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Lao is the soured milk of the 6th-century Qimin Yaoshu. Cow or sheep milk is heated slowly over a dung fire, skimmed, strained through silk and seeded with old sweet lao in a pottery jar, wrapped warm and left overnight. A modern reconstruction with a lactic starter reached pH 3.8, so lao is a sour milk.
Fully documentedFermented milk
Recipe
No fixed amounts recordedThe amounts are the recipe's own ratios in Northern Wei measures (1 dou = 10 sheng). Too much starter, or a sour starter, makes the lao sour.
Cow or sheep milk
Taken in the grass season; a third of the milk is left for the calf or lamb[wikisource]
Good sweet lao from an earlier batchhalf a spoon per sheng of milk
Sour rice gruel (醋飧), ground fineone spoon per dou of milk
Used as the starter when no ripe lao is at hand, far from town; the text says lao set with a sour starter turns sour too[wikisource]
Starter
backslop: old sweet lao, or sour rice gruel when none is at hand
Start
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What changes:Starting material: cow or sheep milk from the grass season
Step 1 of 4
Milk in the grass season
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
L. delbrueckii
Cows are milked from five days after calving and sheep from ten days, once the young are strong. Lao is made from the end of the 3rd or start of the 4th month until the end of the 8th month; after the 1st of the 9th month only a little is made. Output: fresh milk.
Flavour
Not documented
Texture
Not documented
Colour
Not documented
Microbes at work in this step
Not documented for this step.
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
Lao is the soured milk of the 6th-century Qimin Yaoshu. Cow or sheep milk is heated slowly over a dung fire, skimmed, strained through silk and seeded with old sweet lao in a pottery jar, wrapped warm and left overnight. A modern reconstruction with a lactic starter reached pH 3.8, so lao is a sour milk. No study of lao itself was found. In tarag, a related Mongolian soured milk of cows, goats and yaks, Lactobacillus delbrueckii was the predominant lactic acid bacterium across 26 samples does most of the fermenting.
Dried lao (乾酪)Made in the 7th and 8th months. Lao is warmed in the sun, its skin skimmed off until no fat is left, then briefly fried, sun-dried and shaped into balls the size of a pear that keep for years.
Strained lao (漉酪)Made in the 8th month. Rich lao is hung in a raw-cloth bag until it stops dripping, briefly fried and sun-dried into pear-sized balls.
Horse-milk lao starter (作馬酪酵法)Two or three sheng of donkey milk are mixed with horse milk; the sediment of the set lao is rolled into balls and sun-dried as next year's starter.
Su (酥)Lao is churned in a jar in the sun with a dasher, hot and then cold water added, and the butter skimmed off; the butter is then cooked down into butter oil.
Safety
Its recipe boils the milk four or five times before setting it, and bakes an old jar in hot ash before the jar is used again.
In 2010 Hirata and colleagues reproduced the Qimin Yaoshu milk recipes and identified raku (lao) as sour milk. They concluded that its author, Jia Sixie, edited texts gathered from different peoples and did not make the products himself, and that its milk methods came mainly from pastoralists of North and Central Asia (abstract).