HOLDEN — For an enthusiastic audience at the Holden Senior Center, chocolatier John Goodhile last week outlined the history of the plant with which he works — from its ancient origin as a beverage to today’s gem-like creations served in fluted papers and shared on special occasions.

Entering the center’s dining room, the first thing to notice was the dark, warm and velvety rich aroma emanating from the bags of cocoa beans that Goodhile passed around during his program, “Happiness is Chocolate,” which saturated the center with their tropical essence.

As audience members lifted the bags to their noses for a deep and delicious inhale, Goodhile explained that while cacao beans come from all over the world, they can only be grown within 20 degrees latitude of the equator.

At his Jefferson-based business, Stewart’s Chocolates, Goodhile uses beans from Madagascar, the Ivory Coast and Venezuela.

Before setting up his store, Goodhile made a thorough study of chocolate-making, from bean harvest to boxing the finished product.

The cacao tree is a relatively small tree, growing under the canopy of taller trees. It takes about five years for a tree to produce its first fruit, known as a cacao pod. Like wine, the beans that come from the cacao pods have a distinctive flavor or “earthiness” that derives from the soil in which they’re grown. There are three main varieties of beans:  Forastero, Criollo and Trinitario, Goodhile said.

Forastero is the type most used by large candy manufacturers, he said.

Each tree creates about 20 pods that take four or five months to grow and several weeks to ripen. Each pod contains about 40–50 beans that are then set to ferment for five days in special boxes. The trees produce two crops a year for as long as 60 years. Next comes a week or two of fermentation on large trays.

Next, the beans are roasted, during which their color darkens and the characteristic chocolate aroma develops. The beans have thin shells that become brittle once roasted and are removed. That leaves the “nibs,” or the meat of the bean.

The nibs, more than half cocoa butter, are ground into cocoa paste.

It’s the cocoa butter that gives chocolate its structure and shiny quality, Goodhile said.

Nibs and unsweetened chocolate also got passed around for a sniff and a taste.

The heat generated by grinding the nibs causes the cocoa butter to melt and form a paste known as chocolate “liquor.” When the liquor is molded and cooled, it becomes unsweetened chocolate.

Then the chocolatier’s art comes into play. By combining and personalizing chocolate flavors through tempering — the process of heating and cooling chocolate — and adding ingredients like butter and cream, the chocolatier turns out bonbons, those gem-like candies nestled into fluted papers that treat ourselves to on holidays and special occasions.

And yes, chocoholics at the program also got to try one of Goodhile’s bonbons.

Chocolate typically comes in three styles: dark, milk, and white. In the last two years, the French have added a fourth style dubbed “ruby chocolate,” Goodhile said.

Ruby chocolate uses beans that turn purple when roasted and yield a tangy, pink-tinged chocolate.

It’s interesting, Goodhile conceded, “but to be honest with you, don’t bother. I could make it out of white chocolate by adding citric acid.”

There was a steep learning curve to becoming a chocolatier, he said.

After remodeling his grandparents’ house to create an artisanal chocolate kitchen and retail space, Goodhile was happy to book his first order.

“It was for 14 four-piece boxes. It took me three days to fill it to my satisfaction,” he said. “I thought, ‘Oh boy, we’re going to have a problem.’”

The first day Goodhile opened the retail operation, he had just 12 chocolates in the glass case that stretched almost the full length of the store.

Just a few years later, the store at 1116 Wachusett St. is flourishing and has become a mecca for artisanal chocolate fans.