Changes

After prolonged time in a bottle, microorganisms won't be at their peak vitality, and so making a starter for dregs is recommended in general. ''Saccharomyces'' strains may or may not be viable at all after an extended time in a low pH beer, but ''Brettanomyces'' and some lactic acid strains are more acid-tolerant and should be viable. Making a "step" starter is the best practice for ensuring that a high enough population of microbes are pitched. Begin by making a ~100 mL DME starter of usual strength (1.030-1.040 SG) <ref name="preiss">[https://www.facebook.com/groups/MilkTheFunk/permalink/1268830686478476/?comment_id=1269605776400967&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Richard Preiss on step starters for dregs on MTF. 03/27/2016.]</ref>. Hops should not be used unless the brewer wants to try and suppress the ''Lactobacillus'' in the commercial beer (''Lactobacillus'' strains for some commercial breweries are fairly hop tolerant up to 20-25 IBU. See [[Lactobacillus#Hop_Tolerance|Lactobacillus Hop Tolerance]] for more information). If the brewer has only one bottle or wants to keep multiple bottle dregs separate from each other, the starter wort can be poured directly into each bottle and covered with plastic wrap. Alternatively, the dregs from multiple bottles can be combined into a single vessel (such as an Erlenmeyer flask or glass jug) with the starter wort, and covered with sanitized tin foil to allow an exchange of oxygen and CO2. The mouth of the bottle may be flamed with a lighter to kill any wild yeasts that might have landed on the area. The dregs don't need to be "washed" or treated in any special way before being added to the starter wort.

The starter should be stored at room temperature for at least 5-7 days and sometimes longer if growth does not occur within that time. It can be stored at a higher temperature if bacteria is the main microbe that the brewer is after, although avoid going above 86°F/30°C. Monitor the starter for activity during this time to ensure that there are viable microbes. Visual activity may not always be present, may be brief, or minimal. Visual indicators of successful growth include turbidity and continuously produced bubbles on the surface of the liquid. Monitoring the pH and the gravity can assist the brewer with deciding whether or not the commercial sour beer has any viable microorganisms still alive in it. If the starter krausens within 2-3 days then it might have viable ''Saccharomyces'', otherwise strains of ''Saccharomyces'' might be dead (especially if the beer was not freshly bottled and was a low pH sour beer). ''Brettanomyces'' may not show signs of fermentation for up to 3-7 days (in some cases and depending on the viability of the microbes, signs of growth may not appear until up to 2 weeks). Once the starter starts showing signs of fermentation, it should be aged for another 3-7 days to finish fermentation. After the fermentation starts to slow, create a another 1 liter starter of DME wort, and add the original 100 mL dregs starter to it. Repeat the process above, giving the 1 liter starter another 5-7 days of growth <ref name="preiss"></ref>. Pitch the 1 liter starter into a ~20 liter batch, or continue to step up the starter for larger batch sizes. Avoid storing the starter for extended amounts of time because a low pH could result in lower viability over time in an acidic environment; see [[Mixed_Fermentation#Storing_a_Yeast_Cake_or_Sample|Storing a Yeast Cake]] and [[Mixed_Cultures#Starters_and_Other_Manufacturer_Tips|Mixed Culture Starters]] for more information.