There are many different variables throughout the fermentation process that affect how sour beer is produced. In order to better understand our beers and sour beer production in general, we pull small samples from each batch of beer every 10-14 days and specifically track four things: sensory, attenuation, temperature, and pH.
In order to test each batch, we pull a very small sample of beer from the barrel. However, it is incredibly important that we do not allow extra oxygen in the barrel, so we never remove the bungs from the barrel during this process. Instead, we are able to get samples from our barrels by “pulling nails” (often referred to as the “Vinnie Nail”, popularized by Vinnie at Russian River). It’s as simple as it sounds… we grab a pair of pliers and a glass, pull the nail, catch the sour beer as it pours out of the barrel, and then put the nail back in the hole! While sampling is important for testing the beer, it is important not to remove too much beer from the barrel at one time as that could also cause too much oxygen to enter the barrel.
After samples are pulled, our production team first tests the beer on sensory. With over 900 barrels filled, we are sampling sour beer every day. Sight, smell, taste, and mouthfeel of each sample are recorded to assist us in tracking the progress of our different yeast and bacteria experimentations as well as help create exciting new blends. We’ll take notes on how each batch looks, smells, and tastes every 10-14 days so that we can track how it changes over time and know when it has completed fermentation.
Are there still fermentable sugars in the sour beers? Are the yeast and bacteria still fermenting the beer? To answer these questions our production team uses an Anton Paar to measure attenuation and monitor the progression of the fermentation process. The data collected from these readings, show us how much sugar has been converted into alcohol and carbon dioxide over time. If we see weeks of stable readings, we know that yeast and bacteria have fully attenuated the beer and that this batch of beer is either ready to be packaged or blended. Ensuring that our beers have fully attenuated and are fermented dry is very important to make sure that our beers do not over-carbonate in the bottle.
Temperature plays a very important part in yeast and bacteria activity. Yeast and bacteria typically convert more sugar into alcohol and carbon dioxide in hotter temperatures, while fermentation can slow down in colder temperatures. Since the amount of heat present affects how yeast and bacteria act, it also affects how sour beer tastes and smells. Different fermentation temperatures will produce different esters and phenols, which give each batch of beer varying characteristics. The ideal temperature range is somewhere between 50-70F, which is actually one of the main reasons why we decided to start here in Berkeley. Berkeley’s climate hovers in the ideal fermentation temperature range. The size and location of our warehouse provide an excellent space to house our 100 BBL fermentors and over 900 barrels filled with fermenting beer.
The final assessment that we record every 10-14 days is pH level. pH is the measure of how acidic or alkaline a solution is. Bacteria produce acids (most commonly lactic and/or acetic acid), which acidifies our beers and puts the “sour” in them. We track the progress of acid producing bacteria by taking a pH reading. Bacteria are still active if pH continues to decrease, but after consecutive weeks of stable readings we are able to proceed in the blending process.
How do we test pH? First, we calibrate a probe to 7.0 pH by dipping it into a neutral storage solution. We then rinse the probe with water and dip it into the second acidic storage solution to calibrate the probe to 4.0 pH. We rinse the probe one more time with water and then dip it into our beer sample to take a final pH reading.
pH will give us a good idea of how acidic a beer is, however, it doesn’t directly translate to how people perceive acidity on their pallet.
Recording the data from these four assessments allows us to further our understanding of how yeast and bacteria work to create sour beer. We learn more and more as we track each batch of beer in this decades long experiment.
Do you like learning about sour beer? If so, you might enjoy The Sour Hour podcast on The Brewing Network!
The Sour Hour is a podcast made for sour heads, homebrewers, and professional brewers who are interested in spreading knowledge sour beers. The show is hosted by Scott Moskowitz of The Brewing Network and Jay Goodwin from The Rare Barrel, and they are usually joined by special guests on each episode.
The Sour Hour is available for free through iTunes! If you have any questions you’d like Jay and Scott to answer on the show, feel free to email your questions to firstname.lastname@example.org or call 888.401.BEER when they are in the studio!
Here is a list of episodes and special guests that are available at the time of this blog post…
Episode 1 – Michael Tonsmeire, author of American Sour Beers
Episode 2 – Lauren Salazar of New Belgium
Episode 3 – Cory King of Side Project and Perennial Artisan Ales
Episode 4 – Troy Casey of Casey Brewing and Blending
Episode 5 – Tim Clifford of Sante Adairius Rustic Ales
Episode 6 – Q&A Episode
Episode 7 – Nick Impellitteri of The Yeast Bay
Episode 8 – Chad Yakobson of Crooked Stave Artisan Beer Project
Episode 9 - Q&A Episode
Episode 10 – Rudi Ghequire of Rodenbach Brewery
Episode 11 – Jean of Cantillon, Vinnie of Russian River, and Rob and Jason of Allagash
Episode 12 – Jim Crooks of Firestone Walker Barrelworks
Episode 13 – Milk The Funk
Episode 14 – Adrienne Ballou and Garrett Crowell of Jester King Brewery
Episode 15 –Jester King continued
We like to experiment here at The Rare Barrel, and sometimes those results are not only worth tasting, but also worth writing about. One of these experiments that we have been working on is called the Echo Series.
In short, the Echo Series is an experiment where we let the yeast/bacteria/beer and sometimes fruit from one barrel, influence the fermentation and flavors of the next sour beer to fill up that barrel. In order to fully understand what we are talking about though, we’ll give you a little more back story.
When one of our sour beers has finished barrel aging and is ready to be packaged, we will transfer most of the sour beer from each barrel into the blending tank. With the help of a sight glass, we continue to remove most of the sour beer from each barrel, and stop removing the beer when we start seeing yeast, bacteria, and sometimes fruit in the sight glass. We then leave the remaining mixture of beer, yeast, bacteria, and fruit in the bottom of the barrel, which is typically about a few inches of liquid in the bottom of the barrel.. Typically we would rinse the barrels before refilling them, however, with the Echo Series we fill the barrel with another sour beer without rinsing out the previous remnants and let the refermentation process begin. This means that there are still millions of cells of yeast and bacteria transferred over to the next beer… the same yeast and bacteria that have already proven themselves to create a great tasting beer!
Hypnotized, the first beer to be released in the Echo Series, is a red sour that aged in barrels that were previously used to age Ensorcelled (dark sour beer with raspberries). With Hypnotized, we noticed a few significant differences between that beer and its counterpart that we aged in rinsed barrels. Firstly, we found that Hypnotized finished attenuating faster and had a cleaner character (free from off-flavors normally seen in sour beer making) than the same red sour beer aged in rinsed barrels. The more advanced yeast and bacteria that did a great job fermenting Ensorcelled seemed to really help give Hypnotized a terrifically balanced acidity while being clean and highly drinkable. Additionally, we noticed that it picked up a very subtle raspberry character from the un-rinsed barrel, which added another layer of complexity to the flavor profile.
Hypnotized (Echo Series) is our first release in this series. Needless to say, we’re pretty excited about our continued experimentation with re-using advanced yeast and bacteria from the oak. We have a few more Echo Series beers in the works, and look forward to sharing them on draft in the near future.