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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 capric" 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]].