For the traditional Solera process used in sherry, vinegar, and brandy production, 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.
The process of using a solera method in sour beer brewing is traditionally filling a single fermenter with a sour beer, and every 6-12 months taking one third or half (and sometimes more than one half) of the beer out for packaging. That volume is then replaced with new beer or wort. This method provides the brewer with an "everlasting" 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 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 Yeast Autolysis below.
Articles on Solera
- Starting a Solera, by Ed Coffey on HBT. This is a great article on what a solera is, and how to start one for sour beer.
- Michael Tonsmeire has several great articles on Solera. Some noteworthy articles:
- Farmhouse Beer Blog, Outside the Box Solera - Details on Sherry solera production, and how it relates to beer production.
- Adam Kielich's blog on small batch Solera and blending pulls to make a Gueueze.
- Dan Pixley's solera project over the last 3 years in video playlist format.
In addition, see the Blogs Wiki page for blogs that may contain more articles on solera.
Yeast autolysis is the rupturing of dead yeast cells and produces meaty or rubbery off flavors . 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 . 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 .
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 Reusing a sour yeast cake.
Additional Articles on MTF Wiki
- Freccia, Nico. Beat Yeast Bite. Brew Your Own Magazine. April 1997. Retrieved 2/20/2015.
- Tonsmeire, Michael. Second Pull Wine Barrel Solera. The Mad Fermentationist Blog. Retrieved 2/20/2015.
- Tonsmeire, Michael. Second Pull Wine Barrel Solera. The Mad Fermentationist Blog. Comments section, July 30, 2014 at 9:39 PM. Retrieved 2/20/2015.