This article will review the molecules created, changed, or
affected by the performance of yeast that lead to the complex flavors in
beer. It will look at the process parameters and control points that
brewers can potentially use to influence the behavior of processes and
possibly their yeast to “adjust” the various outcomes of fermentation.
In the construction of this topic, the approach taken is basic. The
complexity of the metabolic pathways means that key pathways are diluted
within a maze of coenzymes, enzymes, energy production and usage, and
reduction and oxidation of various cofactors and intermediates. The
material presented attempts to remove the background chemical reactions
that cause the key flavor changes. This allows for a review of the
resultant flavor changes in a manner that is less conflicted and
hopefully more clear regarding what the yeast cell is doing within the
processes of fermentation. The final review adds an understanding of
possible control steps that can be used to shift processes and affect
the end flavor of beers.