Rob Rutledge. Photo: John Barkiple

From Dregs to Richness: Rob Rutledge on Spontaneous Fermentation and the Rise of Sour Beer


Spontaneous brewing has been around for centuries, but it has realized a recent resurgence. Utah-based competitive brewers Pat Winslow and Rob Rutledge have arisen with their own takes on this classic style. Spontaneous brewing involves the cultivation of wild microbes—a microbe that makes the brew acidic is required to achieve the tart pucker of a sour beer. You might have sampled these multifaceted and delicious draughts when savoring Red Rock’s Paardebloem, Squatters529 or Epic’s Tart ’n Juicy Sour IPA. Winslow and Rutledge discuss brewing, sour beers and where the culture is headed.

SLUG: How and why did you start home-brewing? Did you have any past experience with microbiology before you began?

"I think there is a generation of beer drinkers that grew up with sour candies like Atomic Warheads and Sweet Tarts," says Rutledge. "In my opinion, sour beers tend to be some of the most complex beers out there." Photo: John Barkiple.
“I think there is a generation of beer drinkers that grew up with sour candies like Atomic Warheads and Sweet Tarts,” says Rutledge. “In my opinion, sour beers tend to be some of the most complex beers out there.” Photo: John Barkiple.

Rob Rutledge: I wasn’t really good about taking notes when I first started home brewing, so I’m not sure exactly when it was, but it was sometime in 2001 or 2002. A few years before that, my wife bought my father-in-law a home brew kit for Father’s Day. That was the first time I’d ever really heard of people home-brewing, and it was also the first time I stepped into a home brew shop. I’ve always been a DIY kind of guy, whether it’s fixing our cars, doing home improvement projects, whatever, so the idea of brewing my own beer seemed like it could be a lot of fun. My father-in-law never ended up using his kit (I think he liked the idea of drinking beer a lot more than the idea of brewing beer), but that kind of sparked my initial interest in home brewing.

I have to admit, when I first started brewing, my experience with beer was more or less limited to Mexican lagers and an occasional wheat beer. I wish I could say I started home-brewing because I couldn’t get Black Tuesday, Pliny the Elder or Arrogant Bastard here in Utah, but when I first started brewing, I didn’t really know what I was missing.

I think what really did it for me was when my friend Cody and I attended Beer School at Desert Edge Brewing. I’m not sure if they still do it the same way, but Beer School is part education and part four-course dinner. Back then, Chris Haas was the brewmaster, and he would take you down to the brewhouse and explain the brewing process, how all the different equipment was used, and show you some of the ingredients. Next was the dinner, paired with several of their beers. That experience really opened my eyes to the aromas, flavors and overall character associated with different beer styles. After that, I told my wife I wanted to give homebrewing a try, and she was cautiously supportive. I say “cautiously supportive” because she knows firsthand how I have a tendency to dive in headfirst with hobbies. A few weeks later, she surprised me with a starter kit from The Beer Nut, and a couple days later, Cody and I brewed our first home brew, a Mexican Cerveza kit. Like many first-time batches of home brew, the beer wasn’t great, but we made it ourselves, so we enjoyed it.

As a lot of home brewers do when they’re first starting out, I was extract brewing using dry and liquid malt extract. Not long after that, I started steeping specialty grains along with the extract. Next was partial mash batches. I was really enjoying the hobby, so I started making plans to jump to all-grain brewing. I think it was about a year or so after switching to all-grain that I designed and built my mostly-automated HERMS system using a BCS-460 process controller. This was before the “discovery” of the Brew In A Bag (BIAB) method, so I designed a four vessel system consisting of a Hot Liquor Tun, Mash/Lauter Tun, standalone Heat Exchanger and Boil Kettle. My system works great, but if I were to do it all over again, I’d probably go the BIAB route, as there’s a lot less equipment involved.

Regarding a microbiology background, I ended up getting my degree in Business Information Systems, but at different points in time, I had planned on careers in either Sports Medicine/Physical Therapy or Pharmacy. So I would not say I have a background in microbiology, but I took a fair amount of science courses in college, including chemistry, biology, zoology and human anatomy and physiology. A good science background can definitely help understanding some of the finer points of brewing beer, but the lack of it is no reason not to give home-brewing a try.

SLUG: Tell us a little bit about your collaboration with Uinta for the Great American Beer Festival and how these experiences fit into your all-around brewing practices?

