: ''This article is about sour brewing methods using commercial cultures. For other sour brewing methods, see [[Brewing Methods]].''
For the purposes of this article, we are defining a '''mixed Mixed fermentation''' (also referred to as "mixed culture fermentation") as is any fermentation that consists of a combination of ''[[Saccharomyces]]''(brewer's yeast), ''[[Brettanomyces]]''(wild yeast), ''[[Lactobacillus]]''(lactic acid bacteria), and ''[[Pediococcus]]'' cultures(lactic acid bacteria), or other [[Nonconventional_Yeasts_and_Bacteria|microbes that are unconventional to brewing]]. Broadly speaking, there are two styles of mixed fermentations: "sour" mixed fermentations with lactic acid bacteria (''Lactobacillus'' and/or ''Pediococcus'') and "funky" mixed fermentationswithout lactic acid bacteria. "Sour" fermentations Mixed fermentation sour beers are characterized by their higher acidity and tart flavorcaused by the production of [[Lactic Acid|lactic acid]], and require the use of a Lactic Acid Bacteria lactic acid bacteria (abbreviated as '''LAB'''; generally ''Lactobacillus'' and/or ''Pediococcus''). "Funky" fermentations generally do not contain LAB, but instead use Mixed fermentation without lactic acid bacteria are usually fermented with a combination of ''Saccharomyces'' and ''Brettanomyces''. Funky Mixed fermentation beers without lactic acid bacteria may be slightly tartfrom the [[Acetic Acid|acetic acid]] production of ''Brettanomyces'', but are generally not considered to be sour. For both categories, the primary fermentation will be completed by yeasts such as ''Saccharomyces'' and/or ''Brettanomyces''.
The bulk of this This page will focus on information for mixed fermentation sour mixed fermentationsbeers using pure laboratory cultures. For "Funky Mixed Fermentations"mixed fermentation beers without lactic acid bacteria, see the [[Funky Mixed Fermentations]] page. For 100% ''Brettanomyces'' fermentations(technically not a "mixed" fermentation), see the [[100% Brettanomyces Fermentation]] page. 100% ''Lactobacillus'' or ''Pediococcus'' beers do not exist because they do not fully attenuate wort (see [[Lactobacillus#100.25_Lactobacillus_Fermentation|100% ''Lactobacillus'' fermentation]] for details). Other alternative yeast and bacteria can also be used, however this is not conventional even for brewers who make wild/sour beers. For example, [[Spontaneous Fermentation|spontaneous fermentation]] and [[Wild_Yeast_Isolation#Growing_and_Testing_Without_Plating|wild yeast captures]] usually contain a plethora of [[Nonconventional_Yeasts_and_Bacteria|yeast and bacteria that are not conventional to modern brewing]].
It is important to mention that sour brewing in general has very few well-established "rules". While we may categorize techniques for the sake of keeping some sort of manageable structure to this wiki, many methods can be used in conjunction with other [[Brewing Methods]], and new methodologies are constantly being developed that combine elements of more established techniques, as well as slight changes to established techniques. Many of the methods used are determined by the types of microbes the brewer is working with. An article of this length cannot encompass all mixed fermentation methods. Instead it will provide a "big picture" view of the general methodologies. Towards this end, we divide mixed fermentation methods into two approaches: the traditional long fermentation method and an increasingly popular, short fermentation method. They are divided here as a device to illustrate the philosophy of each and facilitate the discussion of the techniques used for each methodology. The distinction of these two methods is however somewhat artificial, indeed many brewers use elements of both approaches to achieve their desired results. Examples of how techniques can overlap to create new techniques can also be found in Michael Tonsmeire's pivotal book on sour brewing, "American Sour Beers".