Words by: Simon Difford
Vodka can be distilled from pretty much anything that can be fermented to make alcohol, but its mostly produced from potatoes, sugar beet molasses and cereal grains. Obviously, what ingredients are used to make a vodka will substantially influence its flavour.
Some crops grow better than others in certain climates and traditions and tastes have dictated that farmers and distillers in different countries favour different crops. The Poles use mostly rye to make their vodka, the Finnish favour barley and the Russians and indeed most other nations tend to use wheat.
Here is a list of raw ingredients and the typical flavour profiles they impart to the vodka:
Wheat: subtle aniseed and pepper, lemon zest.
Rye: nutty sweetness, rye bread, brazil nuts.
Maize/corn: buttery, corn-on-the-cob.
Barley: bready, lightly nutty, brioche sweetness.
Potato: creaminess of texture and fuller flavour often slight vegetable notes.
Grape: strangely, Cîroc, the leading grape vodka has a slight lemon zest character.
Grain, especially wheat, dominates vodka production as the preferred base with the use of potato also well established. So predominant is the use of grain that the latest EU regulations (No. 110/2008) stipulate, "To take into account consumer expectations about the raw materials used for vodka, especially in the traditional vodka producing Member States, provision should be made for adequate information to be provided on the raw material used where the vodka is made from raw materials of agricultural origin other than cereals and/or potatoes." Meaning vodkas made from grape and other non-traditional ingredients must declare this on their labels.
Potato varieties used for vodka production are specifically chosen due to their high starch content, typically 25 per cent compared to 17 per cent for eating potatoes. Small potatoes are favoured for distilling, as they are higher in starch than bigger potatoes which are swollen with water. Even with these high starch varieties it takes 16 tonnes of potatoes to make 1,000 litres of spirit at 96.4% alcohol by volume.
A good bar should offer customers a real choice of vodka styles. Offering five different Polish rye based vodkas but no wheat or potato vodkas would as crazy as stocking five different Irish stouts for your entire beer range.
Leading vodkas, their country of origin and base ingredients:
Absolut (Sweden) - wheat
Belvedere (Poland) - rye
Chopin (Poland) - potato
Cîroc (France) - grapes
Danzka (Denmark) - wheat
Eristoff (Italy) - wheat
Finlandia (Finland) - barley
42 Below (New Zealand) - wheat
Green Mark (Russia) - wheat and rye blend
Grey Goose (France) - wheat
Idôl (France) - Grape
Imperia (Russia) - wheat
Karlssons Gold (Sweden) - potato
Ketel One (Netherlands) - wheat
Luksusowa (Poland) - potato
Oval (Austria) - wheat
Pfau Bramburus (Austria) - potato
Russky Standart (Russia) - wheat
Sipsmith (England) - barley
Smirnoff 21 (Russia origins) - wheat
Smirnoff Black (Scotland) - wheat
Sobieski (Poland) - rye
Stolichnaya (Latvia) - wheat
Svedka (Sweden) - wheat
Tanqueray Sterling Vodka (Scotland) wheat
Ursus Classic (Netherlands) - wheat
VikingFjord (Norway) - potato
Wyborowa (Poland) - rye
Xellent (Switzerland) - rye
Whether vodka is to be distilled from grain, potatoes, sugar beet or grapes, the first step is to produce alcohol using yeast. The process of culturing yeast under conditions to produce alcohol is called fermentation.
When certain species of yeast, most notably Saccharomyces cerevisiae, metabolize sugar they produce ethanol and other alcohols, carbon dioxide and heat. If sugar is present in the raw material being used, as is the case with molasses or fruit, then this can be directly fermented as the yeast has an immediate food stuff. So the fermentation of grapes, molasses and other ingredients containing sugar is straightforward. Indeed, grapes tend to have yeast cells on their skins so merely crushing grapes and leaving them is often enough to start a natural fermentation.
If grain (barley, wheat, corn/maize, rye) is being used the grain will first have to be heated to form a mash. Amylase and diastase enzymes are added to break down the long chains of starch molecules into simple sugars which are perfect for fermentation - mainly glucose and a small amount of maltose.