Rutledge: I am doing a Pro-Am collaboration with Uinta based on some Flanders red ales I’ve brewed. That came about because I won a gold medal for my Flanders Red in The Beer Nut’s Annual Beehive Brew-off competition. Basically, if you are a member of the American Homebrewers Association (AHA) and you medal with an entry in an AHA/BJCP-sanctioned competition, there’s a chance you could be selected to team up with a brewery and participate in the Pro-Am competition at GABF. So long story short, the home brewer and brewery team up to brew the home brewer’s recipe on the brewery’s commercial system. The beer then has to be commercially available, and it gets served in the Pro-Am booth at GABF

Uinta had plans to expand their barrel-aged beer program and were looking for someone to team up with right around the time I won my second gold medal in a row for my Flanders Red. Isaac Winter at Uinta reached out to me about doing the Pro-Am, and I was shocked to say the least. I met with Isaac, and we sampled a couple of my home-brewed versions. I came back a couple weeks later for our brew session, and we brewed a 60-barrel batch on their commercial system.

We did do a couple things differently on the commercial batch compared to my home-brewed versions. First, I tend to use aged hops in most of my sour beers. For those who aren’t familiar with the brewing process, hops are typically added at three points during the boil for bittering, flavor and aroma. The bittering hop addition is usually added at the beginning of the boil. Alpha acids in the hops are isomerized in the boiling wort, resulting in bitterness that balances with the sweetness from the malt. The second addition is usually added with 20 to 30 minutes left in the boil. The major contribution from the second addition is hop flavor, but it can contribute additional bitterness, as some of the alpha acids will isomerize. The last addition is usually added with five or fewer minutes left in the boil. The third addition is where a lot of the hop aroma comes from, and depending on how fast you’re able to chill your wort post-boil, it may not contribute much, if any, bitterness. Besides contributing bitterness, flavor and aroma, hops have natural antiseptic abilities that help keep flavor-spoiling bacteria at bay. This is great when you’re brewing clean beers, but when you’re making sour beers, you don’t want to inhibit souring bacteria. For example, Lactobacillus tends to have a very low hop tolerance, so it has a hard time souring when the beer has much more than about sixish IBUs. Even if you eliminate earlier hop additions and only add late hops for aroma, the Lactobacillus bacteria will tend to struggle because the hop oils coat their cell walls, preventing them from metabolizing the sugars in the wort into lactic acid. Generally speaking, lactic acid is what we’re after with sour beers. Alpha acids tend to degrade over time, so aged hops don’t have the same antiseptic properties and therefore, they work well for sour beer production. Using very low hopping rates accomplishes the same goal, which is what we did with our collaboration beer.

Rutledge attributes attending Beer School at Desert Edge Brewery to the start of his home-brewing. Photo: John Barkiple.
Rutledge attributes attending Beer School at Desert Edge Brewery to the start of his home-brewing. Photo: John Barkiple.

The other main difference is that a lot of the time, I will pitch my souring cultures into the wort on day one. I’ve found that this, along with a low hopping rate (or using aged hops), almost guarantees a low-pH sour beer that I love. That said, we didn’t want to go quite as sour with this beer because not everyone enjoys a super sour beer. Another reason for doing a clean primary is that Brett cultures have the ability to convert certain byproducts from a clean primary fermentation into the classic “barnyard funk” associated with world-class sour beers. These include characters such as hay, leather, tobacco, horse blanket, goat sweat, etc. Some of those elements may not sound very appealing, but they really do work in a sour beer. So pitching a blended souring culture on day one tends to result in a more sour beer with slightly less funk whereas pitching a clean yeast culture in primary followed by a blended souring culture in secondary tends to result in more funk and a less sour beer.

After the clean primary fermentation, we transferred the beer to port barrels that had been previously used for Uinta’s Port O’ Call Belgian-style dark ale. The beer was inoculated in the barrels using Roeselare, which is a blend of a Belgian Ale yeast strain, a sherry yeast strain, two Brettanomyces yeast strains, Lactobacillus and Pediococcus. We also added the dregs from one of my homebrewed Flanders Reds to one of the barrels, so if everything works as desired, there will be some of the same cultures from my home brew in the release from Uinta. We’re planning on blending the barrels the second week of May, so it should be released in the not too distant future.

My Flanders Red entries have taken gold for European Sours at each of the past three Beehive Brew-offs, so I’m hoping we can repeat that at the GABF Pro-Am this year.

SLUG: What is spontaneous yeast brewing? How does it specifically create a low-pH beer?

Rutledge: Usually, we’re talking about two primary styles in relation to spontaneous fermentation. Wild Ales typically include beer fermented with Brett or a blend of Brett and Sach, whereas Sour Ales are fermented with lactic acid bacteria (LAB), Sach and/or Brett.

I think that when a lot of people think of spontaneous fermentation, they’re thinking along the lines of the Belgian breweries of old, where they’d brew their wort and transfer it to coolships (large shallow vessels) to cool overnight. To help cool the wort as quickly as possible, they’d open the shutters, which would carry in whatever wild yeast and microbes that happened to be blowing on the evening breeze. So usually, spontaneous fermentation involves making use of local yeast and microbial cultures. Grain is also covered with a mix of cultures, which can be used for spontaneous fermentation.

