What Is a Citric Acid Used For?

Citric acid usually comes in the form of clear crystals or white powder. Citric acid is used in personal care products and cleaning products and as a medicine.

Citric acid is a naturally occurring chemical that has widespread applications in today’s world. It plays a role in food and cosmetic production, industrial cleaning, and even medicine. 

Citric acid is a compound that’s found in a wide variety of fruit, vegetable, and animal tissues. It’s also been artificially produced in large quantities since the early 20th century. 

Citric acid usually comes in the form of clear crystals or white powder. It’s odorless but has a strongly acidic taste. The taste can also contain sweet and tart components.

This chemical is very soluble in water and reasonably soluble in ethanol. It acts as a weak acid in terms of pH measurements. 

It can be used to create a number of different salts under particular conditions. Examples include sodium citrate and potassium citrate. 

Citric acid is nontoxic and has antibacterial and antiseptic properties that make it appealing for a wide range of applications. 

There are a few different ways to both produce and extract citric acid. Traditional methods extracted naturally occurring citric acid from large quantities of things like lemon and pineapple juice. Natural sources of citric acid include: 

• Lemons
• Limes
• Grapefruits
• Melons
• Pineapples
• Oranges

Today, the most common method for creating the molecule is through sugar-based fermentation. A number of creatures, like molds, are capable of consuming sugar and producing citric acid through the process known as fermentation. Most people are familiar with the idea of fermentation in terms of alcohol production, where organisms eat sugar and produce alcohol as a byproduct. This is a very similar process but with different organisms and a different end product.

Penicillin mold was the first organism that people used for citric acid fermentation. This organism was quickly replaced with Aspergillus niger fermentation. Aspergillus niger is a black mold that’s known to be a common allergen. 

Since the early 1900s Aspergillus niger has been our main source of citric acid. In 2016 alone, 2.3 million tons of citric acid were produced from industrial plants that practice this fermentation on a massive scale. 

The U.S. Food and Drug Administration (FDA) has stated that citric acid is generally recognized as safe. This means that it can be used in manufacturing without any limitations. 

The FDA has specifically stated that all forms of citric acid are safe for human use, no matter how it was made. This means that both naturally occurring and manufactured citric acid (MCA) can be used in a wide range of products. 

Unfortunately, some research suggests that there isn’t enough data on MCA to justify using them so widely. One study reported serious health consequences in four individuals that seemed to be caused by consuming MCA. This included large-scale inflammation responses with respiratory symptoms, joint and muscle pain, and signs of irritable bowel syndrome (IBS). 

The conclusion of the study was that much more research was needed on MCA to see how it affects particularly susceptible individuals. 

For most people, however, citric acid should be perfectly safe to use in most contexts. 

Over 70% of the citric acid that’s produced is used as a food and beverage additive. It’s predominantly used as a preservative, though it does serve other functions.

Some people use it as a natural flavoring compound. It’s found in a lot of soft drinks. You can add squirts of lemon juice to your food or mix in powdered citric acid to increase the acidic flavors in a dish. Sprinkling lemon juice can also prevent foods, like apples, from quickly turning brown. 

There’s even some evidence that consuming citric acid can help your body absorb more of other ingredients that you’re eating at the same time. For example, one Japanese study found that consuming supplements of Citrus sudachi along with a meal that was high in calcium increased the amount of calcium that the men in the study were able to absorb. It also increased how much magnesium and phosphorus their bodies were able to absorb and use.

Citric acid is a common ingredient in many personal care products because it’s very safe. For example, it’s safe to apply products that contain citric acid to a baby’s skin, near your eyes, and on mucus membranes. 

The main use in these products, though, is as a preservative. It helps keep the other chemicals stable. 

Citric acid and its associated salts, like sodium citrate, are used in a wide variety of personal care products, including:

• Chemical skin peels
• Lipsticks
• Soaps
• Hair dyes
• Deodorant
• Hair spray
• Detergents
• Creams and lotions
• Baby products

Citric acid also has a number of medical applications, some of which are relatively recent discoveries. 

Many studies have shown that increasing the amount of citric acid in your urine decreases your risk of kidney stones. It lowers the pH of your urine and makes it more difficult for stones to form. Drinking fresh lemon and lime juice, then, is a great way to add volume to your urine while increasing the amount of this acid. 

Citric acid is a very common disinfectant. It’s so widespread because it’s generally believed to be safe to use around children and pets. Plus, it seemingly doesn’t harm the environment. By itself, it’s a mild cleaner with widespread applications. It’s a common ingredient in: 

• Rust removers
• Metal cleaners
• Hard water removers
• Tarnish removers

Citric acid is good at removing build-up on dishes and glassware. It can remove stains produced by coffee, tea, urine, and even feces. You can use it much like you would use vinegar in many different cleaning operations. 

It’s even used as a large-scale industrial cleaner. Along with heat, it’s one of the most effective ways to clean dialysis equipment for patients with kidney problems. It’s also used in bioremediation, where it helps purify contaminated soils at industrial sites. 

Citric acid seems to be an effective way to combat norovirus, a common human pathogen. This pathogen causes bouts of gastroenteritis in public settings, like schools, and can be easily transmitted on your hands or in your food. Citric acid is effective at killing this pathogen and can even be used on surfaces where cold and flu viruses last for longer than 24 hours.

Many of the uses of citric acid are still being discovered. One example of an emerging way to use citric acid is as a cross-linking molecule. This means that it’s great at helping other molecules weave together. It helps protein fibers bind together, which can be helpful for medicine. It can even combine other materials to produce eco-friendly packaging. 

Another interesting use that deserves more exploration involves the production of other valuable chemicals. For example, citric acid seems to be one of the best chemicals to use for extracting pectin from apples. Pectin is a desirable compound in the modern industrial setting, but supplies are low. New extraction techniques that rely on citric acid could be a great way to obtain more of this chemical at a low cost. 

Overall, the uses of citric acid are quite broad. It’s unlikely that you can go an entire day without encountering some version of the molecule in one of your foods, beauty products, or cleaning supplies.