Potatoes must first be cleaned and their skins removed by scrubbing as the peel is mainly fibre and cannot be fermented. The peeled potatoes are then chopped and moved to a mash vessel where they are cooked by steam to gelatinise the starch. The term 'mash' when discussing potatoes would more usually suggest the mashing of potatoes i.e. macerating the potatoes into small pieces, rather than the conversion of starch to fermentable sugars by heating. Both uses of the term 'mash' are true of this particular mashing process, in which potatoes are continually pumped around, thus reducing the size of the lumps to make a runny mashed potato, so producing a larger surface area for the enzymes to work on.
The runny potato is cooled to 60°C, an ideal temperature for the action of the enzyme which is added to the gelatinised potato to help the conversion of starch to sugars. The mixture is then cooled to around 30°C, at which point the yeast can be added.
Distillers of old would rely on natural airborne yeasts for their fermentation but today's distillers usually add commercially prepared distiller's or brewer's yeasts, or in some cases their own cultured strains of yeast.
Small propagation or starter tanks, rich in sugars may be used to start the yeast before it's added to the main fermentation tank. This allows the numbers of yeast cells to multiply rapidly, making the yeast stronger and better able to process the mash. This practice is particularly necessary when fermenting molasses.
Ethanol is toxic to yeast, thus limiting the ethanol concentration obtainable by fermentation alone. The most ethanol-tolerant strains of yeast can only survive up to approximately 15% ethanol alcohol by volume.
Saccharomyces cerevisiae yeast functions in temperatures from around 18-33°C. As the yeast metabolizes the sugar to produce ethanol it also produces heat so temperature has to be monitored and in some cases controlled by pumping cold water through pipes or surrounding jacket. If the temperature is allowed to rise much above 35°C then the yeast will die and the fermentation will stop.
Saccharomyces yeast not only produces ethanol, it also produces higher alcohols at temperatures above 23.8˚C. These alcohols are called fusel alcohols or fusel oils and tend to have a spicy or peppery flavour. A slow, well-controlled fermentation will produce a better quality wash with lower levels of methanol and fusel.
Depending on the base ingredient, the fermentation process, which can last anything from one day to two weeks, produces a beer-like liquid called 'wash' at 7-15% alcohol by volume.
Ethanol alcohol distilled to more than 95% purity is commonly called 'neutral spirit'. The term used in this context refers to the spirits' lack the flavour. More flavour would have been present if the mash ingredients were distilled to a lower level of alcoholic purity.
It is usual to indicate the type of base ingredient used to make a neutral spirit. For example grape, grain, molasses become grain neutral spirits, grain neutral spirits and molasses neutral spirits.
As continuous column still technology became more sophisticated, a new class of distillers who specialised in producing neutral spirit emerged. These distillers are sometimes referred to as agricultural distillers. The vast investment required to set up a new column still is simply not viable for small distillers who do not have a market for the vast volumes of alcohol such stills are capable of producing.
Two-tier distilling was around even before the column still was invented. It is more efficient to ferment and distil grain near where it is harvested and to ship the high strength alcohol than it is to ship grain or molasses. The high quality and low cost of neutral alcohol produced by large specialist distillers has led most vodka producers to buy in their base alcohol rather than produce it themselves. Many then redistill the base alcohol to further rectify it using column or pot stills.
The vodka producer can import high strength neutral spirit and dilute it with water, bottle and then distribute to his local market.
It is not just the economics of shipping and the inability for small land mass countries such as the UK to meet their grain needs that has driven two-tier distilling. Governments wanting to control and monitor the payment of taxes due on alcohol have often legislated to force distillers to buy in their base alcohol. In the UK such legislation which prevented neutral alcohol being made at the same distillery where such alcohol was redistilled to make gin was only recently overturned. Even today, only a handful of vodka distilleries in the world produce their own base alcohol from grain on the same site where finished vodka is produced.
Purifying or 'rectification' columns remove any remaining off notes or odours from alcoholic spirit. It is common practice in vodka production for a distiller to purchase neutral spirit from an agricultural distiller and then to further rectify that spirit in their own stills.
