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[[File:Green_man_berliner.jpg|thumb|Mike Karnowski from Green Man Brewery Blueberry Berliner Weisse made from a yogurt starter]]''Yogurt Souring'' refers to the method of souring wort using unpasteurized yogurt. Greek yogurt is often made with ''Lactobacillus acidophilus'', a lactic acid producing bacteria that is also associated with some health benefits <ref>[http://en.wikipedia.org/wiki/Lactobacillus_acidophilus Lactobacillus acidophilus Wikipedia page. Retrieved 3/3/2015.]</ref>. Using cultures of ''L. acidophilus'' from yogurt reportedly can make a 3.0-3.5 pH sour wort in 24 hours, without producing vomit/fecal flavors and aromas. To sour 5 gallons of wort with yogurt, make a 1 liter batch of unhopped starter wort the day before brew day. Add 2-4 teaspoons of live yogurt to the starter wort. Maintain a 100-110°F (37.8-43.3°C) temperature for about 24 hours. On brew day, and after the 24 hour sour starter is finished, mash and sparge a low IBU wort as normal, boil for a few minutes, and then chill the wort down to 100-110°F (37.8-43.3°C). Pitch the yogurt starter into the wort, and hold the temperature as close to the 100-110°F (37.8-43.3°C) range as possible. Bubbling CO2 through the wort is advised if possible to prevent potential off flavors, but is not required. Within 24 hours, the wort should be down in the 3.x pH range. Boil the wort, adding any hops that the recipe calls for, yeast nutrient, etc., and then cool the wort down to Saccharomyces pitching temperatures. Bob's your uncle! <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1029598090401738/?comment_id=1030074730354074&offset=0&total_comments=25 Conversation with Mike Karnowski of Green Man Brewery on the MTF Facebook group. 3/3/2015.]</ref>

[[File:Sourgrains.jpg|thumb|100px|Derek Springer's grain starter]] If the brewer wants to use the LAB found naturally on the husks of grains, and doesn't want to risk pitching grains into the entire batch of wort, a Lacto starter culture with grain can be made. The benefit of this is that if the culture contains any vomit, fecal, or putrid aromas, it can be thrown away and tried again. If the starter needs to be dumped, try again with a different malt source; microbial populations can vary greatly between maltsters, harvest years, and malt type <ref>[[Grain#Microbial_Populations_on_Barley|Microbial Populations on Barley]]</ref>. The following is [http://www.fivebladesbrewing.com/lactobacillus-starter-guide/ Derek Springer's grain starter processon the Five Blades Brewing blog] <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1050331444995069/?comment_id=1050399004988313&offset=0&total_comments=18&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Conversation with Derek Springer on Milk The Funk. 4/4/2015.]</ref>:

If the starter is not going to be used right away, storing it in the fridge for up to a couple of weeks should be fine. If the starter still smells sweet/vegital then it should be ok to use. However if the starter starts to produce aromas of feces or vomit, do not use it <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1474146382613571/?comment_id=1474383142589895&comment_tracking=%7B%22tn%22%3A%22R4%22%7D Conversation with Bryan of Sui Generis Blog on MTF. 11/18/2016.]</ref>.  :'''Safety note''': do not drink wort from grain starters. It has been reported that wort soured from grain often carries live ''Salmonella bongori'' for at least two days after souring, which is probably not always safe to consume any of the grain starter until associated with non-lethal food poisoning. This microbe will die during or after it has become beer (see primary fermentation See [[Grain#Malt_Inoculated_Wort|Malt Inoculated Wort]] and [[Wild_Yeast_Isolation#Safety|Wild Yeast Starters and Safety]])for more information.''

===MTF "Reverse Kettle SourMTF Method"===Devin Bell has experienced getting good sourness by co-pitching probiotics with ''L. plantarum'' with yeast, or even after primary fermentation (also known as the "Reverse MTF Sour"). It is claimed that this method allows the yeast character Moved to be expressed more so than with kettle sours. In the case of pitching ''L. plantarum'' after fermentation, the beer turned out like a sour saison, where as co-pitched makes for a better Berliner Weisse or Gose style beer without the "saison" yeast character. This has also improved head retention in his beers. Using no hops seems to be required in order to get acid production from the ''L. plantarum'' probiotics after primary fermentation. Devin clarified that his "best success" is pitching ''S. cerevisiae'' saison strain with a selection of [[Mixed_Fermentation#Souring_Without_Brettanomyces|Mixed Fermentation; Souring Without ''Brettanomyces'' for primary fermentation. After 5-7 days of fermentation, he pitches ''L. plantarum'' (2 shots of GoodBelly or 1 package of Omega Labs OYL-605 for 5-6 gallons of beer) <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1739156616112545/?comment_id=1739183316109875&reply_comment_id=1739749539386586&comment_tracking=%7B%22tn%22%3A%22R%22%7D Devin Bell. Milk The FunkFacebook group. 06/30/2017.]</ref>. Once terminal gravity is reached (1.002-1.004), he bottles right away. The bottles can be served at 8 weeks in the bottle, but start to peak at 24 weeks. This process is really more of a short term [[Mixed Fermentation]] <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1562696320425243/?comment_id=1562702310424644&comment_tracking=%7B%22tn%22%3A%22R0%22%7D MTF discussion with Devin Bell on "reverse MTF kettle sour. 01/26/2017.]</ref>. See also [https://www.facebook.com/groups/MilkTheFunk/permalink/1217518078276404/ this thread by Devin Bell] and [https://www.facebook.com/groups/MilkTheFunk/permalink/1728489143845959/ this thread by Caroline Whalen Taggart]. * [https://www.facebook.com/SouthernBrewersConference/videos/881235365357984/ Devin Bell and Dan Pixley presentation at SBC 2017 on quick souring, including more details on this method.]