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Wort Souring

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Ropiness
'''Wort Souring''' is the process of [[Mixed Fermentation]] where acidifying wort by inoculating it with lactic acid bacteria, usually ''[[Lactobacillus]]'' (although there are also ''[[Pediococcus]]'' cultures available that work well for this technique), is given a "head start" as it's pitched before the yeast so that it will be able to ferment and produce significant amounts of lactic acid before inoculating with yeast to perform the ''Saccharomyces'' completes the main primary alcoholic fermentation. While non-sour beer falls in the range of 3.8-4.6 pH, a final pH between 3.0 and 3.7 is the general target range for the soured wort and also the finished sour beer (although note that [[Titratable Acidity]] is more accurate for measuring perceived sourness). This is a broadly defined technique and there are many variations on souring wort. These include [[Mixed Fermentation|mixed fermentation]] methods such as souring in the primary fermenter, souring in for a secondary vesselshort time period before adding yeast, or pre-boil acidification such as souring in the boil kettle itself with a pure culture of lactic acid bacteria and then boiling to pasteurize the sour wort before yeast is added ('''[[Wort_Souring#Souring_in_the_Boiler_.28Kettle_Sour.29|kettle souring]]'''). There are also various methods of inoculating the wort with ''Lactobacillus''<ref>[https://www. researchgate.net/publication/341353855_The_power_of_sour_-_A_review_Old_traditions_new_opportunities Bossaert, Sofie & Crauwels, Sam & De Rouck, Gert & Lievens, Bart. (2019). The power of sour - A review: Old traditions, new opportunities. BrewingScience. 72. 78-88. 10.23763/BrSc19-10bossaert.]</ref><ref>[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.569 FinallyDysvik, A., Liland, K. H., Myhrer, K. S., Westereng, B., Rukke, E.-O., de Rouck, the brewer has the option of pasteurizing the wort by heating it to kill the ''Lactobacillus'' before adding the yeast for the main G., and Wicklund, T. (2019) Pre-fermentationwith lactic acid bacteria in sour beer production. J. Inst. Brew., 125: 342– 356. https://doi.org/10.1002/jib.569.]</ref>.
Although this process generally does not include the use of ''Brettanomyces'', some creative brewers have applied wort souring techniques to longer aged [[Mixed Fermentation]] beers and barrel aged beers that do contain ''Brettanomyces''.
Many brewers prefer this process over [[Sour Mashing]] because it can be easier to control, and when implemented properly, it produces a clean sour beer in a short amount of time. However, the environment created provides an ideal situation for contaminations and great care should be taken to prevent contamination of both yeast and spoilage microbes (see [[Wort_Souring#Contamination_Concerns|Contamination Concerns]] below).
The possibility of pasteurizing the soured wort also makes this a good method for making sour beers with a lot of residual malt sweetness (e.g. sour barley wines), and also makes it an attractive process for brewers who are concerned about infection issues in their cold side equipment (equipment that is used post-boil) <ref>[http://sourbeerblog.com/fast-souring-lactobacillus/ Miller, Matt. Dec 20, 2014. "Fast Souring with ''Lactobacillus'' – Best Practices, Sensory, & Science". Sour Beer Blog.]</ref>. When souring wort, some brewers first [[Wort_Souring#How_to_Pre-Acidify|lower the pH of the wort to 4.0-4.3]] before pitching ''Lactobacillus''. This sometimes helps the head retention of the beer , and it sometimes helps to protect the wort from contaminating microorganisms. For more information preventing the loss of head retention in sour beers, see the [[Lactobacillus#Foam_Degradation|''Lactobacillus'' page section on Foam Degradation]].
Generally, ''[[Pediococcus]]'' is not used with this method (''Pediococcus'' is generally used in long aged [[Mixed Fermentation]] sours with ''[[Brettanomyces]]''); however, however [[Pediococcus#Commercial_Pediococcus_Cultures|Bootleg Biology]] has released a blend of ''Pediococcus'' strains that are reportedly good effective to use for all wort souring wortmethods.