As the quality of neutral spirit available from agricultural distillers has greatly improved with modern still technology it is now possible to buy base alcohol that does not require further rectification. Hence, many so called "vodka distillers" are merely compounders who purchase high quality neutral spirit and blend it with water to reduce it to bottling strength, often also adding small amounts of sugar or flavouring according to their vodka recipe.
Pot stills are credited with having a discernible rounding affect and adding character, so it is no coincidence that many 'boutique' vodkas such as Ketel One include pot still finishing as part of their production process.
Distilling wash (beer) in a pot still produces a liquid with an alcohol content of around 21% alcohol by volume. Subsequent pot still distillations can be used to increase the strength of the distillate to 70% alcohol by volume and this is exactly how malt whisky is made to this day. Vodka was also once made in this way butj 70% alcohol means there are 30% impurities and while that is OK, even desirable in a spirit that will be mellowed by aging for a minimum of four years in oak casks, this process would produce pretty rough vodka.
Modern fractional distillation in a column still can produce alcohol up to 95.6% alcohol and in an age where vodkas are praised for their 'cleanness' and 'purity', so column stills of one type or another are usually employed in vodka production. In early vodka production, prior to the invention of the column still, various methods of filtration where employed in an attempt to further purify the distillate.
Thankfully, column distillation has not completely displaced the pot still in modern vodka distillation and some of the most premium vodkas, most notably Ketel One, use pots stills in their production process. Rather than start with a pot still, these vodkas are finished in a pot still. The wash is distilled in column stills using fractional distillation to produce a very pure 'neutral spirit' at 95.6% alcohol by volume. This is diluted back to around 50% alcohol by volume using purified or spring water and then redistilled in the pot still. Sometimes very small quantities of botanicals are added to the pot still to add a slight flavouring to the vodka.
Finishing an already very pure distillate in a copper pot still helps produce a softer, some say 'smoother' distillate. The copper the stills are made from plays a chemical part in this process as it acts as a catalyst to promote the formation of esters which impart desirable fruity notes to the spirit. Copper also reacts sacrificially to remove unwanted sulphur compounds - those are the ones that smell of struck matches, drains, rotten eggs, farts and cabbage - none of which make for an appealing vodka.
Copper helps turn these nasty smelling sulphur compounds into easily removed Copper Sulphate (U.S. Copper Sulfate) a copper salt (CuSO4•5H2O). Copper Sulphate (when in its pentahydrate form) is bright blue and when visiting a distillery blue deposits can often been seen on the flow pipe from the condenser (or inside spirit safe). The stills are cleaned with mild caustic solutions every now and then to remove the sulphates.
Pot still finishing will produce a discernibly heavier spirit so vodkas such as Ketel One which employ pot still finishing tend only to use a small proportion of this spirit which they blend with more neutral alcohol so that the pot still affect is not too heavy.
Water forms some 70% of the contents of a bottle of vodka so is crucial to both its taste and mouthfeel.
Distilleries are usually established in locations where there is a good supply of raw materials such as grain or molasses, good transport for the finished product, a reliable power source and most importantly, a plentiful water supply - ideally soft water which is low in salts and ions. Distilleries use a lot of water.
Distillers favour water naturally low in dissolved salts and ions such as sodium, chloride, calcium carbonate, calcium sulphate and magnesium. It is common to find distilleries supplied by artesian wells or natural springs and much is made by marketing departments about the purity of the water used in their vodka production.
Modern water purification technology allows distillers to demineralise water using reverse osmosis to produce pure, tasteless water which will not affect the flavour of the finished vodka.
To affect reverse osmosis, water is pumped through tubes at a very high pressure and then forced through a selective membrane. The larger molecules and ions are unable to pass through the membrane and so are separated from the now demineralised water.
When water is blended with ethanol alcohol there is a reaction generating small amounts of heat. Consequently, some distillers prefer to gradually hydrate their spirit, slowly reducing it to bottling strength. Some choose to let the vodka rest to allow the spirit and water to coalesce, like leaving the molecules in you food to settle down after cooking in a microwave.
