Changes

Esters are also broken down via a process called hydrolysis. Hydrolysis breaks the esters down using the same esterase enzyme within the ''Brettanomyces'' cells that are used to create esters. In general, all acetate based esters, except for phenethyl acetate and methyl acetate, are broken down faster than non-acetate esters by ''Brettanomyces''. In lambic brewing, sometime after the primary fermentation finishes, ''Pediococcus'' begins to produce lactic acid. The formation of lactic acid by ''Pediococcus'' coincides with the appearance and growth of ''Brettanomyces'', which produces more acetic acid. After another 2-3 months, the ester content of the lambic beer changes and reaches an equilibrium. Ethyl acetate and ethyl lactate are greatly increased, while isoamyl acetate is greatly decreased, reaching an equilibrium of these esters. Given a static amount of acetic acid, ''Brettanomyces'' reaches an equilibrium of ethyl acetate within 24 hours, while ethyl lactate equilibrium takes longer and is much more complex. In lambic, the majority of ester production and breakdown occurs within 1-3 months after lactic acid production by ''Pediococcus'' begins, and at a pH of around 3.5 and a temperature of around 15°C or less <ref name="Spaepen"></ref>. Pitching rate of ''Brettanomyces'' has an effect on the breakdown of isoamyl acetate with higher pitching rates breaking down this ester at a faster rate <ref name="MTF_Brett_Secondary"></ref>. As far as we are aware, ethyl acetate is not metabolized further by ''Brettanomyces'', and the level of ethyl acetate will not by be hydrolized over time (although it levels can continue to increase over time with more oxygen oxposure, since oxygen exposure encourages acetic acid synthesis by ''Brettanomyces'' and acetic acid bacteria, and acetic acid and ethanol are then metabolized into ethyl acetate by ''Brettanomyces'').