Changes

Pellicles form when the surface of the beer is exposed to 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> One theory is that the formation of a pellicle allows the organism to access the small amount of oxygen that is present in the headspace of the fermentation vessel. Another theory, and one that may be less accurate according to Dr. Matt Humbard, is that the ''pellicle'' protects the beer from other microorganisms <ref name="matt"></ref>. 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. Another myth is that the sour beer will be ready to package once the pellicle falls out; there is no correlation between the maturity of the beer and pellicle formation or dissipation. Some sour beers never form pellicles.