Important note regarding aluminum pots: souring in an aluminum vessel may strip the aluminum of the protective oxide layer. The oxide layer is only stable at a pH of 4.5 - 8.5. Therefore, kettle souring in an aluminum pot is generally not recommended <ref>[http://www.pfonline.com/articles/aluminum-surface-finishing-corrosion-causes-and-troubleshooting Aluminum Surface Finishing Corrosion Causes and Troubleshooting. W. John Fullen, Boeing Research and Technology & Jennifer Deheck, Boeing, Seattle, Washington, USA. 10/17/2014.]</ref>. Stainless steel (304 and 316) vessels are safe for holding acidified wort or beer, as well as PET and HDPE plastics <ref>[http://www.plasticsintl.com/plastics_chemical_resistence_chart.html Chemical Resistance Chart. Plastics International. Retrieved 01/03/2017.]</ref>.
===''Lactobacillus'' Nutrient Requirements===
Different strains of ''Lactobacillus'' are known to have different nutrient requirements, including some metal ions. ''Lactobacillus'' requires manganese, magnesium, potassium, and sodium, with manganese and magnesium being crucial for their growth. Brewer's wort has many of these nutrients naturally, although zinc is generally deficient. One study looked at WLP672 (''L. brevis'') and found that an increase of magnesium resulted in a faster souring phase, while zinc additions slightly slowed the souring phase. This suggests that in at least the case for this strain of ''L. brevis'', zinc additions should be added after the souring phase for yeast health. Excess magnesium could lead to negative flavor contributions to beer, so magnesium additions should be limited to not exceed 30 mg/l <ref>[https://www.brunwater.com/water-knowledge "Water Knowledge." Martin Brungard. Bru'n Water website. Retrieved 12/02/2020.]</ref>. The addition of zinc also had several effects on the flavor and aroma compounds produced. Therefore, experimenting with different nutrient additions for the souring phase may result in widely different tasting beer <ref>[https://www.mdpi.com/2218-273X/10/12/1599 Chemical Composition of Sour Beer Resulting from Supplementation the Fermentation Medium with Magnesium and Zinc Ions. Aneta Ciosek, Katarzyna Fulara, Olga Hrabia, Paweł Satora, and Aleksander Poreda. 2020. DOI: https://doi.org/10.3390/biom10121599.]</ref>. See [https://www.facebook.com/groups/MilkTheFunk/permalink/4107425732618943 this MTF thread] for more commentary on this study.
==Processes==
===Souring in the Boiler (Kettle Sour)===
Also known as '''kettle souring''', souring in the boil kettle (or another vessel) is a simple process that is often used if the brewer wants to subsequently heat pasteurize the wort. Pasteurizing the wort has the advantage of allowing the brewer to rack the pasteurized wort into a fermenter and pitch brewer's yeast without fear of an ongoing ''Lactobacillus'' infection in their post-boil equipment. This process was originally invented by a German scientist named Otto Francke, and called the "Francke acidification process". It was designed by Francke as a way to shortcut the mixed culture fermentation of Berliner Weisse; however, this process was never really used in Berliner Weisse production because it did not produce a product that resembled Berliner Weisse that was fermented with a mixed culture of yeast and bacteria (including ''Brettanomyces''). See the [[Berliner_Weissbier|Berliner Weisse]] page for more information on the history of Berliner Weisse production methods <ref name="marshall">[https://drive.google.com/file/d/0B8CshC9nxYHdckhlbXFQN1hPbGc/view Kurt Marshall. CBC 2012 Presentation.]</ref><ref>[https://eurekabrewing.wordpress.com/2012/03/10/44-traditional-berliner-weisse/ Samuel Aeschlimann. Eureka Brewing Blog. "#44 Traditional Berliner Weisse". 03/10/2012. Retrieved 09/02/2017.]</ref><ref>[http://barclayperkins.blogspot.com/2020/09/kettle-souring.html Shut up about Barclay Perkins. "Kettle Souring". Ron Pattinson. 09/17/2020.]</ref>.
