Distillation Theory
Simply put, distillation is the process in which a liquid is evaporated (turned into a vapor), recondensed (turned into a liquid), and collected in a container. Distillation is a very old separation technique that separates a liquid mixture into its individual components by heating. The basis for the separation of components is their different boiling points. A mixture of two or more compounds is separated by heating the mixture to a certain temperature and condensing the resulting vapor. The vapor above the boiling mixture becomes richer in volatile components. As a result, the boiling mixture becomes richer in less volatile components. This means that the original mix will contain more less volatile substances.
The Distillation Cut
During distillation, ethanol and water are the two main components which are actually carriers of all other volatile compounds. It could be considered that the ethanol vapor will carry over the compounds favoring spirits aroma and flavor and therefore the quality.
At the very beginning, a high volume of ethanol comes out of the still together with high volatile compounds. Over time, the volume of alcohol is decreased followed by water, and low volatile compounds increased. According to this, the distillate is cut into three cuts or fractions: the head, the heart, and the tail. The heads contain a higher concentration of low boiling point components and mainly contain undesirable compounds. These compounds would give the distillates an unpleasant, strong, and sharp flavor. In the first cut, there is a higher concentration of some toxic compounds, and therefore it must be eliminated. The best part of the run is the middle part of the distillation, the final spirits. It is a distillate rich in ethanol that is carrying pleasant and fruity aroma compounds. The heart cut is a very clean taste lacking the sharp bite of the heads. The last cut is the tail fraction, which has to be eliminated from the heart since it contains unpleasant fatty and oil compounds. In this fraction, the main carrier is water. The water is carrying longer molecules, which are usually unpleasant and can be identified by the distinctive smell of ‘wet dog’. The tail fractions (with or without head adding) are collected and redistilled because they contain a relatively high concentration of alcohol and valuable congeners.
How to Make Cuts During Distillation Run
In order to produce an aromatic, harmonized, and pleasant fruit distillate, it is necessary to know the right time for distillation cut. During the distillation of ethanol and congeners, it is possible to manipulate the separation of volatile compounds, to clean undesirable and to concentrate desirable aroma compounds. The aroma profile of distillates very often depends on the skill of the distiller to cut adequately distillation fractions. The head and tail fractions could be cut on the basis of sensory evaluation of the distiller. The presence and absence of volatile congeners that give a sharp, strong, and unpleasant smell to the head fraction can be cut points for switching to the heart fraction. Also, the tail fraction starts with a flavor that gives a faded, dull character to the distillates, and it should not be difficult for sensory evaluation and separation. Experienced distillers do this very well by smell. Taste and smell still remain the most reliable method of determining when to make a cut.
The second indicator of cut points that can be used is the percent alcohol of the spirits that are flowing out of the still, especially for the separation of the heart from the tail cut. The ethanol strength could be the limiting values for switching from the heart to the tail. This limiting value varies depending on the distillation equipment involved, the fruit variety used, the quality of fermented mash, etc. Finally, the third indicator of the cut points that can be used is the temperature of the vapor before entering the condenser. The distiller can make the first cut in the run when the temperature of vapor in the copper pipe reaches approximately 74–76°C. The heart cut from the tail can be made when the temperature of vapor in the copper pipe reaches around 87–88°C, and the tail distills until the temperature reaches 92–93°C when distillation could be over.
Each of the above-mentioned manners of distillation cut has a shortcoming, and the best way is to use all of them as a guideline for the separation of congeners during distillation.
Alembic Pot Still vs Column Still
One of the most relevant steps in the elaboration of spirits is the distillation process. The distillation process can be used to correct possible mistakes that have occurred during the previous processing of the raw material. In addition, inadequate distillation can cause many defects that are difficult to eliminate by the following technological processes. During the distillation, heat facilitates the fitting of volatile compounds into resulting spirits. For the production of fruit spirits, the alembic pot still and batch distillation column are the most suitable because spirits will retain the decent fruit aroma and flavor. For most of the compounds, there were no differences in concentration regarding the distillation equipment used. However, the concentrations of volatile compounds were influenced by the processing and storage of raw material more than the distillation equipment used.
Alembic stills yield better aroma that comes from fruit, the so-called primary flavor. The alembic pot still produces distillates that retain the character and personality of their source ingredients. This method is slow and requires more labor, but the usage of a simple copper still was preferred by several authors. Also, results showed the distillation of pear wine with less copper alembic leads to a better quality product.
A higher concentration of alcohol and higher separation of other volatile compounds were achieved during distillation in a batch column still, giving a decent aroma of distillates. The greater yield is obtained in recovered ethanol, allowing increased productivity by means of column distillation. This type of distillation is more effective. Nevertheless, the column-distilled spirits contained four times more esters, 20% more higher alcohols, 40% less acetaldehyde, and 10% less methanol than alembic spirits. Some results referred that distillates made by using a distillation column had higher sensory acceptance than distillates made in an alembic pot. According to these authors, sensory acceptance of cleaner fruit spirits (spirits with a lower content of esters, aldehydes, higher alcohols, and methanol) was higher. The art of the distillation run is to obtain the best balance between congeners present.
ACE Copper Column Still for Sale
Also, less aromatic fruit varieties can be used to produce distillates with aromatic characteristics similar to a more aromatic variety if a suitable distillation process in a distillation column is used.
The traditional distillation with an alembic pot still allows limited intervention during the distillation process (only the heating power in the boiler can be manipulated) to modify the composition of the distillate. A more flexible system is the batch distillation column (in which the reflux rate can be varied in a wide range). At the same time, the other investigation showed that the process with a batch distillation column is much less reproducible than alembic distillation.
Some are observed that distillates produced in the alembic pot still are usually stored in wood for many years (e.g., Cognac and Whisky), whereas the distillates produced in the distillation column are stored in glass and consumed as clear spirits. I consider that raw material rather determines whether distillates will be stored in wood or not. The author of this chapter considers the way of aging that is determined by the raw material used rather than the distillation apparatus. In fruit spirits, long aging would mark the primary flavor of the fruit. If the distiller produced a distinctive flavor of some fruit, regardless of the distillation apparatus used, it should protect the pure fruity note, not to give the distillates a strong and too much complex flavor gained during maturation in wood (quaternary flavor). If aromatic fruit spirits need to be stored in wood, then it should be just for a while so they would retain a fruity touch.
