A distillate is an alcoholic product derived from the distillation of a fermentable sugary liquid generally of vegetable origin. Before understanding how the distillation process works and the steps involved in producing an alcoholic distillate, it is interesting to delve into the history of these beverages of ancient origin.

A bit of history

The distilling technique was already known to both the Babylonians and the ancient Egyptians who distilled wine and cider. Around 1000 AD, in the Salerno Medical School, thanks to the Arabs who had perfected the alembic, alchemists and monks began the first distillations of essential oils and alcoholic liquids to create ointments and medicines. Alchemists, in search of the philosopher's stone capable of turning everything they touched into gold, distilled the most varied substances. Then one of them discovered that some distillates, rather than curing plagues, were pleasant to sip and gave a little cheer in those dark times. The subsequent discovery that ageing in wood improved their quality led to the distillates being rested for a long time in small barrels to enrich their aromas and perfect their harmony.

History of distillation

How is a distillate made?

Must preparation

  • Fruit mustcontains simple sugars, which are therefore fermentable. To do so, simply crush the fruit to obtain its sweet juice.
  • Must from cereals or potatoesThey contain starch, which is an insoluble and infermentescible complex sugar. Enzymes are required - under particular temperature and pressure conditions - to break down its chains and transform them first into maltose and then into glucose (fermentable). The must is prepared with hot water or through pressure-controlled autoclave processes.

Must fermentation

Once the must is obtained, selected cultures of yeast, S. cerevisiae, are added, which, over a period of 3-4 days at 18-25 °C, produce between 5-12% vol of ethyl alcohol and many other secondary substances that are crucial to the quality of the distillate, while many others are released directly from the yeast cell.

Must distillation

A physical procedure that separates the volatile components of a fermented product according to their different boiling points with a twofold objective: on the one hand, the ethyl alcohol present is concentrated (from 5-12% vol to 65-94% vol), and on the other hand, the substances that make a distillate valuable are selected and those that make it inferior are eliminated.

Distillation must preparation

Types of distillation

  1. Simple distillationIt is used to separate liquids with large differences in boiling points (even over 50 °C) as it is not effective at similar temperatures. This type of distillation is effective for purifying solvents or removing volatile impurities, but as far as 'drinkable' distillates are concerned, it is only used for small traditional productions where precise organoleptic characteristics are sought or for certain types of whisky and brandy. This type of discontinuous distillation commonly known as still distillation (pot still).
  2. Fractional distillationis used to separate mixtures of liquids with close boiling points through a fractional column to increase separation efficiency. This type of continuous distillation is the most common in the preparation of 'drinkable' spirits and is commonly known as column distillation (column still).
  3. Vacuum distillationis used to separate liquid mixtures of heat-sensitive substances, i.e. with aromatic compounds that would spoil at high temperatures. This technique, uncommon for drinking spirits, lowers the boiling points of the components by reducing pressure.
  4. Steam distillationis used to separate non-volatile or thermally unstable components through the use of steam. This technique, which is infrequent for drinking distillates, is useful in the case of essential oils from plant substances.
  5. Azeotropic distillationIt is used to separate liquid mixtures of substances capable of maintaining their composition intact even during boiling. It is not used for the production of spirits for drinking as it is considered unnecessary, although a possible application may be for the production of very high alcohol distillates.
  6. Molecular distillationis used to separate liquid mixtures of substances that have very high boiling temperatures at atmospheric pressure. Commonly used in pharmaceutical and experimental fields, it is not used for the production of distillates for drinking (image below).
Molecular distillation

Discontinuous distillation (still, pot still)

Discontinuous distillation allows the production of higher quality distillates and is carried out by intermittently feeding the boiler with fermented product. Each load is called crush and is discharged when exhausted; the still is then refilled with new fermented product. This technique takes place in copper pot stills with swan necks, used to produce ìarmagnac, calvados, cognac, grappa and whisky. Specifically, starting with the must, the stages are:

  1. loadingThe still is filled with a certain amount of fermented must, without overloading it to avoid overflowing or burning;
  2. heatingThe wort in the still is heated and as the temperature rises, the alcohols and volatile compounds begin to evaporate before the water as they have lower boiling points;
  3. separationAs the vapour rises within the still, it passes through the distillation head and condenser and cools down in the latter to become liquid again;
  4. collection: the condensed liquid is collected and the still selects the head (contains methyl alcohol and other undesirable volatile compounds), the heart (contains the most valuable part) and the tail (contains heavy compounds with unpleasant tastes);
  5. control and adaptationThe still precisely monitors the temperature and, in the case of values other than those desired, adjusts it to ensure that only the desired compounds are extracted;
  6. finaleOnce the desired amount of distillate has been collected, the process is stopped and the still is emptied, cleaned and prepared for the subsequent addition of must.

