Changes

''''Quality Assurance''' refers to the process if developing standard operating procedures for proactively avoiding quality problems <ref name="Diffen">[https://www.diffen.com/difference/Quality_Assurance_vs_Quality_Control "Quality Assurance vs. Quality Control". Diffen website. Retrieved 03/28/2018.]</ref>. In the brewing industry, this includes avoiding off-flavors from contamination, dissolved oxygen in beer, fermentation and ingredient issues, etc.

===General===

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>