Changes

| Diacetyl/butanedione (butter) || Vicinal diketone <ref>[https://en.wikipedia.org/wiki/Diacetyl "Diacetyl". Wikipedia website. Retrieved 08/29/2020.]</ref> || || 0.1–0.2 ppm in lager and 0.1–0.4 ppm in ales, although flavor thresholds as low as 17 ppb and 14–61 ppb have been reported <ref name="krogerus_2013">[https://www.researchgate.net/publication/259331290_125th_Anniversary_Review_Diacetyl_and_its_control_during_brewery_fermentation Krogerus, K. and Gibson, B.R. (2013), 125th Anniversary Review: Diacetyl and its control during brewery fermentation. J. Inst. Brew., 119: 86-97. https://doi.org/10.1002/jib.84.]</ref>. || Produced by all strains and all species of ''Brettanomyces'' except ''B. naardenensis''; the amount that it is produced varies widely and not much is known about what determines diacetyl levels produced from ''Brettanomyces'' <ref name="colomer_2020_genome" />. ''Brettanomyces'' generally produce very low amounts of diacetyl (0.019 - 0.048 mg/L). It is hypothesized that ''Brettanomyces'' can reduce diacetyl during its maturation phase in a similar way to ''Saccharomyces'' species, but this has not been investigated that we are aware of . It has been reported that diacetyl reduction is faster at a lower pH of around 3.5, which is a typical pH range for sour beer and might be one of the contributing factors to a lack of anecdotal reports of diacetyl in sour beer <ref>[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.381 Michel, M., Meier‐Dörnberg, T., Jacob, F., Methner, F. ‐J., Wagner, R. S., and Hutzler, M. (2016) Review: Pure non‐Saccharomyces starter cultures for beer fermentation with a focus on secondary metabolites and practical applications. J. Inst. Brew., 122: 569– 587. doi: 10.1002/jib.381.]</ref><ref name="krogerus_2013" />.