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Rum is produced from molasses, the final by-product in the manufacture
of raw sugar from sugar cane - indeed, in many Caribbean islands,
producers are legally required to be sugar refiners first and
rum distillers second.
Sugar Cane, saccharum officinarum is one of the taller
members of the grass family with the potential to grow up to 14
feet high under tropical conditions. In these hi-tech days, of
course, much genetic improvement has been made to increase sugar
content, or to give disease resistance, for example.
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| Harvesting
takes place by cutting the cane as close as possible to the ground.
In some places, the fields are first torched to clear away the dead
leaves ("trash") or to drive out snakes, a process which also makes
the cane easier to |
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cut. The method
used to do this depends on the size of the farm and the nature
of the terrain - hand-cutting by machete is still widely used
today, for example, where a farm is too hilly or too small to
benefit from mechanisation.
The cane plant
regenerates by sending out shoots ("ratoons") which grow into
new stalks. As they reach towards the heat and light of the sun
photosynthesis creates sucrose that is stored unchanged (unusual,
since in most other plants, sucrose is converted to starch).
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At the mill, the cane is chopped and then passed through a series
of rollers and grinders that squeeze out the juice from the stems.
The pulverised remains ("bagasse") are often used as fuel and can
even be turned into chipboard. |
The
acidic, green-coloured cane juice ("vejou") is now heated and
clarified before being pumped into evaporators which drive off
excess water. It is then cool-boiled in a vacuum to create a
syrupy mixture from which Grade A sugar crystals are extracted
- the kind that we use to sweeten our coffee and tea. The brownish-black
liquid that remains is known as light molasses (light in both
flavour and colour), often used as a syrup for pancakes or waffles.
After a second boiling, the molasses is darker and thicker -
generally described as black treacle.
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| Blackstrap
molasses, the stuff from which rum is made, comes from a third
boiling and is very thick, sticky, dark and somewhat bitter, though
it still contains approximately 55 percent of uncrystallised sugar
along with a large number of minerals and non-sugar compounds
essential for aroma and flavour. Approximately 1.5 gallons of
molasses are needed to make one gallon of rum. |
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| Fermentation |
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Before the molasses or cane juice can be distilled, it must
first be turned into an alcoholic liquid by fermentation.
This, in essence, is all about yeasts' partiality to sugar
- put them in a warm, sweet liquid and they multiply like
mad, secreting enzymes that convert the sugar into roughly
equal quantities of alcohol and carbon dioxide.
First, a
"live wash" with a sugar content of approximately 15 percent
is created by diluting the molasses with water, the quality
of which is really important. Cane juice, however, can often
be fermented without the addition of water if the sugar
concentration is low enough naturally.
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In the same way that sugar cane has been technologically
adapted to suit soil and climate, various strains of artificial
cultured yeasts are used to contribute to the individual
characters of different rums. However, many producers are
quite happy to rely on the wild yeasts naturally present
in the air to induce fermentation.
In some cases, notably where a heavy, dark style of rum
is desired, "dunder" (the residue left in the still) or
"limings" (the scum that forms on the surface of the molasses
as the sugar is being extracted) may also be added for a
more pungent flavour.
The rate of fermentation can be controlled by temperature
and depends entirely on the style of "dead wash" (the fermented
liquid) required by the distiller. If he wants a light rum,
fermentation can be completed in as few as 12 hours, though
a day or two is normal practice. Slow fermentation - which
can take up to 12 days - produces a heavier type, especially
when the live wash is reinforced with dunder. On completion
of fermentation, the dead wash has an alcohol strength of
between 5 and 9 percent.
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Distillation
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It seems ironic that the water added to molasses for
fermentation is then removed again during distillation.
However, this is the ethos of distillation: to separate
the alcohol from the water in a dead wash. There is
a second objective, however, which is to remove undesirable
flavouring agents in the form of esters, aldehydes,
congeners and acids, while retaining the favourable
ones.
There
are two discrete methods employed in rum production:
pot still distillation and column or continuous still
distillation. In both the principle is the same: when
wash is heated, alcohol vaporises at a lower temperature
than water and these fumes are collected and condensed
to give the spirit.
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Pot
Distillation
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Pot distillation is the more traditional and time-honoured
practice, tending to be reserved for the production
of premium rums of great complexity, subtlety, and finesse.
Each batch of wash has to be heated up separately and
needs careful monitoring, so the process is low and
quite costly as a result.
The dead wash is fed into a circular copper kettle which
helps to remove impurities. Heat is applied and, after
about an hour, the alcohol begins to evaporate. The
vapour is piped to a separate cooler and condensed to
give the spirit that, in most cases, is distilled a
second time to purify and concentrate it further, yielding
a distillate that can contain up to 85 percent alcohol
by volume. The art of the distiller is important because
the first and the last of the vapours that come off
(the "heads" and "tails") contain many volatile poisons
and unwanted fusel-oils. The distiller has to judge
when to collect the safe "heart" of the distillate,
a highly specialised job.
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Column
Distillation
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In contrast to pot distillation, column distillation
allows alcohol to be distilled continuously. This modern
technique was introduced into the Caribbean at around
the turn of the twentieth century and is quite definitely
the more widely used, efficient and economical method,
producing a stronger, purer spirit.
