Tarag (Mongolian yoghurt)

What tarag is

Tarag (тараг) is Mongolia's everyday fermented milk, one of the white foods, цагаан идээ, that herding families make from their animals' milk. Heated milk is mixed with a living starter, covered and kept warm until lactic acid bacteria sour it and the proteins set. It can be spooned, if freshly set and left undisturbed, or stirred and drunk. The taste is clean, sour and milky, sometimes with a trace of cooked milk from the heating.

Cow, yak, sheep and goat milk are all used, and the species changes the texture, because fat, casein, whey protein and minerals differ between them. Camel milk goes into a separate product, khoormog, and mare's milk into airag, so neither belongs under tarag. The Mongolian dictionary defines тараг бүрэх, tarag bürekh, as mixing starter into heated milk, covering it and letting it set. The starter is таргийн хөрөнгө, targiin khöröngö, usually a spoonful of an earlier batch.

English calls it Mongolian yoghurt, and the comparison has limits. Anthropologist Eric Thrift separates ordinary, often drinkable tarag from some industrial products sold under the borrowed word yoghurt, and household tarag is not made with only the two bacteria of standard yoghurt. Studies find a mix of lactobacilli, streptococci, lactococci and yeasts. The main change is still lactic fermentation.

What is known of its history

Tarag belongs to the dairy work of Mongolian pastoral households. Milk flows with the season, the livestock and the pasture, and in the productive summer months families turn it into foods to eat at once or process for storage: heating, culturing, skimming cream, draining curds and drying dairy solids. Tarag fits in as a fermented milk that is eaten directly or turned into curd. The age of Mongolian herding does not date tarag itself.

A firm twentieth-century record is the 1975 study by Jean-Pierre Accolas, Jean-Pierre Deffontaines and Françoise Aubin in Études Mongoles, which separates tarag, a yoghurt-like cultured milk, from unda and airag. Modern microbiology starts with a 2007 study of three nomadic households in central Mongolia, followed by Watanabe's analysis of 31 tarag samples in 2008 and sequencing studies in 2014. Older Korean and East Asian texts use the word tarag, written 타락 or 駝酪, but it could mean milk porridge or milk tea, so they do not describe today's method.

Tarag is still household work, though urbanisation and dairies have changed it. An FAO report describes herders and peri-urban households making traditional products, with larger dairies selling branded versions. A bought starter or packaged tarag is not automatically the same as a family's long-kept culture. Mongolia's National Center for Cultural Heritage documented traditional dairy preparation in 2022.

The microbes and the milk

Tarag is mainly a lactic fermentation. The bacteria turn lactose into lactic acid, and as the pH falls the casein proteins gel. Unlike yoghurt from an industrial starter, tarag carries a community inherited from the last batch, the vessel and the local dairy environment. Lactobacilli matter most, with streptococci, lactococci and other bacteria also found, and yeasts turn up in some samples without making every tarag a significantly alcoholic ferment.

In Watanabe's 2008 study of 31 samples the leading cultivated lactic bacteria were Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus and Streptococcus thermophilus, averaging about 10^8.35 colony-forming units per millilitre against about 10^5.86 for yeasts, which included Saccharomyces cerevisiae and Kazachstania unispora. In a 2014 study of 26 Mongolian samples L. delbrueckii predominated. A 2012 survey of 198 samples from eastern Inner Mongolia recovered 790 lactic isolates of 31 species or subspecies, led by L. helveticus and Lactococcus lactis subsp. lactis. Communities differ by place and by milk, and these are sample results, not a starter recipe.

The chemistry is the usual one. Beta-galactosidase splits lactose, glycolysis makes pyruvate, and lactate dehydrogenase reduces it to lactic acid. Calcium phosphate leaves the casein micelles as acidity rises, and around pH 4.6 the casein forms a continuous gel. Heating beforehand unfolds beta-lactoglobulin, which links to casein and strengthens the gel and its water holding. Proteases free peptides and amino acids, and some cultures make acetaldehyde and diacetyl.

How it is made and why

The ingredients are milk and an active starter. The milk gives lactose, casein, whey protein, fat and minerals, and the starter gives lactic bacteria already used to milk. A retained portion of earlier tarag is the usual starter, and prepared dried dairy products are also mentioned, though they are not interchangeable without testing.

The recipe here is the household method published in November 2019 by Mongolia's livestock genetic-resources authority: 10 litres of sheep, goat or cow milk and about 150 to 200 g of starter, adjusted to how active it is. The milk is warmed gently, a little of it is mixed with the starter to spread it, and that is stirred into the batch. The milk goes into a wooden or enamelled vessel, is covered, kept warm and left alone for about three to four hours until it sets. Neither the warming temperature nor the incubation temperature is stated.

