After almost three years of blogging about sour beer (among other things fermentational) I think most of what I have learned about brewing them at home is buried somewhere in the roughly 250 posts on this site. That said there isn't anywhere on the blog where the bulk of my opinions and experiences have been coalesced for easy reference. I did put up a lengthy post about Brettanomyces a year or so ago, but that covered just one aspect of sour beer production.
What follows is essentially based solely on my experiences, so I won’t talk too much about things I do not have first hand experience with (like biology, pH levels, traditional practices etc…). Enjoy the data dump and please let me know if I failed to cover any topics that you think should be covered here.
Base beer (brewday): In brewing sour beers and tasting many those made by the great number of American craft and homebrewers now trying their hand at it I have realized that you really don’t need to do anything special on brew day. Pretty much any well made base beer can serve as the foundation of a sour beer. The only beers to avoid souring are those that are aggressively bitter/roasty/spiced because these flavors will be exaggerated by the low finishing gravity of a sour beer.
I have brewed and tasted good sour beers based on numerous classic style, including: English Brown/Mild, Porter, Wee Heavy, Imperial Stout, Wit, Belgian Pale, Saison, Biere de Garde, Belgian Blonde, Dubbel, Tripel, Quad (Belgian Strong Dark), Gruit, and Old Ale. Not to mention the classic sour styles, Berliner Weisse, Lambic/Gueuze, Flanders Red, and Oud Bruin.
Completely off-style brewing is welcome for sour beers as well, but in general you want to make a beer with a reasonably high final gravity (to feed the microbes) and low hop aroma (hops will fade and oxidize over the long secondary fermentation). Some of the more out-there beers I have soured include: Honey-Peach Wheat, Orange-Rosemary Dark Saison, a blend of Saison and Biere de Garde, Bourbon Barrel Wee Heavy, Butternut Squash Brown, and Cherry Quadrupel. Not every idea is going to work out perfectly, but there are many sour beers out there to be made that aren’t found in the style guidelines.
You can use the same basic techniques during the mash/sparge/boil that you would for any other style; you don't need special procedures unless you are trying to replicate a classic/historic style (turbid mash for a lambic, no/short boil for a Berliner Weisse etc…). The only thing I would suggest in general is to try to mash a bit hotter than you would otherwise to ensure that there is plenty of residual extract left for the other microbes to chew on after the Saccharomyces is finished.
I have not found aged hops to be a necessity for any sour beers including inoculated-lambics. Since you are adding the microbes yourself you do not need to worry about protecting the beer from wild invaders as lambic brewers must when they are slowly cooling their wort in a coolship, exposed to the microbe-laden air. If you are looking to do a spontaneous/ambient fermentation then aging hops is something you should look into (several years before brewing...).
I do not do much with the water for my sour beers. Just enough to control the mash pH if need be. I do not see a need to mess around with the flavor ions (chloride, sodium, sulfate) in a beer that is already so complex.
Types of Microbes (bugs): Just like a regular beer brewer's yeast (Saccharomyces) is responsible for most of the alcohol production. The following microbes are responsible for the bulk of the souring/funking after that:
Brettanomyces (Brett) – The king of wild yeasts in the brewing world. It helps to breakdown dextrins (chains of sugars too long for Saccharomyces to ferment) and can add a wide range of characteristic esters and phenols to sour beers. These can range from nice ones like pineapple, apple, and pear; through ones that may or may not be appreciated like horse blanket and farmhouse/barnyard; to the vile smoky, Band-Aid, and fecal batch ruiners. These flavors depend mostly on the strain of Brett, but are also influenced by the types of acids and alcohols available.
Pediococcus (Pedio) – Produces most of the lactic acid in most sour beers. It often takes several months to really get working. Certainly strains can cause your beer to become “sick,” that is to become very viscous for a period of time (this has only happened once to me, but it passed after a couple months leaving a nicely sour beer). It can make your beer taste buttery for a time as well, but the Brett will clean this up in time (never use Pedio without Brett). Pedio also plays a role is the production of some traditional sausages.
Lactobacillus (Lacto) – The only time lacto plays a big role is in Berliner Weisses, the rest of the time the IBUs are high enough to keep it at bay (>8 IBU). It can sour a beer faster than Pedio, and is also the dominant player in yogurt production.
Acetobacter – Generally its role is kept to a minimum. It needs oxygen to convert the ethanol (alcohol) into acetic acid (vinegar). That should be some good motivation to keep your airlocks full and your barrels topped off. You can always add a bit of acetic character by adding some vinegar at bottling.
Sanitation: These days I keep a second set of post-boil plastic (tubing, auto-siphon, bottling wand, bottling bucket, and thief) for my sour beers. There is no need to have a separate mash tun, boil kettle, wort chiller, or anything else that touches the wort when it is still hot. I do use the same pool of Better Bottles for fermentation and glass bottles for storage for all of my beers.
