The Bugs that Sour Your Beer (And Why They’re Not All Bad)

by Karl | Last Updated: October 10, 2020

Do the words barnyard, sour, funky, and horse-blanket make your mouth water for a pint? They do for this beer geek.

I’m not alone. The county’s sour beer phenomenon has created an army of mouth-puckered fanatics. Breweries are responding by creating more of these beers than ever before, entering 119 into the Great American Beer Festival sour beer category in 2009 vs. 15 in 2002, as this NY Times article points out.

I got hooked on sours a few years ago after trying my first Belgian Lambic, and recently brewed my first sour homebrew, a Berliner Weisse.

It’s a strange thing for brewers to intentionally sour their beers because it involves using bugs that they are normally scared to death of. But with the controlled use of these critters, they can produce some of the finest suds imaginable.

So if you are wondering who you can thank for that sour flavor, here are the stars of the show. These are the 4 main bugs that brewers use to make sour beer:

Brettanomyces

Sour Beer glass

Brettanomyces is the most common microbe used to sour a beer. So common that beer people refer to it as just “Brett.”  They even talk about Brett as if he’s an old friend.

“What are you doing today? Oh, chillin’ with Brett? Cool, tell him hi.”

Ah beer geeks…

Brett is really just a strain of yeast, the same organism that typically ferments your beer. What makes Brett special is its ability to ferment any type of sugar, including those that normal yeast cannot. It’s also extremely invasive and will take over a brew house and refuse to leave. If not contained, Brett will wreak havoc on a brewery, infecting everything in its path and bringing the brewer to tears.

Used correctly however, Brett will add a great flavors and complexity to beer. Russian River Brewery loves to use Brett and says: “it can add rich aromas and flavors of earthiness, leather, smoke, barnyard, & our favorite descriptor-wet dog in a phone booth.”

Here are some beers that feature Brettanomyces:

Lactobacillus

The rest of the bugs listed are bacteria, and lactobacillus (Or “Lacto.”  Yes, it gets a nickname too.) is one of the most common. Like yeast, bacteria can ferment sugars into alcohol. A product of fermentation from Lacto is lactic acid. Lactic acid gives beer sharp, sour, acidic flavors. Lacto is famous for its use in the Berliner Weisse style of beer. If you ate yogurt today, then you reaped the benefits of lactobacillus.

Here are some beers that feature lactobacillus:

Pediococcus

Pediococcus (“Pedio”, why not?) is a relative of lactobacillus. It produces most of the lactic acid found in lambics. A drawback of Pedio is its tendency to produce diacetyl, a chemical which gives beer a buttery character that is almost always unwanted. To combat diacetyl, Pedio is almost always used with Brett, which cleans up the diacetyl.

You can taste Pedio’s handiwork in sauerkraut, which it produces by fermenting cabbage.

Here are some beers that feature pediococcus:

Acetobacter

Acetobacter isn’t as common as the others, but it still pops up in a handful of beer styles. Acetobacter’s souring agent is acetic acid, the key component in vinegar. Brewers have to be careful with this bug. Even a little bit too much will ruin a beer. Luckily, it needs oxygen in order to ferment ethanol into acetic acid, so dialing down the oxygen exposure will keep it in check.

Aceto takes center stage in Flanders Red/Brown ales. These sour ales from northern Belgium are traditionally aged in wood containing a smorgasbord of microorganisms, with Aceto being one of the main players.

Here are some beers that feature Acetobacter:

Belgians are really the masters of sour beers. They’ve been producing these beers for centuries in open fermentations that invite in wild organisms, and aging in old wood barrels crawling with critters. Lambic brewing is the poster child for this process with its spontaneous fermentation.

The Belgian’s long history of sour brewing gives them a huge advantage over new comer American breweries. Think about it – Belgian beers are aged in old wood barrels, some over a century old. That’s a long time for the microorganisms to evolve and develop complexity that a newer brewer can’t match. Jeff keenly observed this while tasting New Belgium’s take on a Flanders Red Ale.

Nevertheless, some American breweries give the Belgians a run for their money. Russian River is the absolute best in my opinion.

How to brew sour beer?

