== Introduction =='''Sour mashing ''' is a technique for adding acidity to a beer before primary fermentation begins. This is accomplished by the introduction of lactic acid bacteria into the mash after the completion of the mashing processstarch conversion. Sour mashing Performing a sour mash is similar to [[Sour Worting|sour wortingWort Souring]] in that both techniques involve acidification of unfermented wort with lactic acid bacteria before primary fermentation. Many sour brewers prefer [[Wort Souring]] (which includes ''kettle souring'') due to having more control over off flavors produced versus sour mashing.
== Methods of <blockquote>"''Mixed culture fermentation for sour mashing ==Sour mashing procedures fall into the normal all-grain brewday process between completion of saccharificationbeers produces one thing, and any other desired (kettle souring/sour mashing rests, and separation of the wort from the grain) produces another thing. After the normal saccharification rests and If you’re going to make a mashout to 170+ F (76.7+ C) to denature enzymes in the mashmalty red ale that is kettle soured, the mash is cooled to approximately 120 F (48don’t call it a Flanders Red.9 C). At this point Honor the mash is inoculated with lactic acid bacteriatradition. This may be accomplished by addition of a pure culture of ''[[Lactobacillus]]'' or, more commonly, by " - Sean Burke of the addition of a small amount of unused malt, which has ''Lactobacillus'' in addition to other bacteriaCommons Brewery, yeastsKettle Souring Presentation, and molds on the husksCBC 2015.</blockquote>
To help favor ==Methods of Sour Mashing==Sour mashing procedures fall into the growth normal all-grain brewday process after completion of ''Lactobacillus'' over these saccharification, and any other unwanted microbesdesired mashing rests, it is important that and before the separation of the wort from the grain. After the mash be kept anaerobic normal saccharification rests and incubated warm a mashout to 170+ F (generally 100-76.7+ C) to denature enzymes in the mash, the mash is cooled to approximately 120 F/ 37.8-(48.9 C) throughout . At this point the duration mash is more or less pasteurized from the hot temperatures of the sour mash. This can be accomplished by purging In order to reintroduce bacteria into the headspace with CO2 (some breweries go so far as to bubble CO2 through their mash while it is cooling) and covering inoculated with saran wrap at the liquid-air interface to eliminate air contactlactic acid bacteria. The favoring This may be accomplished by addition of a pure culture of ''[[Lactobacillus]]'' over spoilage microbes can also be supported by dropping the initial sour mash pH or, more commonly, by methods such as the addition of acidulated a small amount of unused malt, lactic acid, or starter wort from a which has ''Lactobacillus'' culturein addition to other bacteria and yeasts on the husks (see [[Grain#Malted_Barley|bacteria found on malted grain]] for more information).
Sour mashing may be conducted on To help favor the growth of ''Lactobacillus'' over the other unwanted microbes, it is important that the entire mash or may be conducted on a portion kept anaerobic and incubated warm (ideally 113-120°F/45-48.9°C) throughout the duration of the sour mash. On a homebrew scale, sour mashing only a portion of the grist This can easily be accomplished by conducting a small stove top purging the headspace with CO2 (some breweries go so far as to bubble CO2 through their mash before while it is cooling, and periodically throughout the planned brewdaysouring time) and covering with saran wrap at the liquid-air interface to eliminate air contact. This pre-soured portion The favoring of ''Lactobacillus'' over spoilage microbes can then also be blended in with supported by dropping the initial sour mash pH by methods such as the addition of acidulated malt, lactic acid (preferably), or starter wort collected from the normal mash of the remaining grist during the brew daya ''Lactobacillus'' culture.
Sour mashes typically last between roughly 12 hours and 3 daysmashing may be conducted on the entire mash, or may be conducted on a portion of the mash. After On a homebrew scale, sour mashing only a portion of the grist can easily be accomplished by conducting a small stove top mash has reached before the desired acidity planned brewday. This pre-soured portion can then be blended in with the wort is separated collected from the grain and normal mash of the remaining grist during the boil and fermentation are carried out as normalbrew day.
