Sour beer

Intro

Modern methods for fast souring

Making sour beer doesn't need to be complicated! These techniques are a good alternative to the antiquated kettle souring method.

Lactobacillus plantarum is a game-changer for making sour beer. It's super clean, it produces a robust sourness at room temperature, and it's extremely hop-sensitive.

Being so hop sensitive makes it so that even if you're bad at cleaning, it won't grow or make acid in a hopped beer.

Kettle souring is a relic from when a lot of brewers were sour mashing or using grain for souring wort. In that case it makes sense to kill the wild culture because there may be any number of undesirable bacteria and/or yeast species that would not be good in a fast sour. Using more hop-tolerant species like L. brevis also may lead to concerns for contamination if you don't kill it and don't clean properly. However, I find that proper cleaning is not difficult and cross-contamination does not occur while using one set of equipment even for Brett, Pedio, and other wild microbes. For example I rinse fermenter immediately after use, soak with warm PBW (which is a broad-spectrum anti-microbial), and rinse again. Break down spigot and soak separately. A quick rinse with warm citric acid solution helps remove buildup, followed by another rinse. Any reasonable no-rinse sanitizer is fine immediately before use.

Another common outdated belief is that kettle souring requires heat. While that's true for most species, with L. plantarum that's not the case. This allows us to easily co-sour and post-sour. Avoiding having wort sitting in the kettle for days actually results in less risk of contamination. I've seen lots of contaminated kettle sours.

Most of the desirable flavor from bacteria is expressed within a few days (e.g. lemony citrus, berry, peach, melon, tea, smoke, yogurt, etc). If you leave it go uninhibited, there will indeed be a bit more "complexity" that develops within a couple weeks. A lot of that extra complexity comes from isovaleric acid production, and this might not be desirable to you (I don't particularly like it). Extended aging beyond a couple weeks doesn't do anything, at least for the bacteria blend that I use. I typically suggest adding a small amount of hops via dry hopping or hop tea after it reaches desired sourness (within a few days). While hops don't outright kill the Lacto, the bacteria go into stasis and don't further contribute flavor or acid, thus preventing the isovaleric acid production.

Isovaleric acid (or production of any other unwanted compounds) isn't an issue if you use Brett because Brett just eats anything undesirable and poops out awesomeness. :)

Co-Souring Method

Make unhopped wort. Chill as normal.
Pitch Lactobacillus plantarum and the yeast of your choice.
Ferment as normal, at 65°F or higher.
Optional/recommended add hops when it reaches the desired sourness. (Dry hops or hop tea)
Package as normal.

Post-Souring Method

Same as co-souring, except pitch the Lactobacillus plantarum after 1-2 days of fermentation (or 8-12 hours if using kveik and fermenting hot).

Post-souring is designed to maximize yeast flavor. It's great if you want to use an estery yeast like WLP644 (Sacc Trois) for example, which adds a nice tropical pineapple & mango profile.

Frequently asked questions

Q: Won't the Lacto ruin my equipment or contaminate my other beers?
A: No. Normal cleaning and sanitation procedures easily remove L. plantarum. Furthermore, L. plantarum is extremely hop-sensitive and will not sour your clean beers with hops, even if you directly add it. These techniques actually have LESS risk overall of contamination compared to kettle souring.

Q: Where do I get L. plantarum?
A: Several sources are readily available in the US:

Swanson's L. plantarum capsules can be purchased online (Amazon).
GoodBelly liquid probiotic is available in stores.
Renew Life Ultimate Flora are both widely available in stores. Bonus points if you find a store that keeps it refrigerated.
Lallemand offers pure L. plantarum as WildBrew Sour Pitch.
Other yeast labs sell Lacto blends of L. plantarum mixed with other species, often L. brevis (use these blends at your own risk because they are more hop-tolerant).

Store the Lacto in the refrigerator. The dry capsules will last a very long time.

Q: Do I need to make a starter for the Lacto?
A: It's not needed, however if you use the post-souring process, I do recommend a starter. Starter procedure: After chilling, drain about 200-500mL wort into a sanitized jar. Add the Lacto and a few grams of calcium carbonate. Cover and let sit at room temp. When pitching, decant it off of the calcium carbonate (you don't want the chalk in your beer).

Q: How much Lacto do I pitch?
A: Pitch rate isn't very important. Feel free to use 1-2 capsules or a few ounces of GoodBelly in 5 gallons.

Q: Won't it take months to sour?
A: No. L. plantarum sours quickly (within a couple days) anywhere in the range of 65-100°F. It will finish in the same timeframe as non-sour beer. I've gone from grain to packaging in 3 days.

Q: How long should I boil the wort?
A: Boiling is entirely optional since we don't need to isomerize alpha acids in hops. Mash temperature pasteurizes the wort.

Q: What amount of hops should I add?
A: Anywhere from 0.5 oz to 1 oz per 5 gallons adds a nice hop character (in my opinion) and completely inhibits further souring.

Q: Do the bacteria add flavor?
A: Generally, yes, depending on the source of L. plantarum you use. Frequently the Lacto contributes a nice lemony citrus tartness, notes of berry and melon, and possibly some slight funk. Adding hops after reaching desired sourness will reduce the funk complexity. The Renew Life blend probably adds more flavor than a single species culture and it also creates a more funky profile when used at high temperature (e.g. when souring with kveik at 95°F).

Q: Will it continue to sour if I don't add hops?
A: Yes, possibly, but Lacto's ability to produce acid is self-limiting. Normally this species finishes around pH 3.1-3.3.

Q: What is hop tea?
A: Boil the hops for 5-10 minutes in 300-500mL of chlorine-free water. Dump it into your batch. If you add it at bottling, strain through a hop sock. Added bitterness will be minimal.

Q: Do I need a pH meter?
A: Not really. If you're inclined to stop the souring before it finishes naturally, you can do it by taste. However, pH meter is a good investment for all-grain brewing, as well as monitoring the Lactobacillus fermention. Keep in mind titratable acidity (TA) is the measurement that best correlates with sour taste (unlike pH).

Q: Do I need to pre-acidify the wort?
A: Nope!

Q: Should I pitch more yeast than normal, or add yeast at bottling?
A: Nope!

Q: Can I use yeast cake from a previous batch?
A: Only if there were absolutely no hops in the batch from which you harvested it.

Q: Will the beer benefit from aging?
A: Nope!

Q: Is this beer probiotic?
A: Yes! Hops do not kill the bacteria (they are bacteriostatic, not bactericidal).

Recipes

Coming soon!

Modern methods for fast souring plus Brettanomyces