When it works, the results can be great, but when it doesn’t work, it can be disastrous. The problem with this approach is that the brewer doesn’t have much control over what is blowing in through their windows on the night air, so there’s always the risk of dumping a batch of the wrong kinds of bacteria and/or yeast in to the wort. There are things you can do to mitigate the risks, such as collecting cultures by swabbing plants and fruit in your yard or setting out small containers of growth medium in your yard. Then you can grow up those cultures and use them to ferment small starter batches in hopes of finding some that produce desirable results. When one is found, you simply grow it up into a pitchable-sized starter and use it to ferment your entire batch. The benefit with this type of approach is if things don’t work out, you only risk losing a small starter batch rather than an entire batch of beer. Because of these risks, most commercial wild and sour ale breweries don’t rely entirely on what’s blowing in the wind. They’ll usually do some experimentation until they find a culture or blend of cultures that work, and then they’ll propagate those cultures into pitching sized starters. That said, there are a few craft breweries that have been experimenting with true spontaneous fermentation (without lab propagated cultures). Some that I know of include Jester King, Black Project Spontaneous and Wild Ales, Crooked Stave, Allagash Brewing Company and Russian River Brewing Company. However, even these breweries usually only employ true spontaneous fermentation on a small portion of their portfolios.

The primary component that contributes to sourness in sour beers is lactic acid. In brewing, the main source of lactic acid is from Lactobacillus and Pediococcus. Brett can produce small amounts of acid, but generally speaking, if you want a sour beer, you have to include a LAB strain. Lactobacillus tends to produce lactic acid early on, while Pediococcus is more of a marathon runner. So Lactobacillus is essentially the hare, and Pediococcus is the tortoise. Like yeast, LAB consume sugar in the wort, and lactic acid is one of the byproducts that they produce.

The other acid found in some sours is acetic acid. Acetic acid is essentially vinegar and can be harsh in comparison to lactic acid which tends to be more lemon-like. Acetic acid can add complexity to sour beers, but if the levels get too high it can give the beer a character reminiscent of salad dressing. Brett can produce acetic acid when exposed to excessive amounts of oxygen. Usually, we try to avoid too much oxygen with beer anyway because once you get past the early stages of fermentation, it can result in oxidized beer—not something you really want in a clean beer or a wild/sour beer. Lactobacillus tends to fall into two main groups: homofermentative and heterofermentative. Homofermentative strains primarily produce lactic acid during fermentation whereas heterofermentative strains primarily produce lactic acid and ethanol. Strain selection can be important when employing certain souring techniques. For example, you usually wouldn’t want to use a heterofermentative strain for pre-boil/kettle souring because you’ll be boiling off the ethanol during the boil. Certain strains of Lactobacillus are capable of both aerobic and anaerobic fermentation and can produce acetic acid during aerobic fermentation. I haven’t read anything indicating Pediococcus produces acetic acid, but it definitely produces diacetyl along with lactic acid. Diacetyl is often described as having a butterscotch or buttery flavor and aroma and is in fact used to flavor microwave butter popcorn. Fortunately, Brett can convert diacetyl into much more desirable compounds, so Brett must be used in conjunction with Pediococcus.

SLUG: What do you think is the appeal of this kind of flavor in a beer?

Spontaneous brewing involves the cultivation of wild microbes—a microbe that makes the brew acidic is required to achieve the tart pucker of a sour beer. Photo: John Barkiple.
Spontaneous brewing involves the cultivation of wild microbes—a microbe that makes the brew acidic is required to achieve the tart pucker of a sour beer. Photo: John Barkiple.

Rutledge: That’s a really good question. I think there is a generation of beer drinkers now that grew up with sour candies like Atomic Warheads, Sweet Tarts, etc. If you liked those kinds of candies as a kid, you’ll probably enjoy sour beers as an adult. In my opinion, sour beers tend to be some of the most complex beers out there. I love a good IPA, bourbon barrel-aged stout, smoked porter, but if there’s a sour beer on the menu, I will always start there. It’s kind of hard to describe, but the combination of tart cherry character, stone fruit, chocolate, hints of smoke, leather and so on are just so amazing. These flavor profiles can be quite shocking to someone who has never tried a sour beer before. My rule to the uninitiated is that you have to try three sips of any sour beer before you decide whether or not you like it. They’re usually shocked on the first sip. On the second sip, their palate is starting to adjust to the acidity. By the third sip, they should be able to decide whether or not they’re a sour beer head. Whenever someone tells me they don’t like beer, I almost always steer them towards a Lindemans Framboise. I actually prefer less sweet and more traditional lambics, but Lindeman’s fruit lambics are my go-to gateway beers for people who think they don’t like beer.