The brewing process is the same for any all-grain batch up until the first wort and sparge runnings are collected in the boil kettle. The temperatures that a typical mash out/sparge are not enough to completely pasteurize the wort <ref>[https://onlinelibrary.wiley.com/doi/epdf/10.1002/j.2050-0416.2005.tb00221.x Enhancing the Microbiological Stability of Malt and Beer – A Review. Anne Vaughan, Tadhg O’Sullivan and Douwe van Sinderen. 2005.]</ref><ref>[https://elifesciences.org/articles/04634 Mapping microbial ecosystems and spoilage-gene flow in breweries highlights patterns of contamination and resistance. Nicholas A Bokulich, Jordyn Bergsveinson, Barry Ziola, David A Mills. 2015.]</ref><ref>[http://mmbr.asm.org/content/77/2/157.full The Microbiology of Malting and Brewing. Nicholas A. Bokulich and Charles W. Bamforth. 2013. DOI: 10.1128/MMBR.00060-12.]</ref>. Therefore, the best approach is to heat the wort for a short boil (1-2 minutes) in order to kill a greater degree (2-3 logs more) of thermotolerant microbes <ref name="Heit_boiling">[https://www.facebook.com/groups/MilkTheFunk/permalink/1180630378631841/?comment_id=1180634488631430&reply_comment_id=1180677581960454&comment_tracking=%7B%22tn%22%3A%22R2%22%7D Conversation with Bryan of Sui Generis Blog regarding boiling versus lower temperature pasteurization. 11/18/2015.]</ref><ref>[http://sourbeerblog.com/lactobacillus-2-0-advanced-techniques-for-fast-souring-beer/ ''Lactobacillus'' 2.0 – Advanced Techniques for Fast Souring Beer. 11/18/2015. Retrieved 11/19/2015.]</ref><ref name="pasteurization">[http://www.mbaa.com/meetings/districtpresentations/DistrictPresentations/2011_03_10PasteurizationTechnologies.pdf "District Michigan MBAA Technical Meeting Grand Ledge, MI". MBAA Presentation. 2011.]</ref>. Once all of the wort is collected in the boil kettle (and preferably brought to a boil), the wort is chilled to around 80-115°F (37-46°C), depending on the ''[[Lactobacillus]]'' culture that is being used (see . <blockquote style="background-color: lightgrey; border: solid thin grey; padding:10px;">The optimal fermentation temperature is different for different species of ''Lactobacillus'' as well as different strains within the same species, and fermenting outside of the recommended range can result in the lack of souring. Consult your yeast lab's website and documentation to determine the optimal fermentation temperature range for your given ''Lactobacillus'' product. See also the [[Lactobacillus#Culture_Charts|''Lactobacillus'' culture charts]]. If your ''Lactobacillus'' fermentation temperature range is unknown, the [[Lactobacillus#Culture_Charts|''Lactobacillus'' culture charts]]may provide some guidance based on species if the species is known. Otherwise, experimentation will be needed to find the best temperature (we recommend making different starters and holding them at different temperatures and measuring pH drop over time to find the optimal fermentation temperature). Note that some ''Pediococcus pentosaceus'' cultures such as [[Pediococcus#Bootleg_Biology_on_Sour_Weapon_P|Bootleg Biology's "Sour Weapon P"]] can also be used to kettle sour.</blockquote>Once chilled to the appropriate temperature, the wort in the kettle is inoculated with a culture of ''Lactobacillus''. The chilled wort can alternatively be transferred to another vessel where the ''Lactobacillus'' is added for the acid producing fermentation and then afterwards sent back to the boiler to pasteurize the acidified wort and kill the lactic acid bacteria. Hops should not be added at any point before inoculating the wort with a culture of ''Lactobacillus'' as most species of ''Lactobacillus'' will be inhibited by the presence of even very small amounts hops (1-2 IBU or even just hop material from dry hopping). When using a pure culture of ''Lactobacillus'', it is generally a good idea to [[Lactobacillus#Starters_and_Pitching_Rate|create a 500 mL starter]] for ~5-6 gallons of wort.