It has long been common practice to add small amounts honey to vodka to increase the vodka's viscosity, or mouthfeel, and take the edge off the spirit. Many modern vodkas that are highly regarded for their perceived smoothness have been augmented with trace amounts of sugar, honey, glycerine and/or citric acid.
If vodka labels were required to list ingredients in the same manner as food packaging, then many vodkas would be labelled, "Ingredients: rectified potable water, ethanol rectified from edible raw material, natural honey, sugar, food supplements: glycerine, edible polyhydrate citric acid."
A trace amount of honey is still the preferred softener in modern Russian vodkas, and sugar is the more favoured softener in 'western' vodkas - like honey it serves to mellow the peppery attack of the ethanol alcohol and add mouth feel. Sugar also amplifies flavour and while it is sometimes found in vodka it is more generally used in cognac, indeed it is difficult to find a cognac without a couple of grams of added sugar per litre.
Glycerine, or glycerol, has the food additive identifier E422. It is colourless, odourless and sweet tasting (60% as sweet as sucrose) and is used to sweeten vodka and, perhaps more importantly, to increase the vodka's viscosity without substantially altering its flavour. Until the late 1980s UK law made it illegal to sell vodka made from neutral ethanol alcohol merely diluted with water. The alcohol in vodka brands made or imported into the UK prior to the relaxation of this rule had to be adulterated and most did this with trace amounts of glycerine.
Citric acid is a white crystalline powder which dissolves easily in alcohol. As its name suggests, high concentrations of citric acid are found in lemons, oranges, limes and other citrus fruits. It is naturally present in all aerobic organisms (animals and plants) and excess citric acid is readily metabolized and eliminated from the body. This weak organic acid is widely used in beverages as both a natural preservative and to add an acidic/sour taste. It is also routinely added to vodka.
In 1956, U.S. State Revenue Ruling 56-98, 1956-1 C.B. 811, "concluded that citric acid and sugar were not considered to be flavouring ingredients which would materially affect the taste of vodka or change its basic character so long as the sugar did not exceed two-tenths of 1 percent and citric acid was only added in a 'trace amount'."
The ruling did not quantify 'trace amount' and in 1995, the American Bureau of Alcohol, Tobacco and Firearms (ATF) investigated levels of citric acid in vodka and its effect on flavour. To quote from the resulting ATF Ruling 97-1 document, "Available information indicates that the use of citric acid from this time  until the 1980's was in the range of approximately 49 to 150 parts per million (ppm). However, starting in the 1980's, the quantity of citric acid added to vodka increased significantly." In response to the increased usage of citric acid in vodka, a law was briefly introduced limiting the addition of citric acid to 300 ppm (300 milligrams per litre).
A further quote from that informative 1995 document reads, "ATF has historically taken the position that the addition of citric acid in vodka to a level where it could be detected by the consumer would contribute a distinctive character to the product in violation of the standard identity". In other words, ATF has used the approach known as "threshold testing." This type of testing determines the point at which a taste tester can first detect a difference in taste when compared to reference sample. Since vodka is a product which by definition is without distinctive taste, ATF believes the point at which a taste tester first detects any difference in taste (in this case, citric acid) is the maximum allowable amount of that ingredient. The difference in taste need not be attributable to or identifiable by the taste tester as a specific ingredient.
"In contrast, industry members believe that threshold testing to determine a minimum level at which citric acid becomes detectable has no relevance to the distinctiveness requirements of the vodka standard of identity. In testing conducted by industry, consumers were asked whether samples of vodka containing up to 1,000 ppm of citric acid had a "distinctive character, aroma, taste, or colour." A statistically significant number of participants did not identify the vodka samples containing up to 1,000 ppm of citric acid as having a distinctive character or taste. Therefore, industry believes that the presence of citric acid at levels up to 1,000 ppm in vodka is appropriate."
