Sweet science of genetics

Decoding the cacao genome is good news for chocolate lovers.

No one who loves chocolate needs to be told it is experiencing a golden age. Just the names of cacao types such as Venezuelan Porcelana on chocolate-bar labels shows a deepening hunger for vivid cacao character and artisanship.

On the scientific front, biochemists are unraveling chocolate's heart-healthfulness, and archaeologists are gaining insight into its ancient ritual uses, but plant geneticists are engaged in the most exciting research: decoding the cacao genome, holding promise for farmers, manufacturers, and chocolate lovers alike.

Raymond Schnell, a geneticist who coordinates two programs aimed at constructing an overall genetic picture of Theobroma cacao, spoke recently at Fairchild Tropical Botanic Garden's International Chocolate Festival, in Coral Gables, Fla.

Schnell directs the programs, funded by Mars, at the Subtropical Horticultural Research Station of the USDA Agricultural Research Service.

South Florida's role in chocolate research dates to the 1950s, when the USDA established a quarantine station to stop the movement of cacao diseases among the Americas, Asia and Africa. After disease decimated the cacao crop in Bahia, Brazil, in 1998, threatening Mars' supply, the candy company funded USDA efforts to develop disease-resistant plants to broaden the narrow genetic foundation of cacao plantations in Africa, the world's largest producer.

This program gave rise to far-reaching efforts to collect and accurately identify cacao specimens. DNA testing has revealed that some of the world's great germplasm banks are full of mislabeled specimens - a hindrance to any breeding program meant to exploit a particular cultivar's qualities, from subtle flavor nuances to disease or pest resistance. For the past decade, Schnell's team has been examining germplasm from many collections, trying to set the record straight.

The Coral Gables research station is on property that once belonged to horticulturalist and tropical plant explorer David Fairchild. The weathered gray stone walls that enclose the cacao collection resemble an ancient Mayan temple ruin, just as Fairchild intended. In 1933 he had the garden enlarged as part of a Civilian Conservation Corps project, cannibalizing paving stones from a military airstrip to construct the thick walls. Fairchild knew that unimpeded Gulf Stream breezes made the spot several degrees warmer than surrounding areas. This slight boost plus the absorbed heat the walls radiate back at night raises the temperature in the sheltered garden by 5 to 7 degrees - enough for cacao and other tender tropical plants to survive this far north.

Among the scientists working on the mapping project is Venezuelan-born geneticist Juan Carlos Motamayor, who has shed light on the complexity of genotypes within the species Theobroma cacao. There are 10 known genetic clusters, all native to South America; the number may grow as Motamayor examines cacao samples from Bolivia and Peru.

When the project is complete in two or three years, it will help clarify the genetic origins of cacao and the relationships among its types. It will also allow scientists to select cultivars for farmers that are smaller, faster-growing, easier to prune, and pest- and disease-resistant.

In the end, more accurate knowledge of genetics will turn cacao into a modern crop. The payoff for chocolate lovers will be a secure source for their favorite food and, perhaps, an even richer flavor palette.


Tropical Night Brownies

Makes 16 brownies

10 tablespoons unsalted butter

2 ounces dark chocolate, (70 percent cacao), finely chopped

3 ounces dark chocolate, (58.5 percent cacao), finely chopped

1 cup grated brown loaf sugar, Demerara, sugar or packed light brown sugar

1/2 cup granulated sugar

3 large eggs, lightly beaten

1 tablespoon dark rum

1 teaspoon vanilla extract

1/2 cup plus 1 tablespoon unsifted all-purpose flour

1/4 teaspoon salt

1/4 cup unsweetened medium flaked coconut or 1 cup fresh coconut, grated on the medium side of a box grater

1/2 cup unsalted roasted cashews, coarsely chopped

1/4 cup finely chopped cacao nibs (available through mail order or at Whole Foods)

1. Place a rack in the lower third of the oven and heat to 350 degrees. Grease a 9-by-9-inch baking pan.

2. In a small saucepan over low heat, melt the butter with the chocolate. Remove from the heat and stir in both sugars. Pour into a large mixing bowl and set aside to cool for about 5 minutes. Add the eggs, rum, and vanilla, stirring just until blended. Stir in the flour and salt, then the coconut, cashews, and cacao nibs.

3. Spread the batter in the baking pan. Bake for 22 minutes. Cool thoroughly before cutting into squares.

 

- Courtesy of the Miami Herald and from The New Taste of Chocolate, by Maricel E. Presilla (2009, revised, Ten Speed Press)

 

Note: Preferable brands for 70 percent cacao are El Rey Gran Saman or Scharffen Berger. Preferable brand for 58.5 percent cacao is El Rey Bucare.

Per brownie: 261 calories, 3 grams protein, 31 grams carbohydrates, 14 grams fat, 59 milligrams cholesterol, 58 milligrams sodium, 1 gram dietary fiber.