Fruits and vegetables are excellent sources of many nutrients, vitamins and minerals, One beneficial substance contained in citrus and certain bitter berries is citric acid. According to the Columbia Encyclopedia, citric acid is "an organic carboxylic acid containing three carboxyl groups...It can be extracted from the juice of citrus fruits by adding calcium oxide (lime) to form calcium citrate, an insoluble precipitate that can be collected by filtration."
It is well established in the medical world that certain substances have the ability to relax and even stop muscles from functioning. One such substance is potassium citrate, the salt found in citric acid. During open heart surgery, surgeons inject potassium citrate into the heart to temporarily stop it from beating. This allows the surgeons the opportunity to repair the heart without the risk of injuring the patient due to the constant beating of the heart.
Citric acid has the ability to chelate metals. Chelating is the process of binding a ligand to a metal ion. With this in mind, many laundry detergent companies began adding citric acid to their product to break down the metal deposits in hard water, thus allowing their soaps to work more efficiently.
If needing an effective means of increasing a soil's acidity, lemons or limes can be shredded and added to fertilizers. Lemons and limes contain high amounts of citric acid, accounting for their bitter flavor. If needing an even more potent alternative, citric acid can be purchased in its solid form from various online cooking supply vendors.