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==General Methods and Uses==
===Supplementing another fermentation===
Once the starter of the bottle dregs has sufficiently incubated, it can be pitched into another sour beer. The idea here is that the strong microbes from the commercial sour beer can enhance the overall complexity of the beer, especially if the beer's only in addition to whatever other inoculation was from a culture from a yeast companycultures have been pitched.
===Using as a primary fermenter===
Bottle dregs can also be used a primary fermenter. It is generally advised that mixing different bottle dregs together will provide a greater diversity and thus better results, but using a single bottle may prove to be an educational experience as well. Step the starter up to a 2 liter volume, incubate for another 7 days as above, then pitch into a ~20 liter batch. Alternatively, Jeffrey Crane describes a method of using 1 gallon of wort, which can easily be produced on a normal brew day from a larger batch, to create sour beer from bottle dregs. Essentially this process involves transferring 1 gallon of at wort any time during the boil when there are less than 7-10 IBU's. Another simple option is to make 1 gallon of wort from malt extract (DME or LME). That 1 gallon of wort is then used to pitch the sour beer dregs starter into.<ref>[http://www.homebrewtalk.com/f127/easy-way-make-sour-beers-1-gal-wort-dregs-189748/ Jeffrey Crane] describes how to make 1 gallon sour beers from bottle dregs.</ref> The brewer has the option of allowing the 1 gallon of sour beer to age on it's own, or it can be used as a starter itself for a larger batch. Pitch a smaller amount of the dregs starter for 1 gallon batches (~200 mL). ===Wort Souring, Co-pitching, and Staggered Pitching===If there was no signs of ''Saccharomyces'' fermentation in the dregs starter then another option is to pitch the starter of dregs into the wort, and allow for a day or two to pass before pitching a fresh pitch of ''Saccharomyces''. This has the benefit of allowing the lactic acid bacteria in the dregs starter to sour the wort before competing with ''Saccharomyces'' for sugar. See [[Sour_Worting#Souring_in_the_Primary_Fermenter|souring in the primary fermenter]] for more information on this technique. Co-pitching the dregs with a fresh pitch of ''Saccharomyces'' at the same time will often achieve a less acidic final product depending on how aggressive the bottle dreg cultures are, but can also result in more yeast-driven flavors. Pitching a sour culture after primary fermentation with brewers yeast has been reported to preserve more ''Saccharomyces'' yeast flavor. See the [[Alternative_Bacteria_Sources#MTF_.22Reverse_Kettle_Sour.22|"MTF Reverse Kettle Sour"]] for an example. ''Brettanomyces'' isn't greatly impacted by either pitching rate or if it is co-pitched with ''Saccharomyces'' or pitched after primary fermentation with ''Saccharomyces'', so the health of the ''Brettanomyces'' is not a concern if dregs containing ''Brettanomyces'' are co-pitched with ''Saccharomyces'' or if it is pitched after a primary fermentation with ''Saccharomyces''. See [[Brettanomyces#Primary_versus_Secondary_Fermentation|''Brettanomyces'' primary versus secondary]] for more information.
===Storing Dregs For Later Use===
* Pitch the dregs directly into a fermenter that already has beer in it.
* Have an air-locked vessel, such as a gallon jug or an Erlenmeyer flask, with an airlock on it with a starter beer (or fresh wort) ready to collect multiple bottle dregs.
