BARREL SOURINGUnlike traditional beer-brewing, which is done in a sterile environment to guard against the intrusion of wild yeast, #sourbeers are made in wooden barrels that allow wild yeast strains or bacteria into the brew. Traditionally, Belgian brewers allowed wild yeast to enter the brew naturally through the barrels – an unpredictable process that many modern brewers avoid. The most common microbes (referred to as “bugs”) used are Lactobacillus, Brettanomyces, and Pediococcus.
It is not recommended to use lactic acid for tartness in your barrel aged beer. Natural tartness can be achieved using Lacto and Pedio correctly. Some homebrewers achieve a tart flavor from fruit additions – most commonly cherries (to produce kriek) or raspberries (to produce framboise) – during the aging process, to cause a secondary fermentation.
Barrels are a great place to experiment with sour beers using fruits like cherries, peaches, plums, apricots, strawberries, blackberries and raspberries. The combination of toasted oak, fruit and sour/tart can create some truly unique homebrews.
Make a little extra homebrew and be ready to blend your sour beers with a similar beer fermented with standard brewing yeast (saccharomyces cerevisiae). Because of the uncertainty involved in using wild yeast and souring bacteria, the sour beer brewing process is extremely unpredictable. Having a base beer for blending helps you temper some of the extreme characteristics in a beer like sourness, bitterness or alcohol level.
Keep the beer away from O2 as much as you can when you’re blending — keep the oxygen exposure to a minimum. The barrel beer takes months to ferment and can take years to mature. Blending beer is an art form and takes a brewer a lifetime to master.
Remember that any piece of equipment that comes in contact with your sour beer should be isolated from any “clean” brewing in the future. Brett, Lacto and Pedio and very resilient and are difficult to completely sanitize off equipment. If you don’t do this you may end up with every beer you make being a sour beer. Isolate plastic transfer hoses, airlocks, bungs, connectors, glass/plastic carboys, transfer gaskets and siphons. Basically any soft rubbers should not be used again for clean brewing in the future.