MELBOURNE, Australia—Just before the final round of Australia’s top coffee competition, barista Tilly Sproule stocked up on a crucial ingredient. She bought nearly 20 pounds of dry ice.
She packed the ice into a box, divvied up her coffee beans into small plastic vials and inserted the tubes into the ice. Her goal was to chill her beans to below zero. She wanted them so brittle they would grind more evenly than at room temperature. It was vital, she said, to making an incredible cup of joe.
“Backstage is hilarious,” Ms. Sproule said. “There’s like five or six freezers, I think. Everyone’s on the bandwagon.”
Forget about cold brew. The latest buzz in the caffeine universe is really, really cold beans.
It isn’t just about getting a better grind. Some cafes are freezing their best beans so they’ll last months or even years—far beyond the couple of weeks that roasted beans typically taste their best. Frozen-bean advocates imagine a day when coffee aficionados can behave like wine connoisseurs, poring over long coffee menus to sample numerous vintages.
Scientists say there is little research so far into how best to store frozen beans for the long term. So coffee nerds are trying to figure it out for themselves. Some roasters are trying ultralow-temperature freezers typically used by labs to store biological samples. Others use frozen-food warehouses. Some freeze unroasted beans, others roasted.
“People haven’t done this before,” says Christopher Hendon, an assistant professor of chemistry at the University of Oregon who has studied coffee. “A good analogy for this is: Imagine being the first guy ever to provide aged whiskey. Imagine saying, ‘Hey, 28 years from now, we are going to make some money.’ ”
One thing the coffee experts figured out right away: They had to do better than ordinary consumers who buy a bag of coffee at the grocery store, use some of it and just toss the rest into the freezer.
“Thirty years ago, people said, ‘Oh, freeze all your coffee and it’s better for it,’ ” says Will Young, the owner of Campos Coffee in Sydney. “But then people were doing it badly. They were doing it in open containers, frost forming on the actual bean itself. It was just really embarrassing for coffee.”
Mr. Hendon says coffee beans need to be frozen in an airtight container to keep out excess moisture and prevent unwanted odors from contaminating the beans. More study is needed, he says, to determine how the rate of freezing and humidity affects the beans.
It helps to have a reliable freezer. Mr. Young arrived at his roastery one day last year to find a mini-freezer had stopped working. Inside was unroasted Panamanian coffee that had cost more than $100 a pound. It had been frozen for nine months. It wasn’t anymore.
The unplanned thawing, he says, left the beans tasting no better than a $6-a-pound grade. Still, some of the beans were good enough to use in the regular espresso blend he sells to cafes. That week, he says, cafe customers were “drinking some of the best coffee in the world, just a very small amount of it in each cup.”
Mr. Young upgraded to a freezer that cost about $3,000. He uses it to store ultrapremium coffee from Panama, Yemen and Costa Rica. Preserving it in a freezer just for a year would be a success. Mr. Young says unroasted beans typically start to degrade after six months, even if stored in a climate- and humidity-controlled warehouse.
George Howell, who runs his namesake coffee business in Boston, has about 200,000 pounds of unroasted beans in a warehouse used for frozen food. He also has several ice-cream freezers in his roastery to keep the more expensive beans, including a Guatemalan variety harvested back in 2012.
Still, Mr. Howell says about 10% of his frozen beans still degrade, probably because the beans weren’t properly dried after harvest.
“This has all been trial and error and just following what works,” he says. “We’re not scientists.”
Mike Cracknell, managing director of Vertue Coffee Roasters in Melbourne, tried freezing roasted coffee beans in a sandwich bag in his freezer at home. He says the coffee ended up tasting like rotten fruit. Subsequent experiments with a vacuum seal yielded better results, but he doesn’t think freezing beans will become standard practice for most roasters and cafes.
“It’s over-engineering,” he says. “When the majority of people might be enjoying their large cappuccino or their regular flat white with one sugar, there’s no need to do that.”
Such skepticism isn’t stopping some cafes. Customers at a new Sydney cafe run by ONA Coffee can order from what cafe manager Isaac Kim calls the “reserve menu.” The beans, already roasted, are stored in a freezer in single-serve, vacuum-sealed packs. Some coffee beans peak in flavor about 10 days after roasting and may start to degrade around the two-week mark, Mr. Kim says.
Carol Leong, who stopped by the ONA cafe with friends recently, said it was the first time she saw a barista take beans out of a freezer. “Just then I saw it and I was like, whoa, that’s pretty cool,” she said.
Ms. Sproule, from Tim Adams Specialty Coffee, didn’t win the Australian coffee championships, but she swears by her dry-ice technique. For optimal grinding, she says, she likes to get the beans to at least 58 degrees below zero.
At that temperature, she explains, “you get less fines and less boulders, and more like a shattered, uniform particle size.”
The winner of the contest was Matthew Lewin, who works at ONA. He said he used a portable freezer to chill his beans. At the main roasting facility in Canberra, Australia’s capital, ONA is looking to build a walk-in freezer.
Write to Mike Cherney at email@example.com