=== Unwanted Microbes ===Due to Sour mashes typically last between roughly 12 hours and 3 days. After the mixed culture typically added to a sour mash has reached the desired acidity the wort is separated from the addition of unused grains of malt after the mashing process, unwanted microbes such grain and boiling and fermentation are carried out as ''Clostridium sp''normal. can take old in It is important that wort from a sour mash and produce off flavors such as [[Butyric Acid|Butyric acid]] and possibly is not consumed, especially if it was inoculated with grain, because pathogens have been found to grow in wort soured with grain (see [[Isovaleric AcidGrain#Malt_Inoculated_Wort|Isovaleric acidMalt Inoculated Wort]]).
Some professional brewers have reported stuck or slow sparges when performing a sour mash. This generally isn't a problem on the homebrew scale. Adding rice hulls and resetting the grain bed will help resolve the issue <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/992202820807932/?comment_id=993343157360565&comment_tracking=%7B%22tn%22%3A%22R0%22%7D Conversation with professional brewer Anthony Accardi on MTF.]</ref>. ===Unwanted Microbes===Due to the wide variety of microbial species typically added to a sour mash from the addition of unused grains of malt after the mashing process, unwanted microbes such as ''Clostridium spp''. can take hold in a sour mash and produce off flavors such as [[Butyric Acid|Butyric acid]] and possibly [[Isovaleric Acid|Isovaleric acid]]. Should the sour mash display prominent character of these spoilage organisms, such as rancid aroma /vomit/fecal aromas or moldy patches, it may be advisable to not use the sour mash. If the sour mash is not acidic enough it is possible for human pathogens to be present in the mash(over 4.4 pH), and it may not be advisable to taste the mash, especially if noticeable spoilage aroma is detected. [[Sour Worting|Sour wortingWort Souring]] is generally not as susceptible to these spoilage organisms. ==Microbiology and Biochemistry==The buffering capacity of the mash is higher than wort due to the grain material. This has a positive affect on the growth of lactic acid bacteria. Peyer et al. (2017) found a slight increase in cell growth of ''Lactobacillus'' when incubated in a soured mash versus when souring in wort. However, due to a much higher concentration of sugar content and buffering capacity of the sour mash versus plain wort, less lactic acid was actually produced. This study also found that sour mash beers have almost four times as much acetaldehyde as the co-fermented and kettle soured versions, although this was speculated to be caused by the oxidation of ethanol in the sour mash, which converts alcohol back into acetaldehyde <ref name="peyer_2017">[http://www.asbcnet.org/publications/journal/vol/2017/Pages/ASBCJ-2017-3861-01.aspx Sour Brewing: Impact of Lactobacillus amylovorus FST2.11 on Technological and Quality Attributes of Acid Beers. Lorenzo C. Peyer, Martin Zarnkow, Fritz Jacob, David P. Schutter, Elke K. Arendt. 2017.]</ref>. ==See Also=====Additional Articles on MTF Wiki===* [[Wort Souring]]* [[Butyric Acid]]* [[Lactobacillus]]* [[Alternative Bacteria Sources]] ===External Resources===* [http://www.fivebladesbrewing.com/presentations/berliner-and-beyond-sour-mashing-and-its-applications/ Berliner and Beyond: Sour Mashing and Its Applications. Derek Springer's NHC 2015 audio and slides.]* [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://homebrewingfun.blogspot.com/2010/10/sour-mash-how-to.html "Sour Mash How-To", by Adam Kielich (Brain Sparging on Brewing blog).]* [http://byo.com/kegging/item/1691-sour-mashing-techniques "Sour Mashing: Techniques", BYO, by Dave Green. October 2008.]* [https://byo.com/videos/item/889-how-to-make-a-sour-mash-techniques "How to Make a Sour Mash: Techniques", BYO, September 2000.]* [http://suigenerisbrewing.blogspot.com/2015/07/how-i-sour-mash-recipe.html "How I Sour Mash & a Recipe"; Sui Generis Blog (includes microbiology information).] ==References==<references/> [[Category:Techniques]]