitter. Phenylethylamine stimulates parts of the brain that keep you alert. This produces chemistry similar to that of a person in love.

The next time you and your students have any type of chocolate, you will know the process of bringing it from the cacao tree to you and some of the chemicals that it contains. However, that knowledge is unlikely to affect your pleasure when tasting the ever-popular flavor of chocolate.