Open fermentation, once the only way beer was fermented, has been largely abandoned over the years in favor of more standardized and repeatable brewing methods. However, as modern day brewers look to the past for inspiration, the process is now being revived, breathing life into long forgotten beer styles.
OPEN FERMENTATION PRESENTS A UNIQUE SET OF CHALLENGES.
Brewers have long been indoctrinated in the virtues of sanitation, from their first days on the job. Any exposure to airborne bacteria or wild yeast strains can lead to off-flavors in beer. For this reason, beer is fermented in airtight tanks that are specially designed to allow gas to escape without introducing air into the liquid.
In an open fermentation situation, all of this is thrown out the window. But there are some techniques that allow brewers to effectively control the environment – including thorough sanitizing before and after each fermentation, enclosing the tanks in an airtight room, and carefully controlling human exposure (by people wearing sanitized boots, gloves, and clothes) to prevent contamination.
TRADITIONALLY, BREWERS USED FERMENTERS THAT WERE EITHER OPEN TO THE AIR OR VENTED TO ALLOW RELEASE OF GAS PRESSURE.
Prior to the advent of modern brewing equipment, these vats were typically made of wood, sometimes lined with copper or sealed in some other way. Wide, shallow open-fermenters were favored by brewers in Belgium, where they mastered the art of spontaneous fermentation using airborne yeasts.
The process was passed down over the centuries, until advancements in yeast cultivation changed the brewing landscape in the early 1900s. As a result, the shallow open tanks were often adapted as “coolships” for cooling hot wort, before another transfer of the liquid into airtight tanks for the yeast addition and fermentation. The extra step was necessary due to the fact that yeast dies at uncomfortably hot temperatures, and refrigeration technology had not yet provided a work-around.
FAST FORWARD A HUNDRED YEARS OR SO, AND MODERN DAY BREWERS ARE TAKING INSPIRATION FROM THE PAST.
Let’s take a look at a few reasons why American craft breweries are now turning back to a more “primitive” era of beer-making:
- Tradition – open fermentation is an old process that pays homage to how beer was brewed centuries ago.
- Esters – the formation of fruity esters is greatly increased in an open fermentation tank due to its shallow construction that maximizes surface area of the liquid and exposure to oxygen. Fruity esters can be a desired flavor in many beer styles, particularly Belgian, German, and other European ales.
- Yeast harvesting – the cream-colored foam that forms on the top of fermenting beer, called “kräusen,” can be easily harvested for reuse. The kräusen consists of spent yeast cells, wort protein, and hop resins. Just grab a sanitized jar and scoop, and have at it!
- Gas – open fermentation allows unwanted gasses to escape the tank into the air, rather than being re-absorbed into the beer. Traditionalists will argue this results in a cleaner tasting beer – the way it was intended to be.
OPEN FERMENTATION WILL BE A NEW ASSET TO THE CHARLOTTE LOCATION.
Our new Charlotte brewhouse will allow Catawba brewers to experiment with open fermentation for the first time, offering new opportunities to fulfill our mission to create and educate, perhaps in some unprecedented ways.
Our open-top vessels will be unlike their historical forebears in that the tanks actually have a thin glass wall for viewing fermentation as it happens. You’ll be able to enjoy a beer and observe the spectacle of bubbling CO2, yeast colonies rising and falling, and the rolling kräusen in a virtual Beer Aquarium!
These one-of-a-kind, hand-made fermenters were made possible through a collaboration with specialty glass manufacturers, Corning, Inc., and tank manufacturer, Marks Design and Metalworks. Everything in the compact brewhouse is designed to be visible and accessible, for a uniquely interactive customer experience.
Stop by our Charlotte tasting room and ask our staff to tell you a little more about the tanks – or share your newfound knowledge with them. Look for beer to fill the open-fermenters very soon, and get ready for a show!