13,703
edits
Changes
added a "pre-acidifying" guide
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>. Once all of the wort is collected in the boil kettle, 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.
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 recommended to fill the head space of the kettle with CO2 because oxygen can encourage off flavors such as rancid cheese from [[Butyric Acid]] and/or [[Isovaleric Acid]], which are produced by microbes that are naturally present on the grain. Keeping the temperature between 113-120°F (45-48.8°C) will encourage the Lactobacillus resident on the grain and will discourage other bacteria. Lowering the pH of the wort to under 4.4 will also discourage many other bacteria from thriving in the wort during the incubation period. There currently is no formula for how much lactic acid to add to a volume of wort due to the different buffering capacities of wort and water, but using 1 ml of 88% lactic acid per .1 shift in pH for 5 gallons of wort is a good starting measurement. 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). 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 no other microbes are allowed inside the kettle.
[http://beerandwinejournal.com/sour-wort-berliner/ James Spencer provides an article] that fully explains his process, as well as a step by step video guide and tasting on Beer and Wine Journal <ref name="james_spencer" />.
===How to Pre-Acidify===
Pre-acidifying the wort has several benefits, such as discouraging unwanted microbes that may have accidentally got into the wort, and helping to prevent [[Lactobacillus#Foam_Degradation|Lactobacillus foam degradation]]. There currently is no formula for how much lactic acid to add to a volume of wort due to the different buffering capacities of wort and water, but 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 ''Lacto''. Begin by adding 5 mL of food grade lactic acid to the wort. Stir gently, then take another pH reading. Continue to add 1-2 mL of lactic acid until the wort has the desired pH.
==See Also==