How Is Citric Acid Made?

Virtually all citric acid produced commercially today comes from microbial fermentation. Think of it like this: we feed starch or sugar to tiny organisms—most commonly a fungus called Aspergillus niger—and they “eat” those ingredients, then naturally produce citric acid as a byproduct of their metabolism.

The entire manufacturing process breaks down into four key steps:

1. Raw Material Prep: Turning Starch Into “Sugar Water”

First, we need to give the microbes their food. The most common industrial raw materials are starchy crops like corn, sweet potatoes, and cassava.

Milling & Liquefaction: We grind the corn or tubers into a fine powder, mix it with water to make a slurry, and add an enzyme called amylase. When heated to high temperatures, this enzyme breaks the starch down into smaller sugar molecules (dextrins and oligosaccharides).
Saccharification: We cool the liquefied mixture and add another enzyme, glucoamylase. This fully breaks those small sugars down into pure glucose. After filtering out any impurities, we’re left with a clean glucose solution—this is the “food” that feeds the microbes in the next step.

2. Microbial Fermentation: When Aspergillus nigerDoes Its Work

This is the most important step in making citric acid.

Inoculation: We take a pre-grown, active culture of Aspergillus niger(a type of mold) and add it to a sterilized tank filled with the glucose solution we made earlier.
Fermentation Reaction: Inside the tank, we keep the temperature between 30°C and 38°C and constantly pump in sterile air—Aspergillus nigerneeds lots of oxygen to make citric acid. We also add small amounts of sulfuric acid to keep the environment very acidic, with a pH of 2.0 to 2.5.
Acid Production: After about 3 to 5 days of fermentation, the Aspergillus nigeruses its natural metabolic processes (glycolysis and the tricarboxylic acid cycle) to turn most of the glucose into citric acid, which builds up in the liquid inside the tank.

3. Extraction & Purification: Isolating Citric Acid

Once fermentation is done, the liquid (called fermentation broth) has citric acid mixed with mold cells, leftover sugar, and other impurities. We need to purify it, and the classic method is called the calcium salt process:

Filtering & Neutralization: First, we filter the broth to remove all the mold cells and solid waste. Then we add calcium carbonate (or lime milk) to the filtered liquid. The citric acid reacts with the calcium carbonate to form an insoluble solid called calcium citrate, which settles out.
Acidification: We collect and wash the calcium citrate solid, then add sulfuric acid. This reaction swaps the calcium out, turning the calcium citrate back into liquid citric acid and a solid called calcium sulfate (also known as gypsum).
Final Purification: We filter out the gypsum solid, then treat the crude citric acid solution with ion exchange resins (to remove leftover metal and mineral ions) and activated carbon (to remove color). The result is a clear, colorless, highly pure citric acid solution.

4. Concentration & Crystallization: Making the Final Crystals

Now we turn the pure liquid into the white crystals or powder you see in stores.

Evaporation & Concentration: We send the purified citric acid solution through evaporators, where heat removes most of the water, leaving a thick, highly concentrated citric acid solution.
Crystallization & Drying: We cool the thick solution, which makes citric acid form solid crystals. We spin these crystals in a centrifuge to separate them from the remaining liquid, then dry them with hot air. The final product is the common white, granular or powdered citric acid you buy—either anhydrous (no water) or monohydrate (with one water molecule per citric acid molecule).

Quick Note: In the past, people used to extract citric acid directly from fruits like lemons and oranges, or make it through chemical synthesis. But both methods are way too expensive, produce very little citric acid, or can’t meet food safety purity standards. Today, these methods are almost never used. Roughly 90% of the world’s citric acid is made using the Aspergillus nigerfermentation process we just explained.

PMC’s authoritative analysis on the production of citric acid

Is Citric Acid Bad For You?

As we just covered, the citric acid made by modern factories is actually a natural substance—produced by Aspergillus nigerduring fermentation. When eaten in moderation, following food safety guidelines, it’s completely safe for humans and non-toxic. That said, too much of anything can be harmful. People who eat large amounts long-term, or those with certain health conditions, do face some potential risks.

The Safety & Benefits of Moderate Citric Acid Intake

Citric acid is a natural part of your body’s normal metabolism (it’s a key step in the tricarboxylic acid cycle, which makes energy for your cells). Once you eat it, your body breaks it down quickly—it doesn’t build up or stay in your system.

