13,590
edits
Changes
→Ropiness
===Oxygen===
There is no scientific basis for the idea that a small amount of oxygen itself that is dissolved during wort souring has a great effect on the flavors that ''Lactobacillus'' produces. Regardless, some brewers report more consistent results when purging oxygen with CO<sub>2</sub>. See [[Lactobacillus#Effects_of_Oxygen|Effects of Oxygen on ''Lactobacillus'']] and [https://www.facebook.com/groups/MilkTheFunk/permalink/1778865588808314/ this MTF thread] that discusses the anecdotal experience of brewers who do not purge with CO2CO<sub>2</sub>. The effects of oxygen on the beer could lead to other stability issues with the beer because the exposure to oxygen during wort production is thought to play a role in beer staling (see [[Aging and Storage]]), although hot side aeration is also thought to be a minor problem if at all <ref>[http://beersmith.com/blog/2014/01/31/flavor-stability-in-beer-with-dr-charlie-bamforth-beersmith-podcast-74/ Charlie Bamforth. Interview on BeerSmith about Hot Side Aeration. 01/31/2014. Retrieved 08/18/2017.]</ref>, and the impact of hot side aeration on sour beer has not been studied. Some brewers believe that purging all oxygen out of the system will help to prevent contaminating microbes that are aerobic (microbes that require oxygen) from creating [[Isovaleric_Acid#Kettle_Souring|isobutyric acid]]. Oxygen does not play a role in the production of [[Butyric Acid]] in wort soured beers because this compound is produced by anaerobic bacteria (bacteria that requires the absence of oxygen). Air/dust can carry contaminating microbes, which is a potential problem (see [[Wort_Souring#Contamination_Concerns|Contamination Concerns]] above), however, if the air is filtered somehow before entering the fermenting vessel then the oxygen itself shouldn't pose a problem to souring wort. Follow the links in this paragraph for more information.
===Yeast Harvesting===
It is generally recommended to not re-use yeast that has fermented a soured wort. This has a stressful impact on the yeast. Some brewers have reported trying this, and not having good results <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2119435291418007/?comment_id=2119664111395125&comment_tracking=%7B%22tn%22%3A%22R%22%7D Ryan Sandlin. Milk The Funk Facebook group thread on re-using kettle sour yeast. 06/06/2018.]</ref>. However, some [https://www.facebook.com/groups/MilkTheFunk/permalink/2017284411633096/ commercial brewers] have claimed that repitching WY3711 as many as 100 (in one case) to 2000 (in a second case) generations in soured wort conditions has not posed a problem for them. If this is attempted, repitching the yeast from the middle of the yeast cake will select for the more acid tolerant cells. Some yeast strains may not be able to adapt to these conditions as well as others (more data is needed), however, it has been shown that ''S. cerevisiae'' can adapt to acidic conditions and become more tolerant of low pH conditions from generation to generation. See [[Saccharomyces#Fermentation_Under_Low_pH_Conditions|terminal acid shock]] for more information.
Daniel LePage and Spencer Britton from Creature Comforts reported a "metallic" off-flavor from excess iron accumulation. The brewery found that yeast uptook most of the iron during fermentation and then released it over time. Removing as much of the yeast from the beer and as soon as possible resolved this issue. Creature Comforts resolved this by dumping the yeast from the bottom of the fermentation vessel daily for the first three days of yeast fermentation . They suspected that the iron is coming from storing the ''Lactobacillus'' culture after souring in a keg before repitching it for the next batch (Creature Comforts has been repitching the same ''Lactobacillus'' culture for 6 years at the time of their World Brewing Congress presentation in 2020). Iron build up also happened slowly in after packaging in cans, which supports their hypothesis that the yeast initially uptake the iron, but then begin to release it over time <ref>[http://sites.libsyn.com/315398/episode-116-kettle-souring-w-daniel-lepage-from-creature-comforts Bru Lab Podcast Episode 116: Daniel LePage, Director of Quality at Creature Comforts in Athens, Georgia, joins Cade in the lab this week to chat about kettle souring.]</ref>(~40 mins in).See also the [https://www.masterbrewerspodcast.com/194 MBAA Podcast episode 194 interview with Daniel LePage.]
===Ropiness===
Tonia Cornett of 10 Barrel reported having experienced a kettle sour beer becoming "ropy" (see [[Pediococcus#.22Ropy.22_or_.22Sick.22_Beer|Ropiness]]). The issue was resolved by boiling the wort <ref>[https://beerandbrewing.com/podcast-episode-252-tonya-cornett-of-10-barrel-brewing/ Tonia Cornett. Craft Beer & Brewing Magazine podcast episode 252. 08/05/2022. Retrieved 09/16/2022.]</ref>(~38 mins in).
==See Also==