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The process of Scotch Malt Whisky
making:
The malt whisky production process begins in the malt barn. Barley,
which has previously been steeped in water for 2 days, is spread out over
the floor and allowed to germinate for 5-7 days. During germination, the
starch in the barley becomes soluble, thus preparing it for conversion
into sugar. Throughout this period the barley must be turned at regular
intervals to control temperature and rate of germination.
The starch in the barley is now
converted, via a natural process, into soluble sugars.
Today there are only a few distilleries
that have their own malt barns, Bowmore
Distillery
being one of them. The majority of the distilleries have their malted
barley produced commercially to their own specifications.
Once the barley has reached the desired
stage of germination, the green malt is transfered to the kiln mesh floor
where it is dried to halt the germination process. Heat and smoke billow
up from beneath the kiln floor and filter through the green malt. When
this drying is complete, the barley is said to be malted. Peat is burnt to
impart the unique smoky flavour into the moist green malt. The malt takes
on a wonderful smoky smell and taste.
At the end of kilning, the malt is ground
to a powdery substance called grist. Around 8 tonnes of grist is poured
into a mash tun where it is mixed with hot water at a temperature of
63.5˚C. This infusion allows the soluble starch in the grist to be
converted into a sugar solution. The solution, known as worts, is drawn
from the mash tun and transferred to the washback for the next process. A
further two waters are added to the mashtun to complete extraction. The
third water is used as the first water for the next mash.
The remaining husks of barley, known as
draff, are removed and used as cattle feed.
The sweet wort is transferred into a
wooden washback. The total amount collected is 40,000 litres. Yeast is
added which starts a natural process converting the sugar into alcohol.
Fermentation takes approximately 48 hours. The fermented wort, now known
as wash, has an approximate strength of 7% alcohol, and tastes like a
sweet, smoky beer.
Malt Whisky is traditionally distilled
twice, the first distillation taking place in the wash still. The wash is
transferred from the washback into the wash still. Steam filled coils heat
the liquid until the alcohol becomes vapour and rises up the still, over
the swan neck and into a condenser, where the vapour is then condensed
back into a liquid known as low wines.
The low wines are directed through the
spirit safe, where the strength and temperature are monitored by the
stillman. It then passes into receiving vessels. The collective low wines
average strength is 20% alcoholic volume.
The low wines then pass onto the spirit
still for a second distillation. The top fractions of the spirit (known as
foreshots) and the end (known as feints) then pass into the feints
received, ready for the next distillation to take place. Only the 'heart'
or the middle cut of the spirit is collected as new spirit to be drawn off
into casks for maturation.
The spirit and sample safe is the only
means by which the stillman can monitor the strength and temperature of
the spirit, allowing him to determine when the spirit is of a suitable
quality.
The new spirit is drawn off into oak
casks, which have been specially selected by the master blender.
These casks are stores in cool, dark
warehouses where they breathe, taking in some of the characteristics of
the enviroment in which they lay. At Bowmore,
the seawater, battering against the cellar walls, is strong determinant in
the flavour of our whisky. A proportion of the whisky in each cask
evaporates annually. This is known as the "angels' share".
Whisky can only be called Scotch Whisky
if it is distilled and matured in oak casks for a minimum of three years
in Scotland, but many of the casks that are filled at
Bowmore lie in the warehouse for many more
years before bottling.
Bowmore's distillery manager Ian McPherson ('Percy').
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