Gearhead: Pasteurization’s Place in Craft Beer’s Battle

Brewers looking to perfect their beer are proving that pasteurization has a place even at small breweries.

John M. Verive May 9, 2020 - 14 min read

Gearhead: Pasteurization’s Place in Craft Beer’s Battle Primary Image

The tunnel pasteurizer at Cycle Brewing in St. Petersburg, Florida.

In the spring of 1871, after France had lost to a coalition of German states in the Franco-Prussian War, the pioneering French scientist Louis Pasteur, like so many of his countrymen, was stricken with “revanchism”—a bitterness in defeat and a desire to exact revenge over the loss of Alsace and Lorraine. Pasteur wanted to strike his own blow against the Germans, one that would hit where it hurt most: in their beer glasses. Pasteur’s idea was to use his science to solve the problem of beer spoilage. Better French beer, his plan went, would help the French brewing industry grow into a global powerhouse that would put the breweries of Munich and Dortmund and Bamberg to shame.

He applied the scientific method to the often muddy, sour beers of the day, and while he didn’t like beer all that much, fragments of Pasteur’s notes from the experiments—housed at the Huntington Library in San Marino, California—reveal a hands-on approach to the problem of beer spoilage. On one page, dated March 7, 1871, Pasteur catalogs samples received from Veltins Brewery in the Ruhr Valley and includes not only gravity readings and observations of the beer under the microscope but also tasting notes. Other undated pages deal with bottles of Löwenbräu, Bass Ale, and an unnamed sample from the Belgian Ardennes. Pasteur may not have liked to drink beer, but as with French wine and the beetroot liquor before that, he did find a way to combat the spoilage microbes. He modified the process he patented in 1865 for “pasteurization” of wine, then shared his method with breweries around France, hoping they would brew a “beer of revenge” to overtake German beer as Europe’s standard. While his method worked, it was a Danish brewery, Carlsberg, that won the most renown with his techniques. At the newly commissioned Carlsberg laboratory, Emil Christian Hansen furthered Pasteur’s work and developed a method to refine the brewery’s yeast cultures, eventually isolating a single pure culture of lager yeast that would revolutionize brewing around the globe. Friday night would never be the same again.

Helping beer to travel across continents and arrive at far-flung markets in drinkable condition, pasteurization became widespread in 20th century brewing, decades before its adoption in dairy and juice industries. Unlike beer, which does not support microbes harmful to humans, fruit juice and especially milk can harbor deadly pathogens, and untold millions had been sickened before the government mandated pasteurization of milk. But be they harmless acetobacter or deadly Salmonella, pasteurization works the same way: liquid is heated until any microbes within are killed. How hot for how long varies by the liquid and the types of microbes targeted. In the brewing industry, there are two main methods of generating the desired amount of Pasteurization Units (or PUs—a measurement of how many microbes are destroyed): a high-temperature, high-speed process referred to as flash pasteurization; or batch pasteurization, which holds the product at a lower temperature for a longer time.

Antithetical to the Craft Ethos?

At San Francisco’s venerable Anchor Brewing Company, pasteurization has been an integral part of the process since then-owner Fritz Maytag designed the upgraded brewery in the 1970s. “We’ve been flash pasteurizing for as long as anyone here can remember,” says Scott Ungerman, Anchor’s director of brewing operations. He retells a bit of company lore about how the brewery, down to its last two accounts because of inconsistent product rife with microbial problems, was saved when Maytag added a flash-pasteurization system based on a heat exchanger. Maytag’s process stuck, and today every packaged beer at Anchor is pasteurized. Ungermann says pasteurization’s effects on beer flavor are overblown and mitigated with a gentle touch of PUs. The process is an important aspect of Anchor’s identity and perhaps even a part of the “house character” of Anchor’s brews.


Pasteurization’s place in the craft-beer industry is controversial. Long considered the purview of the largest industrial lager breweries, pasteurization was a black-sheep technique among America’s first wave of independent breweries—a process that compromised flavor quality for shelf-stability. At first it seemed antithetical to the craft ethos. Then the craft-beer industry grew up. The rise of nationally distributed brands meant more bottles traveling farther and sitting longer in warehouses and on shelves. Drinkers’ palates developed, and brewers grew more adventurous with their recipes. Additions of fruit or other natural products grew in popularity, and barrel aging became more common. The microbial load in craft beer climbed, driving down shelf-stability and costing brewers money and consumer confidence. Many have turned to pasteurization to stabilize their product. They’re discovering that the flavor impacts of the process are not always as detrimental as common belief would suggest.

The Opposite of Detrimental

For Florida’s Cycle Brewing, a tunnel pasteurization unit was also a business-saving tool. Known for hype-worthy IPA releases alongside big barrel-aged brews, the brewers were careful to observe the microbial load of blending components; they even attempted a low-level pasteurization of some bottles by turning their mash tun into a makeshift batch pasteurizer. But the specter of beer-spoiling infections arose in one of their most sought-after releases and threatened the brewery’s existence.

“We were lucky, until we weren’t,” says Cycle Brewing’s President Doug Dozark. He describes an infection in bottles of their barrel-aged stout Monday in 2018. Faced with hundreds of unhappy customers who’d spent $20 on bottles of bad beer, Cycle Brewing initiated a buyback program to preserve goodwill. Between the buybacks and the cost of brewing the adjunct-laden beer, the brewery lost tens of thousands of dollars—to say nothing of the untold cost to their reputation. “The only test that would tell us exactly what went wrong doesn’t exist yet—it requires a time machine,” he quips, but he says the specifics are not as important as the fix: a tunnel pasteurizer from Smart Machine Technologies.

