You have been making guacamole all day long for the big party, and you dont want it to turn brown on top before the guests arrive. The solution: Sprinkle a liberal amount of fresh lemon juice over it and it will stay fresh and green. The flavor of the lemon juice is a natural complement to the avocados in the guacamole. Make the fruit salad hours in advance too. Just squeeze some lemon juice onto the apple slices, and they will stay snowy white.