Citric acid, an acid found in citrus fruits such as lemons or oranges, is used in many culinary applications, including cheese making and baking. Most important to the home chef, citric acid prevents browning or discoloration of many fruits. It is completely safe and, in small quantities, doesn't change the taste of the fruit. Citric acid is available in powdered or liquid form at most grocery stores, usually near the canning or preserving items.
Mix the citric acid solution in a large bowl. The ratio of citric acid to water depends upon the fruit. Quick-browning fruits, such as apples, require a much smaller ratio than slowing browning fruits, such as nectarines. Reference the citric acid container for exact measurements, but, as a general rule of thumb, use 1 to 3 tsp. per cup of cold water.
Prepare the fruit. Peel, core and slice the fruit you want to dip. Set in a mesh strainer that fits inside the bowl.
Place the strainer in the bowl. Allow to sit for up to 15 minutes.
Remove the strainer from the bowl and allow the fruit to drain. Store the fruit in a zip-top bag or air-tight plastic container.