There are various ways of inoculating the wort. A reliable method is pitching a pure culture of ''Lactobacillus'' or a blend of ''Lactobacillus'' cultures. Alternatively, a handful of unmilled malted barley can be added to the kettle for inoculation, similar to how [http://www.lowoxygenbrewing.com/ingredients/a-sauergut-reactor/ sauergut] is made, instead of a pure culture since the husks of [[Grain|grain]] carry many microorganisms. If unmilled grain is added it is thought that filling the head space of the kettle with CO<sup>2</sup> (or another gas like argon or nitrogen; always provide proper ventilation when working with any gasses <ref>[https://www.brewersassociation.org/press-releases/brewers-publications-presents-gose-brewing-a-classic-german-beer-for-the-modern-era/ Allen, Fal. "Gose: Brewing a Classic German Beer For the Modern Era". Brewers Publications. 2018. Pg 126.]</ref><ref>[https://beerandbrewing.com/dictionary/DfG8FdFjfm/nitrogen/ Nick R Jones. "The Oxford Companion to Beer definition of nitrogen". Craft beer & Brewing Magazine website. Retrieved 10/21/2018.]</ref>) will help decrease off-flavors such as "footiness" from [[Isovaleric Acid]] which are produced by aerobic microbes that are naturally present on the grain <ref name="khris_johnson">Personal correspondence with Khristopher Johnson of Green Bench Brewing Co. and Dan Pixley. 05/24/2016.</ref>. Keeping the temperature between 109-115°F (42.8-46°C) will encourage the ''Lactobacillus'' resident on the grain and will discourage other bacteria. Temperature consistency is critical during this process <ref name="young_grains">[https://www.facebook.com/groups/MilkTheFunk/permalink/1356058381089039/?comment_id=1356464531048424&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Jeff Young from Blue Owl Brewing Co on souring from grains. 07/21/2016.]</ref>. Lowering the pH of the [[Wort_Souring#How_to_Pre-Acidify|wort to under 4.5 (ideally 4.0 - 4.3 when souring with grain)]] with lactic acid or phosphoric acid will discourage other unwanted bacteria and wild yeast from thriving in the wort during the incubation period. This will also help with head retention (see [[Lactobacillus#Foam_Degradation|''Lactobacillus'' and head retention]]) <ref>[[Lactobacillus#Foam_Degradation]]</ref>. Souring with grains should occur within 1 or 2 days if done correctly <ref name="young_grains"></ref>. Do not consume wort that has been soured with grains until after it has been fully fermented by yeast because there is a chance that food poisoning pathogens will be present until ethanol is produced. See [[Grain#Malt_Inoculated_Wort|Blue Owl Brewing's grain inoculation methodology and data]] for more information on inoculating with grain. Consider [[Alternative Bacteria Sources]] for more reliable approaches to using "wild" ''Lactobacillus'', or ''Lactobacillus'' from sources other than yeast labs.