6 Mistakes I Made Brewing My First Sour Beer

Earlier this month I brewed my first sour beer. I have read books, taken classes, and tasted many a sour beer (good and bad). None of this adequately prepared me for brewing my first sour, but it did give me the confidence to try.

Before I get down to how it all went wrong, you should know something about my home brewery:

I am a female homebrewer who brews with my boyfriend, Jon. I would like to follow that sentence with the fact that brewing a sour was my idea! (Look forward to more articles zooming in on this topic of women in brewing.)

At the end of the day, I am very lucky to have a teammate in this hobby. Jon loves brewing beer as much as I do. When you have help, you don’t have to keep an eye on every detail. The problem of course then becomes: you don’t always keep an eye on every detail…

For our first attempt at a sour beer, we decided our best course of action was to use a kettle souring process. We had a few reasons for using this technique:

  1. Keep our equipment clean. No infection in any following brews. No contaminated equipment.
  2. Seemed the simplest. Just toss in some grains right?
  3. We could control the outcome by keeping an eye on pH and sourness during the whole process.

We wrote a recipe for a sour smoked saison we named “Smokezon Mother Pucker”.

Probably way too much going on for one beer, but why the hell not, right? If you’re gonna do it, do it all the way.

We figured this would be a two day project. A Sunday/Monday deal. Mash one day, boil 24 hours later.

Or so we thought…

Mistake #1: Missing our mash temperature

The first issue arose during the mash. Our strike temp was too low, so we had to add extra liquor to increase the temperature.

We were aiming for a lower mash temp for a very fermentable wort, considering this was supposed to be a saison. However, we were still too low. After boosting the temperature we continued on with the hour-long mash.

Lesson: Missing the mash temperature is not the end of the world. Have extra hot water at the ready just in case. The problem was easily resolved. No need to stress, yet.

Mistake #2: Using new equipment = unexpected effects

We were eager to use our newest pieces of equipment on this brew day (because why not complicate it even more?).

We got a Chugger pump for Christmas and chose to use the pump to vorlauf and transfer to the kettle. During the vorlauf process, we also wanted to mash out and halt all enzymatic activity before starting the souring process. When I say we, I mean Jon — he was very determined. But it made sense. We didn’t want conversion of any sort still taking place and also didn’t want anything else odd in our beer, just the sugars and the lacto we would be adding soon.

To use the pump we had to remove the mash tun lid for recirculation and then prime the pump.  Before doing so, we added hot liquor to raise the temp to mash out during the vorlauf process.

But, as soon as we started the pump we lost 10°F.  As a result, we had to add even more hot liquor to get closer to mash out temps and recirculate even longer. Then we had to sparge properly, all of which took well over an hour. Fun.

Lesson: If you are using new equipment, be prepared for unexpected results. It’s best to try out new gear on a familiar recipe versus something experimental.

Our attempt at chilling the pot
Our attempt at chilling the pot

Mistake #3: “Duh” cooling

We didn’t think ahead enough about chilling the wort to the correct temperature for lactobacillus action. We knew we would need the temperature much lower to get the lacto going, but didn’t contemplate how exactly we were going to do that.

In retrospect, we should have either used our immersion chiller to get the wort down close to 110°F or run the wort through the plate chiller (also a new toy) on the way to the kettle to get to that temp. Instead, after transferring to our lidded kettle that had been purged with CO2, we let the wort sit there for a couple of hours.

Not the worst thing ever but a real pain in the ass at the end of our mash day.  Eventually, we hit the right temp. We tossed in a healthy handful of wheat malt and sealed everything up with foil.

Lesson: Go over your plan before starting. Write it down and make sure it’s realistic.

Mistake #4: Too efficient

We had tested using our oven with a lamp in it as a means of temperature control. We added a pot full of water to see if the temp held steady. We used a single, 150-watt bulb, left the pot in overnight and it worked. The temperature of the water dropped to 108°F or so, which was a little bit lower than we wanted after twelve hours, but close enough for us to know it was a usable option.

On the day of the real brew, we decided to up the temperature control by covering all the vents of our oven with foil. This proved to be over doing it.

