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added section "Maintaining a Lactic Acid Bacteria Culture"
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 ~4.4 pH. 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 - 4.5 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 4.0 - 4.4 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===
It is possible to maintain a ''Lactobacillus'' culture from batch to batch of beer. One method that is common with commercial brewers is to collect an appropriate volume of the soured wort (after souring, but before pitching yeast). Commercial breers will often use a designated corny keg or sanke keg (depending on the colume that is required). After souring, wort will be transferred using a closed system into the keg. The keg is then refrigerateduntil it is needed for the next batch. Storing the soured wort cold is recommended, however the ''Lactobacillus'' might perform differently based on a number of variables such as how long it is stored (longer storage means less viability). Re-pitching might lead to an increase in acid production as well. we recommend experimenting with this process until repeatability can be achieved.
Homebrewers can use a similar process. For a 5 gallon batch of soured wort, collect around 1 liter of wort before pitching yeast. Keep the culture cold until the next use. If the culture is kept for more than a couple of months, then [[Lactobacillus#Starters_and_Pitching_Rate|create a 500 mL starter]] to ensure that the bacteria culture is still viable.
Yeast contamination is a concern when storing soured wort, especially in a sealed vessel such as a keg. If a yeast contamination goes unnoticed, then the keg can become heavily pressurized and potentially dangerous even when stored cold. We recommend regularly checking a keg of soured wort to ensure that over-pressurization does not occur, or use a spunding valve.
==Contamination Concerns==