Slate is making its coronavirus coverage free for all readers. Subscribe to support our journalism. Start your free trial.

Bread making is enjoying a pandemic-driven renaissance right now, but it’s hitting one hitch: No one can find any yeast.

Shortages of dry yeast have been a consistent complaint since business shutdowns and stay-at-home orders have kept most Americans eating in—and hoarding many dry and canned goods to prepare. While some supply chains have begun to catch up with demand surges for certain products, yeast has been one area where they’re struggling to keep up. Robb MacKie, president and CEO of the American Bakers Association, said the industry was unprepared for the run on yeast because there’s usually a lull in demand for bread products and ingredients in the first quarter of the year, while the peak typically comes during the November and December holidays. The pandemic has flipped that schedule on its head, he said, with demand surpassing what producers would expect even in the busy season.

As with toilet paper and hand sanitizer and pasta, it’s tough for the dry yeast supply chain to accommodate an astronomical surge in demand. John Heilman, vice president of manufacturing for Fleischmann’s Yeast producer AB Mauri, roughly estimates that it’ll take a month or two until shoppers will see a consistent supply of dry yeast on shelves. “I’ve been with the company for five years, and this is by far the highest demand I’ve ever seen,” he said, noting that there’s been as much as a 600 percent increase year over year. In the past there have been demand spikes during large snowstorms, but those don’t even come close to what Heilman is seeing now. (He also said that demand for fresh yeast, which the company also produces, has been softening during the pandemic, because so many restaurants have either limited their offerings for takeout or have closed down altogether.)

Yeast are single-celled fungi that come in 1,500 different species; humans have been cultivating them to make breads and alcoholic beverages for 5,000 years. Nowadays, as Quartz outlines, industrial-scale production for retail involves mixing molasses with yeast strains that have been bred to select for traits that are optimal for baking. The yeast is then placed in a series of fermenters where it’s fed oxygen and sugar, allowing it to reproduce. The resulting product goes into a centrifuge to separate out the solids, which can then be aerated, filtered, dried, and packaged.

But the supply chain issues may not have anything to do with these ingredients. Instead, a major problem seems to be getting all that yeast packaged.

Heilman, who oversees three Fleischmann’s Yeast plants in the U.S., has been trying to ramp up production by staffing facilities to max capacity and asking workers to hold off on vacations. “From a molasses standpoint and growing the yeast itself, there’s plenty of capacity,” he said. “Where we wound up maxed out is our ability to package.” The facility in India where the company gets its jars was shuttered, and materials for paper packets have also run low. The extra staff that the plants are recruiting will mostly be aiding this packet packaging effort, as well as drying the yeast.

There’s another hurdle that makes it difficult to quickly scale up yeast production. While plants may be able to streamline production domestically by hiring more people and working longer hours, certain segments of the process are restricted by a biological clock. “Yeast takes a certain time to go from one cell to two cells,” says Sudeep Agarwala, a yeast geneticist who works for the biotech firm Ginkgo Bioworks.* “You can do everything you can to speed it up, but there’s a hard limit to how fast they can double.” Yeast also needs to consume sugar gradually—a production plant can’t force-feed the cells at a faster clip. Heilman says that the process at his plants is maxed out at 10 days to make the most product in the shortest amount of time. Trying to cut that time results in lower volumes per batch. Having more equipment at a plant’s disposal could eventually help to deliver larger volumes, but it’s impossible to get it shipped and installed on such short notice.

Yeast plants have also had to implement more health measures for their employees. According to MacKie, facilities across the country have been doing temperature checks, putting up plexiglass shields, and distributing personal protective equipment. “We need to keep these plants operational and protect the employees,” said MacKie. “We are worried.”

Friends, I learned last night over Zoom drinks that ya'll're baking so much that there's a shortage of yeast?! I, your local frumpy yeast geneticist have come here to tell you this: THERE IS NEVER A SHORTAGE OF YEAST. Here's where I'm a viking. Instructions below. — shoelaces3 (@shoelaces3) March 29, 2020

If you can’t find yeast at the store, there are DIY options. As Agarwala outlined in a viral Twitter thread, you can grow yeast by placing old flour, water, and dried fruit (or ale) into a jar. Allowing that mixture to ferment in a warm place for 24 to 48 hours should yield yeast that you can use in baking projects. The resulting product won’t act as predictably and consistently as what you’d buy in a store, but it may imbue your baked goods with a certain distinctive character. “It’s the difference between asking the drama kids to do something versus asking the honor students,” Agarwala told me. “With the drama kids it’ll be a month late, but creative and interesting and beautiful. If you want something done immediately and make sure it gets done, you ask the honor students.” The yeast you make at home might bubble a bit differently, give the bread unusual flavors and air pockets, and take a little longer to help the dough rise. Given that many peoples’ schedules are slightly less packed than usual, though, you probably have the time to make your bread the slow, weird, magical way.

Correction, April 16, 2020: This post originally misspelled Ginkgo Bioworks.

For more on the impact of COVID-19, listen to What Next.