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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 capryccapric" 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). Some sour beer brewers strive to achieve autolysis in their beers with the belief that it could improve mouthfeel and react with other compounds to produce favorable flavors, similar to how autolysis is sometimes desired in winemaking in the form of [https://www.thekitchn.com/wine-words-lees-aging-179813 lees aging] or [https://www.thekitchn.com/wine-words-btonnage-191331 bâtonnage ]<ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/3177292242298968/ Lars Meiner, Richard Preiss, and Alex Seitz. milk The Funk Facebook group thread on autolysis. 01/03/2019.]</ref>.

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(and those flavor contributions are not desired), 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]].

The term "solera" has deep roots in the history of Sherry production dating back as far as the late 1800's. As such, the term has a fairly strict and traditional meaning in the Sherry and wine industry. See [https://www.sherrynotes.com/2013/background/sherry-solera-system/ this article by Ruben Luyten] for an in-depth definition of the solera system as it is known in the Sherry industry. As In short, in a part of the traditional solera system, multiple tiers of wooden casks are used in with the top/youngest tier being referred to as the ''sobretabla'', the middle tiers as ''criaderas'', and the oldest/bottom tier being called the ''solera'' (the term ''solera'' refers to both the oldest/bottom tier of casks and the entire system). There appears As a portion of Sherry leaves the ''solera'' casks to be packaged, they are refilled from the second oldest tier of ''criaderas'', which are then refilled from the third oldest, until the youngest ''criaderas'' (''sobretabla'') is refilled with new wine. This process is called ''fractional blending'' <ref>[https://www.sherrynotes.com/2013/background/sherry-solera-system/ Ruben Luyten. "The Solera system". The Sherry Notes websites. 08/28/2013. Retrieved 10/30/2018.]</ref>.  There is no known use of the term "solera" in the wine industry to apply refer to a single tier blending system (there is a term for this is referred to as in the wine industry, "perpetual blending" in the wine industry). As such, some brewers and likely Sherry makers and wine makers argue that unless a solera consists of multiple tiers, such as the system at [https://www.youtube.com/watch?v=bjMB0E_KeYI Cambridge Brewing Co. for Cerise Cassée], which is the oldest known traditional solera for beer solera since starting in 2004, that it is not a true solera. Therefore, using the term "solera" for single vessel systems misguides consumers by changing the definition of the word to include processes that do not completely resemble the solera process of Sherry making. The alternative and established term , "perpetual blending", which has been applied in wine world to refer to single vessel blending systems <ref>[http://www.champagneguide.net/information/glossary Peter Liem. Champagne Guide. "Glossary of Terms". 2009. Retrieved 03/06/2018.]</ref>, has been offered as an alternative and more accurate word to use for single-vessel blending systems. The term "pseudosolera" has been proposed as well since the phrase "pseudo" has been used to refer to "pseudolambics" in the homebrewing community, although there is no precedence of using this term in the wine industry like there is with the term "perpetual blending". See [https://www.facebook.com/groups/MilkTheFunk/permalink/2012252492136288/?comment_id=2013130782048459&comment_tracking=%7B%22tn%22%3A%22R%2311%22%7D these arguments made from Will Meyers of Cambridge Brewing Co.] and [https://www.facebook.com/groups/MilkTheFunk/permalink/2009645332397004/?comment_id=2009649935729877&comment_tracking=%7B%22tn%22%3A%22R0%22%7D wine blogger Otto Forsberg].

* The term has been used since at least 2002 by Jeff Renner in an article of Zymurgy Magazine and then later in 2006 by a homebrew club to describe a single-vessel blending system for homebrewers <ref>[https://www.homebrewersassociation.org/attachments/0000/6021/JFzym02-Solera.pdf Jeff Renner. "Solera Ale: Beer That Gets Older As You Drink it". Zymurgy Magazine. Jan/Feb 2002.]</ref><ref>[https://aabg.org/new-member-info/bourbon-barrel-barley-wine Ann Arbor Brewers Guild. Walloon Solera Ale in Sweden. 2006. Retrieved 03/06/2018.]</ref>. A 200-year-old single vessel sour beer "solera" [https://hundraarigtol.se/det-svenska-vallonolet in Sweden ] was the inspiration for the latter article, however, it is not clear if appears as though the owners of this barrel did not refer to it as a "solera". In fact, the Swedish term that was used, which dates back to the early 17th century, was "hundred-year beer" or "hundraårig öl" (see [https://aabg.org/new-member-info/bourbon-barrel-barley-wine/waloon-solera-ale-in-sweden/ this Ann Arbor Brewers Guild blog post] and this [http://www.garshol.priv.no/blog/311.html Larsblog blog post]). * Reversing the relatively recent precedence in the brewing industry and the homebrewing hobby of calling single-vessel blending systems something other than "solera" will be impractical now.* The brewing of the fresh beer in a steel fermenter could be viewed as the "first stage of a solera", so as long as fresh wort is not added, it is still a solera (this argument is countered by the fact that Palomino wine is first fermented in a fermenterfermentation vessel, then racked into casks, but the fermenter fermentation vessel itself is not considered a part of the solera system <ref>[https://eng.sograpevinhos.com/enciclopedia/guia_vinho/vinificacao/jerez_palomino Sogrape Vinhos website. "Making Sherry Wine". Retrieved 03/06/2018.]</ref>).

===See also===MTF Threads:* [https://www.facebook.com/groups/MilkTheFunk/permalink/4077032142324969 MTF post on technical process of running a true solera for sour beer.] Videos and other resources: