[MM-MALTS-L] Sulfurous whisky

[Peter Wood]

Hello Paul

No one else has responded to your interesting comments about American oak
sherry butts being the reason for a decline in sherry bottlings, but I am
intrigued. I don't know enough about the use of Quercus alba (I guess that
is what you mean by American oak) casks for sherry, so I can only raise
questions, not answers. I guess it is common knowledge that organo-sulfur
compunds are produced from barley protein breakdown during the mashing and
fermentation process, and that both contact with copper during
distillation, and oxidative reactions during maturation reduce the
concentrations of methyl polysulfides to acceptable levels. Also there is
some acceptance that sterilising sherry butts with sulfur dioxide leads to
sulfurous flavours that survive maturation (though I've never seen an
explanation of the chemical processes involved). But how does the light
charring affect the process - less active charcoal to remove the sulfur
compounds perhaps? And where does the American v. European oak chemistry
and wood structure come into play? I'm aware that they provide different
proportions and type of cask-derived congeners during maturation
oxidation-ethanolysis, but how does this affect sulfur aroma? I'm not
suggesting it doesn't, just wondering why and how?

Regards
Peter wood