At its simplest, the construction comprises two column
called the "analyser" and the "rectifier". Thanks to
a clever design that utilises the physics of heat exchange,
the wash is broken down into its constituent vapours
(analysed) in the analyser and the vapours are selectively
condensed (rectified) in the rectifier.
In
practice, it's possible to control the strength of rum
produced in a continuous still because the condensate
can be drawn off the rectifier at various heights -
the higher up the rectifier, the stronger the spirit
and a distillate of 95 percent
alcohol
by volume is easily attainable. Incidentally, the spirit
of either distillation method emerges water-white in
appearance. Any colour in the finished product comes
form wood-ageing and/or caramel.
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Heavy
versus Light
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One of the fundamental precepts of distillation is that
the higher the alcoholic strength of the distillate,
the purer it will be. Highly rectified, column-distilled
rums, therefore tend to be crisp, clean and dry with
subtle aromas and only a whisper of molasses character
(some even approach vodka in their neutrality) and are
described as "light". By contrast, pot still rums, which
cannot be distilled beyond 85 percent alcohol by volume,
are relatively "heavy" in flavouring agents.
As a rule, the slower the fermentation, the heavier
the rum because other micro-organisms have the chance
to pitch in and work alongside the yeasts, contributing
their own set of flavours. They simply don't have timeto
do this during a rapid fermentation.
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| Ageing |
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Put the new clear spirit into an oak barrel, leave it
for a few years or so and there's no doubt that it will
improve dramatically. And this does not apply to dark
rum only. White rums can benefit greatly, too. An aged
white rum though innocent-looking can harbour intensely
deep, lingering and wonderfully integrated flavours.
Like so many processes, the advantages of oak-ageing
were discovered by accident. In the old days, the raw
spirit used to be bottled directly from the still which
remains more or less true for today's unaged white rums
(though it's now more usual to filter and dilute them
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first). When producers started to make more rum than
could be consumed, however, the excess was stored in
oak barrels that were also convenient vessels in which
to transport the spirit. It was soon noticed that the
white spirit soaked up colour and also developed a much
superior taste.
Exactly what takes place during the ageing process remains
on of nature's best-kept secrets, but the marriage between
spirit and wood is magical. The rum saps tanning, flavour
and colour from the wood and, because wood is porous,
it allows the rum to breathe, causing complex oxidative
changes to its chemical make-up.
The age or provenance of the barrel seems to make little
difference, though once-used bourbon casks are popular
and some are first re-charred on the inside. What is
known for sure is that a small cask (normally 250 litres
in capacity) is crucial to good quality - the smaller
the barrel, the greater the oak's influence. Any colour
acquired by a rum that is to be sold as a white style
is removed by charcoal filtering before bottling.
As a rule, light-type rums are aged for anything from
one to three years while heavy-types spend a minimum
of three years in barrel. With each passing year, the
contents become softer, smoother and more mellow and
can age successfully for up to 20 years before starting
to lose flavour, providing the climate is cool and damp.
It ages much faster in hotter, drier environments and
seldom improves beyond seven "tropical" years, one "tropical"
year being roughly equivalent to two to three cooler-climate
years. Age statements have to be treated with some caution,
therefore: yes, the older the rum, the better it will
be, but the place of ageing is also of great importance.
Over the years some rum is lost to the atmosphere through
evaporation. This is known as the "Angel's Share" and
also as "Duppy's Share" in Jamaica ("duppy" being Jamaican
for a ghost or spirit). In temperate climates this loss
accounts for about two percent of the contents of a
barrel annually, but in Jamaica for instance, this figure
climbs to six percent. It's quite normal, then, for
producers to attempt to slow down the rate of evaporation
by diluting the new spirit to about 80 percent alcohol
by volume before ageing. Luckily, the more attractive,
subtle effects of oak maturation happen to be extracted
at lower strengths.
The cooperage, where the ageing barrels are traditionally
fabricated, is filled with the sounds of hammering,
a glorious stirring euphony not unlike the old, rhythmic
Caribbean spiritual music. Coopering is an art in itself,
although sadly it is disappearing in favour of automated
barrel manufacture.
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Blending
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The majority of rums are created form a blend of rums
of different types and ages, and, in the case of some
of the large-volume, international brands, may be made
up of rums form different countries of origin. Caramel,
spices and flavourings are also added at the blending
stage if desired (though the latter can be added before
or during distillation).
This is where the expertise of the master blender comes
into play. His unenviable job is to ensure that the
contents of every single bottle are consistent in terms
of both flavour and quality - after all, the consumer
expects and demands their favourite brand to taste exactly
the same every time he or she buys it. Naturally, the
specification of each brand is a well-guarded secret.
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Once
the various constituents of the blend have been selected
and bulked together, they are allowed to "marry" for
a while before being reduced to bottling strength by
the addition of pure water. Here again, the quality
of the water is critical.
Talking of strength, it's always wise to study the percentage
alcohol given on the label before tucking into any rum
with gusto. Some of them are so incredibly strong that
you wouldn't want to breathe over a naked flame having
taken even the tiniest of sips!
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