Changes

Producers of spontaneously fermented beer typically do not oxygenate their wort <ref name="Beer Temple interview with De Garde"></ref> (~27 minutes in) and traditional producers conduct fermentation for a long time period (1-3+ years) in wooden vessels. The long fermentation process allows the different microbes present to carry out their slow metabolism of the complex carbophydrates present in the beer, developing the flavors and acidity associated with spontaneous beers (-------). The wooden fermentation vessels are frequently oak wine barrels in the 220-400 L (58-105 gal) range but other woods such as chestnut are used and the vessels may also be large tuns or foeders holding upwards of 45 HL (about 1200 gal, or about 34 bbl). These barrels provide two primary benefits for the fermentation - they allow a small amount of oxygen permeability and they provide a environment which houses some of the microbes active in the fermentation (notably Brettanomyces, which can penetrate up to ---- (ref) into the wood and in some cases can metabolize compounds present in the wood such as cellobiose, which is produced from toasting of the wood) (----ref---). While a controlled micro-oxidation can be beneficial to the beer, too much oxygen exposure can lead to excessive acetic acid and/or ethyl acetate production (either from ''Brettanomyces'' or ''Acetobacter'') (----ref).

On a homebrew scale a fair amount of attention has been paid to the topic of oxygen permeability in different fermentation vessels and closures <ref>[http://www2.parc.com/emdl/members/apte/GingerBeer.pdf Raj Apte's oxygen permeability table]</ref> <ref>[http://www.mocon.com/assets/documents/PPS_Article_highq.pdf Better Bottle closure study]</ref> <ref>[https://www.youtube.com/watch?v=boLqmFIzUZ0&list=PLibE2BjPG_8H0IZe4fS2FD4uidCFhgzBn&index=4 Dan's video discussing airlocks and fermenters]</ref>. It has been suggested that sealing a glass carboy with a wooden dowel or chair leg can result in similar oxygen permeability as a wine barrel. While Although this was quite a clever idea for replicating oxygen exposure, this is not recommended as it can lead to breakage of the glass carboys <ref name="Mad Fermentationist Oak">[http://www.themadfermentationist.com/2007/02/8-homebrew-barrel.html Mad Fermentationist $8 homebrew barrel]</ref>. While micro-oxygenation may be an important part of some spontaneous production it may be getting too much attention in homebrew carboy conditions <ref name="Mad Fermentationist Oak">[http://www.themadfermentationist.com/2007/02/8-homebrew-barrel.html Mad Fermentationist $8 homebrew barrel ]</ref> (see comments) relative to other controls such as temperature, microbes, and time. See the [[Barrel]] page for discussions on the barrels available to homebrewers.

Regarding fermentation temperature, commercial producers looking for balanced acidity and flavor/aroma complexity prefer cooler fermentation temperatures in the range of the high 50s to low 60s F (~13-18 C) <ref name="Spontaneous Sour Hour">[http://www.thebrewingnetwork.com/membersarchive/sourhour2015_05_wildfriendship.mp3 The Sour Hour Episode 11 with Rob Tod and Jason Perkins from Allagash, Jean Van Roy from Cantillon, and Vinnie Cilurzo from Russian River]</ref> (~1:14 in)(3 Fonteinen had temperature controlled cellars, -----Armand highlighting the importance of aging temperature. Unfortunately this temperature control failed and resulted in the rbewery nearly going out of business <ref>[https://www.lambic.info/Brouwerij_3_Fonteinen lambic.info 3F]</ref>. This temperature range allows slow and balanced fermentation by the diverse array of microbes present. Warming the fermentation too much results in enhanced production of acidity which is out of line with what the lambic producer is aiming for. This can be used to the advantage of the brewer when producing certain non-lambic inspired spontaneously fermented beers (see below, Alternative applications of spontaneous fermentation).