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'''Sour Definitions within the sour beer''' is any beer inoculated with microbes other than traditional ale or lager yeast, whether you pitch with lab cultures, rely on microbes that have infiltrate your breweryworld are difficult and complicated, or add bottle dregs from a sour or wild beerbut we will try and cover the basics here.

A '''wild Sour beer''' is one any beer inoculated with lactic acid bacteria, as well as any fermentative yeast such as ale or lager yeast or even ''Brettanomyces''. Sour beer is most distinguished by the presence of lactic acid, which makes the beer taste sour. The yeast and bacteria can be sourced from many places, including lab cultures, microbes that has been spontaneously inoculated “in come from nature or the wild”environment around you, or bottle dregs from commercial sour beers.

A '''clean beer''' is any beer that is not your sour, funky, or wild beer; in other words your typical ale or lager. A '''funky beer''' is a term generally used by brewers to refer to beer that is fermented with ''Brettanomyces'', but not lactic acid bacteria. There is a common misconception that ''Brettanomyces'' makes beer sour, but under normal brewing conditions it should not make beer sour. ''Brettanomyces'' does not make lactic acid, but it does make acetic acid, which tastes like vinegar. Brewers do their best to limit the amount of acetic acid that is made by ''Brettanomyces'', which is controlled by limiting its exposure to oxygen. A '''kettle sour beer''' is a beer that has been soured for a short time in a sanitary vessel (usually the boil kettle) and then boiled to kill the lactic acid bacteria, and then finally fermented as a normal beer. These types of beers generally do not contain ''Brettanomyces''. This process has the benefits of creating a sour beer very quickly and greatly reducing any risk of infecting one's cold side brewing equipment (fermenters, hoses, packaging equipment, etc.). Kettle soured beer has the reputation of being less complex than other forms of sour beer.  A '''spontaneously fermented beer''' is a type of sour beer that has not been inoculated by any lab cultures but only by the yeast and bacteria present in the environment. This is the typical method used by the Belgian lambic brewers, but there are also many brewers in the rest of the world that have successfully created sour beer this way. Other terms have been used by brewers and can refer to different things or have different definitions depending on who you're talking to. For example, the term '''wild beer''' is used by some to refer to spontaneously fermented beer, and others to refer to any sour beer or funky beer that isn't kettle soured. ===Resources==='''Before''' getting started making a sour beer, we recommend reading these resources. It is also recommended that you understand the basics of brewing before getting started into sour beer brewing.* The book "American Sour Beers: Innovative Techniques for Mixed Fermentations," by Michael Tonsmeire. This book is very friendly for brewers who are new to mixed fermentation brewing. This is probably a better resource to begin with before diving deep into this wiki. * This wiki! Specifically, these pages: [[FAQ]], [[Mixed Fermentation]], [[Wort Souring]], [[Gose]], [[Berliner Weissbier]], [[Mixed Cultures]], [[Alternative Bacteria Sources]], [[Lactobacillus]], and [[Brettanomyces]].

When brewing sour beer, there are a few more players to the “yeast” side of the ingredients list. In addition to ''Saccharomyces'' or “Sacch”, which is commonly referred to as "brewers yeast", in wild beer brewing the brewer is also often dealing with ''Brettanomyces'', which is another genus of yeastthat is closely related to ''Saccharomyces''. ''Brettanomyces'' yeasts produces novel fruity and sometimes funky flavors often over a long period of slow fermentation. Bacteria are used to produce sourness in the form of lactic acid. These bacteria are called "lactic acid bacteria", and or "LAB" for short. Specifically, they are ''Lactobacillus'' and ''Pediococcus'', which are both . Other bacteria. such as ''Acetobacter'' (acetic acid bacteria) and ''enterobacterEnterobacter'' do (enteric bacteria) sometimes play a part in some sour fermentations, however , they are not often intentionally added.

===''Brettanomyces''===There are two major species of ''Brettanomyces''used in brewing: ''B. Bruxellensisbruxellensis'' and ''B. Anomalaanomalus''(sometimes called "Brett claussenii" by yeast labs). Despite other strains mentioned, there are only five species of Brett, with these two being the species most commonly used in brewing. ''Brettanomyces'' produces a lot of fruity esters that are pleasurable in beer. It also produces what we will later refer to as the “funk” when it comes to wild beers. While it is capable of producing some acetic acid when in the presence of oxygen (think vinegar), funk is what is typically described. Despite providing desired esters, funk , and a little bit of acetic acid, it is important to note that ''Brettanomyces'' can also be responsible for less desired flavors: feet, hard boiled egg, and some solvent-like nail polish flavors.Pure commercial cultures of ''Brettanomyces '' are available at most yeast suppliers(see [[Brettanomyces#Commercial_Cultures||''Brettanomyces'' cultures]] for a comprehensive list). ''Brettanomyces''does NOT provide a universal flavor. Just like the various ''Saccharomyces'' strains most brewers are familiar with, each ''Brettanomyces'' strain can produce a vast array of different flavors, depending on the particular strain, temperature and time.

===''Lactobacillus''===''Lactobacillus'' is a rod shaped bacteria that can grow with or without oxygen and produces lactic acid - most people are familiar with the sourness found in yogurt, sauerkraut , pickles, and so on. ''Lactobacillus'' converts sugars to lactic acid (and sometimes CO2 and ethanol). It can produce varying complexities of sourness from the one dimensional to the more complex, depending on which type is used.

===''Pediococcus''===''Pediococcus'' is a bacteria that also produces lactic acid, although generally slower than ''lactobacillusLactobacillus'' (''P. pentosaceus'' from Bootleg Biology's "Sour Weapon P" culture is an exception; this culture is good for kettle souring and other fast souring brewing methods). The sourness tends to be thought of as more aggressive than ''Lactobacillus''and is often thought to produce more of a complex sourness. It can also produces sometimes produce off flavors (diacetyland "ropiness", which turns the beer into the thickness of syrup) so it needs to have something to help clean up any unwanted flavors – like ''Brettanomyces'', which converts it to other compounds with less aggressive flavors. There is some discussion that ''Pediococcus'' thought of “complexity” is merely perceived by brewers because it works longer than ''Lactobacillus''does. This “complexity” could be simply because ''Pediococcus'' can lower the pH more than ''Lactobacillus''.