All chocolate in the world is made through complex steps that start from fresh cocoa seeds, which, if cut open lengthwise, denote unexpectedly romantic hues, ranging from the deepest purple to the palest pink, up to the purest white.
How does color change and evolve from purple and pale cocoa seeds to brown chocolate bars?
Cocoa seeds are chock-full of characteristic polyphenols (natural antioxidant substances contained in fruits and vegetables) called flavonoids, a group of bioactive compounds that promote cardiovascular, cognitive, and anti-aging health benefits. Cocoa flavonoids’ subclasses include flavanols and anthocyanins.
Anthocyanins, even if present in cocoa as the minor polyphenolic portion, are the natural pigments responsible for coloring also berries, cherries, eggplants, purple potatoes, red wine, and other reddish-purple fruits and vegetables.
If cocoa seeds were badly processed, anthocyanins still in their primitive status would confer tannic sensations (the astringent and drying feeling of limited mouth lubrication) and bitter accents in finished chocolate. In exceptional cases, the cocoa seed content may be entirely white for lacking anthocyanins as a recessive genetic variant’s morphological expression, like in the prized Porcelana variety from Venezuela. The rare pale-hued and anthocyanin-free cocoa seed varieties are highly appreciated for conferring sophisticated flavors similar to a jam of fresh and dried fruits in the finished chocolate product, with a “rounded” palatibility—that is, without the astringency typically associated with unripe fruits.
Once properly transformed, the natural polyphenols in cocoa, combined with other nutrients present in the seed, significantly contribute to the sought-after nutty, fruity, floral, and spicy flavors typically appreciated in high-quality specialty or fine chocolate.
Like grapes for wines, cocoa polyphenols’ type and composition vary, being strongly influenced by genotype, origin, ripeness, and processing.
The first—and most critical—step for chocolate flavor development is fermentation, a process initiated as soon as the external lemonade-tasting mucilage surrounding the cocoa seeds is exposed to air and the local environment. Naturally rich in citric acid (the natural acidic substance giving lemons their typical sour taste), the virgin mucilage enclosing each cocoa seed in a cocoa pod helps preserve the freshness and color of the seeds resting undisturbed in the cocoa pod before being cracked open. As the environmental microbial contamination is irreversible, the gooey pulp protecting the cocoa seed starts being broken down by a diversity of microorganisms (yeasts, lactic bacteria, and acetic bacteria), which all affect the destiny of the cocoa bean.
Like wine and bread making, yeasts are the first microorganisms that overeat on the mucilage’s sugars, turning them into alcohol. Once sugars are depleted, lactic bacteria kick in, transforming the mucilage’s citric acid into lactic acid (which confers softer notes to the initial mix) and smaller sugar molecules. Finally, acetic bacteria metabolize the alcohol made by the yeasts in acetic acid, raising the fermenting batch’s temperature to 50°C.
During fermentation, the heat, alcohol, and organic acids generated externally throughout different metabolic reactions gradually leak into the internal sections of the cocoa seed. Enzymes get activated, which are small proteins catalyzing a specific metabolic response, oxidizing polyphenols and binding them to other nutrients to form the flavor precursors typically associated with dark chocolate. In this complex process, the bright colors of anthocyanins fade out, transforming cocoa seeds into cocoa beans, where progressive dehydration promotes reactions between smaller molecules of sugar and protein fragments.
At the end of fermentation, which typically lasts from 3 to 7 days—depending on the genetic variety and processing method—cocoa beans are slowly dried for a few days to reach an optimal 6‒8% humidity and avoid the proliferation of molds.
Cut open for visual inspection, cocoa beans adequately fermented and dried will show the typical brown color of chocolate we all know. However, it’s only through a careful roasting step that the multitude of cocoa flavor precursors formed during fermentation will lead—through controlled time-temperature conditions for optimal Maillard reactions—to the typical taste of dark chocolate we all love.