What is calcium hydroxide?

Calcium hydroxide is an odorless white powder. It’s used in industrial settings, such as sewage treatment, paper production, construction, and food processing. It also has medical and dental uses. For example, root canal fillings often contain calcium hydroxide.

Calcium hydroxide has several forms and names, including:

  • calcium dihydroxide
  • calcium hydrate
  • calcium(II) hydroxide
  • food-grade lime
  • hydrated lime
  • lime
  • pickling lime
  • slack lime
  • slaked lime

Food-grade lime is the form of calcium hydroxide used in food.

Pickling lime is sometimes used during the pickling process to give pickles an extra crunch. It’s a form of food-grade calcium hydroxide. Traditional canning recipes usually suggest soaking freshly sliced cucumbers or other vegetables in pickling lime for 10 to 24 hours before canning them. During this step, the calcium in pickling lime binds to pectin, making it firmer.

Today, many recipes recommend avoiding pickling lime. This is because pickling lime has been linked to botulism. Botulism is a rare but serious illness that can lead to paralysis. While only a few cases have been reported, many feel the risk isn’t worth it.

A number of recipes offer alternatives to keep your pickles crunchy. These include soaking vegetables in ice water for four to five hours before pickling or using pickling salt.

If you still want to use pickling lime for canning, just make sure you use food-grade calcium hydroxide. Carefully follow the manufacturer’s instructions. Make sure you also follow the safety tips mentioned later.

Here are some of the other ways calcium hydroxide is used in food:

Corn products

People in Central America have been using calcium hydroxide to process corn for thousands of years. They soak raw kernels in water mixed with calcium hydroxide. This process makes it easier to process corn into flour. It also releases important nutrients from the corn, such as niacin.

Today, most products made with corn flour (masa harina) — such as tortillas, sopes, or tamales — contain calcium hydroxide.


Calcium hydroxide is also used to process certain sugars. For example, sugar cane and sugar beets are sometimes prepared using a refining process called carbonatation. During carbonatation, an untreated sugar solution is mixed with calcium hydroxide. This process removes impurities and improves the stability of the product.

Fortified fruit juice

Fruit juices are sometimes fortified with calcium for added nutritional value. There are many ways to do this. Adding calcium hydroxide is just one of them.

If you want to use pickling lime for home canning, make sure you thoroughly rinse it off vegetables before canning them to avoid any botulism risks.

Canned pickles are safe to eat because they’re soaked in an acidic liquid, typically vinegar, and acid kills bacteria. However, pickling lime is alkaline. This means it neutralizes acids. If pickling lime is left on vegetables, the acid might not be strong enough to kill bacteria.

You can avoid this by thoroughly rinsing pickles before combining them with an acidic liquid for canning.

Food-grade calcium hydroxide is generally safe. However, if you work with industrial-grade calcium hydroxide, ingesting it can result in calcium hydroxide poisoning. This can lead to severe injury or death.

Some signs and symptoms of calcium hydroxide poisoning include:

  • vision loss
  • severe pain or swelling in your throat
  • a burning sensation on your lips or tongue
  • a burning sensation in your nose, eyes, or ears
  • difficulty breathing
  • abdominal pain, nausea, and vomiting
  • vomiting blood
  • blood in the stool
  • loss of consciousness
  • low blood pressure
  • low blood acidity
  • skin irritation

Swallowing industry-grade calcium hydroxide is a medical emergency that requires immediate treatment. If you suspect you’ve ingested industry-grade calcium hydroxide, call your local poison control number for advice.

Calcium hydroxide has many uses across different industries, including food production. It’s also sometimes used in the form of pickling lime for home canning.

While it can make your pickles extra crunchy, it also neutralizes acidic pickling juices. This reduces their antibacterial properties.

Without acid strong enough to kill bacteria, canned pickles can cause botulism. Reduce your risk by thoroughly rinsing pickling lime off your pickles before canning them.