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The brewing process is the same for any all grain batch up until the first wort and sparge runnings are collected into the boil kettle. The temperatures that a typical mash out/sparge reach should be enough to pasteurize the wort <ref name="pasteurization">[http://science.howstuffworks.com/life/cellular-microscopic/pasteurization4.htm Heat pasteurization]</ref>, however we advise heating the wort for a short (1-2 minutes) boil in order to kill a greater degree (2-3 logs more) of thermotolerant microbes <ref name="Heit_boiling">[https://www.facebook.com/groups/MilkTheFunk/permalink/1180630378631841/?comment_id=1180634488631430&reply_comment_id=1180677581960454&comment_tracking=%7B%22tn%22%3A%22R2%22%7D Conversation with Bryan of Sui Generis Blog regarding boiling versus lower temperature pasteurization. 11/18/2015.]</ref><ref>[http://sourbeerblog.com/lactobacillus-2-0-advanced-techniques-for-fast-souring-beer/ ''Lactobacillus'' 2.0 – Advanced Techniques for Fast Souring Beer. 11/18/2015. Retrieved 11/19/2015.]</ref>. Once all of the wort is collected in the boil kettle (and preferably brought to a boil), the wort is chilled to around 80-120°F (37-48°C), depending on the ''[[Lactobacillus]]'' culture that is being used. Once chilled to the temperature that is appropriate, the wort in the kettle is inoculated with a culture of ''Lactobacillus''. Hops should not be added at any point before inoculating the wort with a culture of ''Lactobacillus''; most species of ''Lactobacillus'' will be inhibited by the presence of hops. When using a pure culture of ''Lactobacillus'', it is generally a good idea to [[Lactobacillus#Starters_and_Pitching_Rate|create a 500 mL starter]] for ~5-6 gallons of wort.
There are various ways of inoculating the wort. A reliable method is pitching a pure culture of ''Lactobacillus'', or a blend of ''Lactobacillus'' cultures. Alternatively, a handful of unmilled malted barley can be added to the kettle for inoculation instead of a pure culture, since the husks of grain carry many microorganisms. If unmilled grain is added, it is thought that filling the head space of the kettle with CO2 will help decrease off-flavors such as "footiness" from [[Isovaleric Acid]], which are produced by aerobic microbes that are naturally present on the grain <ref name="khris_johnson">Personal correspondence with Khristopher Johnson of Green Bench Brewing Co. and Dan Pixley. 05/24/2016.</ref>. Keeping the temperature between 109-113°F (42.8-45°C) will encourage the ''Lactobacillus'' resident on the grain and will discourage other bacteria <refname="young_grains">[https://www.facebook.com/groups/MilkTheFunk/permalink/1356058381089039/?comment_id=1356464531048424&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Jeff Young from Blue Owl Brewing Co on souring from grains. 07/21/2016.]</ref>. Lowering the pH of the [[Sour_Worting#How_to_Pre-Acidify|wort to under 4.5 (ideally 4.0 - 4.3)]] will also discourage many other bacteria from thriving in the wort during the incubation period. This will also help with head retention <ref>[[Lactobacillus#Foam_Degradation]]</ref>. Consider [[Alternative Bacteria Sources]] for more reliable approaches to using "wild" ''Lactobacillus'', or ''Lactobacillus'' from sources other than yeast labs.
If a pure culture of ''Lactobacillus'' bacteria is used it is ideal but not necessary to fill the head space of the fermenter with CO2 gas (some brewers have reported that this will help reduce sulfur in the finished beer). Keeping positive pressure in the kettle with CO2 will help prevent contaminates that create [[Butyric Acid|butyric acid]] and other off-flavors from entering the kettle due to negative pressure, and is often the approach that commercial brewers take <ref>Personal correspondence with Steph Cope of CraftHaus Brewing Co. 02/06/2016.</ref>. The kettle should be held at the desired temperature for 24-72 hours (in some cases longer, but no longer than 5 days). Depending on the strain of ''Lactobacillus'', and the desired sour level, the time of incubation is ultimately a variable that is up to the brewer (see the ''[[Lactobacillus]]'' page for suggested temperatures and times for specific strains). The kettle lid should be firmly in place and optionally sealed with plastic wrap so that other microorganisms do not get in. Potential for formation of [[Butyric Acid]] and [[Isovaleric Acid]] when using only a pure culture is extremely slight to none assuming contamination does not occur.
This process is very similar to sour worting in the kettle. This method is ideal for those who wish to use grains to introduce ''Lactobacillus'' to the beer. If done properly, the formation of [[Butyric Acid]] and [[Isovaleric Acid]] should be minimal.
The wort is mashed and sparged as normal (and alternatively brought to a short boil), and is then lowered to somewhere between 113-120°F (45-48.8°C). This temperature favors ''Lactobacillus'', while discouraging Enterobacteriaceae. Optionally, the mash pH can be lowered to 4.4 with lactic acid or acidulated malt to further discourage Enterobacteriaceae activity. Once the desired temperature (and optionally pH) is reached, a handful of fresh malted unmilled grain is added to the mash and allowed a few minutes to inoculate the mash with the microbes found naturally on the grain husks. The wort is then transferred to a second vessel such as a glass carboy. The vessel should be filled to the very top, minimizing the oxygen levels inside the vessel. The vessel should be stored in a heated environment that maintains a temperature between 113109-120°F 113°F (4542.8-48.8°C45°C) for 1 to 4 3 days depending on how much acidity the brewer wants (3 days is a good rule of thumbthe faster the souring process the better; Jeff Young from Blue Owl achieves the desired acidity in about 18 hours usually) <ref name="young_grains"></ref><ref name="james_spencer">[http://beerandwinejournal.com/sour-wort-berliner/ Spencer, James. December 15, 2014. Beer and Wine Journal.] </ref>.
Once the 1 to 4 day time period has been reached, the wort is transferred to the boil kettle and boiled as normal. Boiling will kill all of the microorganisms in the wort, and will provide the option for adding hops and other kettle additions. Just as with kettle souring, the wort doesn't have to be boiled, but can be instead heat pasteurized at 170°F (76.6°C) for 15 minutes <ref name="pasteurization" />, or at 140°F (60°C) for 15 minutes if a yeast contamination produced a significant amount of alcohol. Once boiled or pasteurized, the wort can be chilled and handled in the same way as the above methods for wort souring.