Submerging cut fruits and vegetables in water with a slight acid content keeps them from turning brown during food preparation, and helps firm the texture and remove odors from offal.
I. Add 1 tablespoon cider vinegar or distilled white vinegar or 2 tablespoons lemon juice to each 1 quart water.
II. See Antibrowning Solutions for Canning Fruits and About Freezing Fruit for acidulated solutions appropriate for those applications.