Changes

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).

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 brewers will often use a designated corny keg or sanke keg (depending on the volume that is required). After souring the wort a small portion will be transferred using a closed system into the keg. The keg is then refrigerated until it is needed for the next batch. Storing the soured wort cold is recommended for lengthening the viability of the ''Lactobacillus'' culture while also inhibiting the growth of any potential contaminants, 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 and finding the right pitching volume/storage time 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 in a jar before pitching yeast. Keep the culture cold until the next use. Don't seal the jar completely tight in case refermentation occurs in the jar. 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.

==Contamination Concerns==