Doubanjiang

Doubanjiang is a spicy, savory Chinese bean paste made from fermented broad beans (fava beans), chili peppers, soybeans, salt, and flour. It goes by several names, including douban, toban-djan, broad bean chili sauce, and fermented chili bean paste. This paste is a defining ingredient in Sichuan cuisine, often referred to as its "soul." Key dishes like mapo tofu, Sichuan hotpot, yuxiang-flavored preparations, and shuizhu rely on it. Outside Sichuan, versions vary: in Guangdong and Taiwan, the Sichuan-style spicy paste is called la-doubanjiang to set it apart from milder local varieties.

The most famous type is Pixian doubanjiang, named after Pixian (now Pidu District in Chengdu, Sichuan). It undergoes a long fermentation process under sunlight, often exceeding three years. A traditional rhyme describes the method: "flip it over during daytime, expose it at night, sunbathe it in sunny days, cover it when it rains." The unique flavor of Pixian doubanjiang is tied to its origin—Pixian sits on plains with ample sunshine, high humidity, and clean water, fostering microbial flora essential for fermentation. The paste has a reddish-brown color and a deep, complex umami. It is typically fried in oil first to release its color and aroma before other ingredients are added.

Pixian doubanjiang is a geographical indication (GI) product, with quality standards last updated in 2006 (GB/T 20560-2006). Its ingredients must include erjingtiao chili from Pixian and vicinity, broad beans from Sichuan or Yunnan (meeting GB/T 10459 standards), and underground water from Pixian (meeting GB 5749 standards). The production process involves: soaking and de-shelling broad beans, making a qu starter, and fermenting them into sweet broad beans for over six months; salting, crushing, and fermenting the erjingtiao chili; mixing the two cultures in a specific ratio; and sun-drying the mixture for another three months. The final product is graded into three classes. Premium grade is red-brown, coated in glistening oil, with strong chili aroma and rich savoriness, and broad bean bits that are crisp, fragrant, and disintegrate when crushed, leaving a lasting aftertaste. Grade I is lighter red-brown, partially oil-coated, with moderately rich chili aroma and savoriness. Grade II is red or light red-brown, glistens but lacks an oil coating, with bean bits that are not fragrant and no lasting aftertaste. Quantitative limits include total acids (as lactic acid) ≤ 2.0 g/100g and salt (NaCl) between 15–22 g/100g. Optimal process conditions are 56% water, 10% added salt, 40°C fermentation temperature, and 40 hours of qu starter-making.

Other types exist. Homemade or factory-produced doubanjiang rarely matches the long fermentation of Pixian versions. Hongyou doubanjiang, a red chili oil paste, is sometimes confused with Pixian doubanjiang but is not fermented and often includes extra spices from any chili variety. Binzhou watermelon doubanjiang from Shandong is a non-spicy paste made from soybeans, watermelon, flour, and salt, typically fermented without chemical additives. Outside Sichuan, doubanjiang is often not spicy.

Beyond mapo tofu and Sichuan hotpot, doubanjiang is used in dishes like twice-cooked pork, yuxiang shredded pork, Kung Pao chicken, stir-fried pork, and shuizhu pork.