For starters: Your guide to the sweet spot where science meets sourdough

·3 min read

Chances are, you've got something growing in your fridge.

When COVID-19 forced most people into their homes back in March, the ensuing baking boom coincided with a yeast shortage, so hordes of bored at-homers took the step into sourdough.

Now they've found themselves in a relationship with a blob of bacteria — the sourdough starter — that needs to be kept alive with regular feedings and exercise.

Michael Gaenzle is a University of Alberta professor of food microbiology whose relationship with his sourdough starter has already lasted 15 years.

And that's nothing, the microbiologist told CBC Radio's Edmonton AM this week.

"The oldest sourdough is far more than 100 years old," he said. "Some of the bakeries in San Francisco, these credibly claim that they've kept it active since the 1849 Gold Rush."

Jane Sponagle/CBC
Jane Sponagle/CBC

Unlike most bakers, Gaenzle's relationship with sourdough was all business in the beginning. After that, you could say, it grew on him.

As a master's student with an interest in food biochemistry, the organisms of sourdough and their impact on bread quality became Gaenzle's thesis topic, and it continues to be part of his ongoing research. A recent project involved seeing if sourdough could be used to replace sugar in hamburger buns, he said.

"I started baking — but only after I work with the organisms in the lab," he said.

The beauty of sourdough is that it allows you to bake bread without yeast, thus explaining its rise to popularity in the early days of the pandemic when the baking product joined toilet paper as the toughest-to-find items at the grocery store.

"For example, when the gold prospectors went into the Yukon in the wilderness, they all carried some starter," Gaenzle said, "because the next convenience store, which would provide baker's yeast, was a little bit too far away."

Starting a starter is as easy as mixing flour with water and waiting. "After one or two days it will start to smell a little bit funny. But after some refreshments or feedings, the right organisms will start to outcompete the funny smelling ones," he said. "And then usually after a dozen or so refreshments you will have a good sourdough."

The process can be sped up with a little plant material, such as onion peels or flowers. Or you can really cut to the chase and get some starter from a friend, he said.

Dave Bajer/CBC
Dave Bajer/CBC

The ongoing care and feeding of a starter is exactly what it sounds like, he said. Add a little flour. Let the starter grow as it gives the bacteria some "exercise," throw a little bit of it away and put the remainder back in the fridge.

A baker would do this two or three times a day, 365 days a year, he said. But you don't have to.

"Sourdough is an adaptable ecosystem," he said. "If you keep it in the fridge for four weeks then you take it out for a baking day, that's perfectly fine.

"The secret of sourdough is that you really need to keep the organisms active and growing, which means after some time of extended storage in the fridge it's advisable to give it a couple of feedings."

Gaenzle said every sourdough takes on unique properties based on how it is treated by its owner. It's one of many reasons that bakers will maintain such a serious relationship with their starter.

"You never change a winning team," he said. "Once you have the right organisms in your sourdough, you try to keep them alive and happy."