Changes

==Avoiding Cross Contamintation==

While most microorganisms cannot survive in beer due to the hops, low pH, alcohol content, and shortage of nutrients, certain species are considered to be beer spoilage organisms due to their ability to form biofilms and survive in beer and make a potential impact on the beer's flavor by producing acidity, phenols, and turbidity with just a few surviving cells. These species include [[Brettanomyces|''Brettanomyces'']] species, numerous [[Lactobacillus|''Lactobacillus'']] species, ''Pediococcus damnosus'', ''Pectinatus cerevisiphilus'', ''P. frisingensis'', ''Megasphaera cerevisiae'', ''Selenomonas lactifex'', and [[Saccharomyces#Saccharomyces_cerevisiae_var._diastaticus|''Saccharomyces cerevisiae'' var. ''diastaticus'']]. Other species of microbes do not grow in beer but can become contaminants earlier on in the brewing process (for example during kettle souring). These species include enterobacteria such as ''Clostridium'' species, ''Obesumbacterium proteus'' and ''Rahnella aquatilis'', and wild ''Saccharomyces'' that might not be able to grow in finished beer. Other species are considered "indicator" species because they do not directly cause spoilage of beer, but indicate that there is a hygiene problem. These include ''Acetobacter'', ''Gluconobacter'', and ''Klebsiella'' species, as well as aerobic yeasts. Biofilm forming spoilage organisms include a much wider range in beer tap systems due to the availability of oxygen and higher temperatures at certain points in the tap system. Of particular concern here is the ability of ''E. coli'' serotype O157:H7 to survive in tap systems, which has had a couple of documented occurrences in contaminated apple cider <ref name="storgards_2000">[http://www.vtt.fi/inf/pdf/publications/2000/P410.pdf Process hygiene control in beer production and dispensing. Erna Storgårds. VTT Publications 410. 2000.]</ref>

Sources for contamination can occur as "primary" contaminations (yeast pitching, and brewhouse related contaminations), or as "secondary" contaminations (packaging and cellaring), as well as in tap systems. They are usually not sudden occurrences, but a result of continued growth of microorganisms in a problem area. Historically, re-pitching yeast was often a source of contamination, however, more recently this has become less of a source for contaminations due to better education and techniques. Typical sources for contamination also include unclean equipment such as thermometers, manometers, valves, dead ends, gas pipes, leaks in any part of the system (especially at heat exchangers), wort aeration equipment, and even worn floor surfaces. More than half of documented contaminations come from the packaging system. These are typically the sealer (35%), the filler (25%), the bottle inspector (10%), dripping water from the bottle washer (10%), and the environment close to the filler and sealer (10%). In regards to the environment as a source of contamination, this has been found to be from airborne contaminants near the filler and crowner. The higher the humidity and the more airflow, the more chances of airborne contamination. In tap systems at taverns, 'one-way' valves that are attached to kegs have been found to be a source of contamination, as well as the dispensing line <ref name="storgards_2000" />.

Many microorganisms can form ''biofilms'' which is defined as a community of cells of one or more species that are attached to each other and/or a surface and are embedded in a matrix of extracellular polymeric substances (EPS), including polysaccharides and proteins, similar to a [[Pellicle|pellicle]]. Biofilms allow microbes to survive less vigorous cleaning and sanitizing regiments and chemicals and has become a concern in the food industry as well as in the brewing and wine making industries <ref>[https://onlinelibrary.wiley.com/doi/abs/10.1111/1541-4337.12087 Iqbal Kabir Jahid and Sang‐Do Ha. 2014.]</ref>.