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==Yeast Autolysis==
Yeast autolysis is the rupturing of dead yeast cells and produces meaty or rubbery off flavors <ref>[http://byo.com/kegging/item/182-beat-yeast-bite Freccia, Nico. Beat Yeast Bite. Brew Your Own Magazine. April 1997. Retrieved 2/20/2015.]</ref>. When it comes to sour beers, Lambic producers often let their beers age in barrels on the trub for up to four years without effects of off flavors from yeast autolysis. The hypothesis is that the ''[[Brettanomyces]]'' will metabolize the off-flavor compounds produced by the bursting ''[[Saccharomyces]]'' cells, and use them as nutrients <ref>[http://www.themadfermentationist.com/2013/05/second-pull-wine-barrel-solera.html Tonsmeire, Michael. Second Pull Wine Barrel Solera. The Mad Fermentationist Blog. Retrieved 2/20/2015.]</ref>. Therefore, many people have reported that they have successfully avoided yeast autolysis in solera projects, as well as just allowing sour beer to remain in the primary fermenter for the entirety of its aging. However, as the solera ages, trub buildup can potentially become be a problem for logistic reasons (such as clogging ports). Will Meyers of Cambridge Brewing Company reported an eventual autolysis issue with his solera <ref>[http://www.themadfermentationist.com/2013/05/second-pull-wine-barrel-solera.html Tonsmeire, Michael. Second Pull Wine Barrel Solera. The Mad Fermentationist Blog. Comments section, July 30, 2014 at 9:39 PM. Retrieved 2/20/2015.]</ref>. Lauren Limbach of New Belgian Brewing reported tasting "goaty", "dog food", "caprilic and capryc" flavors in barrels that had not been cleaned out after a few years, and upon rinsing the barrels out with de-aerated water the resulting beers were "bright and beautiful" (the barrels were filled with clean beer and not inoculated; assumably the microbes surviving in the wood were enough to produce good results) <ref>[https://soundcloud.com/craftbeerbrew/podcast-episode-21-new-belgiums-wood-cellar-director-blender-lauren-limbach Lauren Limbach. Craft Beer and Brewing Magazine Podcast. Episode 21. 02/16/2018.]</ref> (~37 minutes in).
Whether or not the brewer elects to refill the solera with wort or fresh beer can also potentially play a role in yeast autolysis issues eventually creeping up in a solera. If flavor issues from yeast autolysis are going to occur, adding wort will create a thicker trub, which could lead to autolysis issues faster. In either case, theoretically, these issues can be avoided. One method for avoiding off flavors from yeast autolysis is to rack some of the trub out of the solera when the seasonal pulls are taken. Another method is to rack the solera to another vessel once a year or every other year. Once removed from the trub, the ''Brettanomyces'' should be able to clean up the off flavors over time. See also [[Mixed_Fermentation#Reusing_a_Sour_Yeast_Cake|Reusing a sour yeast cake]].
See also:
* [https://www.facebook.com/groups/MilkTheFunk/permalink/1966542510040620/ Will Meyers of Cambridge Brewing Co. shares his experience with autolysis and running the oldest commercial solera program for sour beer in the US.]
re-ordered sections
For the traditional '''Solera''' process used in Sherry, vinegar, and brandy production, [http://en.wikipedia.org/wiki/Solera ''see the Wikipedia article on Solera'']. In beer, particularly sour beer, a single stage Solera process has been discovered to be a reliable and easy way to continuously make sour beer. Some have argued that this is a misuse of the word "solera" and that it should only be applied to multiple tiered systems (see [[Solera#Claims_of_Misuse_of_the_Traditional_Meaning|Misuse of the Traditional Meaning]] below).
The process of using a solera method in sour beer brewing has become the term used for filling a single fermenter with a sour beer, and every 6-12 months taking one third or half of the beer out for packaging (and perhaps sometimes as much as 70% is taken out). There is no defined rule for what the limit is to take out and still be considered a "solera" in beer. The maximum percentage is also variable in wine. For example, in Sherry a maximum of 35% can be removed legally, although 10-15% is more typical, but other wine styles may not have a defined percentage (ref needed) <ref>[https://www.sherrynotes.com/2013/background/sherry-solera-system/ Sherry Notes website. "The Solera System". 08/28/2013. Retrieved 03/06/2018.]</ref>. The volume that is removed is then replaced with new beer or wort. This method provides the brewer with a "perpetual" sour beer that takes less time to age because of the blended components. Over time the beer can continue to develop and change, and the brewer has the option of trying to steer the beer by altering the recipe for the wort or beer used to refill the solera. As a rule of thumb, the larger the fermenter the better. This will allow for larger seasonal pulls from the solera, thus producing more beer. The term could also be applied to a multi-vessel solera in beer, which has been argued is a more accurate use of the term, although multi-vessel solera systems in sour beer production are less common due to the potential for over exposure overexposure to oxygen.
