Changes

The ester profiles of the co-fermentations (both the staggered and co-pitch) were a little bit subdued compared to the primary fermentations with ''Brettanomyces'', indicating that primary fermentations with ''Brettanomyces'' produces higher amounts of esters versus co-fermentation of ''Brettanomyces'' with ''S. cerevisiae''. For example, lower levels of ethyl caproate, ethyl butyrate, ethyl caprylate, ethyl decanoate, ethyl nonanoate, and ethyl lactate, were seen in the co-fermentations versus the ''Brettanomyces'' primary fermentations with some of these compounds dropping below flavor threshold levels (ethyl caproate, for example). The ester production of ''Brettanomyces'' peaked at 14 days, and then esters slowly degraded. In the co-fermentations, the ''Brettanomyces'' appeared to be degrading acetate esters produced by the ''S. cerevisiae'', such as phenyl ethyl acetate, and producing higher amounts of of ethyl acetate. Phenol production began as soon as ''Brettanomyces'' was pitched, and this has been hypothesized to play a large role in replenishing NAD⁺ to alleviate the initial lag growth phase in ''Brettanomyces''. Interestingly, levels of 4-ethylphenol were produced at a faster rate in the 100% ''Brettanomyces'' fermentations, but by the end of the 21 day trial period the the 100% ''Brettanomyces'' ferments had slightly lower concentrations of 4-EP versus the co-fermentations with ''S. cerevisiae'', indicating that perhaps 100% ''Brettanomyces'' fermentations produce more phenols up front, but after some time of aging co-fermentations can produce slightly higher levels of phenols (see Figure 19) <ref name="Tyrawa_Masters" />.