Chocolate’s Darkness Actually Starts from Purple and Pale Hues

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 called flavonoids, a group of bioactive compounds that have scientifically been proven to 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 would confer tannic and bitter sensations in finished chocolate. In exceptional cases, the cocoa seed content may be entirely white for lacking anthocyanins as the morphological expression of a recessive genetic variant, like in the prized Porcelana variety from Venezuela. These rare pale-hued and anthocyanin-free cocoa seed varieties are highly appreciated for conferring milder but silkier cocoa notes in the finished chocolate product.

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 single-origin chocolate (chocolate made from cocoa grown in particular regions or estates.)

Like grapes for wines, the type and composition of cocoa polyphenols 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 virgin mucilage helps preserve the freshness and color of the seeds resting undisturbed in the cocoa pod before being cracked open. As the 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 have an effect on the destiny of the cocoa bean.

Yeasts pig out on the sugars of the mucilage, turning them into alcohol. Once sugars are depleted, lactic bacteria kick in, transforming the citric acid of the mucilage in lactic acid and smaller sugar molecules. Finally, acetic bacteria metabolize the alcohol made by yeasts in acetic acid, raising the temperature of the fermenting batch up to 50°C.

During fermentation, the heat, alcohol, and organic acids generated externally throughout the different metabolic reactions gradually disperse to the internal sections of the cocoa seeds, activating enzymes which oxidize polyphenols and complex them with other nutrients, mainly proteins, to form the flavor precursors of chocolate. It’s in this complex process that the bright colors of anthocyanins fade out, transforming cocoa seeds into brown beans.

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 a residual 7% humidity.

Cut open for visual inspection, cocoa beans that have been 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 to the typical taste of chocolate we all love.