Fennel, lemon balm and elderberry are not typical soda flavors one might expect to see lining the shelves of a convenience store. But what makes Laura Killingbeck’s array of fizzy drinks unique isn’t necessarily the natural ingredients – it’s the omission of high fructose corn syrup.

Killingbeck’s ongoing series on fermentation recently returned to Round the Bend Farm to teach locals how to brew live-culture sodas. Attendees removed their shoes and got cozy inside the living room of the farm’s communal home where they sampled effervescent, earthy drinks out of small mason jars.

After a taste test, Killingbeck started the class by holding up another type of drink for contrast.

“Typically when we have a manufactured fizzy beverage, it often has high fructose corn syrup in it,” she said while holding up a bottle of Polar Beverages’ Diet Double Fudge soda. “It’s an ingredient that’s been associated with a lot of health problems, including diabetes, heart disease and increased obesity rates.”

“There’s also a lot of funny things in here because there’s almost certainly not double fudge in here,” she continued. “There’s a lot of coloring agents, preservatives and artificial flavoring agents.”

She said modern sodas are replicas of a product that was formerly made with herbs, juices and real ingredients. Root beer and ginger beer, for instance, used to be made with ginger root and burdock root and were marketed as healing tonics.

The kinds of sodas that Killingbeck creates are made from water kefir culture, which is not the same as dairy kefir and looks something like amber-colored gelatinous mounds. Water kefir starter kits are available for purchase online.

The kefir is essentially a microbial culture, sometimes referred to as a SCOBY, a symbiotic colony of bacteria and yeast. When fermented in sugar water, the microorganisms will consume the sugars and give off carbon dioxide.

The soda recipe happens in two parts, or two separate rounds of fermentation. The first ferment follows a formula: Dissolve half a cup of sugar in seven cups of water. Then add half a cup of the culture grains.

The mixture should ferment at room temperature for one to two days. During that period, the gelatinous cubes will grow in number as they consume the sugar in the water, producing carbon dioxide in the process.

When it’s ready, the water can be poured through a plastic strainer to remove the kefir.

At that point, the fermented water can be funneled into empty, plastic soda bottles. Killingbeck recommends leaving some room at the top to allow for gases to form. This is also the point in the process where a variety of ingredients can be added to change the flavor of the soda.

During the seminar, Killingbeck created a blackberry soda by adding a cup of juice to the ferment. Apple cider, herbal infusions and syrups are all possibilities. A sugar source can also be added to enhance sweetness.

Killingbeck recommends using a soda bottle for this secondary ferment because the pliable plastic will become taut when the soda has become adequately carbonated.

“By capping it tightly in a bottle that’s meant to hold carbonation, we can capture the bubbles inside the bottle,” she said. “This is a totally different method than an industrial soda. Industrial soda is forcing carbon dioxide mechanically into a bottle.”

After all the desired ingredients have been added, the bottle should be capped and left to ferment at room temperature for another 24 to 48 hours. Before the soda can go into the fridge, the pressure needs to be released. She recommends doing this slowly while pointing the bottle away from others.

“What you don’t want to do is put your fully carbonated bottles in the fridge and have someone open them up without knowing,” said Killingbeck.

“Lessons learned…” she added while looking off into the distance, shaking her head. “Many lessons.”

The final entry in Killingbeck’s fermentation seminar series will be held on Nov. 14 at Round the Bend Farm. The class, which begins at 9 a.m., will teach participants about making a variety of products from dairy kefir.