Most sauces have more than one function in a dish. A sauce that adds a counterpoint flavour, for example, may also introduce textural and visual appeal. Sauces generally serve one or more of the following function or purposes.
1) Add Contrast In Taste:
Sometimes sauces are used to add a contrast in taste to another food. Apple sauce with fresh roast pork serves the same purpose. Broadly speaking any condiment or mixture of food, which serves to contrast with or compliment another food, can be termed a sauce. In this broad sense, a peanut butter and jelly mixture would be a sauce to a piece of bread if they were served together.
2) Add Sharpness and Tanginess:
Some sauces are used to add sharpness or tanginess to a portion of bland food. A remoulade sauce served with shrimp is an example of a piquant sauce.
3) Add Texture:
Many sauces include a garnish that adds texture to the finished dish. Chicken Chasseur is enhanced by a sauce finished with tomatoes and mushrooms. A dish that has a distinct texture, such as pan-fried soft-shelled crab, is enhanced by a smooth sauce.
4) Add Flavour:
A sauce that includes a flavour complementary to a portion of food brings out the essence of that food. The mild sweetness of poultry is heightened by a sauce flavoured with tarragon. The rich flavour of the beef is highlighted by a pungent sauce made with green peppercorns, which deepen and enrich the overall taste.
5) Add Appearance:
Sauces may add to the appearance of food, sometimes as a coating which is poured or brushed over the food to give a pleasing appearance to an otherwise uninteresting item. the chaud-froid sauce made with cream or mayonnaise and gelatine is used to coat various food items.
6) Add Moisture:
A sauce can add moisture to naturally lean foods such as poultry, fish. A sauce can also compensate for the drying effect of certain cooking techniques, especially broiling, grilling, sautéing, and roasting. Grilled foods may be served with a warm butter emulsion sauce like béarnaise or with compound butter. Beurre blanc is often served with shallow-poached lean white fish to add a bit of succulence to the dish.
7) Add Eye Appeal:
A sauce can enhance a dish’s appearance by adding lustre and sheen. Lightly coating a sautéed medallion of lamb with a jus lié creates a glossy finish on the lamb, giving the entire plate more eye appeal. Pooling a red pepper coulisbeneath a grilled salmon steak gives the dish a degree of visual excitement by adding an element of colour.