Vinegar (醋) is among the most important condiments in Chinese cooking. One of the so-called "Seven Essentials" of the traditional Chinese kitchen (along with firewood, rice, oil, salt, soy sauce and tea), vinegar's importance in Chinese culture extends beyond cuisine and even into the language: In Mandarin, "to eat vinegar" (吃醋/chīcù) means to be jealous of somebody or something.
Vinegar is said to have been invented in China during the Xia Dynasty in around 2000 B.C. and has been commercially produced from as early as the 1st century A.D. It is particularly prized for its sourness (one of the four essential tastes, along with salty, sweet, and bitter), and it is also widely used in Traditional Chinese Medicine for the treatment of all manner of ailments, from high blood pressure to athlete's foot; TCM practitioners use vinegar to promote warm (yang) energy, and it is said to be particularly effectively when taken in autumn.
Chinese vinegars are usually made from a combination of ingredients that often includes rice (both white and black), but may also utilize wheat, millet, and sorghum. The color of Chinese vinegars ranges widely, from clear to inky black, and so too does the taste, from strongly acidic to smoky and mild.
Sichuan is one of China's four most famous producers of vinegar; the other three are Zhejiang, Shanxi, and Fujian. Sichuan's capital of vinegar production is Langzhong, in the northeast of the province, where, unique among Chinese vinegars, bran is the primary ingredient.
Baoning vinegar is the most famous and widely used brand made in Langzhong, but others do exist. I particularly like that made by the Langzhou (阆州) company, which is sweeter than the Baoning variety. The Langzhou Vinegar Company still uses traditional production methods, as described below.
First, rice and dried corn kernels are steamed and then added to a mixture of bran and over 60 traditional Chinese medicines and herbs. This mixture is left to ferment in sealed containers for up to 60 days and then mixed with spring water and seeped for two to three days. Finally, the liquid is strained, boiled, bottled, and sold.
In Sichuan, black vinegar is more commonly used than white vinegar, but the latter does appear, particularly in cold dishes. Black vinegar can be bought at dried goods (干杂) stalls at markets, while supermarkets usually stock a wide variety of many different types.
Perhaps the most famous Sichuanese dish that uses vinegar is the ridiculously easy-to-make Tiger-Skin Peppers (虎皮青椒/húpì qīngjiào), a recipe for which I've adapted from Fuchsia Dunlop's Sichuan Cookery and provided on the right. The green pepper you use for this dish can vary—if you like it spicy, go for the long, thin ones; if not, go for a larger variety.
4 green peppers (capsicum)
1 to 2 tablespoons black vinegar
½ teaspoon sugar
Salt to taste
1. If using large green peppers, quarter and discard the seeds and stems. If using the small kind, just squash slightly with the side of your cleaver. Mix the sugar and salt into the vinegar until completely dissolved.
2. Heat about 2 tablespoons of oil in a wok until smoking, and then add the peppers. Stir-fry over medium heat for 5 to 6 minutes, or until the peppers are tender and their skins blistered and streaky.
3. Finally, remove the peppers to a serving dish, drizzle with the vinegar mixture, and serve.