Whisky matured on oloroso sherry casks and color / coloring

[Peter Wood]

There was a paper by J.R. Mosedale (1995) Effects of oak wood on the
maturation of alcoholic beverages with particular reference to whisky.
Forestry 68: 203-230. It contains a number of statements relevant to the
present discussion. Here are some which seem particularly pertinent.

"....reported differences between French and American oak casks, each
constructed identically by the same cooper...Total extracts new US cask 176
mg/100ml and New Limousin cask 232 mg/100ml...colour relative to a standard
respectively 11 and 20" Meaning the Limousin gave more flavour and colour.

"Spanish sherry casks may be manufactured from either American or European
oak, and it is possible that a single cask may include both types of wood..."

"In general there is evidence for variation between both geographic regions
and local populations in wood properties affecting flavour. However there
is much uncertainty over the pattern, degree and causes of this variation."

A study on Limousin v. Troncais oak showed that wood colour and spirit
extract colour of the former was yellow, and of the latter was pink. In
other words, the oak species influenced the spirit colour.

"...it should be noted that a finished 190L cask will normally contain in
the region of 31 pieces of wood....These are likely to derive from
different trees, or even provenances, and therefore the variation in cask
effect may be less than if each cask derived from a single tree."

"It is now accepted that the influence of the botanical species of oak on
the matured whisky, although modified by cask treatment and age, is
undoubtedly a major factor.....the suitability of wood may vary not only
between species but also between different geographical regions."

To sum up it would seem that flavour and colour is species dependant, with
European species giving more flavour and colour. But to be honest - you
cannot see the wood for the trees.

My annecdotal evidence (me talking to myself after a few drams) suggests
that sherry matured whisky may well be coming lighter coloured as more
American oak is used for sherry casks. Here is part of a message I posted a
couple of years ago about an Old Malt Casks Glen Elgin 12y. 

"It is said to be from a sherry cask, but to me it had all the attributes
of a Speysider matured in a Bourbon hoggie. Light golden colour, vanilla,
cloves, high cis- to trans- beta methyl gamma octalactone ratio (that was a
bit of showmanship), roses and cardboard. Perhaps just a hint of petit
grain oil that could indicate a sherry butt. "  

I received an off-list message from an OMC employee assuring me that it
really was from a sherry cask. I have since observed other sherry-casked
whiskies that did not conform to my previous experience of say, old-time
sherried Macallans (ie before they became marketting-silly and unable to
spot a 2$ note when they saw one) and I now believe this is likely to be
caused by increased use of Q. alba caskwood. Actually I quite like, almost
prefer, the austere flavours of a well-matured american oak Speysider to
the glutinous syrup that comprises much sherried whisky these days.

Peter Wood

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