* If the brewer wants to keep the dregs separate from other cultures or does not have another vessel available as previously described, leave the last quarter inch of the beer in the bottle itself. Recap the bottle if possible, and place it in the refrigerator. If it is not possible to recap the bottle because it is a corked bottle or a wider diameter than the brewer's bottle capper/caps, cover the bottle with plastic wrap or tin foil and a rubber band. Keeping the beer cool should prevent spoilage, although this is not guaranteed without more sanitary procedures such as purging the bottle with CO2 and capping it. Although brewers have successfully stored bottle dregs beers like this for months, it is generally advisable to make a starter for the dregs at least withing within a few weeks so as to avoid any potential spoilage.* ''Brettanomyces'' remains more viable over time if it was co-fermented with ''S. cerevisiae'' than if it was fermented by itself ([[100%25_Brettanomyces_Fermentation|100% ''Brettanomyces'' beers]]). Contrarily, ''S. cerevisiae'' loses viability over time faster when it is co-fermented with ''Brettanomyces'' <ref name="Hubbe">[https://www.facebook.com/groups/MilkTheFunk/permalink/1407620509266159/ Effect of mixed cultures on microbiological development in Berliner Weisse (master thesis). Thomas Hübbe. 2016.]</ref>. This is something to keep in mind when using dregs. ===Dregs From Natural Wine===Since natural wines are spontaneously fermented and often contain lower amounts of sulfite or no added sulfite, some beer brewers have attempted using the bottle dregs from commercial natural wines. See [https://www.facebook.com/groups/MilkTheFunk/permalink/3645548365473351/ this MTF thread] for experiences doing this.
==Potential Problems and Issues==
[[File:Mold dregs.jpg|thumbnail|right|([https://www.facebook.com/photo.php?fbid=1590340977863716&set=gm.1006273332734214&type=1&theater Starter made from bottle dregs from Monte Subite Geuze.] The green colored stuff is mold.) Photo provided by Matt Fanning.]]* ===The Dreaded Killer Champagne/Wine Yeast===In general, wine yeast is not a concern when it comes to using bottle dregs (even when making a starter). Many commercial sour beers are bottle conditioned with fresh wine or champagne Champagne yeast. If this yeast is still viable, it may is possible that it could contribute to the fermentation profileif pitched during primary fermentation when simple sugars are still available, however if the Champagne/wine yeast is pitched after primary fermentation then it usually won't have a big impact. While [[Saccharomyces#Killer_Wine_Yeast|killer wine strains]] can kill ale or lager yeast (killer ''Saccharomyces'' strains do not kill ''Brettanomyces'' or lactic acid bacteria), and potentially lead to autolysis off-flavors, reports of autolysis in aged sour beer are next to none, and in general autolysis is not a concern in beers containing living ''Brettanomyces'' since ''Brettanomyces'' can consume the compounds that are released during autolysis <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1779575335404006/?comment_id=1782868198408053&reply_comment_id=1783095121718694&comment_tracking=%7B%22tn%22%3A%22R%22%7D DeWayne Schaaf on autolysis flavors. Milk The Funk Facebook group. 08/07/2017.]</ref>. If this pitched into a beer that has already fermented the maltose and glucose, wine and champagne yeast won't have a significant food source, and therefore won't have an impact on the beer as far as producing flavor byproducts (most wine and champagne yeast strains are not efficient at fermenting maltotriose). Champagne/wine yeast could produce flavor compounds such as esters and thiols if it is introduced into wort during primary fermentation. When dregs containing viable Champagne/wine yeast are added to a starter, then that yeast will often grow into a healthier population, which could then have a large flavor impact from the Champagne/wine yeast if the starter is pitched into primary. If flavor contributions from bottling yeast are a concern(esters, thiols, etc.), then cooling the beer and leaving the sediment behind before building a starter may help to alleviate the problem, however , at least some the wine/champagne Champagne yeast will probably still be in suspension in the beer. The Dregs or a starter from dregs containing Champagne/wine yeast could be added after primary fermentation, which would eliminate any potential for the Champagne/wine yeast having a significant impact on the flavor as far as producing esters from fermentation. Additionally, the long term survival of many wine strains of ''Saccharomyces '' yeast is usually limited in a low pH sour beer, so if the bottled beer has aged for 6+ months then the chances of viable wine yeast being in the bottle are low <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1268830686478476/?comment_id=1269605776400967&reply_comment_id=1270016239693254&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Richard Preiss on MTF. 03/28/2016.]