Inoculation: I have gotten the best results adding all of the microbes at the start of the fermentation together with the primary Saccharomyces strain. I don’t generally make a starter for the bugs unless I am using pure cultures (for something like a 100% Brett beer). This is because the different microbes have different required conditions for growth. Yeast strains (including Brett) need oxygen, Pedio on the other hand can’t deal with oxygen. pH can also be an issue since the acid produced for bacteria can damage yeast cells (remember this when considering waiting to pitch a primary yeast to give the bacteria a head start).
Pretty much any standard yeast will do for primary fermentation. I have made great sour beers with American/English/Scottish/Belgian Ale, German Lager, and Saison strains. Some character from the primary yeast may remain in the finished beer, but most of the esters will be destroyed by the various other microbes (primarily Brettanomyces) over the long secondary fermentation. The biggest impact the primary yeast will have on the finished beer is the attenuation level (low attenuating strains will leave more sugars for the other microbes leading to beers with more sourness and funk).
I have not gotten enough sourness by doing a clean fermentation followed by microbes in secondary. This seems to work in barrels where the bugs are receiving some oxygen through the wood, but in a carboy the resulting beer generally lacks the sour assault that I crave. Adding microbes after primary fermentation is a fine idea if you just want some funk because Brett seems to be able to produce esters without a lot of gravity change.
I usually rack sour beers on the same sort of schedule I would a regular ale. I wait until primary fermentation is mostly complete and a good deal of the yeast/trub has settled out (2-3 weeks). Then I rack to a Better Bottle (or barrel), add the oak (if any), and slap on a stopper and airlock. Not much more to it than that.
If after 6 months or so the beer still has not shown any signs of souring I will often add the dregs from a few more bottles or sour beers to try to kick things off. As a last resort I may also add some malt extract to feed the microbes.
I would save ambient fermentation for after you get a good number of sours going. I have not tried it, so for the time being I don’t have much to say about it except that it is riskier than pitching known cultures either from a lab or bottle dregs. Even the best lambic breweries blend most of their barrels to reduce variability, if you try an ambient fermentation try to get several going so you have some blending options.
You can and should repitch yeast cakes from sour beers. Each time you repitch you will get more funk and sourness because the bacteria will grow faster than the yeast. It does not have a huge batch to batch impact in my experience, but it is something you will notice if you do for multiple batches. I generally only repitch 1-2 times, but that is more because I only generally want to do some non-sours as well. I have a friend who has been repitching and saving the same mixed culture for years without any problem.
Wood/Oak: A classic component of sour beers is the wood (almost always oak) barrel. Ideally you would get a group of friends (or a big enough system) and brew enough to fill an entire used commercial barrel (50-60 gallons). Used wine and bourbon barrels are relatively cheap and easy to find (generally for around $100). While this may seem like a lot of beer and effort, in my experiences using full sized barrels can create sour beers with flavors that are simply not possible in any other way.
However I realize that this is not an option for everyone on every batch (including me). You should also consider:
Small barrel – I have not used these, but for better or worse they will let in proportionally more oxygen and lose more beer than a large barrel due to their higher surface area to volume ratio and thinner staves. The smaller the barrel the more this will be a concern.
Oak cubes/chips – Cubes/beans are your best bet because they take longer to give up their flavor due to their lower surface area. Around an ounce of cubes is a good place to start for a mild oak flavor. I boil them for about 10 minutes to removes some of the harsh fresh oak flavors that are usually stripped out by whatever is in the barrel before the beer. Sour beer can be pretty delicate and thin and it can be easily overwhelmed by harsh tannins or oak flavors. You can always add more after a few months if you want more oak character.
If you want to mimic wine/bourbon/port/brandy barrel aging you beer just soak the cubes in the alcohol before adding them to the beer (adding some of the alcohol of choice straight to the beer can also help boost this character). In general wine pairs best with sour beers, but a spirit can work well with bigger/bolder sours.
Wooden dowel, chair leg, peg - I played around with these for awhile, but never got results I couldn’t replicate with cubes. In my experience this setup can cause problems due to pressure build-up and cracked carboy necks due to the wood swelling. You can get around some of these problems by putting the oak through a stopper, but so far I haven't tasted a beer to make me think it is worth the effort.
Aging Vessel: If you aren't going to go with a barrel, there are several options to consider when deciding what vessel you want to age your sour beer in. Since the beer will age for so much longer than a standard beer things that wouldn't matter otherwise like the amount of oxygen that can diffuse through the material start to matter.
Better Bottle - What I use because they don't have the risk of breaking that glass carboys do. I also like the wider opening for getting fruit or hops in/out. They may let a negligible amount of oxygen in, but opening the stopper once will let more in than months of aging.
