Poaching is particularly suitable for delicate food, such as eggs, poultry, fish and fruit, which might easily fall apart or dry out. For this reason, it is important to keep the heat low and to keep the poaching time to a bare minimum, which will also preserve the flavor of the food.
The poaching liquid is called court bouillon and a classical court bouillon consists of an acid (wine, lemon juice) and aromatics (bouquet garni and mirepoix). The liquid should ideally be around 160–185 °F (71.1–85 °C), but when poaching chicken, it is vital that the chicken reach an internal temperature of at least 165 °F(74 °C) in the core, in order to be ingested safely.
Poached eggs are generally cooked in water and vinegar, fish in white wine, poultry in stock and fruit in red wine. Typically an egg is poached just to the point where the white is no longer runny and the yolk is beginning to harden around the edges.
Water is a relatively efficient conductor of heat, but it also has a fairly low limit to its maximum potential temperature (212 °F (100 °C) at sea level). As such, it is a technique that applies itself to a broad spectrum of methods and results. It is used to regulate food at a low temperature for extended periods, as with sous-vide. It is also used to rapidly raise the temperature of foods, as with blanching. While it cannot achieve caramelization, which to many is very desirable, many find the delicate nuance of so-called "blanc" foods very pleasant.