If a pure culture of ''Lactobacillus'' bacteria is used it has historically been recommended to fill the head space of the fermenter with CO<sup>2</sup> gas or another type of gas like argon or nitrogen to purge the oxygen (oxygen does not cause ''Lactobacillus'' to produce [[Butyric Acid|butyric acid]] or [[Isovaleric Acid|isovaleric acid]], but some brewers have reported that purging oxygen will help reduce sulfur in the finished beer). Purging oxygen could also discourage [[Mold|mold]] growth. Mold growth during the souring process has been reported from time to time by homebrewers, and if mold grows in contact with the wort then it probably should be discarded (see the [[Mold]] page for more information) <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2144219142272955/ Pavel Dunn. Milk The Funk Facebook group thread on mold growth during kettle souring. 06/23/2018.]</ref>. However, many homebrewers and some professional brewers have reported having success without purging with CO<sup>2</sup> <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1778865588808314/ Various members of Milk The Funk. Milk The Funk Facebook thread on purging kettle sours with CO<sup>2</sup>. 08/03/2018.]</ref><ref>[https://www.milkthefunk.live/podcast/2018/4/2/episode-004-kettle-souring-with-adi-hastings-from-omega-yeast-labs Adi Hastings. Milk the Funk "The Podcast"; Episode #004. 04/02/2018. Retrieved 04/16/2018.]</ref>(~20:30 mins in), and a [http://brulosophy.com/2018/04/16/the-impact-of-open-fermentation-on-kettle-sour-beer-exbeeriment-results/ Brulosophy blind triangle test] was unable to find a significant difference between a kettle sour that was CO<sup>2</sup> purged and one that was soured in an open vessel. Using some CO<sup>2</sup> to keep positive pressure in the kettle could help prevent contaminants that create [[Butyric Acid|butyric acid]] and other off-flavors from entering the kettle due to negative pressure, and is often the approach that commercial brewers take <ref>Personal correspondence with Steph Cope of CraftHaus Brewing Co. 02/06/2016.</ref>. The kettle should be held at the desired temperature for 24-72 hours (in some cases longer, but no longer than 5 days- slower acidification increases the chances of the growth of contaminating microbes and off-flavor production from contaminating microbes and/or unwanted alcohol production from contaminating yeast). Depending on the strain of ''Lactobacillus'', and the desired sour level, the time of incubation is ultimately a variable that is up to the brewer (see the ''[[Lactobacillus]]'' page for suggested temperatures and times for specific strains). The kettle lid should be firmly in place and optionally sealed with plastic wrap so that other microorganisms do not get in. Potential for the formation of [[Butyric Acid]] and [[Isovaleric Acid]] when using only a pure culture is extremely slight assuming that contamination does not occur. Temperature shifts during kettle souring are not a concern as long as the temperature does not get too high or low for the specific ''Lactobacillus'' culture. Some species, such as ''L. plantarum'', create acidity at room temperature so some brewers will pitch this strain at around 90-100°F and let the temperature fall to room temperature during souring. Other species might not perform as well at colder temperatures so maintaining a fairly consistent hot temperature is desirable. If the temperature is allowed to fall, take precautions on not allowing any dust to get sucked into the fermenter since temperature decreases will create a vacuum inside the fermenter (flushing with CO<sup>2</sup> is a good way to prevent a vacuum).
In order to address the challenges of creating a sealed environment in a commercial boil kettle, which is often left open to the environment through the boil stack, some commercial brewers find it beneficial to rack the wort from the boil kettle to a mashtun, brite tank, fermenter (often dedicated), or another vessel that seals and purges well to sour in. The mashtun or other vessel is first cleaned, sanitized, and often purged with CO<sup>2</sup>. Once the wort is in the vessel, and at the correct temperature for the given culture of ''Lactobacillus'', the ''Lactobacillus'' is pitched into the vessel and the vessel is sealed off. If the vessel is sealed and air tight temperature shifts from cooling won't suck air into the vessel and a potentially more sanitary souring fermentation will occur. Using a fermenter or brite tank (if there are multiple) has the advantage of not occupying a bottleneck vessel such as the mashtun or boil kettle, but has more risk if the fermenter is not dedicated to kettle souring. Dedicating removable soft parts like gaskets and hoses will minimize the risk of infection originating from the fermenter or brite tank if it is not dedicated to souring <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1778027798892093/ Various professional brewers. Milk The Funk Facebook post about souring in a mashtun, brite tank, or other vessel for commercial brewers. 08/02/2017.]</ref>.
