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===Reducing Microorganisms===
Several generalized procedures are used for limiting the number of unwanted microorganisms. These include acid washing yeast that is re-pitched (kills bacteria but not wild yeast that is tolerant of low pH), keeping beer cool (slows the growth of microbes in general), filtration (removes yeast), pasteurization (kills vegetative cells in the finished beer, but not spores - most beer spoilers are killed at 15 [http://wiki.zero-emissions.at/index.php?title=Pasteurization_in_beer_production pasteurization units (PU)] and all are killed at 30 PU using a recommended pasteurization temperature of 66°C ), and aseptic or hygienic packaging. Note that some strains of ''Lactobacillus'' have been shown to survive pasteurization temperatures; see [[Lactobacillus#Tolerance_of_Extreme_Temperature|''Lactobacillus'' Heat Tolerance]]. Packaging systems should be frequently flooded with hot water between 80-95°C or saturated steam (every 2 hours in the summer and every 4 hours in the winter). UV light or disinfecting chemicals are also used. The filler and crowner should be disinfected frequently as well. Packaging in an aseptic room with HEPA filtration and higher air pressure within the room compared to outside, along with special clothing, is another method that larger breweries use to remain aseptic <ref name="storgards_2000" />.
Most brewing equipment should be designed for good hygiene. Pits and crevices should be avoided, and all surfaces should be smooth when possible. All equipment and pipelines should be self-draining. Valves are a typical source of contamination because they are not easily CIP'ed, especially plug valves and ball valves (although butterfly, gate, and globe valves are also difficult to CIP) <ref name="storgards_2000" />. Horizontal surfaces and wet surfaces are more prone to biofilm formation. In one study that compared biofilm formation in bottling lines versus canning lines, it was found that canning lines develop less microbial biofilms and contaminations than bottling lines due to not having rinsing stations, labeling stations, and simpler constructions than the bottling lines that were studied <ref name="Storgårds_2006" />. However, some canning lines cannot use caustic for cleaning, or it is not common practice, but use foaming agents instead which are less effective at removing biofilms (see [[Quality_Assurance#Efficacy_of_Cleaning_Agents|efficacy of cleaning agents below]]). The lack of use of caustic cleaners in canning lines has been identified as a source of contamination issues with [[Saccharomyces#Diastatic_strains_of_Saccharomyces_cerevisiae|diastatic strains of ''Saccharomyces cerevisiae'']] in canning lines <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1561762887185253/?comment_id=1791471917547681&reply_comment_id=2017381731623364&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Caroline Smith from Lallemand. Milk The Funk Facebook group post on diastaticus contamination. Feb 2018.]</ref>.