You will notice that some fruits and vegetables turn brownish when sliced. The natural color can be preserved with a little help from lemons. When you boil potatoes, add a teaspoon of lemon juice to the water. For apples and avocados, sprinkle just a bit over the slices. You can keep guacamole also green, just add a little lemon juice so it wont turn brown when you make it ahead. Washing fruits and vegetables with a mixture of lemon juice and water will also disinfect the produce. It will get rid of any pesticide residue as well. Plus, your produce will surely smell good.