Tunnel pasteurizers treat packaged beer by running it through temperature-controlled zones. Inside, a spray of hot water heats the beer to about 140°F (60°C) for a set amount of time. Dozark likes this method better than in-line flash pasteurization because it eliminates the risk of microbial pick-up on the packaging line. As for the flavor-impacts of pasteurization, Dozark says that for the barrel-aged or malt-heavy beers that are pasteurized, the effects on flavor are the opposite of detrimental. “Pasteurization alters the product,” he says, noting that hoppy brews are especially delicate, “but with malt-heavy beers something else happens. The flavor rounds out, the beer tastes lightly aged.” He likens it to reverse bottle shock, pleasantly melding the big flavors of the barrel-aged stouts. Dozark says that the unpasteurized draft releases of the same beers don’t taste as filled out as the heat-treated bottles and that he is sleeping soundly knowing that they meet his standards of flavor stability.


Anytime brewers work with barrels, they worry about what microbes are lurking within the porous wood and where in their brewery the bugs might take root uninvited. But there’s another vector for contamination that’s common among flavor-forward craft breweries: all those other ingredients that are so fashionable today. From farm-to-fermentor fruit additions to the nuts and spices poured into pastry stouts, all those natural additives add a host of bacteria and wild yeasts at various stages in the process.

At Cigar City Brewing, also in Florida, one of their favorite beers involves adding raisins and cinnamon to a brown ale; they turned to pasteurization to help bring Oatmeal Cookie to a wider market. The risk of some raisin-borne wild yeasts re-fermenting Oatmeal Cookie, turning it into bottle bombs on warm store shelves, was unthinkable for the brewery, and the flash pasteurizer from GoodNature Products provides peace of mind.

“I don’t think pasteurization should be a bad word in the craft industry,” says Sean Sasscer, Cigar City’s director of brewing operations. “If you’re serious about quality, you’ll look at every tool available.” He likes the flexibility of the flash pasteurizer, and beyond treating beers with fruit, coffee, or cacao additions, it has led to more efficiency when blending barrel-aged components. “A lot of barrels that taste really exciting are the ones that test high for spoilage organisms,” he says. These are the same organisms that brewers are careful not to introduce into delicate areas of the brewery—such as the packaging line. Pasteurizing blends before packaging puts those barrels back on the blender’s palette, and Sasscer estimates it’s saved about 2 percent of their barrels from premature retirement.

Sasscer also agrees with Dozark’s impression that the process improves the flavor of some beer. “Maybe it’s another Maillard reaction,” Sasscer says, unsure of the exact effect he tastes, “but whatever it is, it rounds off the harsher edges and produces a gentle age-like characteristic.” While the effect on flavor is small-but-perceptible, the effect on shelf-life is obvious. Sensory panels have analyzed 120-day-old samples and noted little flavor degradation. Sasscer calls it “amazing.”


Pete Whitehead has been selling GoodNature flash pasteurizers for 24 years. When the company introduced its brewery-specific solutions at a craft trade show five years ago, he felt the industry’s resistance to pasteurization. “Nobody would talk to me,” he says. But some craft breweries are warming to the idea of pasteurizing some of their products, and Whitehead says that the culture of collaboration in the industry has helped the acceptance spread.

Brewers, it turns out, share more than hard-to-find hops and yeast pitches. They also share knowledge. Whitehead says that the operating procedures for pasteurization in craft breweries didn’t exist until the brewers started talking to each other about what worked best. Over-pasteurized beer was common at first, as brewers would err on the safe side and overcook product, but there’s a point of diminishing returns. Brewers are learning where the target is to ensure the stability and maximize the flavor of their beer. It’s a moving target that’s different for every beer and every pasteurization process. “The brewers are doing a lot of work to collect data and build a library of SOPs,” Whitehead says.

The idea that “unpasteurized” is always a positive characteristic that helps differentiate craft beer from industrial lager is an old one. Like the theory of spontaneous generation that Pasteur disproved when he showed that yeast causes fermentation, brewers looking to perfect their beer are proving that pasteurization has a place even at small breweries. Flavor and quality are the two best weapons that craft brewers have in their protracted conflict with boring beer, and pasteurization can help brewers bring both to bear in the battle for your beer money.


The Goodnature CBP1800 craft-beer pasteurizer.

Beer Pasteurization: Want to Try It at Home?

Homebrewers don’t usually need to worry about long shelf stability, but there are a few reasons why you might. Here are a few practical ways to replicate the controversial industrial process of pasteurization.


While pasteurization is more common at larger breweries, there are options for brewers working out of kitchens and garages, too.

Ad hoc pasteurization is a viable alternative when you only occasionally need to increase the microbial stability of your beer. Perhaps you’ve brewed a batch and you want to store a handful of bottles for the long term. Or maybe you worry about the sanitation of your bottling equipment, and you want some insurance on bottles destined for competitions.

Do-it-yourself options include stovetop methods, sous vide devices, or even the dishwasher. But extreme caution should be taken with any makeshift method as bottles are known to explode if they are heated too much or too fast.

A simple method—though one that can process only a few bottles at a time—is to heat a pot of water to above 140°F (60°C). Then place the bottles in the water and let them slowly warm into the pasteurization zone, holding them between 140–160°F (60–71°C) for 20 minutes, before gently cooling the bottles to room temperature. (See “Experiment: Home Pasteurization” on for further details on the process and how it affects flavor.)

Commercial breweries that want to pasteurize the odd batch of barrel-aged beers or others with a higher microbial load can take a page from Cycle Brewing’s playbook and reconfigure their mash tun to pasteurize bottles. It’s a slow, labor-intensive process, but the only extra equipment recommended is a temperature probe to accurately monitor the process. You can read more about the technique, and why Cycle stopped using it, on their website: