Bacteria | Occurrence in brewery environments | Off flavour/aroma and odour | Visual poilage effects | Metabolic products |
Acetic acid bacteria [2] [21] [24] [26] | ||||
Acetobacter | Wort, beer dispenses and cask condition ales and barrel aged ales, brewery biofilm. | Sour, vinegar | Haze, Ropiness | Acetic acid |
Glucanobacter | Wort, beer dispense and cask condition ales | Sour, vinegary | Haze | Acetic acid, acetate |
Zymomonas | Primed beers (not found in lagers) | Fruity, rotten apple, rotten egg, sulphudic | Haze Ropiness | Acetaldehyde and H2S |
Enterobacteriaceae [26] | ||||
Obesumbacterium | Pitching yeast and fermenting wort | Parsnip, sulphury | Haze | Dimethyl sulphides (DMS), diacetyl, higher alcohols and N-nitrosamines, acetoin |
Citrobacter | Brewing liquor , fermenting wort | Parsnip, sulphury |
| Dimethyl sulphides (DMS), diacetyl, lactic acid, acetaldehyde |
Rahnella | Pitching yeast, Early stages of fermentation (wort) | Fruity, sulphury, | - | Dimethyl sulphides (DMS), diacetyl, methyl acetate, ethyl acetate |
Klebseilla | Fermenting wort, biofilm | Unpleasant odour | - | 4-vinylguaicol, Dimethylsulphides (DMS), diacetyl. |
Obligatory anaerobes [72] [76] [77] [99] | ||||
Pectinatus | Low alcohol unpasteurised beer, beer filling area, biofilm | Rotten egg, unpleasant odour | Turbidity | Acetic acid, propionic acid, lactic acid, succinic acid, H2S, acetoin, methyl mercaptan and other sulphur compounds |
Megasphaera | Low alcohol, unpasteurised beer, beer filling area, biofilm | Unpleasant odour | Turbidity | H2S, butyric acid, isobutyric acid, caprioc acid, valeric acid, isovaleric acid. |
Selenomonas | Pitching yeast | Unpleasant odour | Turbidity | Acetic, lactic, and propionic acids. |
Zymophilus | pitching yeast or brewery waste | Unpleasant odour | Turbidity | Acetic acid and propionic acid |