Naturally in Food: It’s found in lots of fresh fruits, especially lemons and oranges. A little citric acid makes your mouth water and your stomach produce acid, which boosts your appetite and helps you digest food better.
Helps Absorb Nutrients: In your gut, citric acid binds to minerals like calcium, iron, and zinc. This makes it easier for your body to absorb these important nutrients.

Potential Risks of Long-Term Excessive Intake

Citric acid itself is barely toxic, but most citric acid added to processed foods is in products that are also high in sugar and acid. Eating too much of these foods can cause specific problems:

Damages Tooth Enamel: This is the most direct risk. Drinking lots of citric acid-containing drinks (especially sugary sodas) over time softens and wears away the hard enamel on your teeth. This leads to sensitive teeth, thin enamel, and even cavities.
Worsens Digestive Issues: Eating too much citric acid on an empty stomach, or all at once, irritates the lining of your stomach. This can cause acid reflux, stomach pain, and heartburn. For people who already have gastritis or stomach ulcers, this irritation can make their symptoms much worse.
Disrupts Calcium Balance: One common concern with too much citric acid is that it can make your body lose calcium over time. This raises your risk of low blood calcium, which can lead to muscle spasms and uncontrollable twitching in your hands and feet.
Boosts Aluminum Absorption: This is an often-overlooked risk. If citric acid touches aluminum foil while cooking (like when you grill food wrapped in foil), it makes the aluminum leach into your food. Eating too much aluminum long-term is bad for your nervous system health.

Simple Daily Tips to Avoid Risks

Watch Out for Sour Snacks: Be careful with super sour treats like sour powder candy, lemon drops, some spicy snacks, and trendy sour candies. Eat them in small amounts, and rinse your mouth with water right after to protect your tooth enamel.
Special Groups: Be Cautious: If you have chronic gastritis, stomach ulcers, sensitive teeth, or kidney disease, try to limit foods with lots of added citric acid.
Read Food Labels: A little natural citric acid from fresh fruit is good for you. The real concern is the concentrated citric acid added to processed snacks, drinks, and packaged foods.

How Long Does Citric Acid Stay in Your Body?

Correction: The following section originally referenced lactic acid—this has been fixed to citric acid.

Citric acid breaks down extremely fast in your body. Most of it is fully processed and eliminated within a few hours to 24 hours. Unlike heavy metals or hard-to-break-down chemical additives, it never builds up in your system. Instead, your body turns it into water and carbon dioxide and flushes it out quickly.

How Your Body Breaks Down Citric Acid

Citric acid metabolizes so fast because it’s a natural, normal part of your body’s energy-making process (the tricarboxylic acid cycle).

Absorption: When you eat or drink something with citric acid, your digestive tract absorbs it quickly into your bloodstream.
Energy Production: The citric acid travels to your cells’ mitochondria (the “powerhouses” of cells) and joins your body’s energy cycle. Enzymes break it down rapidly, turning it into carbon dioxide and water—and releasing energy your body uses.
Elimination: The carbon dioxide from breakdown leaves your body when you breathe out. Extra water and small waste products are mostly flushed out through urine.

What Affects How Fast It Metabolizes?

Even though citric acid breaks down efficiently, a few things change how long it takes:

How Much You Eat: A small amount—like eating a lemon or sipping lemon water—metabolizes fully in a few hours. A huge dose (way more than you’d ever eat in a normal day) might take a little longer for your body to process the excess.
Your Metabolism: Your liver is the main organ that breaks down citric acid. Young people usually process it faster, while older adults or people with weak liver/kidney function might take a bit longer.

A Medical Example: Dialysis Patients

To show how fast citric acid metabolizes, doctors have a clear example. In some blood dialysis treatments, citrate salts are added to dialysis fluid to prevent blood clots. Studies found that even in dialysis patients with non-working kidneys, citric acid has a half-life of only about 49 minutes.

This means as long as your body’s basic metabolism works, if you stop eating large amounts of citric acid, your blood levels drop back to normal quickly. It’s almost impossible for it to build up and poison you.

So unless you eat massive amounts of high-concentration citric acid every day for a long time, you don’t have to worry about it sticking around or straining your body.

How Do You Know If You’ve Eaten Too Much Citric Acid?

The easiest way to tell if you’ve overdone it on citric acid is to watch for clear warning signs: digestive upset, sensitive teeth, or weird muscle symptoms. As we said earlier, citric acid breaks down fast—but eating a lot of citric acid snacks or drinks in one sitting will trigger immediate physical reactions.

