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Fermented milk from Tibet, Nepal, Bhutan and the Himalayan highlands

Shyow / sho (Tibetan and Himalayan yoghurt)ཞོ

Shyow is the set yoghurt of Tibet, made mostly from yak milk. Households boil and cool the milk, skim off fat by hand, seed it with the last batch and leave it overnight at the cold ambient temperature of the high plateau. It ends very sour, near pH 3.9, with Limosilactobacillus fermentum as the main lactic bacterium.

Fully documentedFermented milk24 h – 4 days

Recipe

No fixed amounts recordedHousehold method with no fixed amounts in the sources. For dahi in general FAO gives 0.5 to 1 percent of old curd as the seed.
Yak milkHigher in fat, crude protein, lactose and dry matter than cow's milk[wu2009]
Shyow from the previous batchBackslopping as the starter[wu2009][wu2023]
Starterbackslop: yoghurt from the previous batch

Total time across the recorded steps: 24 h – 4 days

Start
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pH 6.5–6.5

What changes: The yak milk is boiled and left to cool

Step 1 of 4
Boil and cool the milk
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
pH 6.5–6.5
Measured
Which microbes the steps name, step by step
Lactic acid bacteria
Yeasts
L. fermentum

Output: boiled, cooled milk.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

heat kills the milk's own bacteria

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Shyow is the set yoghurt of Tibet, made mostly from yak milk. Households boil and cool the milk, skim off fat by hand, seed it with the last batch and leave it overnight at the cold ambient temperature of the high plateau. It ends very sour, near pH 3.9, with Limosilactobacillus fermentum as the main lactic bacterium. Made in 4 steps over 24 h – 4 days. The longest step, leave overnight at ambient temperature, takes 24 h – 4 days (Wu X.H 2009) and runs at 6.8–12.6 °C (Wu X.H 2009). Lactobacillus (Limosilactobacillus) fermentum, 83.0–85.2 % of identified isolates by district and Lactobacillus helveticus and Lactobacillus curvatus do most of the fermenting.

Key numbers
Main step24 h – 4 daysReported[wu2009][dewan2002]Leave overnight at ambient temperature
Temperature6.8–12.6 °CReported[wu2009]Leave overnight at ambient temperature
AciditypH 6.5–6.5Measured[wu2009]Boil and cool the milk

What makes this one different

Shyow is soured at the plateau's cold ambient temperature and ends lower in pH and higher in lactic acid than commercial cow-milk yoghurt, with L. fermentum, not yoghurt bacteria, as the main lactic species.

Related ferments

Variants

  • Sho (Nepal)FAO records sho as the Nepali name for dahi, the boiled-milk curd set with old curd.

Safety

The milk is boiled before seeding. In the survey the fermented yak milk had better sanitary quality than the fresh yak milk.

History and sources

Every number is labelled with how it is known. How this atlas is made

Wu et al. (2023) say fermented yak milk in the Gannan Tibetan region (Gansu) has a long history, with thousands of years of inheritance among Tibetan herdsmen. That study covers Gannan, not the four Tibetan districts surveyed by Wu et al. (2009).

  1. [wu2009] Wu X.H., Luo Z., Yu L., Ren F.Z., Han B.Z., Nout M.J.R. 2009, A survey on composition and microbiota of fresh and fermented yak milk at different Tibetan altitudes, Dairy Science and Technology 89:201–209 (Wageningen repository copy)paper
  2. [fao-tmp] FAO 1990, The technology of traditional milk products in developing countries, Animal Production and Health Paper 85, section II.2.3 (Dahi)gov
  3. [dewan2002] Dewan S. 2002, Microbiological evaluation of indigenous fermented milk products of the Sikkim Himalayas, PhD thesis (Botany), University of North Bengal, chapter 4 (dahi, which the Bhutias and Lepchas call shyow)paper
  4. [wu2023] Wu S., Yang X., Gao H., Shi C., Wang L., Lu D., Li Y., Zhang J., Zhang W., Wen P. 2023, Research on bacterial community characteristics of traditional fermented yak milk in the Tibetan Plateau based on high-throughput sequencing, PeerJ 11:e14733paper