Changes

[[File:Brussels brett blend pellicle1.jpg|thumb|Pellicle from The Yeast Bay Brussels Brett Blend; courtesy of Dan Pixley]][[File:Lactobacillus pellicle.jpg|thumb|Lactobacillus pellicle; courtesy of Matt Humbard]] A '''pellicle''' is an aggregation of cells, proteins, and long chain sugars (monosaccharides and polysaccharides) formed on the surface of a beer. It is often formed by [[Brettanomyces]], [[Pediococcus]], or [[Lactobacillus]]. It can also be formed by [[Saccharomyces]] in rare occasions <ref name="matt">[http://phdinbeer.com/2015/01/30/beer-microbiology-what-is-a-pellicle/ Beer Microbiology – What is a pellicle? A PhD in Beer blog. Dr. Matt Humbard. 01/30/2015. Retrieved 04/26/2015.]</ref>, as well as ''Acetobacter spp'' <ref>[http://www.ncbi.nlm.nih.gov/pubmed/24559734 Pellicle of thermotolerant Acetobacter pasteurianus strains: characterization of the polysaccharides and of the induction patterns. Perumpuli PA, Watanabe T, Toyama H. Aug 2014.]</ref>.

''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. Additionally, 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.  ==Handling/Racking==Most brewers will advise that if it all possible, try not to disturb the pellicle too much when taking a sample from the fermenting vessel, racking, or moving the fermenting vessel. If taking a sample or racking, gentle pierce the top of the pellicle with the racking cane or wine thief. If the pellicle does break up, don't worry too much. It will usually reform if oxygen is still present in the headspace. While packaging the beer, try not to disturb the pellicle too much and let the pellicle remain on the surface of the beer so that aggregates of particles do not get packaged into the final product.  ==Pellicle Formation In Bottles== [[File:Pellicle bottle.JPG|thumb|Pellicle formation in a bottle a few days after packaging; courtesy of Dan Pixley]]Often a pellicle will form on the surface of the beer inside the bottle shortly after packaging. This is no different than the pellicle forming in the fermentation vessel, and presumably occurs because of the oxygen in the headspace of the bottle. The pellicle will eventually settle out either on it's own during aging, or when the bottle is refrigerated. Other than for aesthetics, there should be no concern if this happens.