Digestive “Warning Signs”

This is the most common and obvious symptom of too much citric acid.

Stomach Discomfort: Citric acid makes your stomach produce extra acid. If you feel sudden acid reflux, a burning chest pain (heartburn), nausea, or stomach ache right after eating sour snacks, you’ve exceeded your stomach’s tolerance.
Digestive Issues: People with sensitive guts might get bloating or diarrhea—symptoms that feel like a stomach bug.

Tooth “Warning Signs”

Teeth are super sensitive to acid, and the damage gets worse over time.

Tooth Sensitivity: If your teeth never hurt when you eat cold/hot/sour food, but suddenly they ache when you drink cold water or breathe in cold air, acid has started wearing down your enamel.
Visible Tooth Damage: If your teeth lose their shine, look cloudy like frosted glass, feel rough, or have small pits or chalky white spots, the acid has caused permanent damage.

Muscle & Nerve Reactions

This is rare in daily life—it usually only happens from eating an extremely large amount (like accidentally drinking concentrated citric acid solution) or long-term overconsumption of citric acid additives.

Muscle Cramps: Too much citric acid messes with your calcium levels, making your body lose calcium and lowering blood calcium. The main symptoms are unexplained numbness, cramps, and even uncontrollable twitching in your hands and feet.
Severe Weakness: In very rare, serious cases—like eating industrial-grade citric acid or a massive amount of food-grade citric acid—you might have severe vomiting, pale skin, extreme tiredness, a fast heartbeat, or even trouble breathing. If this happens, vomit immediately and go to the emergency room right away.

What to Do If You Notice Symptoms

If you have mild stomach or tooth discomfort, don’t panic. Stop eating sour foods right away, drink lots of warm water to dilute the acid, and let your body flush it out. If you have severe, ongoing stomach pain or obvious muscle cramps, see a doctor to get checked out.

Is Citric Acid Harmful for People With Kidney Problems?

You can’t simply say citric acid is “good” or “bad” for people with kidney disease—it depends on how they eat itand their blood potassium levels.

In short: Small amounts of citric acid as a food additive are usually safe, even helpful. But citric acid from fresh fruits (like lemons and oranges) can be risky because those fruits are high in potassium.

The Big Risk: High Blood Potassium (Hyperkalemia)

This is the biggest concern for people with kidney disease.

Fruits = Hidden Potassium: Fruits with natural citric acid (lemons, oranges, grapefruits) are also high-potassium foods. Healthy kidneys filter out extra potassium, but damaged kidneys can’t. Eating lots of these fruits to get citric acid can raise blood potassium to dangerous levels, which can cause irregular heartbeats or even cardiac arrest.
Potassium Citrate in Processed Foods: Some drinks and additives use “potassium citrate.” For kidney patients, this can also raise blood potassium. Always check the ingredient list on packaged foods.

A Surprising Benefit: Citric Acid Can Help Kidney Patients

Many people don’t know this: A little citric acid acts like medicine for some people with chronic kidney disease.

Fights Acidosis: Chronic kidney disease often causes “metabolic acidosis”—when your body becomes too acidic. Citric acid breaks down into bicarbonate (a base) in your body, which neutralizes excess acid and eases strain on the kidneys.
Doctors Prescribe It: Doctors sometimes prescribe sodium citrate or potassium citrate to treat acidosis or prevent kidney stones in patients. So if your blood potassium is normal, small amounts of citric acid won’t hurt your kidneys.

Avoiding Digestive Issues

Kidney disease often causes nausea, vomiting, and loss of appetite (from waste buildup or medications). Citric acid’s sour taste stimulates stomach acid. If you already have acid reflux, stomach ulcers, or no appetite, too much citric acid can make these issues worse and make it harder to absorb nutrients.

Simple Tips for Kidney Patients

Check Labels: When buying snacks or drinks, look for “citric acid” or “sodium citrate” in small amounts. If your blood potassium is normal, you can eat them in moderation.
Limit Fresh Fruit: If your doctor put you on a low-potassium diet, avoid high-potassium fruits like lemons and oranges. Don’t drink concentrated lemon juice for vitamin C or citric acid.
Follow Your Doctor’s Orders: If your blood potassium is high, or you take potassium-sparing diuretics, ask your doctor before eating foods or taking medications with potassium citrate.