Black vinegar is a type of vinegar which originated in China and spread across much of Asia, along with many other originally Chinese foods. It can be made with a wide assortment of ingredients, and an array of formulas produce it, so there is an immense variance in taste. Like other vinegars, black vinegar is made by fermenting something, in this case grain, and then allowing the resulting liquid to age. After aging, the vinegar is bottled for sale.
Many cooks compare black vinegar to balsamic vinegar, since the two foods have similar flavor profiles. Both are typically aged, leading to a more complex, rich flavor. Both are also dark in color, with the black variety ranging from reddish brown to true, inky black. However, the base ingredient is grain, not grapes, and this leads to a different end flavor. In addition, high quality balsamic vinegar is usually fairly uniform in flavor, while high-end black vinegar varies widely in taste from nation to nation and province to province.
Rice, wheat, millet, sorghum, and barley are all fermented to make black vinegar. Many people prefer vinegar made from rice, since it has a slightly sweet flavor to compliment the familiar acidic note found in vinegar. One of the most popular varieties is Chinkiang, which is made with glutinous rice and malt, leading to a sweet and complicated flavor.
Many traditional Asian foods incorporate this vinegar, especially in certain regions of China. For this reason, many cooks keep a bottle of their favorite around as an all purpose seasoning. In Japan, a lighter version called kurozu is sold as a health tonic, since consuming small amounts of vinegar every day may be beneficial.
The seasoning can also be used in cuisine from other nations as well, of course. Black vinegar is sometimes added to marinades and bastes, as well as dressings and sauces. It can also be used straight as a dipping sauce, added to braises, or used in meat curing.
The best way to choose black vinegar is to find a version which you prefer. This may require some experimentation, since the options are so varied. To begin with, you should read labels closely, since different grains have different flavors, and some companies sell cheaper knock-offs that lack the complexity of the real thing. Some recipes may call for a specific type as well, in which case you may want to use the type specified for an authentic flavor.