Citrus fruits, such as lemons and limes, have the most concentrated levels of citric acid. Grapefruits and a variety of oranges contain citric acid that's less concentrated and are therefore more appealing to the taste buds.
Lemons and limes can be juiced to obtain the full benefit of their concentrated citric acid and vitamins. The juice can then be added to drinks or other foods to minimize the acidity of the juice. Much of the citric acid, which is actually found in the rind, can be largely avoided by eating or juicing only the segmented inner flesh of the fruit.