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fixed pre-souring pH
Another method of finding out how much acid to add would be to pull a measured portion of the wort out, and add acid in measured amounts until the desired pH is reached. The amount of acid added can then be scaled up to the full volume of the wort. A.J. Delange suggests that the buffering capacity of wort might be half that of the mash (based on the kilograms of malt used in the mash) <ref name="delange_brungard">[http://www.homebrewtalk.com/showthread.php?t=587124 A.J. Delange. Homebrewtalk Thread. 07/19/2016.]</ref>.
Trial and error might be the most practical approach for homebrewers that don't have an abundance of wort to spare for finding out how much acid to add to a sample and scaling that up. Post boil, the wort pH is generally around 5.0 - 5.2. Adjusting the pH of wort before pitching ''Lactobacillus'' can then be done fairly easily by taking a trial and error approach. Using 1 mL of 88% lactic acid per .1 shift in pH for 5 gallons of wort is a good starting measurement. As an example, say that 5 gallons of wort has a pH of 5.0 just before pitching the ''Lactobacillus'' culture. Begin by adding 5 mL (1 US teaspoon) of food grade lactic acid to the wort for a target of around 4.4 pH (or somewhere between 4.2 and 4.8; target 4.0 - 4.3 if souring with grain or some other non-purified source of bacteria to help inhibit the growth of unwanted bacteria that could produce off-flavors). Stir gently, then take another pH reading. Continue to add 1-2 mL of lactic acid until the wort has the desired pH. Derek Springer has observed that it takes about one tablespoon (15 mL) of 88% lactic acid to reach a pH of 4.2 - 4.8 for 5 gallons of wort <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1290987234262821/?comment_id=1291031577591720&comment_tracking=%7B%22tn%22%3A%22R3%22%7D Conversation with Derek Springer on MTF regarding acidifying wort. 04/24/2016.]</ref>; however a higher amount may be required if the brewer's water is high in bicarbonate (24 mL for 5 gallons of wort to reach a pH of 4.4 was reported by Sean McVeigh for his water which contains 375ppm of bicarbonates <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1290987234262821/?comment_id=1291031577591720&reply_comment_id=1291118190916392&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Sean McVeigh on MTF on acidifying wort. 04/23/2016.]</ref>). Once a pH of 4.2 - 4.5 8 is reached, pitch the ''Lactobacillus'' culture. This small amount of lactic acid shouldn't have much of an impact on flavor. If a more precise method for determining the required amount of lactic acid is required, a sample of the wort can be pulled and lactic acid or phosphoric acid can be added to it until the target pH is reached, and then that amount can be scaled up (a micropipette might be required to measure very small amounts of lactic/phosphoric acid).
===Maintaining a Lactic Acid Bacteria Culture===