Apples and bananas are well known for their tendency to brown quickly when exposed to air. Oxidization causes the cells on the exposed surfaces of these fruits to change color. Several methods will stop apples from browning and they range from just stirring the fruit to the use of a commercial preservative. It is best to inform guests if you do use a preservative to prevent browning apples, in case of allergies.
Put the apple slices in water. In "1101 Businesses You can Start from Home," the author suggests cutting the apples under cold water.
Use other fruits and fruit juices. Mix two tablespoons of lemon or lime juice with one quart of water and put the slices in. Mix the cut apples with slices of kiwi. You can also coat the apple slices with a few tablespoons of orange or pineapple juice.
Sprinkle one teaspoon of vinegar on the apples.
Place the cut apples in a mixture of salt and water.
Keep the apples natural if you plan to use them almost immediately. In "The New Elk Hunter's Cookbook," the author suggests just stirring the apples every few minutes to prevent oxidization.
Keep the apples white longer. Sprinkle lemon juice on the slices, place them in a non-clear container and seal it. Non-clear containers limit the process of oxidization.
Use soda. Soak the apple slices in a soda high in citric acids, such as one with lemon lime.
Mix 3 cups of water with two crushed tablets of vitamin C. Remove the apples from this mixture when you are ready to use them.
Try a commercial preservative, such as "Fruit Fresh." This will be available in the spice section of your local retail store.