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[[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. Many commercial sour beers are bottle conditioned with fresh wine or Champagne yeast. If this yeast is still viable, it is possible that it could contribute to the fermentation profile under the right conditionsif pitched during primary fermentation when simple sugars are still available, however in most cases if the Champagne/wine yeast from bottle dregs is pitched after primary fermentation then it usually won't have a significant big impact on a beer if they are pitched after primary fermentation has finished. For example, While [[Saccharomyces#Killer_Wine_Yeast|killer wine strains]] can kill ale or lager yeast, and potentially lead to autolysis off-flavors, however reports of autolysis in aged sour beer are next to none, and many believe that 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 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 yeast will probably still be in suspension in the beer. 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 Champagne 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>.