The second stage of distillation further purifies and concentrates the distillate.
In addition to pure ethanol and water, low wines contain large amounts of less pure alcohols and oils, primarily esters, aldehydes, furfural, and other compounds of hydrogen, oxygen, and carbon. Hundreds of these organic chemicals have been identified in malt whisky, and chemists believe there are hundreds more that have yet to be isolated. They are collectively known as congeners or (in the United States) congenerics. Although they are considered impurities, they are what give malt whisky its distinctive flavor and therefore cannot be completely removed. The key is to accurately control the levels of these components in the remaining distillate.
The impure alcohol is distilled off at the beginning and end of the second distillation. The early distillates are called foreshots, while the later distillates are called feints or after-shots. Only the middle distillate is kept, which is called the cut.
The cut point must be determined very precisely, as too many undesirable compounds, or fusel alcohols, can make the distillate unpalatable. The skill of the distiller lies in creating a distillate with a high enough level of fusel alcohols to ensure the unique flavor of the whisky.
When the temperature in the still reaches 84°C (183°F), foreshots begin to flow. If they flow earlier, it usually means that there will be a longer and more alcoholic distillate to come. Because the foreshot contains impurities, it has a high alcohol content and a sharp, pungent smell. The distiller closely watches the foreshot flow into the "spirit safe". This is a box with copper rims and a glass front. The distiller tests the purity of the foreshot by adding water to it, which is called the "demisting test". If the distillate becomes cloudy after adding water, it is not pure enough. The distiller also uses a hydrometer to measure the strength of the spirit. Before the distillate is clear, he allows the foreshot to flow into a receiving tank for the first and last stills for redistillation. Once the distillate is clear, the distiller directs the outflowing distillate into a holding container by operating a pipe in the spirit safe. Some distilleries omit the testing in the liquor safe and instead process the first distillate according to a specified time.
The distiller determines the timing of the cut based on the "demisting point". In any case, the cut occurs when the alcohol content of the spirit drops to 72% to 75% (ABV), which usually takes 15 to 30 minutes. As we will see, the timing of the first cut is critical to the characteristics of the final product.
The initial runoff from the second distillation is rich in highly desirable aromatic esters (after impurities have been removed, of course). These esters have a pleasant, fruity aroma reminiscent of pear candy, banana and rose. They are valuable flavor enhancers in malt whisky, helping to enhance the overall flavor of the whisky. There are at least 100 different esters in malt whisky - the most important from an aromatic and chemical perspective are isoamyl acetate and ethyl caprylate. About halfway through the second distillation, another group of aromatic compounds begins to emerge from the spirit. These are the "feints". As the distillation continues, the feints become increasingly concentrated and the ester content decreases.
Initially, the smell of the distillate is fresh and biscuit-like, but then it becomes porridge-like and gradually develops leathery smells, followed by a brief honey aroma phase. However, after this, the aroma of the distillate quickly deteriorates and becomes unpleasant, such as sweat, fishy smell and vomit. In chemical terms, the early acceptable grain distillate is nitrogen-containing organic compounds, while the later unacceptable distillate is sulfur-containing organic compounds. The latter can be extremely strong in aroma intensity (even at a concentration of one trillion can be detected), and its smell is often described as sulfide, rubbery or eggy.
As the concentration of the tailings increases, the distiller must stop collecting the whisky before its smell becomes unpleasant, even though the alcohol concentration is still high. This marks the end of the cut point, and this timing is critical to the overall flavor of the whisky, as some of the heavier tailings components have already appeared. The longer the distiller takes before stopping the collection, the richer the tailings flavor and the fuller the body of the whisky; but if the whisky is cut too early, the whisky will not show the flavor characteristics it should have.
Distillers are often tight-lipped about the ABV at which they stop collecting whisky.
Some, particularly in Speyside, who seek a lighter style of whisky, will cut at up to 69% ABV, while others looking for a heavier flavour will cut down to 60%. Unfortunately, this decision is sometimes made by accountants rather than artisans who strive for excellence.
The third key aromatic group in malt whiskey is phenolic compounds. We have already discussed their origin in peat. Phenolic compounds usually start to show up in the distillate about one-third of the way through the cut, but unlike the other two key aromatic classes, their concentrations neither rise nor fall significantly. Some blenders grade whiskey by measuring the balance of esters, tail distillates, and phenolic compounds.
As the distillation process continues, the temperature of the still rises to 100°C (212°F), the boiling point of the de-alcoholised low wines.
The speed at which the still is run affects the purity and flavour of the wine. If the still is running too fast, the tailings will rush into the still too quickly, giving it a harsh, pungent flavour. In fact, a strong estery aroma in the still is often a sign that the still is running too fast. Some stills even have steam control meters that automatically adjust the amount of steam to ensure that the wine is flowing out at the required steady rate, which usually varies from 9 to 23 gallons (41 to 104 litres) per minute. It is ideal to let the still "rest" for a while before changing the still's running mode, as a well-rested still will produce a lighter wine.
