Changes

There is no basis for the idea that small amounts of oxygen that could get dissolved during wort souring has a great effect on ''Lactobacillus''. 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 can play a role in beer staling (see [[Aging and Storage]]). Some brewers believe that purging all oxygen out of the system will help to prevent aerobic contaminants 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.