Darasun

Making alcohol from milk

Khurenge is a traditional Buryat fermented dairy beverage that occupies an important place in one of the world's more unusual systems of alcohol production.

In Buryat and related Mongolic terminology, forms including khurenge, körüngge, kyurenge and airag occur, although their meaning and use differ between regions.

The spirit produced by distilling fermented milk is commonly known as darasun or tarasun. Other Buryat expressions include togoonoi arkhi and khurengyn arkhi.

These names reflect a connected dairy-production system rather than one standardized beverage.

The raw material is usually milk from domesticated livestock, principally cattle in the household processes studied in modern Buryatia.

The first product is a sour, mildly alcoholic, sometimes effervescent fermented milk. The second is an alcoholic distillate made from it.

Further products arise when cream, curd and whey are separated or processed.

The central technological challenge is that milk contains comparatively little fermentable carbohydrate. Most of its solids are fat and protein, neither of which ordinary brewing yeast can directly convert into substantial amounts of ethanol.

Milk fermentation can therefore produce acidity and modest alcohol concentrations, but obtaining a stronger beverage usually requires distillation.

The tradition is particularly valuable for understanding how pastoral societies developed fermentation technology around the resources reliably available to them.

Historical evidence

The Buryat belong to the wider Mongolic-speaking cultural world of eastern and southern Siberia, Mongolia and adjacent regions.

Fermented dairy products have long been associated with Mongolic pastoral economies.

The history of milk distillation is more difficult to date precisely than the history of fermented milk.

A major interdisciplinary study published in 2026 combined ethnography, microbiology and historical linguistics to examine khurenge and darasun.

The word körüngge, associated with starter culture, appears in the Mongolian legal code Khalka Jirum, revised in 1709. A provision records a penalty for stealing a starter culture.

This gives unusually strong evidence that maintained fermentation cultures had economic value in the early 18th century.

An earlier reference to the word darasun appears in a 14th-century Mongolic glossary, while an inscription on a Yuan dynasty vessel, dated to 1260–1368, includes a related term interpreted as wine or an alcoholic beverage.

Those records establish historical terminology but do not independently prove that every use of the word described distilled cow's milk.

The 2026 study also discusses references to tarasun in Siberia during the 17th and 18th centuries, including material recorded by J. G. Gmelin in 1736.

By the 18th century, the historical record supports an established beverage tradition with social and economic importance.

The deeper history of fermented milk is undoubtedly connected to pastoral life, but precise claims that a modern household recipe was invented in a particular ancient century cannot be established.

The traditional dairy-processing system

The process begins with milk.

In contemporary Buryat households, whole milk may be mechanically separated into cream and skim milk.

The cream, known in some local terminology as zookhei, can be processed into butter, while the skimmed fraction can be used for milk tea or fermentation.

This makes fermentation one branch of a broader dairy economy.

Milk intended for khurenge may be pasteurized or used without prior heat treatment. The investigated household tradition commonly used unpasteurized milk, while commercial approaches differed.

The next requirement is a maintained starter culture.

A portion of previously fermented khurenge is retained and introduced into new milk. This practice is called backslopping in food microbiology.

The retained culture is described as khurengen ekhe, or mother khurenge.

Backslopping transfers a community of microorganisms adapted to the food and household process.

Unlike a single-strain yogurt starter, it can carry numerous bacterial and yeast species. The balance between them changes according to milk composition, environment, storage, temperature and previous batches.

A documented contemporary household fermentation

One of the most useful aspects of the 2026 research is its account of actual quantities used by households in Buryatia.

The reported practice uses 40–50 litres of milk, introduced into a 70-litre barrel already containing 10–15 litres of khurenge from the previous cycle.

The vessel is kept at ambient temperature, commonly in an outbuilding.

The locally reported preferred temperature is approximately 20°C.

The fermentation typically proceeds for 2–3 days.

During fermentation, the liquid is stirred 2–3 times daily. Stirring breaks up the accumulating foam and helps redistribute the culture.

A frothy layer forms at the surface as gas is produced. Beneath it, whey separation may occur, while coagulated proteins accumulate lower in the vessel.

These details are measurements and observations from a documented modern practice. They do not automatically validate raw-milk household production elsewhere.

They are nevertheless unusually valuable compared with generic descriptions that simply say to leave milk until sour.

The microbiology of khurenge

Khurenge fermentation involves both bacteria and yeasts.

Lactic acid bacteria metabolize available carbohydrates and produce lactic acid. This lowers pH, changes the behavior of milk proteins and develops sourness.

Yeasts can produce ethanol and carbon dioxide. Their activity contributes alcohol and a lightly fizzy texture.

The 2026 study identified substantial populations of lactic acid bacteria alongside smaller yeast populations.

Among the microorganisms identified were lactobacilli and yeasts belonging to groups including Trichosporon and Monosporozyma.

The household and commercially produced samples differed in their microbial composition, demonstrating that the name khurenge does not guarantee one identical culture.

Two sampled batches illustrate the point.

These figures are measured sample characteristics, not recommended targets for every household.

They also explain an interesting sensory difference. A beverage with lower pH may taste sharper and more acidic even if its ethanol content is lower.

The alcohol-producing organisms do not work in isolation. Lactic acid bacteria compete for nutrients, modify the chemical environment and influence which yeasts can remain active.

Other organisms may consume oxygen, break down proteins or produce minor aroma compounds.

The final character of the beverage therefore reflects the behavior of the whole microbial community.

Ethanol, % ABV — 1.5% — 2.1%

pH — 3.3 — 3.7

Titratable acidity — 240°T — 160°T

Lactic acid bacteria — 8.2 multiplied by a power of ten in CFU/g that did not survive the handover of this research — 2.7 multiplied by a power of ten in CFU/g that did not survive the handover of this research

Yeasts — 4.2 multiplied by a power of ten in CFU/g that did not survive the handover of this research — 1.2 multiplied by a power of ten in CFU/g that did not survive the handover of this research

Why milk alcohol is limited

Fresh milk contains lactose, a disaccharide composed of glucose and galactose.

