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→Notes On Safety
It is well documented that many pathogens can grow in wort when the pH is above 4.5 and ethanol is not present or very low. While it may be possible for pathogens to grow in the environment created by adding chalk to the starter, the chances of this are very low. There are a few reasons for this low risk. Firstly, typical brewing sanitation regimes and the use of commercial pure cultures of ''Lactobacillus'' should prevent unwanted microbes from contaminating the starter media. Additional steps can be taken with [[Quality Assurance|quality assurance]] to ensure the purity of the starter. Secondly, once the starter is added to wort and the wort drops below a pH of 4.6, any contaminating microbes will be killed. In the case of [[Wort_Souring#Souring_in_the_Boiler_.28Kettle_Sour.29|kettle souring]], any contaminating pathogens will be killed during the second boiling step. Finally, yeast fermentation will ensure that pathogens are not able to survive once the pH levels drop below 4.6 and ethanol is produced. For example, a similar pattern of pathogenic bacteria being killed by yeast growth and/or lactic acid bacteria growth can be seen in [[Spontaneous_Fermentation#Microbial_Succession_During_Fermentation|spontaneous fermentation]] where enteric bacteria are often inherently present during the early stages of fermentation, but are quickly killed as the pH drops and ethanol levels rise.
Storing the growth media with a pH above 4.5 for more than 3-4 days could result in a very small risk of botulism growth. Therefore, if the starter is going to be stored anaerobically for more than a few days, a target pH under 4.6 should be achieved to prevent the growth of botulism or other pathogenic contaminants. Additionally, the starter should be stored cold to further inhibit the growth of most potential contaminating microorganism species. For more information on the general risks of pathogens in beer/wort/starters, see the [[Wild_Yeast_Isolation#Safety|Wild Yeast Isolation Safety wiki page]], the [[Mold|Mold wiki page]], [https://suigenerisbrewing.com/index.php/2017/01/05/fact-of-fiction-can-pathogens-survive-in-beer-the-rdwhahb-edition/ this Sui Generis Blog post], and [https://beerandwinejournal.com/botulism/ this article on the small risk of botulism in wort that is stored for more than a few days by Chris Colby].
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