Continuous distillation

Continuous distillation is achieved by continuously feeding fermented distillate into the boiler. The distillate is continuously extracted and this process is therefore more automated, efficient and economical than batch distillation. This technique is used for the production of rum, tequila, grain whisky and industrial alcohol production. Specifically, starting from must, the steps are:

  1. pre-heating: Before entering the distillation column, the must is often pre-heated to increase the efficiency of the process;
  2. power supplyThe must is constantly fed into the distillation column (which consists of a series of floors, with each floor having a slightly lower temperature than the one below), without interruption;
  3. separationWhen the wort enters the column, it starts to rise and as it rises, it cools down, allowing some of its components (such as alcohol) to evaporate;
  4. extractionalcohol vapours reaching the top of the column are condensed and collected as a continuous distillate;
  5. controlThere is an automatic control to maintain constant temperature and flow, thus ensuring uniform distillate quality;
  6. removalThe heaviest residues, those that do not evaporate, are removed from the bottom of the column.
Continuous distillation column distiller

Distillation: stabilisation

Before bottling, almost all distillates undergo the REDUCTION of the alcohol content, refrigeration and filtration. The reduction in alcohol content is achieved by mixing demineralised water that is absolutely odourless, tasteless and low in mineral salts until the desired alcohol content is reached.

La REFRIGERATION at - 10°/ -20° for a few hours allows the condensation and precipitation of the heavier substances, which are generally not very noble and sometimes cause turbidity. These are then separated and removed with the FILTRATION through cellulose and cotton filters, microscopic fossils (diatoms) and finely crushed rocks (perlites) or microporous membranes.

Eventually a RETURNS for which the law permits the possible addition of up to 2 % of sugar to give smoothness and amplify aromatic persistence.

Some claim that the addition of sugar also serves to mask poor distillates, but this is false since adding it would also enhance the defects. Furthermore, the addition of caramel or burnt sugar influences the colour to the point of making even young spirits appear aged, but often brings unpleasant flavours and retronasal sensations.

Optional Procedures

  1. Ageingsome spirits (whisky, brandy, rum...) are aged in wooden barrels to add olfactory and taste-olfactory complexity.
  2. FiltrationSome distillates are filtered to remove impurities or to refine the flavour. A famous example is the cold filtration of whisky, which can influence both its smoothness and its transparency.
  3. DilutionAfter distillation, many distillates are diluted with water to achieve the desired alcohol content. Dilution is optional and the degree of dilution varies depending on the product and the producer's preference.
  4. AromatisationSome spirits, such as liqueurs, can be flavoured with herbs, spices, fruit, or other ingredients.
  5. Mixingsome distillates can be blended together to create a homogeneous end product (e.g. blended whisky).
  6. RestAfter distillation and before bottling, some distillates may be left to rest for a period to allow the flavours to harmonise.
  7. Refinement: Some spirits may undergo a second ageing period in different casks to add additional layers of flavour. For example, some whiskies may be finished in casks that have contained sherry or port.
distillate ageing

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Questions & Answers

What does the word 'proof' on a distillate label mean?

The word 'proof' on a spirits label refers to a measure of the amount of alcohol contained in the drink. Originally, it was a term used in England to describe the potency of alcohol, based on a test involving the addition of gunpowder to liquor. If the liquor was strong enough for the gunpowder to ignite, it was considered 'proof'.

Today, the proof measurement system is more standardised and scientific. In the United States, proof is exactly twice the percentage of alcohol per volume (ABV). Thus, a spirit labelled '80 proof' has a 40% of alcohol per volume.

How high should a distillate be?

The alcohol content of a distillate can vary greatly depending both on the type and on the specific regulations of the country of production. In general, most distillates have an alcohol content ranging from 40% to 50% in volume of alcohol (ABV, Alcohol by Volume).

Why do you concentrate the alcohol to such high values if you then dilute the distillate to e.g. 40% vol?

The high concentration of alcohol in distillates before their eventual dilution has several reasons:

  1. flavour extractionDuring distillation, alcohol acts as a solvent, extracting aromas and essential oils from the raw materials, so a higher concentration of alcohol can extract a richer and more complex aromatic profile;

  2. conservationalcohol, especially high alcohol content, has preservative properties and this is particularly important during the ageing process, which can last for many years;

  3. ripeningalcohol has extractive capacities that increase proportionally as the alcohol content increases, so a higher alcohol content can influence the way the distillate interacts with the wood and absorbs its compounds;

  4. standardisationProducing distillates with a higher alcohol content and then diluting them allows greater control over the final product and a uniform quality standard between batches;

  5. reduced transport and storage coststransporting and storing high alcohol distillates is more space and cost efficient;

  6. commercial and regulatory powerDiluting the distillate serves to satisfy both consumer preferences and the regulations of any specifications or marketing countries.