The barrel can be refilled with either fermented beer or wort. Choosing to refill with wort could eventually lead to a lot of trub build up, however, there might not be any negative flavor effects from doing so. Wort will ferment in the barrel and might cause a blow off unless there is adequate headspace (in which case the brewer should top up the barrel after the wort ferments). Choosing to refill with beer that is first fermented with brewers yeast or with a mixed culture might be more practical for avoiding blow off issues and for group barrel projects for homebrewers because individual brewers can brew the refill beer at any time, and then meet to refill the barrel. See [[Solera#Yeast_Autolysis|Yeast Autolysis]] below.
==Yeast Autolysis==
Yeast autolysis is the rupturing of dead yeast cells and produces meaty or rubbery off flavors <ref>[http://byo.com/kegging/item/182-beat-yeast-bite Freccia, Nico. Beat Yeast Bite. Brew Your Own Magazine. April 1997. Retrieved 2/20/2015.]</ref>. When it comes to sour beers, Lambic producers often let their beers age in barrels on the trub for up to four years without effects of off flavors from yeast autolysis. The hypothesis is that the ''[[Brettanomyces]]'' will metabolize the off-flavor compounds produced by the bursting ''[[Saccharomyces]]'' cells, and use them as nutrients <ref>[http://www.themadfermentationist.com/2013/05/second-pull-wine-barrel-solera.html Tonsmeire, Michael. Second Pull Wine Barrel Solera. The Mad Fermentationist Blog. Retrieved 2/20/2015.]</ref>. Therefore, many people have reported that they have successfully avoided yeast autolysis in solera projects, as well as just allowing sour beer to remain in the primary fermenter for the entirety of its aging. However, as the solera ages, trub buildup can potentially become be a problem for logistic reasons (such as clogging ports). Will Meyers of Cambridge Brewing Company reported an eventual autolysis issue with his solera <ref>[http://www.themadfermentationist.com/2013/05/second-pull-wine-barrel-solera.html Tonsmeire, Michael. Second Pull Wine Barrel Solera. The Mad Fermentationist Blog. Comments section, July 30, 2014 at 9:39 PM. Retrieved 2/20/2015.]</ref>. Lauren Limbach of New Belgian Brewing reported tasting "goaty", "dog food", "caprilic and capryc" flavors in barrels that had not been cleaned out after a few years, and upon rinsing the barrels out with de-aerated water the resulting beers were "bright and beautiful" (the barrels were filled with clean beer and not inoculated; assumably the microbes surviving in the wood were enough to produce good results) <ref>[https://soundcloud.com/craftbeerbrew/podcast-episode-21-new-belgiums-wood-cellar-director-blender-lauren-limbach Lauren Limbach. Craft Beer and Brewing Magazine Podcast. Episode 21. 02/16/2018.]</ref> (~37 minutes in).
Whether or not the brewer elects to refill the solera with wort or fresh beer can also potentially play a role in yeast autolysis issues eventually creeping up in a solera. If flavor issues from yeast autolysis are going to occur, adding wort will create a thicker trub, which could lead to autolysis issues faster. In either case, theoretically, these issues can be avoided. One method for avoiding off flavors from yeast autolysis is to rack some of the trub out of the solera when the seasonal pulls are taken. Another method is to rack the solera to another vessel once a year or every other year. Once removed from the trub, the ''Brettanomyces'' should be able to clean up the off flavors over time. See also [[Mixed_Fermentation#Reusing_a_Sour_Yeast_Cake|Reusing a sour yeast cake]].
See also:
* [https://www.facebook.com/groups/MilkTheFunk/permalink/1966542510040620/ Will Meyers of Cambridge Brewing Co. shares his experience with autolysis and running the oldest commercial solera program for sour beer in the US.]
==Claims of Misuse of the Traditional Meaning==
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==Articles on Solera==