Heating before inoculation reduces competing microbes and changes the whey proteins so a firmer gel forms. Heritage accounts describe boiling the milk and sometimes skimming the cream, which changes fat and mouthfeel. The milk must cool before the starter goes in, since heat kills the bacteria. The instructions warn that too little starter or poor insulation delays setting, while too much warmth makes the milk rise or release whey, and they advise cooling the set tarag before opening it, because disturbing a warm curd encourages whey to separate. A cool rest improves the flavour.

Other methods exist. A 2016 chapter on Mongolian dairy foods describes boiled milk, a starter percentage, controlled warm incubation and a titratable acidity endpoint, and research from Mongolia and China documents tarag kept going by repeated transfer in cooler conditions. These cannot be merged into one recipe. A modern batch should use pasteurised milk, clean equipment and a characterised starter run to that culture's own temperature and acid endpoint.

Variations

Tarag differs by region, household and animal. Mongolia's dictionary separates элгэн тараг, elgen tarag, freshly set thick tarag left undisturbed, from исгэлэн тараг, isgelen tarag, tarag made sourer by further fermenting or standing, and names cow's-milk (үхрийн) and sheep's-milk (хонины) tarag. Cow's milk is widely used, and yak milk is important in highland areas. The same starter on different milks gives different gel strength, viscosity and flavour.

Fieldwork in Dundgovi on three nomadic families found Lactobacillus helveticus, L. fermentum, L. kefiri and related species across ordinary and isgelen tarag, and L. delbrueckii subsp. bulgaricus in one tarag, so household products cannot be assumed to hold just the two industrial yoghurt bacteria. The 2014 work on tarag from Arkhangai, Bulgan, Dundgovi, Tov, Ovorkhangai and Omnogovi found L. delbrueckii dominant but varying between samples.

Eastern Inner Mongolia in China shows strong regional contrasts: a 2014 sequencing study found Streptococcus at 12.07 per cent of bacterial reads in its Mongolian samples and 0.71 per cent in Inner Mongolian ones, and Lactococcus at 3.66 and 21.86 per cent. Household instructions describe a warm, covered fermentation that sets in hours, while naturally maintained cultures in Mongolia and China are described with longer, cooler fermentation, giving a different balance of bacteria and yeasts. Commercial tarag and laboratory-selected cultures are further variants.

Eating and using it

Tarag is eaten from a bowl when freshly set and drunk when stirred. It runs from mild when new to pronounced when old, and it needs no sugar, fruit or thickener; flavoured packaged versions are separate products. Mongolian cooks often call it a thin yoghurt, while the dictionary recognises thick, freshly set tarag too, so the difference is texture, not a defect.

It sits in the seasonal dairy economy beside airag, khoormog, cream, butter, cheeses and dried curds, which herders and peri-urban households make in the productive season. Tarag can be used directly and also supplies the acid dairy base for later foods. One is аарц, aarts, a soft sour curd: a Mongolian culinary source makes тарагны аарц, taragny aarts, by heating the tarag and separating the coagulated curd from the liquid. Aarts can be pressed, shaped and dried into ааруул, aaruul, a long-keeping dried curd, though aaruul can also come from other fermented milks.

Tarag also keeps itself going: a portion of a good batch is set aside as the next starter, and some regions use dried dairy material to restart fermentation at the start of the milk season. Successive transfers can change the culture.

Reading results and problems

Good tarag smells of clean fermented milk and has the texture its method calls for: a coherent curd if left alone, fluid if stirred. Judge it against the traditional method and not against a commercial yoghurt, and look for no odd colour or mould.

Milk that does not set may have had too little live starter or poor insulation, which the Mongolian instructions both name as causes of slow setting. Too much heat makes it overflow or release whey. Cooling the curd before handling reduces whey separation. A little clear or yellowish whey after stirring or cooling is normal; a lot suggests over-acidification, a weak gel or unsuitable heating, and the milks of different animals behave differently.

Yeasts are found in real tarag, so detecting them does not make a batch spoiled. But vigorous bubbling, swollen containers, heavy foaming or a strong alcoholic smell are not expected in a warm-fermented, yoghurt-type process. The Mongolian expression тараг сагах describes tarag rising and overflowing from too much fermentation, and a gassy batch is not safe to eat for that reason alone. Sequencing identifies DNA, including from dead or scarce organisms, and read abundance is not the same as viable cell count.

Raw milk can carry Campylobacter, pathogenic E. coli, Listeria, Brucella and Salmonella, and contaminated tools or starter can bring organisms back after heating. Repeated backslopping can shift the culture. Use pasteurised milk, a known starter and a measured acid endpoint (Utah State University Extension uses pH 4.6 or below for yoghurt, general guidance and not a tarag-specific limit), refrigerate promptly, and discard anything mouldy, foul-smelling or oddly coloured. A large 10-litre batch cools slowly in an insulated vessel. No shelf life is established. Claims that tarag cures disease or is automatically probiotic need evidence for an identified strain, dose and outcome.