Chocolate through the ages followed a circuitous path

By Jeff Mitton          

On a bleak, wintry day I went to the CU greenhouse to photograph tropical flowers in bloom. The greenhouse, managed by Thomas Lemieux with assistance from Janice Forbis, has a rich collection of species from tropical environments. In a hallway a tree with large seed pods caught my attention. This was a cacao tree, the source of the seeds or beans that can be coaxed to yield chocolate.

Cacao trees, Theobroma cacao, grow 13 to 26 feet tall in tropical forests. They have been widely planted, but they thrive only 20 degrees latitude north or south of the equator. A related species, Theobroma grandiflorum, grows twice as tall and is used to make cupulate or cupuacu chocolate.

Although most chocolate is produced in Africa, cacao trees are native to South and Central America. Climate studies suggest that when North America was at the height of the most recent glaciation, cacao trees would have been restricted to the border of Brazil and Peru and the southern portion of the border of Brazil and Colombia.

 The seeds are protected by a variety of alkaloids that make them bitter and unappealing to birds and monkeys. Two of the alkaloids, theobromine and caffeine, make chocolate stimulating and invigorating.There are numerous genetic lineages of cacao, many of which can be traced to Peru. It is believed that cacao was first domesticated in Peru, where the pulp from the fruit was fermented to produce a mildly alcoholic beverage. This practice did not die out—a tequila-like alcohol is produced in Peru and Ecuador and is available in the United States.

The flowers and seed pods appear on the trunk and the oldest and largest branches, a flowering pattern called cauliflory. Cacao pods are large, six to twelve inches long and as they ripen they turn from green to one of five colors, depending on the variety: red, purple, orange, yellow or green.

Inside the pod are 20 to 60 cacao seeds or beans suspended in a mucilaginous white pulp. The pulp is sweet and fragrant and was probably the initial incentive for domesticating cacao. The seeds are protected by a variety of alkaloids that make them bitter and unappealing to birds and monkeys. Two of the alkaloids, theobromine and caffeine, make chocolate stimulating and invigorating.

A series of steps are followed to develop and extract the chocolate flavor from the seeds or beans. First, the beans and pulp are removed from the pods and fermented at 120 F for five to six days. This causes the seeds to germinate and then die (a prerequisite of the chocolate taste) and for enzymatic processes to diminish the alkaloidal bitterness.

Beans are then dried in the sun for one to two weeks to further reduce the alkaloids. Roasting the beans for 90 minutes at 215 F further reduces bitterness and brings out the chocolate flavor. After roasting, the dried, crumbly nibs are removed from their bean shells. Finally, grinding the nibs yields the two products of this laborious process—the sweet cacao butter and the solids, called cocoa. Cacao butter and cocoa are joined in a variety of proportions to produce chocolates with a wide range of tastes.

The Olmec Civilization cultivated cacao approximately 3,000 years ago in the humid forests of Central America. Little is known about their preparation of cacao, but the plant is clearly depicted in stone sculptures.

Cacao was passed from the Olmec to the Maya and then to the Aztec. Mayans and Aztecs prepared a frothy chocolate drink that was consumed by royalty and some other privileged ranks, but not shared with common people. Cacao beans were so valued that they were used as currency.

Europeans first came in contact with cacao during Columbus’ fourth trip to the New World, in 1502. His men captured an immense trading canoe that contained sacks of cacao beans, though they did not know what the beans were used for.

One of the most well documented introductions of cacao to Europe occurred in 1544 when Dominican Friars brought Aztec nobles to Spain to meet Prince Philip. Within a century chocolate was a favorite drink of the noble and privileged across Europe.

For most of the time that cacao has been domesticated, it has been consumed as a drink. The techniques for producing solid chocolate were elaborated and refined relatively recently, between 1815 and 1847.

A word of caution—theobromine is a stimulant for humans but it is toxic to dogs and cats.

Jeff Mitton, mitton@colorado.edu, is a professor in the Department of Ecology and Evolutionary Biology at the University of Colorado. This column first appeared in the Boulder Camera.

March 16, 2015