DAN PEARSON was working in northern Peru two years ago with his stepson Brian Horsely, supplying gear and food to mining companies, when something caught his eye.
“We were in a hidden mountain valley of the Marañón River and saw some strange trees with football-size pods growing right out of their trunks,” Mr. Pearson said by telephone last week. “I knew nothing about cacao, but I learned that’s what it was.”
It was, he would learn after sending samples of seeds and leaves to the Agricultural Research Service of the United States Department of Agriculture, one of the rarest, most prized varieties of cacao.
“The DNA of this material is pure Nacional,” said Dr. Lyndel Meinhardt, a scientist with the service. “These are very rare.”
Until the early 20th century, Nacional, a member of the Forastero family, one of the three main genetic categories of cacao, was widely grown in Ecuador, then the world’s largest cacao producer. But it succumbed to disease, which even cross-breeding could not resist. Some Nacional still grows in Ecuador, though most is not pure. At least one chocolate company, Kallari, says it uses it in blends.
But with the help of the Swiss chocolate expert Franz Zeigler, beans that Mr. Pearson and his stepson buy are being made into slabs of pure Nacional chocolate. “The magnitude of this find is bigger than anything I have known,” Mr. Zeigler said.
The chocolate is intense, with a floral aroma and a persistent mellow richness. Its lack of bitterness is remarkable.
One reason may be that Nacional cacao has a rare and precious characteristic: some of the beans are white, not the usual purple, and those from the Marañón Canyon are about 40 percent white. White beans, which Dr. Meinhardt said have fewer bitter anthocyanins, produce a more mellow-tasting, less acidic chocolate. Dr. Meinhardt said white beans are mutations that happen when trees are left undisturbed for hundreds of years.