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Wort Souring

729 bytes added, 17:50, 9 March 2018
added Yeast Harvesting
===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. 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 CO2. 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. However, some https://www.facebook.com/groups/MilkTheFunk/permalink/2017284411633096/ commercial brewers] have claimed that repitching WY3711 as many as 100 to 2000 generations in soured wort conditions has not been a problem. If this is attempted, repitching the yeast from the middle of the yeast cake will select for the more acid tolerant cells. It has been shown that brewers yeast can adapt to acidic conditions and become more tolerant of low pH conditions over time. See [[Saccharomyces#Fermentation_Under_Low_pH_Conditions|terminal acid shock]] for more information.
==See Also==

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