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===Re-yeasting===
(In progress)
When bottling or priming a keg at packaging time, the brewer should consider re-yeasting. In a long aged beer, especially an acidic beer, the ''Saccharomyces'' will mostly be dead already. This leaves ''Brettanomyces'' in charge of conditioning the beer. Although some lactic acid bacteria are capable of producing CO2, their contribution is probably negligible. It is also possible that homofermentative LAB will consume a portion of the sugar before the ''Brett'' has a chance to produce CO2. Re-yeasting is a very effective way to ensure proper CO2 levels in an aged sour beer. Another benefit of re-yeasting is that it tends to help avoid [[Tetrahydropyridine]] production.
Commercial producers and MTFers have had success re-yeasting with their mixed culture, wine yeast, and champagne yeast. The specific yeast you choose is up to you, and we recommend that you try a couple different yeasts out to find the one you prefer. When re-yeasting at bottling, it is not recommended to add new highly attenuative yeast to make sure that the bottling yeast you add cannot ferment additional carbohydrates remaining in the beer <ref name='Sour Hour episode 6'/> (~41 minutes in). Re-yeasting with a yeast that beer has already seen should eliminate the possibility of continued attenuation as long as the beer is already at final gravity. Another benefit of re-yeasting is that it tends to help avoid [[Tetrahydropyridine]] production.
The yeast required for carbonation is very little. A good rule of thumb to use is to use 10% of the yeast that you would normally use for a primary fermentation. For example, for dried yeast use ~2 grams of yeast for 5 gallons of beer <ref name="priming_calc">[http://jeffreycrane.blogspot.com/2015/06/blending-calculator-ph-abv-and.html Blending Calculator - pH, ABV and Carbonation. Jeff Crane. Blending Calculator - pH, ABV and Carbonation. Bikes, Beer, & Adventures Blog. June 12, 2015.]</ref>. Rehydrating the yeast is recommended. See [http://jeffreycrane.blogspot.com/2015/06/blending-calculator-ph-abv-and.html Jeff Crane's "Blending Calculator" (extension of Michael Tonsmeire's "Blending Calculator")] for a re-yeasting and priming calculator.