Initially, the temperature seemed to be holding well around 115°F, but when we woke up the morning after the mash we were up around 123°F.

Too efficient.

We knocked the temp down, uncovered a few vents and let it go for the rest of the day.

We took our pH that morning using test strips and it was right around 4.5 — exactly where it was the night before.  We took the pH again when we got home that evening (when we were planning on boiling) and it had still not budged, 4.5 again, and there was little noticeable sourness despite a clear change in odor and some visible signs of activity.

This was likely because we hadn’t given the lacto that is naturally found on the grain husks the right environment in which to work.  We wanted more sourness and realized we needed to let the souring process continue.

Lesson: Once you have tested a method, don’t changed it. Adding more variables will create inconsistencies.

Side Mistake: Well it was a good night, I think…

I came home somewhat, let’s call it over-indulged, that night. I don’t remember why or how, perhaps after-work beers. Regardless, there was no brewing happening Monday night no matter what the pH was.

Lesson: Know your limits.

So we had to wait until Tuesday night. When I got home Tuesday afternoon I took the pH.  It finally dropped — 3.8. Not as low as I was hoping. Then I tasted it. Quite sour. We were a go for our boil, Finally!

Mistake #5: Read up on your yeast strain!

We used Wyeast Belgian Saison yeast. Now, maybe using this yeast in and of itself was not a mistake, but after researching it and speaking with a number of people about their experiences, we found it is notorious for stalling out after initial fermentation.

This yeast gave us some trouble. Our OG was 1.064 and the yeast managed to get us down only to about 1.048 before stalling for a week.

Yikes!

We went back and forth with what to do. Finally we decided to use a packet of Belle Saison dry yeast we had in the fridge to jump-start our fermentation.

Perhaps it was the low pH or perhaps it was only having fermentation going at room temperature, but either way we needed to get things moving.

Even with the second pitch of yeast things went very slowly. We added heat by wrapping the fermenter with an old heating pad from my dancing days.

The beer finally finished around 1.014. Not as dry as we wanted, but it no longer tasted like drinking lemonade, so we went with it.

Lesson: Research any new ingredients you are going to use. Ask around.

Mistake #6: Hubris

We made this beer for an event: the Homebrew Jamboree that was part of NYC Beer Week. I knew about this event for months in advance. We gave ourselves plenty of time to make this beer, but who brews this much of an experimental beer for an event? It could have gone terribly, terribly wrong… and nearly did.

(We did have a backup plan. We had a few other beers in kegs that we could have brought if it came down to it.)

That being said, it ended up a success!

I know it does not sound like that’s possible, but the beer came out very nice, if a bit over sour. It was a big hit at the Jamboree. We kicked our five gallon keg and got tons of compliments.

I feel like the most important point to make is:

Lesson: I liked our beer and I had fun making it. (Whether Jon thinks so or not, since he gets the brunt of my stress most brew days). Isn’t that why we all homebrew? To make something WE want to drink? To stress over all these “mistakes” isn’t necessary.

A wise man once said something about relax… don’t worry… build your own Sour Beer Homebrewery

How to Build Your Sour Beer Homebrewery

Barrel Blowoff

Sour beer has taken the craft beer world by storm. Some are even calling it the new IPA. Just like other trends in pro brewing, this one has trickled down into the ranks of die-hard home brewers. Making clean beer is no easy task.

Neither is making sour beer.

I’m still nowhere near an expert in Saccharomyces, yet (in true homebrewer fashion) my brain is saying,“let’s play around with Brettanomyces, Lactobacillus, and Pediococcus!”As homebrewers, we can afford to go way out on the limb and risk a batch.

If we botch it, we aren’t flushing a hundred thousand bucks down the drain. BUT… when you start playing with bugs, you can risk your entire homebrewery if you aren’t careful.

When brewing sours you, can add brett (wild yeast) and lactic acid producing bacteria such as lactobacillus and pediococcus — all of which are microorganisms which love sugar. These little guys tend to be a bit more resilient than brewers yeast.

They also produce some off flavors that aren’t desired in clean beers.In this post, I’ll outline the steps I’ve taken to keep my sour beers sour and my clean beers clean.

