Acidulated Water

Acidulated water is simply water combined with a small amount of acid, most commonly vinegar, lemon juice, lime juice or white wine.  It is used to keep foods, such as apples, pears, potatoes or avocado, from discoloring after being cut.  Some cooks poach eggs in acidulated water made from vinegar. The acid causes egg protiens to cook at lower temperatures and has a tendorizing effect. 

Combine 1.5 tablespoons vinegar or 3 tablespoons lemon juice or 1/2 cup white wine with 1 quart of water.

References:

McGee, H. (2004). On food and cooking: The science and lore of the kithcen. New York: Scribner.