See also:
* [https://www.milkthefunk.live/podcast/2018/4/2/episode-004-kettle-souring-with-adi-hastings-from-omega-yeast-labs MTF "The Podcast" interview with Adi Hastings of Omega Yeast Labs on kettle souring] and [https://www.milkthefunk.live/podcast/2018/11/26/episode-007-lactobacillus-microbiology-with-dr-bryan-heit-of-sui-generis-brewing-blog episode #007 ''Lactobacillus'' microbiology with Dr. Bryan Heit].* [https://fb.watch/5I4mUUvQKC/ Brewing Network, Brew Strong interview with Fal Allen from Anderson Valley Brewing (author of "Gose: Brewing a Classic German Beer for the Modern Era") on kettle souring in commercial breweries.]
===Souring in the Primary Fermenter===
==Various Other Concerns==
===Failed Souring===
There are instances where wort souring fails for seemingly unknown reasons. Use a species or strain of ''Lactobacillus'' that is adapted well to souring wort within 24 hours, such as ''L. plantarum''. The lactic acid bacteria sometimes do not survive well during storage over long periods of time, so viability should be checked for long stored or mishandled cultures. Contamination with yeast can also prevent souring in some instances but not all. The use of hops should be avoided even for hop tolerant species (unless the brewer is experienced enough to predict the souring based on their lactic acid bacteria), and especially avoided if using ''L. plantarum''. Residual iso-alpha acids on the walls of kettle tanks/heat exchangers/piping could be enough to inhibit some strains of ''Lactobacillus'', specifically ''L. plantarum'', so kettles/heat exchangers/piping that have previously held highly hopped wort might need to be scrubbed clean before being used as a souring tank <ref>[https://www.stitcher.com/show/craft-beer-brewing-magazine-podcast/episode/episode-199-alex-flores-of-urban-south-kettle-sours-the-hard-way-85931878 Alex Flores. Craft Beer & Brewing Podcast. Episode 199: Alex Flores of Urban South Kettle-Sours the Hard Way. Retrieved 09/16/2021.]</ref>(~21 mins in)[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. Retrieved 10/06/2023.](~30 minutes in).
 
===Not Boiling and Dimethyl Sulphide (DMS)===
This is generally not a concern. See [[Dimethyl Sulfide]] for an explanation why.
===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==
===External Resources===
* [https://www.youtube.com/watch?v=LuVoydgzK8w Kettle souring; video presentation by Escarpment Labs.]
* [https://www.falsebottomedgirls.com/podcast/episode/d1c37e22/episode-25-whats-the-strain-its-lactobacillus False Bottom Girls Podcast Episode 25: What's the Strain? It's Lactobacill(us)!" - In depth discussion on kettle souring.]
* [http://suigenerisbrewing.blogspot.com/2015/07/how-i-sour-mash-recipe.html "How I Sour Mash & A Recipe"; Sui Generis Blog (includes Wort Souring and microbiology information).]
* [http://www.fivebladesbrewing.com/year-sour-mash/ "Year of the Sour Mash" by Derek Springer. This series of articles were written for his NHC 2015 presentation.]
* [http://brulosophy.com/2016/11/14/boil-vs-no-boil-berliner-weisse-exbeeriment-results/ "Boil vs. No-Boil Berliner Weisse | exBEERiment Results!" on Brulosophy blog.]
* [https://byo.com/article/catharina-sour-brazilian-kettle-soured-fruit-beer/ Catharina Sour – A Brazilian kettle-soured fruit beer.] See also thoughts on this style making it to the BJCP Style Guidelines [https://www.facebook.com/groups/MilkTheFunk/permalink/2167029939991875/ on MTF].
* [https://beerandbrewing.com/podcast-episode-252-tonya-cornett-of-10-barrel-brewing/ Tonia Cornett from 10 Barrel. Craft Beer & Brewing Magazine podcast episode 252.]
* [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.]
==References==

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