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'''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 starch conversion. Performing a sour mash is similar to [[Category:TechniquesWort 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. <blockquote>"''Mixed culture fermentation for sour beers produces one thing, and (kettle souring/sour mashing) produces another thing. If you’re going to make a malty red ale that is kettle soured, don’t call it a Flanders Red. Honor the tradition.''" - Sean Burke of the Commons Brewery, Kettle Souring Presentation, CBC 2015.</blockquote> ==Methods of Sour Mashing==Sour mashing procedures fall into the normal all-grain brewday process after completion of saccharification, and any other desired mashing rests, and before the separation of the wort from the grain. After the normal saccharification rests and a mashout to 170+ F (76.7+ C) to denature enzymes in the mash, the mash is cooled to approximately 120 F (48.9 C). At this point the mash is more or less pasteurized from the hot temperatures of the mash. In order to reintroduce bacteria into the mash it is inoculated with lactic acid bacteria. This may be accomplished by addition of a pure culture of ''[[Lactobacillus]]'' or, more commonly, by the addition of a small amount of unused malt, which has ''Lactobacillus'' in addition to other bacteria and yeasts on the husks (see [[Grain#Malted_Barley|bacteria found on malted grain]] for more information). To help favor the growth of ''Lactobacillus'' over the other unwanted microbes, it is important that the mash be kept anaerobic and incubated warm (ideally 113-120°F/45-48.9°C) throughout the duration of the sour mash. This can be accomplished by purging the headspace with CO2 (some breweries go so far as to bubble CO2 through their mash while it is cooling, and periodically throughout the souring time) and covering with saran wrap at the liquid-air interface to eliminate air contact. The favoring of ''Lactobacillus'' over spoilage microbes can also be supported by dropping the initial sour mash pH by methods such as the addition of acidulated malt, lactic acid (preferably), or starter wort from a ''Lactobacillus'' culture. Sour mashing may be conducted on the entire mash, or may be conducted on a portion of the mash. On a homebrew scale, sour mashing only a portion of the grist can easily be accomplished by conducting a small stove top mash before the planned brewday. This pre-soured portion can then be blended in with the wort collected from the normal mash of the remaining grist during the brew day. Sour mashes typically last between roughly 12 hours and 3 days. After the mash has reached the desired acidity the wort is separated from the grain and boiling and fermentation are carried out as normal. It is important that wort from a sour mash is not consumed, especially if it was inoculated with grain, because pathogens have been found to grow in wort soured with grain (see [[Grain#Malt_Inoculated_Wort|Malt Inoculated Wort]]).

== Introduction ==Sour mashing is Some professional brewers have reported stuck or slow sparges when performing a technique for adding acidity to a beer before primary fermentation beginssour mash. This is accomplished by generally isn't a problem on the introduction of lactic acid bacteria after homebrew scale. Adding rice hulls and resetting the completion of grain bed will help resolve the mashing process. issue Sour mashing is similar to <ref>[[Sour Worting|sour wortinghttps://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.]] in that both techniques involve acidification of unfermented wort with lactic acid bacteria before primary fermentation</ref>.

== Methods of sour mashing =Unwanted Microbes===Sour mashing procedures fall into Due to the normal all-grain brewday process between completion wide variety of saccharification, and any other desired mashing rests, and separation of the wort from the grain. After the normal saccharification rests and microbial species typically added to a mashout to 170+ F (76.7+ C) to denature enzymes in the sour mash, from the mash is cooled to approximately 120 F (48.9 C). At this point the mash is inoculated with lactic acid bacteria. This may be accomplished by addition of a pure culture unused grains of ''[[Lactobacillus]]'' or, more commonly, by malt after the addition of a small amount of unused maltmashing process, which has unwanted microbes such as ''LactobacillusClostridium spp'' . can take hold in addition to other bacteria, yeasts, a sour mash and produce off flavors such as [[Butyric Acid|Butyric acid]] and molds on the huskspossibly [[Isovaleric Acid|Isovaleric acid]].

To help favor Should the growth sour mash display prominent character of ''Lactobacillus'' over these other unwanted microbesspoilage organisms, such as rancid/vomit/fecal aromas or moldy patches, it is important that the mash may be kept anaerobic and incubated warm (generally 100-120 F/ 37.8-48.9 C) throughout the duration of advisable to not use the sour mash. This can be accomplished by purging If the headspace with CO2 (some breweries go so far as to bubble CO2 through their sour mash while is not acidic enough it is cooling) and covering with saran wrap at the liquid-air interface possible for human pathogens to eliminate air contact. The favoring of ''Lactobacillus'' over spoilage microbes can also be supported by dropping present in the initial sour mash (over 4.4 pH by methods such as ), and it may not be advisable to taste the addition of acidulated maltmash, lactic acid, or starter wort from a ''Lactobacillus'' cultureespecially if noticeable spoilage aroma is detected. [[Wort Souring]] is generally not as susceptible to these spoilage organisms.

Sour mashing may be conducted on ==Microbiology and Biochemistry==The buffering capacity of the entire mash or may be conducted 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 portion slight increase in cell growth of the ''Lactobacillus'' when incubated in a soured mashversus when souring in wort. On a homebrew scale However, sour mashing only due to a portion much higher concentration of sugar content and buffering capacity of the grist can easily be accomplished by conducting a small stove top sour mash before the planned brewdayversus plain wort, less lactic acid was actually produced. This prestudy also found that sour mash beers have almost four times as much acetaldehyde as the co-fermented and kettle soured portion can then versions, although this was speculated to be blended caused by the oxidation of ethanol in with the wort collected from the normal 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 the remaining grist during the brew dayAcid Beers. Lorenzo C. Peyer, Martin Zarnkow, Fritz Jacob, David P. Schutter, Elke K. Arendt. 2017.]</ref>.

Some professional brewers have reported stuck or slow sparges when performing a ===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 generally isn't a problem 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 the homebrew scaleBrewing blog).]* [http://byo.com/kegging/item/1691-sour-mashing-techniques "Sour Mashing: Techniques", BYO, by Dave Green. Adding rice hulls and resetting the grain bed will help resolve the issueOctober 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). ]

=== Unwanted Microbes =References==Due to the mixed culture typically added to a sour mash from the addition of unused grains of malt after the mashing process, unwanted microbes such as ''Clostridium sp''. can take old in a sour mash and produce off flavors such as [[Butyric Acid|Butyric acid]] and possibly [[Isovaleric Acid|Isovaleric acid]].<references/>

Should the sour mash display prominent character of these spoilage organisms, such as rancid aroma 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, and it may not be advisable to taste the mash, especially if noticeable spoilage aroma is detected. [[Sour Worting|Sour wortingCategory:Techniques]] is generally not as susceptible to these spoilage organisms.