Changes

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.

Deciding whether or not to boil the wort can also depend on whether or not there was a considerable amount of alcohol produced, which commonly happens when the wort is contaminated with yeast. Pure cultures of ''Lactobacillus'' do not show typical signs of fermentation that we are used to seeing with yeast fermentations, such as forming a krausen, producing a lot of CO2, or fermenting wort more than ~1.005 gravity points (see [[100% Lactobacillus Fermentation]]). If a yeast contamination produces a significant amount of alcohol during the souring process, then this presents a problem when it comes to boiling. Although 100% pure ethanol boils at 173.1°F/78.4°C <ref name="boiling_of_alcohol">[http://chemistry.about.com/od/moleculecompoundfacts/f/What-Is-The-Boiling-Point-Of-Alcohol.htm Boiling temperature of ethanol]</ref>, the lower the concentration of ethanol in the wort (technically beer at this point), the higher the temperature required for boiling off the ethanol. For example, at 5% ABV it takes approximately 197°F/92°C for the ethanol to boil <ref>[http://www.clawhammersupply.com/blogs/moonshine-still-blog/12243869-making-moonshine-still-temperature Making Moonshine: Still Temperature. Retrieved 01/11/2016.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1212116758816536/?comment_id=1212140998814112&comment_tracking=%7B%22tn%22%3A%22R%22%7D Conversation with Russell Carpenter on MTF. 01/11/2016.]</ref>. Time is also required to boil off the ethanol, so this may not be as big of a concern as it first appears (''warning: vaporized ethanol is highly flammable)''. Another and perhaps more important consideration is that, unlike unfermented wort, boiling and high heat pasteurization temperatures can have a negative effect on the flavor of fermented beer. Beer already has anti-bacterial properties, such as low pH, presence of alcohol, and hops (although hops may not be present in wort being soured), so higher pasteurization temperatures aren't necessarily required for beer. For these reasons, the beer industry commonly heat pasteurizes beer at 140°F/60°C for 15 minutes, and this is also adequate for pasteurizing soured beer <ref>[http://www.sciencedirect.com/science/article/pii/S0023643806002854#bib16 A suitable model of microbial survival curves for beer pasteurization. Sencer Buzrul. 2006.]</ref>. In the case of an accidental yeast contamination during the souring process, another option is to simply dump the batch and start again with a pure culture of ''Lactobacillus''.

The process is very similar to the kettle souring technique, except the wort is never pasteurized after it is soured. The all grain brewing process is the same for any all grain brewing process, except that after the boil the beer is only chilled to the recommended temperature for the ''Lactobacillus'' strain that the brewer is going to use. Using grain husks for souring with this method is not advised since the grain will stay in the fermenter during primary fermentation, and unwanted microbes on the grain husks would potentially have a longer exposure to the wort. Instead, the brewer should use a pure strain of ''[[Lactobacillus]]''. As a result of not using grains to sour the wort, there is less concern of developing [[Butyric Acid]] or [[Isovaleric Acid]] with this method. Even still, lowering the pH of the [[Wort_Souring#How_to_Pre-Acidify|wort to under 4.5 (ideally 4.0 - 4.3)]] will also discourage contaminating bacteria from thriving in the wort during the incubation period. This will also help with head retention <ref>[[Lactobacillus#Foam_Degradation]]</ref>. There is also the option of [[Mixed_Fermentation#Reusing_a_Sour_Yeast_Cake|using a sour yeast cake]] from another sour beer as the bacteria inoculation.

After the desired acidity level is reached from the incubating ''Lactobacillus'' bacteria, the brewer can crash cool the fermenter down to the temperature that is desired for the primary fermenting yeast. Both ''[[Saccharomyces]]'' and ''[[Brettanomyces]]'', or a blend can be used as primary fermenting yeast. ''Brettanomyces'' is often chosen because of it's higher tolerance of a low pH environment (3.4- pH <ref name="low ph">[http://www.homebrewtalk.com/f127/no-hop-berliner-weisse-415067/index3.html#post5280971 Michael Tonsmeire on HBT]</ref>), although many ''Saccharomyces'' strains have been successfully used (see the [[Wort_Souring#Souring_in_the_Boil_Kettle|Souring in the Boil Kettle]] section above). If the chosen yeast requires aeration and the brewer has the ability, the sour wort should be aerated before pitching yeast. Brewers have had good luck using Fermentis dry yeast products in non-aerated wort. Re-hydrating the dry yeast as per the manufacturer's instructions and with a yeast nutrient such as Go-Ferm is effective <ref>[http://www.scottlab.com/product-102.aspx Go-Ferm]</ref>. The wort is then fermented out as normal. The brewer can consider other [[Brewing Methods]] such as pitching ''Brettanomyces'', a mixed culture, or commercial sour beer dregs into secondary.

* [http://www.fivebladesbrewing.com/year-sour-mash/ "Year of the Sour Mash" by Derek Springer. This series of articles were written for his NHC 2015 presentation.]

* [http://sourbeerblog.com/lactobacillus-2-0-advanced-techniques-for-fast-souring-beer/ "Lactobacillus 2.0 - Advanced Techniques for Fast Souring Beer", by Matt Miller of Sour Beer Blog.]

==References==