The width of the cut-how much of the still and tails are retained-has a profound effect on the flavor of the final product. The later portion of the second distillation is introduced into the still and tails tanks along with the earlier portions for distillation again. The still is run until the alcohol concentration of the still drops to 1% ABV, at which point the remaining liquid, called "spent lees," is discarded. The total amount of tails and spirit from the second distillation is about one-twelfth to one-thirteenth the volume of the original fermented liquid in the still.
In whisky production, the number of distillations usually depends on the desired flavor profile and the traditions of the region in which it is produced.
The most common distillations are double and triple, and which method is most appropriate depends on the specific goals and process requirements.
Most single malt Scotch whiskies are distilled twice. This helps retain more flavor and complexity in the whisky. The advantages of double distillation include:
Retain more flavor substances
Double distillation can remove unnecessary impurities (such as methanol and other volatile components) while retaining more flavor substances such as aromatic esters and phenols, making the whiskey richer, full-bodied, and with a unique malt aroma.
Stronger flavor
The liquor obtained from double distillation is usually heavier and fuller-bodied, suitable for distilleries that want to reflect more grain, peat smoke or wooden oak barrel flavors in their whisky.
Lower cost
Compared to triple distillation, double distillation is a less expensive process because it reduces distillation time and energy consumption.
Triple distillation is mainly used for Irish Whiskey. For example, famous Irish distilleries such as Midleton and Bushmills often use this method. Triple distilled liquor usually has a clearer and lighter taste. Its main advantages include:
Lighter and smoother
Triple distillation can effectively remove more impurities, making the wine taste softer and smoother, with lighter fruity and floral aromas, so it is often described as more "clean" and "delicate".
Reduce harsh taste
The high purity of triple distillation means that the liquor contains almost no components that would bring rough or pungent smells, such as certain heavy phenols or sulfides.
Perfect for young whiskey
Because triple-distilled whiskey is purer, it is easier to achieve a balanced taste in a shorter aging time, which makes triple distillation particularly suitable for the production of young whiskey.
As for single distillation and multiple distillation, it is very rare. However, some regions (such as the United States producing corn whiskey) will use single distillation, which retains very original grain and fermentation flavors. Some experimental or special whiskeys may be distilled multiple times (more than three times) to obtain an extremely light flavor, but this is usually a rare exception.
The number of distillations can indeed affect the flavor concentration, complexity, and smoothness of the rum.
Double distillation is suitable for rum with a strong flavor, while triple distillation is more suitable for a refreshing taste. In addition, based on Mr. Guan Xianglin's experience in brewing and distilling hundreds of times in the past six years, he found that the choice of the number of distillations also depends on factors such as raw materials, temperature control during the brewing process, and the design of the distiller (such as the shape and size of the pot distiller). Therefore, the Gaoligong Mountain series of rum was ultimately decided to be triple distilled, that is, three precise distillations were performed using a full copper pot tower distiller to obtain the final flavor diversity, three-dimensional aromatic layers, a light and gentle body, and a smooth and clear taste. This is the original local agricultural rum .
As for the "cutting point", it is also the most critical "technology".
If the foreshots ( the "fore-distillates" mentioned above ) are cut too early, all the fusel alcohols, especially the fusel alcohols that are harmful to the human body, will be mixed in, which may not guarantee the safety of rum for the human body and the pure taste. Many distilleries are reluctant to discard the foreshots, thinking that it is a pity to discard it because of its "high alcohol content". However, they do not know that such foreshots contain a large amount of methanol and other harmful ingredients. In addition, the tails (the "feints" mentioned above) cannot be cut too late. Usually, the tails are rich in heavier fusel alcohols and phenolic compounds, such as thiols, phenols, nitrogen-containing and sulfur-containing compounds. If there are too many of these ingredients, the flavor of rum will become too pungent, rough and even have an unpleasant smell (such as pig food, rubber, sour smell, rotten eggs or sweat smell). However, the right amount of tails can add a complex original sugarcane aroma or a heavy body to rum, so its content needs to be precisely controlled.
In other words, a healthy and delicious rum contains sufficient ethanol and various chemicals that give it a unique flavor. The liquor at this stage has the fruity, floral, and woody aromas of aromatic esters, as well as the original flavor of the raw materials, but it is not too strong, has a light taste, and makes people feel wonderful and extremely pleasant after drinking.
In general, "how to cut the wine" determines the direction and quality of the final flavor of the rum. It finds a delicate balance between removing impurities and retaining flavor substances, ensuring that the rum has both ideal body and flavor complexity without bringing too much rough and pungent impurity flavor. Therefore, the judgment of the cutting point is one of the most critical links in the entire distillation process, and it is also the core step to determine whether the rum can achieve the expected style and quality.
