Sweet and sour is a generic term that encompasses many styles of sauce, cuisine and cooking methods. Commonly used in China, it has been used in England since the Middle Ages, and remains popular in Europe and America today.
Some authors say that the original sweet and sour sauce came from the Chinese province of Hunan, but the sauce in this area is a light vinegar and sugar mixture not resembling what most people, including the Chinese, would call sweet and sour.
Many places in China use a sweet and sour sauce as a dipping sauce for fish and meat, rather than in cooking as is commonly found in westernized Chinese cuisine.
This style of using sauces is popular amongst Chinese who tie certain sauces to particular meats such as chili and soy for shrimp and vinegar and garlic for goose. There are, however, some dishes, such as the Cantonese sweet and sour pork or Loong har kow, in which the meat is cooked and a sauce added to the wok before serving.
Not all dishes are cooked; some, such as "sweet and sour fruit and vegetable" salad from the eastern regions of China, also find their way in Chinese cuisine. This dish combines salad vegetables such as cucumber, tomato, bell pepper, and onion with a mixture of pineapple, vinegar, and sugar to make a cold served dish.
In China traditionally the sauces are made from mixing sugar or honey with a sour liquid such as rice vinegar, soy sauce, and spices such as ginger and cloves. Sometimes a paste made from tomatoes is used but this is rare and normally restricted to western cooking.