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Lime (Chemical)

The chemical lime in the form of Calcium Hydroxide (aka Edible Lime, Hydrated Lime, CaH2O2) is used in some food processing, and has been for millennia.

Lime (in the form of Calcium Hydroxide) is used in South America in processing corn. Corn is soaked in water to which Calcium Hydroxide has been added. The corn swells, loosening the husks. The corn is then rinsed to wash away both the Calcium Hydroxide water and the husks. This has been done for millennia. Though this was a very efficient way to husk the kernels of corn, negating the need for tiresome work or advanced tools and machinery, there was a vital nutritional side-benefit that happened, even though people didn't realize it. In addition to adding a bit of calcium, more importantly, the process released the niacin in the corn and made it available to the body. The connection between the Calcium Hydroxide treatment, niacin and pellagra was not made until the 1930s. New World natives began developing pellagra when they were put on reserves and given food, especially untreated corn.

After the corn is treated in this way, it can be dried and ground into a corn flour such as "Masa Harina."

Tortillas are made from Masa Harina, which is the flour made from corn treated with Calcium Hydroxide. It gets somewhat confusing, though, when you learn that Mexicans, such as those in Monterrey, Mexico will sometimes add "lime" when they are making tortillas. At this stage in the game, though, what they are adding is juice from the lime fruit, not lime the chemical -- Calcium Hydroxide.

Calcium Hydroxide can also be used in making sugar -- it helps the cane pulp matter in the sugar syrup to coagulate, so that it can be removed.

Clearing up the confusion about lime (the chemical)

Unfortunately, the same word in English -- "lime" -- is used for several different things, and that's not even counting the fruit!

But, it's important to understand the different types of lime (the chemical): in particular, the distinction between Calcium Oxide and Calcium Hydroxide is very important. Some food writers mix these up, giving out potentially dangerous information. Calcium Oxide is very dangerous; never use it.

Lime starts out as calcium carbonate. Calcium carbonate can be derived from limestones, coral, chalk or from the shells of mollusks such as oysters or clams.

Calcium Oxide

Heating up calcium carbonate drives out carbon dioxide, leaving Calcium Oxide.

Calcium Oxide is also called Quicklime (when water is added, it heats up and bubbles like it's boiling, make it seem alive. "Quick" used to be used in a sense that meant alive, as in the "quick and the dead".) It is also called unslaked Lime.

It is very dangerous to use, as it will react with any water, even the slightest amount of perspiration or moisture on your skin, and burn you severely. The steam given off is not toxic, but it is very hot and can scald and burn.

Calcium Hydroxide

To make Calcium Hydroxide, Calcium Oxide (Quicklime) is treated with water. It heats up, evaporates the water, and leaves behind a white powder. This converts Quicklime from Calcium Oxide to Calcium Hydroxide. When Calcium Hydroxide is mixed in water, it creates a very alkaline solution. This is also called slaked Lime, as the lime has been treated with as much water as it will take up, "slaking" (satisfying) its thirst.

Pickling Lime

Pickling Lime is Calcium Hydroxide, but a food-grade quality version of it with no impurities. See separate entry.

Agricultural Lime

Ground Limestone. The main active component is the calcium carbonate in the stone.

Literature & Lore

Calcium Oxide has a very high melting temperature, 2572°C. It can be heated so hot that it will emit a white light without melting. Before theatres used electricity to power the stage lights, lime would be heated with a flame, to give off a light directed at the stage -- and voilà, you had the "Limelight".

Language Notes

The name for the chemical lime doesn't come from the fruit. It comes instead from a very old word related to the words "loam" and "slime", and to the German word for clay, "Lehm". In Old English, the word for the chemical lime was "lïm".


Stolpa, Debbie and Marilyn Herman. Food Preservation - Dill Pickles, Crisp and Quick. University of Minnnesota Extension. Retrieved October 2009 from: http://www.extension.umn.edu/distribution/nutrition/00043.html

See also:

Technical Terms

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Also called:

Chaux (French); Kalk (German); Calce (Italian)


Oulton, Randal. "Lime (Chemical)." CooksInfo.com. Published 22 March 2004; revised 04 February 2015. Web. Accessed 03/21/2018. <http://www.cooksinfo.com/lime-chemical>.

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