SLUG: Can you give some insight into the difference between fermenting with Lactobacillus vs. Brettanomyces? Do you use any other organisms for your souring process?

Rutledge: I think I covered this a bit [earlier]. I’ve never tried fermenting with only Lactobacillus. I’ve read about people that have, and they indicated that the finished beer was a little boring and not nearly as complex compared to mixed fermentations. Lactobacillus alone usually can’t ferment to completion, meaning it tends to go dormant before reaching the desired final gravity. I have done several 100-percent Brett fermentations, and I really like the results. Brett doesn’t really result in a low-pH beer as it doesn’t produce a significant amount of acid (unless it’s exposed to excessive amounts of oxygen), so it really can’t produce a sour beer on its own. However, 100-percent Brett fermentations can result in tropical fruit flavors and aromas, so they tend to work really well in hop-focused beers like IPAs when paired with hops that exhibit tropical fruit and citrus notes. 100-percent Brett fermentations are usually pretty clean and don’t have the typical barnyard character that you get from mixed Sach/Brett fermentations.

SLUG: What about your specific brewing process makes you unique?

Rutledge: I don’t know that I do much that’s completely unique. It’s kind of a matter of standing on the shoulders of giants. The folks that brew sour beer are a great group and are very willing to share info in regards to tips, tricks and process specifics. For example, Vinnie Cilurzo of Russian River has freely shared tons of process information in regards to sour beer production. Chad Yakobson of Crooked Stave has made his Brett research available to all via the Brettanomyces Project ( Jay Goodwin of The Rare Barrel hosts a podcast for The Brewing Network called The Sour Hour that focuses exclusively on sour and wild ale production, including a lot of process detail. I’ve even had Jason Yester of Trinity Brewing reach out to me directly to help me with a sour IPA recipe. Generally speaking, you either sour your beer pre-boil or post-boil. Pre-boil techniques include sour mashing or kettle souring. Post-boil souring is the more traditional method that involves adding souring cultures in the fermenter.

I generally employ three different methods for sours. For my Berliner Weisse, I sour post-boil by pitching Lactobacillus about five days before pitching Sach and Brett. This results in a somewhat aggressively sour beer with just a hint of Brett funk. The benefit of this method is that it’s a fairly quick turnaround, so you can be drinking this beer within 6 to 8 weeks, and I think it’s slightly more complex than kettle souring.

For sour beers with lots of hop character, like sour IPAs, I use a kettle souring method. This ensures the Lactobacillus are able to sour without being inhibited by the hops that will make their way into the finished beer. I perform a normal mash and transfer the wort to the boil kettle and raise the temp to 170 degrees Fahrenheit for 10 minutes in order to pasteurize. Then I sour using Lactobacillus until the pH gets down to around 3.4. I then proceed with the boil, adding as many hops as I want without having to worry about their effect on the souring bacteria. After the boil, the pre-soured wort is chilled and fermented using yeast. I’ve also started using this method for brewing other styles, like Gose. The benefit of this method is that it provides for a quick turnaround, and other than blending, it’s the only way to sour highly hopped beers. The drawback is that it’s not as complex as long-term souring.

For my Flanders Reds, Oud Bruins and most other sour beer styles, I tend to sour post-boil with blended cultures. About 50 percent of the time, I’ll pitch the blended cultures on day one, and the other 50 percent of the time, I’ll do a clean primary fermentation followed by a blended culture pitch in secondary. These beers usually involve fairly high mash temperatures, which results in fewer simple sugars and more complex sugars, which means a long-term food supply for the Brett and bugs. The drawback to this process is that it may take a year or more for the beer to mature and sour, so it’s not a quick turnaround. The benefit is that the long process tends to yield a very complex, finished beer.

SLUG: Are you a part of a home-brewing community in Utah/Salt Lake City? If so, how could someone new to home brewing become involved?

Winslow: I’m a member of Zion Zymurgist Homebrew OPerative Society (ZZHOPS). The best way to get in contact with the group is via the contact info on our website,, or through our Facebook page.

We typically meet once per month and hold a club competition focusing on a particular beer style. So we’ll socialize for a bit and sample each other’s project beers, then judge that month’s competition entries, then socialize some more. It’s a great group of brewers, and everyone is welcome regardless of brewing experience.

If you haven’t tried out the aforementioned local brews, you can start on the national stage with sours from Allagash Brewing Co., Crooked Stave, Russian River and New Belgium. For the fledgling home-brewer thirsting to get involved or a well-rounded wort-wizard searching for a community, there are always local brew clubs to participate in. Rutledge is a member of Zion Zymurgist Homebrew OPerative Society ( Winslow, on the other hand, runs with O-Town Hop Heads brew club ( Best of brewing to you all, and pucker up!