Glass Carboy - Just make sure you don't break one full of year old sour beer. The big advantage of these is that no oxygen can get in and they are easy to sanitize.
Bucket - I have yet to try aging a sour beer in one, but my friends who have do not seem to be getting objectionably acetic results as some people suggest (due to their high oxygen permeability). It may depend on things like temperature and specific microbe varieties. I also don't like the fact that you have to open them to look at the beer.
Conical/Keg - I don't use either, but the advantage of stainless is that like glass it is easy to sanitize and impervious to oxygen. If I had the money for a conical I probably wouldn't tie it up for several years with beer. A keg on the other hand seems like a fine place to do your sour beer fermenting if that is something you are interested in if you don't mind the obstructed view.
Aging: The longer you can age a sour beer in the fermenter the better, as they will almost always improve for a couple years. A moderate temperature is best in my experience (anywhere from the low 60s up into the 70s). A higher temperature will encourage more rapid souring, while a lower temperature will lead to a more balanced (less aggressive) beer.
A pellicle is a sign that there is oxygen in the head-space more than anything else. I have had fantastically sour/funky beers that never grew more than a light skin, and terrible beers that grew huge pellicles because too much oxygen was getting in. In general it is not something I would worry about too much either way (unless you are trying to brew a clean beer).
Just like any other beer you are best off aging sour beers where they get as little light as possible (I generally just use the boxes they come in or a pillow case with a hole cut to let the airlock through). It is also nice if you can keep them somewhere out of the way so they are out of sight and out of mind, making it easier to wait for them to age.
In addition to adding a distinct flavor, fruit adds sugar, and acids as well. Most of the sugars added by the fruit are eaten by the bugs and critters which in turn cause them to produce more acidity and boost the production of other flavorful byproducts. The acids add a different character to the sourness since they are either malic or citric, both of which are a bit sharper than the lactic acid produced by the microbes in beer (malolactic bacteria will convert malic to lactic acid, so that is something to consider if you do not like the acid character of a fruited sour beer). In addition to their main constituents fruit also adds anti-oxidants, that’s right the same compounds that help prevent damage to your DNA from free-radicals also prevents oxygen molecules from creating off-flavors in your beer as it ages.
The acid of the beer really helps to make the fruitiness pop in a way that most "clean" fruit beers do not. The actual amount of fruit you need will depend on the variety of fruit, quality/freshness, base beer, and amount of fruit flavor you are aiming for. In general .5 lbs per gallon is the low end (good for assertive fruits like raspberry), and 2.5 lbs/gal is the high end for more subtle fruits, or if you have a bigger/darker base beer.
You will not get a sweet-fruity sour beer unless you kill the yeast and bacteria present using heat/chemicals/filtration before adding the fruit (this is what Lindemans does to make their lambics). If this seems too difficult you can add fruit juice to a plain sour beer in the glass (this is a good way to soften the beer for people who do not like something so dry and sour).
I generally like splitting a batch leaving half plain and adding fruit to the rest. This way I get two beers for the effort of one. It also makes for some interesting comparisons. Sometimes I like the fruited half more, other times the plain portion does it for me. I usually wait for at least six months before adding fruit, this gives me a chance to taste the beer and see which fruit I think would work well with it and it give the bugs a chance to get established so they are the ones fermenting the fruit sugars and not the primary yeast.
Bottling: Before bottling I wait until airlock activity has ceased, the gravity has not changed in at least a month, and the flavor is where I want it. I have never had an issue bottling while my beers still have a pellicle, but it can be an indication that something is going on. I would also be cautious bottling any sour beer with a gravity over 1.010 (unless it has a high ABV, or had other extenuating circumstances).
I generally reyeast with wine or neutral ale yeast at bottling. 2 grams of dry yeast rehydrated in 90-100 degree water is my standard rate for 5 gallons, but a little extra won't hurt anything. This ensures timely carbonation and not much change in flavor immediately after bottling. I generally use cane/beet/table/white sugar, it is cheap, effective, and doesn’t impart a flavor of its own. Candi and corn sugars are also fine choices, but tend to be a bit more expensive. I try to avoid using any variable agricultural products for priming like honey, maple syrup, or malt extract since it adds some guesswork (particularly when you are talking about a multiple microbe culture).
Some sour beers, particularly those aged in wood barrels or with the oak dowel/peg can be completely flat at bottling time. This is different than the usually assumed .5-.8 volumes of CO2 most priming calculators assume the beer is holding onto. As a result if your beer tastes wine flat you should consider adding some extra priming sugar (or be willing to accept a lower carbonation level than the your calculations might predict).
