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Monique Keiran: Thank yeast for that chocolate

Last year, a team of researchers from the University of British Columbia and elsewhere uncovered the earliest-known use of cacao seeds as food.

Last year, a team of researchers from the University of British Columbia and elsewhere uncovered the earliest-known use of cacao seeds as food.

In the rainforests of present-day Ecuador, on the edge of the Amazon River Basin, the archeologists identified cacao residues in 5,300-year-old stone mortars, ceramic bowls, bottles and jars.

The findings push back the origin of cacao’s use as food by about 1,500 years and 2,200 kilometres further south than had previously been assumed.

In contrast, the oldest-known evidence for wine-making is 8,000 years, from Asia Minor.

Demand for cacao products has only grown since those Stone Age days. The ancient Mayans and Aztecs drank a bitter cacao drink. Colonization of the Americas by Europeans and the marriage of cocoa with sugar sparked a taste for luscious, chocolatey drinks and bonbons that continues worldwide today. The global annual market for chocolate is estimated to be worth about $100 billion.

For our part, Canadians each consume an average of 5.5 kilograms of chocolate every year. And Easter sees much of that nibbling, with $104 million spent on Easter bunnies and chocolate eggs.

The seed, or bean, of the Theobroma (“food of the gods”) cacao tree is the source of all things chocolate — chocolate liquor, cocoa solids, cocoa butter and chocolate. The tree is native to tropical Central and South America and grows best in a narrow swath along the Equator, in hot, humid climates with regular rains and short dry seasons.

But it’s a long journey from a tropical seed to what we call chocolate. Much of it is made possible by microbes.

Once they’re harvested, cacao beans are collected and placed in large wooden boxes or piled on the ground on the farms in the tropical heat and sun. A white, gooey pulp surrounds the beans, and local yeasts colonize and feed on the pulp, fermenting it.

This unappetizing, burping, smelly process transforms cacao seeds into the precursor ingredients for delectable, melt-in-your-mouth chocolate.

For decades, researchers have worked to improve cocoa fermentation by identifying and controlling the microbes involved. In much the same way that the yeasts that convert grape juice into wine influence its flavour and quality, differences in yeasts yield different flavours and quality in the resulting chocolate.

While this microbial effect means specialty, bean-to-bar producers can work to tailor chocolate to specific flavours, less-desirable microbes lead to foul-tasting product or incomplete fermentation.

But, a few years ago, researchers found that they had the yeast solution all along. They found that some of same yeast species used to make beer, bread and wine yield highly rated and more consistent chocolate than wild, local yeasts do.

The researchers characterized more than 1,000 strains of Saccharomyces yeasts. Some of the best performers came from the farms, while others came from the beer, wine, bioethanol and sake industries. When the scientists crossed the best strains, they produced hybrids that performed even better.

While microbes make the pod-to-plate journey possible, they can also be a leading threat to supply. In addition to volatile raw material prices, over-reliance on a few varieties, unsustainable farming practices and social unrest, a fungus has decimated cacao plantations throughout much of the tropical Americas during the past 60 years.

Frosty pod rot sounds like a breakfast cereal, but it’s bad news for cacao farmers and chocolate lovers. The disease attacks growing cacao pods, eating their insides and outsides.

The fungus was once confined to Colombia, Ecuador and western Venezuela. Since 1956, it has spread to 11 countries in the region. Frosty pod rot has wiped out many plantations in some areas. Brazil is the only cocoa-producing country in the continental Americas still free of the disease.

Researchers are working to understand and control the fungus. Meanwhile, in an effort to circumvent the challenges facing new-world cacao producers, most cultivation has shifted to West Africa, where outbreaks of Ebola — another microbe — and social and political unrest have been percolating for years.

Food of the gods or food of spoiled 21st-century humans — for good or ill, chocolate’s availability, continued existence and desirability depends on micro-organisms.

Think on that as you nibble your chocolate-bunny ears.