Douchi

• douchi

  Mandarin

  One word for several products. Douchi made with different moulds, or with bacteria alone, differ in salt, in age and in smell, and the studies read here name each by the place it comes from.

Savoury and salty, with some bitterness. In seven douchi from Sichuan and Chongqing glutamic acid was the most abundant free amino acid, followed by aspartic acid, and the amino acids that taste bitter were together the largest group, which the authors say matched their tasting.

Asked which words applied to three douchi, a hundred consumers used sauce-like, smoky, nutty, roast, caramel and flower for what they liked, and sour, beany, sulphur and alcohol for what they did not. The types differ. Liuyang douchi was the smokiest, which the authors put down to guaiacol; Yangjiang douchi was more sour and nutty; Pingjiang douchi, aged for a year, held the most volatile compounds and scored on every note. A separate study of seven douchi from Sichuan and Chongqing found no volatile compound common to all seven.

Dark. A study of Yongchuan douchi, the Mucor-type product of Chongqing, describes it as dark in colour, and a review says the Aspergillus mould gives the beans a dark colour.

Soft, in the one description read: a study of Yongchuan douchi calls it soft in texture.

• Guaiacol — The smoky note of Liuyang douchi. Leaving it out of a rebuilt aroma made a difference a trained panel could detect. No smoke is involved: the authors attribute it to the mould breaking down phenolic material in the bean.(what guaiacol is)
• Phenylacetaldehyde — The compound whose omission mattered most in Yangjiang douchi and one of three that mattered in Pingjiang douchi; the authors note it as the honey-like odorant of soy sauce.
• Dimethyl trisulfide — A sulphur compound that contributed to the smell of Yangjiang and Pingjiang douchi, probably formed from the methionine of the bean. In one Yongchuan douchi it stood far above its odour threshold, and it was one of five odorants that made salt water taste saltier.
• 2,5-Dimethylpyrazine — A nutty-smelling pyrazine found in Yongchuan douchi. With 2-ethyl-3,5-dimethylpyrazine it raised the saltiness a panel perceived in salt water.(what 2,5-dimethylpyrazine is)
• Glutamic acid — The most abundant free amino acid in seven douchi from Sichuan and Chongqing, released as the bean protein is broken down.

Rinse the saltier types, chop roughly or leave whole, and fry briefly in oil with garlic, ginger or chilli before adding the rest. Taste before salting the dish, since some types hold more than a tenth of their weight in salt.

A seasoning used for savouriness and smell. One study describes it as widely used as a condiment in Chinese dishes and gives fried fish, meat, vegetables and canned foods as examples; another says it is eaten as a dish in its own right as well as cooked with. In kitchen practice it is chopped with garlic in Cantonese cooking for steamed spare ribs and fish and for black bean sauce, goes into mapo tofu and twice-cooked pork in Sichuan cooking, and is usually fried in the oil at the start.

Smell it. Sound douchi smells savoury and sauce-like; a sharp sour or alcoholic smell is what the consumer panel disliked.

• Fresh fluffy mould on the surface
• A sharply sour or alcoholic smell

• Loss of aroma from an open packet
• Fresh mould growth on beans kept damp

Fabaceae

An erect, bushy annual herb, 0.2–1.5 m tall and brownish or greyish hairy, with leaves of three leaflets and small purple or white pea flowers. The pods are slightly curved, 3–15 cm long, and hold two or three seeds as a rule. The seeds are usually round, and yellow, green, brown, black or mottled.

China. The studies describe douchi as a traditional Chinese fermented soybean product; the soybean itself was domesticated in the eastern half of north China, according to the handbook account of the plant.

• China (Liuyang, Pingjiang and Yangjiang) — major producer. Three named types compared in one aroma study: Liuyang and Yangjiang douchi made with Aspergillus from black soybeans, Pingjiang douchi made with Mucor from soybeans.
• China (Sichuan and Chongqing) — major producer. Where Mucor-type douchi is mainly made; Yongchuan and Tongchuan douchi are the typical products.
• China (Yangjiang, Guangdong) — major producer. Aspergillus-type douchi made by natural fermentation. One study puts its sales at about 12,000 tonnes a year and 40 per cent of the national market, without giving a year.
• China (Enshi, Hubei) — notable producer. Home-made by farmers from their own soybeans, with no starter, in a dried and a wet kind.
• China (Longnan and Qingyang, Gansu) — notable producer. Bacterial douchi made at home by villagers, with nothing added to start the fermentation.

1. Soaking and cooking — The soybeans are steeped in water, cooked and left to cool.
2. Growing the culture — Mould or bacteria grow on the cooked beans, a stage the studies call zhiqu. In the traditional product nothing is added: the organisms come from the surroundings and the raw material.Why: The organisms supply the enzymes that break down the protein, starch and fat of the bean.
3. Washing — In the Aspergillus-type process the mould-covered beans are washed before they are salted.Why: To remove the mycelium and spores, which would otherwise make the douchi taste bitter.
4. Salting — Salt is mixed in. The amount differs widely by type: under 3 per cent in Liuyang douchi, over 10 per cent in Yangjiang douchi.
5. Ageing — The salted beans are left to ferment further. Traditional Mucor-type douchi takes more than ten months and Pingjiang douchi a year; low-salt Liuyang douchi takes far less time.Why: This is where most of the smell and taste form.

The season matters to the traditional product. Mucor grows only at low temperatures, so traditional Mucor-type douchi can be made only from November to February.

• Sold as douchi, fermented black beans, salted black beans or preserved black beans.
• A savoury, sauce-like smell, with no sharp sour or alcoholic note.
• The type or place of origin, where the packet gives it: the types differ in salt and smell.

• Soybeans — a declarable allergen in the EU and US

Douchi is old, and how old is stated more confidently than it is shown. A review of fermented foods says it has been made in China for over 3,000 years; a food-chemistry paper says more than 2,000. The review points to two things: douchi found in Tomb No. 1 at Mawangdui, a Han tomb in south-central China which it dates to 165 BC, and a mention in the Shi Ming, a dictionary of the Han period, which it calls the earliest written reference. It describes douchi as having begun as a way of preserving soybeans, and the Aspergillus type as the oldest and the most widely made.

1. About 165 BC · Mawangdui, south-central China

   Douchi was among the foods placed in Tomb No. 1 at Mawangdui, according to a review of fermented foods.

   The date is the review’s. The excavation report was not read, so the identification is given on the review’s word.

2. Han dynasty

   Douchi is mentioned in the Shi Ming, a dictionary of the period, which the same review calls the earliest written reference to it.

   The review gives the dynasty and no year, and the dictionary itself was not read.

A review reports douchi from Tomb No. 1 at Mawangdui, which it dates to 165 BC. It gives no detail of the find, and no excavation report was read.

One study puts the sales of Yangjiang douchi at about 12,000 tonnes a year, which it gives as 40 per cent of the Chinese market, without a year or a source. Another notes that the traditional naturally fermented product could not meet demand, which is why industrial Mucor-type and Aspergillus-type douchi developed.