There is a direct relationship between amino acids in the wash and the higher alcohols a yeast produces. It is a pretty direct reaction, at least in the cases I read with very high yield. Add an amino acid, and yeast spits out an alcohol, for example in the case of leucine the yield of isoamyl alcohol is over 80%.
Usually the general thought most distillers have is to reduce production of these fusels. But as we all know, alcohols are half of esters, so specific amino acids could be used to manipulate the ester profile of spirits, dunders, whatever.Amino acid ---> Fusel alcohol
Leucine ---> Isoamyl alcohol
Valine ---> Isobutanol
Isoleucine ---> Active amyl alcohol
Phenyl ---> 2-phenylethanol
Tyrosine ---> p-hydroxyphenylethanol / tyrosol
Tryptophan ---> Tryptophol
Methionine ---> Methionol
There has been plenty of good chatter lately about the acid side of the ester equation, mostly which bacteria produce desirable carboxyllic acids, and the general process of ester formation. So we know how to manipulate the acid half. All our fermentations produce a majority of ethanol (yay), making ethyl esters predominate. Of course all fermentation also produce some fussels too, but with this info they can be increased and targeted.
I've long had the notion of making a "rhum grand arome", a flavor bomb so strong it is only used in blending. I'm excited by the notion of targeting the esters not just by acids, but by specific alcohols too.
E.g., supplement with leucine, have acetic acid present and end up with bananas or pears (isoamyl acetate). And/or with butyric acid present you get apricot or mango (isoamyl butyrate).
I won't bother sharing any sources, apparently this is basic yeast metabolism that has been known so long it only shows up in the summaries of current research mostly bogged down in elucidating the genetic pathways.