Many conventional brewing strains of Saccharomyces cerevisiae cannot ferment lactose directly.

A mixed dairy culture may include microorganisms capable of utilizing lactose or products of its breakdown.

During fermentation, sugars are divided between several metabolic pathways. Some are converted into lactic acid; some into ethanol and carbon dioxide; others become microbial biomass or additional metabolites.

This is one reason milk is a less efficient ethanol substrate than a concentrated cereal mash or fruit juice.

It also explains why the ethanol concentration does not simply continue rising as long as the milk stands.

Fermentation is restricted by carbohydrate availability, competing metabolism and the changing acidic environment.

The resulting beverage is both a sour dairy food and a low-alcohol drink.

Its chemistry resembles neither plain yogurt nor a conventional grain beer exactly.

From khurenge to darasun

Distillation separates volatile compounds from the fermented liquid by exploiting differences in their evaporation and condensation behavior.

When khurenge is heated in suitable apparatus, ethanol and water enter the vapor phase in different proportions from those in the original liquid.

Condensation produces a distillate containing a higher concentration of ethanol.

Traditional dairy distillation can use a cauldron-based system, reflected in names associated with the Buryat term for cauldron.

One documented household yield is approximately 1 litre of darasun at 10–11% ABV from 10 litres of khurenge.

The directly measured darasun sample in the 2026 study contained 11.2% ABV.

Further distillation can produce progressively stronger fractions. The research describes experimental stages reaching approximately 40% and 75% ABV after repeated processing.

These are particular measured stages, not the normal strength of every beverage sold or served as tarasun.

Traditional terminology differentiates products or grades associated with repeated distillation, including arza and horzo.

Names and numbering of distillations vary by region, and it is important not to assign every traditional name one immutable ABV.

The first distillate may be relatively weak compared with familiar modern spirits. Multiple passes are necessary for substantially stronger alcohol.

The flavor of a milk distillate

Darasun is not simply neutral ethanol made from milk.

Volatile compounds carried over during distillation contribute recognizable dairy aromas.

The 2026 research records milky and cheese-like notes, alongside subtler animal, leather and dried-herb characteristics.

The resulting flavor can therefore retain a sensory connection with the fermented dairy raw material.

The balance depends on the khurenge, apparatus, heat management, fractions collected and any subsequent distillation.

Milk proteins and fat create additional challenges. If fermented dairy is heated carelessly, proteins can stick to hot surfaces, producing scorching and undesirable aromas.

Traditional distillation knowledge includes maintaining the apparatus and preventing the dairy material from burning.

A distillation vessel is therefore part of the technology, not merely a means of boiling liquid.

Using the remainder of the milk

Distillation leaves substantial material behind.

The remaining curd and dairy solids are not necessarily waste.

Different Buryat dairy systems can recover curds, concentrate them or dry them for later food use.

This is related to broader Mongolic pastoral technologies in which soured milk supplies drinks, butter, dried cheese and other products.

Terms such as aarsa, aruul and related regional names require attention to local meaning. They should not all be treated as identical cheeses.

Some describe concentrated sour dairy material; others refer to dried curd products.

The practical principle is that milk is separated and transformed repeatedly, allowing different fractions to be used for different purposes.

Butter captures much of the fat. Fermented drinks make use of liquid and carbohydrate. Curd products retain protein and minerals. Drying can make dairy solids portable.

This is why fermentation and distillation belong in the larger pastoral food system.

Regional variation

Buryat households, commercial processors, Mongolian producers and neighboring Tuvan or Khakas communities share some technological principles but do not necessarily use identical terminology or recipes.

The microorganisms in maintained starters can differ between families.

Raw material also changes the outcome. Cow milk, mare milk, camel milk and yak milk differ in their relative fat, protein and carbohydrate composition.

Mongolian airag, for example, is particularly associated with fermented mare's milk, while Buryat khurenge in the documented contemporary study was based on bovine milk.

That distinction affects fermentation chemistry, texture and the potential alcohol yield.

Tuvan araga and other milk spirits are related technologies, but separate cultural records are necessary to describe their distinctive names and processes.

Recognizing a successful fermentation

A typical khurenge develops sourness, a milk-based aroma and gas production.

The investigated samples were white, thick, acidic and slightly effervescent.

Foaming and separation are not automatically defects because they are part of the documented process.

Buryat production knowledge also identifies an undesirable condition called arabka.

It is associated with unpleasant bitterness, abnormal odor, a lack of expected foam and excessive settling of coagulated material beneath whey.

This defect may reflect a shift toward undesirable proteolytic activity or insufficient normal acid fermentation.

However, a normal sour aroma does not prove that raw-milk fermentation is free of pathogens.

Safety and practical limitations

The research records household raw-milk fermentation, but that should not be confused with a modern validated manufacturing method.

Raw milk may contain disease-causing microorganisms, including organisms not reliably detected by smell or appearance.

For commercial or experimental work, pasteurized milk and characterized cultures provide a more controllable starting point.

The existence of an active inherited culture does not by itself demonstrate microbiological safety.

Distillation introduces additional considerations, including fire risk, alcohol vapor, apparatus material, legal restrictions and product-quality controls.

Repeated distillation can increase alcohol strength dramatically. A spirit originally derived from milk can become as strong as other concentrated alcoholic beverages.

Alcohol content should therefore be measured rather than inferred from the drink's name or from the number of distillations.

The figures reported in the 2026 study are valuable technical observations, but they are not complete safety instructions for building or operating a still.