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==Characteristics==
===Introduction===
Pellicles form when the surface of the beer is exposed to even small amounts oxygen <ref>[http://www.themadfermentationist.com/2009/11/brewing-sour-beer-at-home.html Brewing Sour Beer at Home. The Mad Fermentationist Blog. Michael Tonsmeire. 11/06/2009. Retrieved 02/28/2015.]</ref> Why microbes in sour/funky beer form a pellicle when exposed to oxygen is unknown. The most likely hypothesis is that the formation of a pellicle allows the organism (particularly [[Brettanomyces]], which prefers aerobic fermentation) to access the small amount of oxygen that is present in the headspace of the fermentation vessel. Another hypothesis, and one that may be less accurate according to Dr. Matt Humbard, is [http://phdinbeer.com/2015/01/30/beer-microbiology-what-is-a-pellicle/ Dr. Matt Humbard], is that the ''pellicle'' protects the beer from other microorganisms ] <ref name="matt"></ref>. Yet another hypothesis that is often cited is that the pellicle protects the beer from oxygen itself <ref>[http://jesterkingbrewery.com/pellicle-photos Jester King Blog on Pellicles. Retrieved 09/24/2015.]</ref>, however arguments for this hypothesis are lacking.
Popular thought is that the formation of a pellicle is not indicative of the quality of the sour beer that is being produced; it is only an indication that oxygen has entered the fermentation vessel and that the microbes are reacting to that exposure. One myth about pellicles is that the sour beer will be ready to package once the pellicle falls out; there is actually no correlation between the maturity of the beer and pellicle formation or dissipation. Some sour beers never form pellicles, and turn out fine as well, so the formation of a pellicle has no correlation with the quality of the beer.