The ATF concluded, "The actual presence of critic acid in vodka has not raised any consumer health or safety issues since being introduced in vodka production in 1956, nor has it resulted in any known consumer deception. Moreover, consumers have been purchasing vodka which contains citric acid in varying ranges of up to approximately 1,000 ppm for more than a decade without any complaints being received by ATF. Based on all of the above, ATF has therefore concluded that a level of up to 1,000 ppm citric acid is an industry standard that will continue to maintain the current standard of identity for vodka, which has been followed for well over a decade, while meeting ATF's statutory mandate to protect consumers." Consequently, in the USA vodka may contain up to 1,000 ppm of citric acid (1 gram per litre).
Poland has traditionally frowned upon the use of additives in vodka and Polish legislation which came into effect on 1st January 2013 stipulates that vodka made in Poland may not contain any additives except water. The same legislation allows for flavouring and additives in flavoured vodka but specifies that these must be natural and that no more than 100g of sugar is used per litre. So, if you want vodka free of additives, buy Polish vodka.
Anyone who uses a Brita Filter to make their tap water more palatable will recognise the benefits of activated carbon filtration. Activated carbon filters can be used to remove the organic impurities that affect the colour, smell and taste of vodka, without affecting its alcohol content.
Early separation processes simply involved leaving the spirit to stand until solid particles had fallen to the bottom of the tank. Later fining processes used coagulants such as milk or eggs which solidified around the contaminants so encouraging them to sink.
Russians attribute the invention of charcoal filtration to a chemist by the name of Theodore Lowitz who in 1780 was commissioned by the Tsar to make the national drink more hygienic. He used charcoal made from charred hardwoods to remove fusel oils and other contaminates left by the relatively primitive distillation methods of the time. The Swedes and Poles also lay claim to the invention of the process.
While distillation methods have improved to the extent that it is possible to produce near pure ethanol alcohol, some distillers still choose to use charcoal filtration for to its cleaning and softening effect on the spirit - it is particularly useful for removing oily contaminates.
The use of different charcoals made from different woods has varying effects on the distillate. Birch charcoal remains the most popular but the charcoal recipe used by many distillers is a closely guarded secret. Of course, there are vodka distillers that say, "charcoal is for barbecues."
Over the years many different substances have been used for vodka filtration including cloth, wool, paper, sand and other stone fragments. During the 1990s race to develop vodkas perceived as being ever more premium, filtration materials became ever more exotic, with garnet crystals and even crushed diamonds being used as a filtration medium.
Every bottled spirit should at least pass through a particle filter (usually cellulose). Some producers use cellulose pads impregnated with activated carbon as they claim this helps enhance the visual 'polish' and the shine of the spirit.
It is also common to chill and then filter vodka at low temperatures. During chilling to temperatures between -2°C and as low as -12˚C long chain protein molecules precipitate out of the spirit, ie they change from being dissolved in the liquid into solids again, and are then filtered out using particle filters. If these long chain protein molecules are not removed the vodka could become hazy when stored at low temperatures. However, some vodka producers would rather risk precipitation claiming that chill filtration strips out mouthfeel and flavour provided by the fatty acids.
In his book 'Kindred Spirits 2', drink writer Paul Pacult writes, "How vodkas are filtered also affects their character. Charcoal filtering, the most prevalent, imparts a hint of sweet smokiness, almost a sooty quality. Quartz crystals lend a stony, mineral-like kind of taste while cloth or fibre panel filtering gives off an aroma of parchment or cotton fabric."
Quality starts with the raw materials. Remember the saying? "You can't make a silk purse out of a sow's ear."
Quality testing can start even before the raw material that will make the vodka has been put in the ground as some producers will test the soil for its nutrient levels prior to sowing seeds. Certainly grain and other ingredients will be tested for quality prior to use. The same will be true of the water and even the bottles.
At every stage of the vodka making process samples will be taken and tested using chemical analysis such as gas chromatography. However, ultimately human organoleptic testing is the best check of quality and trained tasting panels are almost always used to test batches prior to bottling.
As important as the testing is the recording and identifying of the test batches throughout the process right through to the finished bottle. The small barely visible number printed on the neck of most bottles identifies not only the day and hour when that vodka was bottled, but will often also allow the distiller to trace the batch of grain used to make it.