</ref>. Many brewers have had success using bottle dregs that were conditioned with killer strains of Champagne or wine yeast, and many consider it to be not a big concern due to the reasons previously mentioned. If the brewer wants to guarantee that only ''Brettanomyces'' and/or bacteria are cultured, then they must use isolation techniques to do so <ref>[http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602008000200007 Occurrence of killer yeast strains in industrial and clinical yeast isolates. MARCELO E BAEZA* , MARIO A SANHUEZA and VÍCTOR H CIFUENTES. 2008.]</ref>, or verify with the producer of the beer being used to see if Champagne or wine yeast was used for conditioning. See the [[Packaging#Re-yeasting|Packaging and Re-yeasting]] page for more details on killer wine yeast strains. ===Potential for Mold Growth===Mold growth, although rare, is a possibility. If mold begins to grow, throw out all of the beer and start over. See [[Mold]] for examples of identifying mold versus pellicles. ===How Old is Too Old?===A frequently asked question is, "How old of a bottle can I use to grow dregs?" This is ultimately an impossible question to answer, but the general advice is to try and use a bottle that is as young as possible, preferably less than one year old. Although ''Brettanomyces'' and lactic acid bacteria can survive for long periods of time in bottles, the conditions are still stressful on these organisms and not enough information on viability over time has been collected to answer this question for every given bottle of sour beer. Old bottles might not lead to growth in the starter. Signs of fermentation should be observed, including visual signs like cloudy wort, bubbles or a pellicle on the surface, and measured signs such as a drop in pH and gravity in the starter (measured signs of fermentation are better indicators of active fermentation than visual indicators). That said, ''Brettanomyces'' has been cultured from bottles of beer that are 10+ years old. For example, microbiologist [https://www.facebook.com/groups/MilkTheFunk/permalink/1352210248140519/ Richard Preiss has been able to culture ''Brettanomyces'' from very old bottles of commercial German Berliner Weisse]. Culturing microbes from very old bottles like these often requires agar plates and streaking techniques. If there are not enough viable cells in an older bottle of commercial sour beer, using a simple starter to grow them may fail because the starter may fail to ferment fast enough before other microbes such as mold take hold. If this is the case, for safety reasons do not consume the wort and consider growing the microbes from a different, fresher bottle. Using autoclaved or pressure cooked wort and jars might help with preventing other microbes from growing. ===Is There a List of Viable Bottles?===In general, almost all craft breweries do not pasteurize their mixed fermentation sour beer products. A few examples that do include New Glarus, New Belgium's sour beers prior to 2018 <ref>[https://beerandbrewing.com/the-best-18-beers-of-2018/ "The Best 18 Beers of 2018". Craft Beer and Brewing Magazine. Jamie Bogner , John Holl Oct 19, 2018.]</ref>, some [https://www.lambic.info/index.php?title=Special%3ASearch&profile=default&fulltext=Search&search=pasteurized Belgian lambic based beers (gueuze, kriek, framboise, and faro)], and most [[Flemish_Red-Brown_Beer|Belgian Flanders Red Brown beers]]. The only list of viable commercial bottles that we know of is [http://www.themadfermentationist.com/p/dreg-list.html Michael Tonsmeire's list of unpasteurized commercial sour beers.] Tonsmeire has stated that he will no longer maintain this list because of the effort needed to do so. For this reason, we also do not track unpasteurized commercial sour beers. If you are curious if a particular brewery pasteurizes or kettle sours their sour beer, it is recommended that you contact the brewery and ask them if the bottles dregs can be used to make sour beer. Most breweries will be friendly enough to answer your question.
==See Also==
* [[Brettanomyces]]
* [[Saccharomyces]]
* [[Sour WortingWort Souring]]
* [[Mixed Fermentation]]
* [[Wild Yeast Isolation]]