I brew ten-gallon batches of beer split into two fermentors. The last batch that I kegged had one infected fermentor, while one remained uninfected. One bucket showed a white powdery substance covering the remnants of the krausen, as well as an oily and whitish film on the surface; the other looked normal. I understand that there are only a few organisms known to grow in beer. Is there a way to identify which bug has contaminated the brew?
Perhaps the various organisms are different colors? Perhaps the texture varies?