Meat is marinated before cooking to improve its flavor and to make it more tender. Many stir fries and braises require marinade. The length of marinade depends on the size of the pieces of meat: for meat shreds or thin slices 30 minutes is sufficient, but for chicken joints 3-4 hours are necessary, while whole birds may need to be marinated for 12 hours or more.
A basic marinade for 150g (5oz) pork consists of 2.5ml (1/2 teaspoon) rice wine, to suppress any strong flavors, 5 ml (1 teaspoon) soy sauce, to improve the color and add to the flavor; 2.5 ml (1/2 teaspoon) sugar, which in small quantities greatly enhances the flavor of the dish, and 2.5ml (1/2 tsp) cornstarch, which creates a film of starch over the meat and protects its texture when it is dipped into hot fat. The quantities and ingredients in marinades vary with different recipes. The amount of marinade should be just sufficient to coat the meat or fish, if the meat quantity is doubles there may be no need to double the amount of marinade.
Beef and mutton are often marinated with a little oil to prevent them from becoming dry. A basic cooking marinade for 150g (5oz) of these meats would be 5ml (1tsp) soy sauce, 2.5ml (1/2 tsp) rice wine, 5ml (1 tsp) cornstarch, and 5 ml (1tsp) oil. Dry sherry or Japanese sake make perfectly acceptable substitutes for Chinese Rice Wine.
A basic marinade for chicken, prawns or white fish in stir fried or braised dishes is 2.5 ml (1/2 teaspoon) rice wine, pinch of salt, 5 ml (1 tsp) cornstarch and 10ml (2 tsp) white of egg for 150g (5oz.) of meat.