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David on Technical Topics – Cognac Distillation, The Wine Reduction Distillation – The Wine Reduction

In the 16th and 17th centuries, the brandies produced in the Charente were reduced by distillation as this made them easier to ship abroad.   The risk of low alcohol wines going off before they reached their destination was avoided and the intention was to cut them back with water before they were consumed.  But the Cognaçaise soon found that keeping the strong wines in barrels changed them for the better and so they started to learn the skills of distillation.

The basic concept of distillation is that you boil the wines, collect the vapours that escape and then allow them to condense back into a liquid. It sounds ridiculously simple but there are many things that can go wrong unless the process is carefully controlled.

Cognacs are double distilled, that is to say that after the first distillation the wines are re-introduced into the still to be distilled a second time.  During the process most of the chemical changes in the wine occur,  at a temperature of less than 40 degrees, during the first distillation.  Careful consideration must therefore be given as to that which is put into the still. Most modern day cognac distillations include the lees; this is anything but the juice.  Most lees used consist of the pulp of the grape.  In some cases the skin is also added but the pips and stalks are not as they will introduce an unacceptable bitterness.  Some purists will filter out the lees and distil just the juice but this provides a cognac with less flavour and ultimate complexity.  It is the yeast in the wine that contains esters which enrich the cognac and provide more flavour.

The first distillation is regarded by many as the most important as this is when the essential qualities of the fruit are extracted. The slower the cooking the more thoroughly the flavour in the wine is absorbed into the resulting brouilli (a cloudy and non-descript liquid at a strength of between 28 – 32 degrees). The brouillis is undrinkable and it is quite impossible at this stage for the distiller to determine the qualities of the final liquid.

The second distillation is known as the Bon Chauffe (good heating).  Not all the newly distilled liquid or eau de vie is used. The first quantity, of around half a percent, is known as “the heads” and is discarded as it is too strong and will probably clog with some of the solids. The last part of the distillation, “the tails”, will be too weak.  They can be re-introduced into the still but this is in itself a major decision.  If the tails are used they will be distilled twice more and will create a level of neutrality in the final spirit. The middle part, which is probably greater than 95%, will be stored in new barrels for a few months to provide the new spirit with an initial boost of flavour and colour. The distillation range of the second boiling must be between 67 – 72.4 degrees, above this range the spirit will be burnt and below it there will be insufficient refinement in the final cognac.

To read more Technical Topics go to our Brandy Education page.

David on Technical Topics – Cognac Distillation, The Still

Cognac Still
Cognac Still

The cognac distillation process is the most technical part of making the golden nectar. It is the stage where the wine is reduced to a spirit, which we refer to as ‘eau de vie’. Distillation is carried out twice. The first time it changes the wine to a ‘brouillis’, a cloudy liquid with a strength of around 27 – 30% alcohol, and then it is distilled again.   In this article we will consider the distillation equipment required and next month we will explore the process.

The complete distillation process is controlled by the Bureau National Interprofessionel du Cognac (BNIC) and every distiller must comply with the rules that protect the name of ‘Cognac’. The process usually starts at the end of October once the grapes have fermented and changed into a relatively low alcohol, acidic wine.

The bulbous, onion shaped, original design of the cognac still is largely accredited to the Dutch in the seventeenth century and has not changed significantly since. Sitting on top of this still is the chapiteau or still head. This is where the vapour rises after boiling and before continuing into the swan’s neck, an appropriately named pipe extending from the top of the still head. Eventually the vapour enters the serpentin, a large coil in a water tank, where it condenses before entering a tank ready for the second distillation.

Different still designs can influence the cognac’s final flavour. Firstly the size of the still is important. The smaller the still the more distinctive the cognac it produces whereas larger stills tend to provide more neutral flavours. The problem of neutrality is also created by the shape of the still head. Large, wide onion shaped stills allow the vapour to drip back into the still, a process known as rectification, and so the spirit is re-distilled. Conversely, narrow, shallot shaped heads allow the vapour to leave the still faster, with less risk of it condensing, before it has rounded the swan’s neck.

The other choice distillers must make is whether or not to use a chauffe-vin , a type of heat exchanger which sits between the still and the serpentin (condenser). This enables the warmth of the hot vapour to warm the wine before it enters the still for boiling whilst the initial temperature of the wine cools the vapours to initiate condensation.

Next month I will look at the Distillation Process.  To read more Technical Topics, go to our Brandy Education page.