It’s pretty easy to do if you take these two key steps: 1) Purchase duplicate equipment and 2) Dedicate a separate room for sours.

Building Your Sour Brewing Laboratory

Sour beer can be produced in a few ways.

  1. There is kettle souring, where wort is produced and kept in the kettle at a temp of 100-120°F. Once your desired temp is reached, you pitch your lactic acid producing bacteria. Then for 18-48 hrs the temperature is held constant and the beer sours until your desired pH is reached. Once the pH is reached, you resume to a boil to kill your bacteria. This is then moved to your fermentation vessel and brewers yeast or brettanomyces is pitched.
  2. There is clean primary fermentation with Sacchromyces with souring inoculation happening in a secondary fermenter.
  3. There is primary fermentation with the chosen bugs.

Each method can produce some great beers, but for this post I will focus on the last two.Whether you are doing this with clean sacch fermentation then inoculation in secondary, or if you’re doing straight to the primary, the equipment you need is the same. Here is a list of the duplicate items that I have that make sure my sour brewing doesn’t effect my clean brewing.

  • Extra sour kegs
    Tubing
  • Racking Cane
  • Airlocks
  • Bungs
  • Fermentation vessels
  • Space
  • Growlers
  • Bottle bucket & bottle wand (I used a bottling gun now that I boil and use for both clean and sour beers)
  • Kegs (for fermentation and for finished beers)

The most overlooked gadget for brewing sours isn’t gadget at all — it’s space. That’s physical space as in a separate room, in the basement, or at buddies house. Once you get a beer dosed with bugs it takes time, and most of all, patience. You won’t be churning out IPAs if all your fermentation space is taken.

This is where extra carboys, buckets, and even small barrels come in handy. Warning: Be careful when doing sour beer fermentation in buckets because of slow oxygen creep over long periods of time, which can help acetobacter take hold and ruin a beer you have been waiting a year to drink.My personal stash for sour beer consists of about 75 growlers, six glass carboys, eight sixtels, ten 15.5 gallon sankey kegs (shown in Keezer), six 31 gallon spirit barrels, and six wine barrels.

sour beer barrels

Growlers? You make growlers of sour beer?” Nope. These guys I use house my yeast library. Every time I drink a sour beer that I really enjoy, I keep those dregs (the yeasty stuff at the bottom).

Over the years I have always keep my yeast vials. Never had a use for them until now. I will save the dregs for later or put them in a starter right away.

Why is it that all this extra equipment is needed? Well, these little guys are tough. They can survive until another sugar source pops up. Once they start munching, they start multiplying. That’s when your clean beer goes bad. Doesn’t sanitizer kill them? Not always. Typically a nice hot bath at 178°F or hotter for 15 minutes to kill the bugs will do the trick, but not always. Also, not all equipment is high temp proof and you may end up melting something.

But is 2 sets of gear enough?

There are essentially 3 categories of beer:

  1. Saccharomyces beer – Using an isolated ale or lager strain to ferment out your beer. This represents most homebrewers produced.
  2. Brettanomyces/Saccharomyces beer – Mix fermented beer with isolated yeast and wild yeast strains. Sometimes 100% brett is used.
  3. Brettanomyces/Saccharomyces/Bacteria – Fermentation with clean yeast, wild yeast, and bacteria.
Dreg Farm

In a perfect world you would have a separate set of equipment for all three categories, but I have relied on only having two sets: One for Sacch-only beers and one for Brett/Sacch & Brett/Sacch/Bacteria beers. I’d much rather have my brett beers get a little tart from bacteria than to have my clean beers get funky or sour.

Of course, you could take the chance at not buying extra equipment, but all your “clean” beers will eventually turn to the dark side. For that reason I highly recommend NOT doing this. Just shell out the dough when you can. It’s worth it.

My advice is to slowly start acquiring the equipment. Next thing you know you’ll have enough beer to start blending, which is the most critical part of producing great sour beer.

It’s so much fun to explore the diversity and uniqueness of the sour beers you can create.

Lead marketer, brewer, dad, and husband. Pretty much an all-round awesome guy.