TORONTO -- With more people spending time at home due to the continued spread of COVID-19, many are turning to baking as a way to keep busy. But with more people reaching for the apron, grocery stores are facing shortages of key baking ingredients, including yeast.

Thankfully for those who can’t buy yeast, many are sharing their DIY recipes online.

One of these people is Sudeep Agarwala. The yeast geneticist and biological engineer based in Boston recently took to Twitter to share his recipe for homemade yeast using things many of us have at home.

Agarwala says his thread was inspired by a friend who told him she couldn’t find any yeast at the store to make her own bread.

This shortage of yeast exists across North America, according to Sylvain Charlebois, professor of food distribution and policy at Dalhousie University. He attributes this to the drastic change in consumer behaviour as a result of people spending more time at home.

“Before, consumers went [grocery shopping] to buy a finished food product for that day or the next couple of days,” Charlebois told via telephone on Monday. “Now, consumers are walking into grocery stores looking for ingredients for the next couple of weeks.

“That’s a huge paradigm shift.”

Another reason for the shortage of yeast, he explains, has to do with its unique supply chain. Seeing as yeast is typically used in small amounts, it’s not something people often stock up on. As a result, the rapid rise in demand for it caught many companies by surprise, says Charlebois.

“Pre-COVID, grocers never felt compelled to stock up on yeast because people didn’t bake [as much],” he said. “Manufacturers weren’t necessarily ready for this kind of shock.”

But according to Agarwala, there’s never a shortage of yeast, given the fact that you easily make your own with just three ingredients.

“Yeast is all around you – you can just cultivate it and use it to make what you want,” Agarwala told on Monday over the phone.

His recipe includes fruit – preferably dried – such as grapes, raisins, prunes, or apricots. According to Agarwala, fresh fruit works too, but he suggests not washing it. This may not be the best idea unless you grew the fruit yourself and trust that it’s not contaminated, he says.

Place the fruit into a jar with two to three tablespoons (30 to 40 millilitres) of water. Then add an equal amount flour, enough to make a loose, wet dough. Agarwala says he prefers white flour, but it doesn't have to be fresh -- even months-old flour can be used. It also doesn’t have to be organic or high in gluten.

The next ingredient is time. He recommends keeping the mixture warm (but not hot), and offers some suggestions on how to store it at the perfect temperature.

After about 12 hours, bubbles will start to appear, Agarwala says. Once a day or two has passed and the paste has loosened, take a tiny piece of the mixture and add to it two to three tablespoons (30 to 40 millilitres) of water. Add flour and repeat the process. This time, he says, the bubbles should appear much faster.

If at first you don’t succeed, try, try again says Agarwala, using a different fruit or flour if necessary. He also encourages people to get creative by using old bread lying around at home or bread crumbs. You can even make yeast using beer or wine – since you’ll be cutting back on so much of your original mixture, the original flavours won’t be there when you finally bake, he says.

The thread, posted March 29, now has more than 27,000 retweets and 115,000 likes on Twitter. This level of engagement is something Agarwala says he was not expecting.

“I didn’t realize anyone would read this,” he said. “Here’s something I’m passionate about and this stupid tweet I post on a Sunday morning, and now I see people discovering yeast for themselves – I think it’s wonderful.”

The scientist has several hypotheses for why his tweets performed so well.

“The uncharitable way of seeing all of this is that people are bored,” said Agarwala. “The slightly more charitable way is that they’re scared, and they just want to be prepared and have control over something.”

But perhaps the most relevant explanation lies in the fact that many are feeling increasingly disconnected from the world around them, he says. Agarwala describes physical distancing as alienating, and with social interaction so fractured these days, many are likely looking for a sense of human connection. Baking, he says, helps fill this void.

“Being able to get involved in making your own food, it approximates that,” said Agarwala. “Being involved in the cultivation of something on your kitchen counter…feels like a way of cultivating the formalisms of human connection, even when you don’t have it.”

Adding another layer of connectivity is the use of social media. With so many people using platforms like Twitter, Facebook and Instagram to share what they’ve made and the process behind it, interaction between them increases. Whether they are baking bread or something completely different, social media has become a source of inspiration for consumers, says Charlebois, and its use has given people more of a reason to bake.

“Social media has become a source of information and inspiration for chefs that need training in their own kitchen,” he said. “What happens on social media will certainly influence consumers and their priorities in the kitchen.”

Charlebois says he expects this type of consumer behavior to continue – in fact, he even describes it as the beginning of a new era.

“More people are looking at doing things on their own, by themselves,” he said. “We’re leaving a period where convenience and instant gratification were valued – now, simplicity is much more valued than ever before.”