The carbonation level is up to you. Higher carbonation tends to increase the sense of acidity (dissolved carbon dioxide is carbonic acid) and give you the impression of body in very thin beers. In general I aim for moderate-low carbonation, but that is the way I like most of my beers. In the end it is just about what you think would taste good for your beer.
In my pale sour beers (especially those with wheat) I often get an odd cereal/cheerio finish for a few months after bottling that wasn’t there in the bottling bucket. It fades with time, but it is annoying while it lasts. In general if a sour beer doesn’t taste good give it more time (recently the brewer at Bullfrog Brewery told me how terrible his Gold Medal winning Beekeeper Honey Sour Saison was for several years, to the point he considered it lost, before it turned the corner).
Once the beer is bottled it will age like any other. Lower temps will slow aging, while higher temps will produce faster changes in the flavor. It is worth hanging onto bottles for many years. Most of my sours seem to be getting better and better as time goes on, some are now at nearly three years in the bottle.
General Tips: Be patient. Try to avoid taking samples too often, it introduces oxygen and steals good beer from your future self.
Get a new sour beer going every few months to build up a pipeline if you can. It is easy to look forward a few months to the next beer that will be ready, but it will drive you insane thinking about the fact that the beer you just brewed won't be ready to drink for at least a year. If you have a big enough system it just steal 5 gallons (or even less if you have some smaller fermenters) of wort now and then to sour. Having plenty of beers souring also opens up the world of blending (which pretty much every good production sour brewery does) when you have multiple batches ready around the same time.
Don’t skimp on ingredients. Spending a bit more now is worth it in the end, especially when you are investing such a huge amount of time/effort/thought into a beer. This is especially true of things like fruit, spices, and sugars, go to places that specialize in the ingredient, Ethnic Markets, Spice Shops, Farmer's Markets etc...
Make friends with other homebrewers interested in sours, particularly those who live near you. Try their beers and have them try yours, some of the best sours I have had have been fermented in the basements and closets of other homebrewers.
Try as many commercial sour beers (for inspiration and microbes) as you can and ask questions of any commercial brewer who makes sours you enjoy. Most of them are very passionate and happy to help an equally passionate homebrewer. Asking about technique rather than recipes will generally get you more useful information.
Take as many notes on your beers as you can. These will help you to avoid mistakes or recreate successes in the future. With sour beers your technique evolves slowly since the feedback loop takes years instead of weeks like clean beers. My sours have steadily gotten better, but I still have beers aging that I made mistakes (or miscalculations) on that I have fixed in more recent batches.
If you want a hoppy sour beer, go with dry hops right before bottling (or in the bottle or keg). This will give you the mature acid/ester profile with the fresh hop kick.
For much much much more on how to brew sour beers, read my book: American Sour Beers!
Beatification Batch 001 Clone - Wine Barrel Sour Pale based on Russian River's beer
Big Funky - High Gravity Sour
Bourbon Barrel Wee Heavy - Unintentionally Sour, but still tasty
Brett Pale Ale - 100% Brett A American Pale Ale
Deviant Cable Car - 10 gallons of pale oaty sour beer with Al B's Bugfarm
Cable Car Clone - Soured blend of Saison, Bier de Garde, and Lager
Bourbon Cherry Brett Dark Belgian - Inspired by Cuvee de Tomme
Flanders Pale Ale - Flanders Red without the Red, half aged on Pluots
Flanders Red Again - My second attempt at the style, starter for the wine barrel
Funky Dark Saison - With rosemary, orange peel, and caramelized raisins
Funky Dark Saison #2 - With black cardamom, and caramelized dates
Funky Flower - Honey, chamomile, wheat based sour
Funky Rye Mild - English mild with rye that took an unexpected turn
Inspired by Sebastian - 100% Brett C table saison
Inspired by Sebastian - 100% Brett A table saison
Lambic The First - My first (terrible) attempt at a Lambic
Lambic Mrk 2 - Me second, too strong, attempt at a Lambic
Lambic 3.0 - My first attempt with the traditional turbid mash
Mo' Betta Bretta Clone - 100% Brett C beer based on the Pizza Port beer
Mo' Betta Bretta Clone #2 - 100% Brett A beer based on the Pizza Port beer
No-boil Berliner Weisse - My first attempt at the style
No-boil Berliner Weisse 2 - Half with Cabernet juice
No-boil Berliner Weisse 3 - Half left at a Lambic OG, the rest watered down to the usual 1.033
Perpetuum Sour - A pale sour, solera aged in a red wine barrel
RodenTons - My first attempt at a Flanders Red, half aged on blackberries
Sour Bourbon Barrel Porter - A strong porter aged in a second use Bourbon Barrel
Sour Squash - Lightly spiced, sour, butternut squash, brown ale
Temptation Clone- Chardonnay spiked pale sour based on the beer from Russian River
Sour Beer Links: