The Chemistry of Chocolate: An Introduction

Photo: A cacao fruit containing white, pulp-covered cacao seeds. Though the pulp is sweet and tart, the inner seed itself– there is a blown up inset of one of them cut in half– which is what is eventually ground into chocolate, is quite bitter and un-chocolate-like. (click the photo to enlarge)

Chocolate has perhaps the most complex flavor of any food in the world. This is due to the chemical makeup of the cacao (or cocoa beans) with which the chocolate is made, but also to the very complicated processes to which the cacao is subjected, including harvest, fermentation, drying, roasting, refining, conching, aging and tempering. These processes ultimately lead to a food with a flavor that is so chemically complex—with the running count now numbering over 600 possible volatile compounds–that scientists cannot even tell us exactly which compounds give chocolate its magnificent, delectable and unmistakable “chocolateness.” Researchers think that this quintessential chocolate note is probably due to a multiplicity of chemicals, or maybe that it is due only to a handful of chemicals that are present in very small quantities–but since they have very low odor thresholds, are nevertheless quite important–or maybe that it is due to both; how’s that for clarity? And so it is, that at the start of the 21st century, as we find ourselves capable of regularly flying into space, cloning plants and animals, and building supercomputers the size of wristwatches, we still don’t yet understand the essence of chocolate.

However, even though there is so much we don’t yet know about chocolate, we do know one thing: Chocolate is delicious, and many people, if asked to choose between their favorite chocolate and any other beloved food, would not hesitate to choose the item made from the fruit of a plant that Carolus Linnaeus deemed Theobroma, or “Food of the gods”—yes, chocolate (Theobroma cacao in full). Yet despite the fact that cacao has such a delicious sounding name, in reality, cacao just off the tree tastes quite bitter, astringent, otherwise harsh and not chocolaty in the least. How can this little seed that initially tastes quite awful be chocolate’s number one ingredient?

The answer is to be found above in the title of this series. Indeed, every step of the chocolate-making process involves quite complex chemical changes within the cacao, and it is our control over the processes that cause these changes that eventually reveals to us a flavor of beauty: that of finished chocolate of course!

Over the next several months we will be looking in some detail at the various steps of chocolate making, starting with the cacao tree itself, as we discuss the chemistry involved in each step, and where applicable, the history of developments in cacao processing that have led to changes in the chemistry of the finished product. We will answer many chocolate-related chemistry questions along the way, and our answers will raise new questions, but in any case, by the end of this series readers will have a very good idea of the types of changes undergone by our friend cacao during its metamorphosis into chocolate. Let the fun begin…