13,703
edits
Changes
fixinf 4.5 pH notes to be 4.4
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. 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 4.5 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 1ml of 88% lactic acid per .1 shift in pH for 5 gallons of wort is a good starting measurement.
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. 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.
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 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 4.5 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 113-120°F (45-48.8°C) for 1 to 4 days depending on how much acidity the brewer wants (3 days is a good rule of thumb) <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" />. ''Caution: the wort gravity may also be tested to check for alcohol presence. Alcohol can be more easily boiled off since it boils at 173.1°F (78.37°C) <ref name="boiling_of_alcohol" />.'' Once boiled, the wort can be chilled and handled in the same way as the above methods for wort souring.