Citric Acid: Natural vs Manufactured. Does the Source Matter?

Citric acid is everywhere. It’s in sodas, candy, canned tomatoes, packaged hummus, frozen meals, and nutritional supplements. It’s one of the most produced food chemicals in the world, with annual production over 2.8 million metric tons globally (USDA, 2022).

It also shows up on “avoid these additives” lists with alarming regularity. The argument usually goes: it’s made by a mold, so people with mold allergies should avoid it. Let’s look at whether that holds up.

What Citric Acid Is

Citric acid is a tricarboxylic acid. It has three carboxylic acid groups (-COOH) on a six-carbon chain. Chemist Carl Wilhelm Scheele first isolated it from lemon juice in 1784.

Its chemical name is 2-hydroxypropane-1,2,3-tricarboxylic acid. If you recognize the Krebs cycle from biology class, you’ll recall citrate (the ionized form of citric acid) as one of its key intermediates. Your cells produce and consume citric acid constantly as part of normal energy metabolism.

Natural sources of citric acid include citrus fruits (lemon juice is roughly 5-8% citric acid by weight), tomatoes, berries, and many other fruits and vegetables. The molecule itself is not exotic or synthetic. It’s a fundamental organic acid that’s been part of the food supply since the beginning of food.

Industrial Production: The Mold Fermentation Story

Before 1919, commercial citric acid was made by extracting and purifying it from Italian citrus fruit. Then chemist James Currie discovered something useful: Aspergillus niger, a common black mold, produces large amounts of citric acid when fed sugars under the right conditions (Currie, 1917).

This was a major industrial breakthrough. Mold fermentation is dramatically cheaper and more scalable than citrus extraction. By the 1920s, it had replaced citrus extraction almost entirely. Today, essentially all commercial citric acid comes from this process.

Here’s how it works:

1. A strain of Aspergillus niger is grown in a fermentation vessel.
2. The mold is fed a high-sugar medium, typically glucose syrup from corn starch or molasses from sugarcane or sugar beets.
3. Under controlled conditions (low pH, specific temperature, limited nutrient stress), the mold’s metabolic pathway produces more citric acid than it can use internally and secretes it into the fermentation broth.
4. The broth is filtered to remove the mold biomass.
5. Citric acid is precipitated, filtered, and purified through multiple steps including activated carbon treatment.
6. The final product is dried, milled, and tested for purity.

The finished product is pure citric acid. The Aspergillus niger mold and essentially all of its proteins are removed. What you’re adding to food is the same molecule you’d find in a lemon.

What Citric Acid Does in Food

Citric acid earns its place in processed food by doing several useful things at once:

Acidulant and flavor agent. Citric acid adds tartness and brightness to food. It’s the reason sour candy is sour and the reason a tomato-based pasta sauce tastes livelier with a bit of added acid. It enhances the perception of other flavors, particularly fruity notes.

Preservative. Citric acid lowers pH, which slows or stops the growth of most spoilage bacteria and many molds. It also directly inhibits some enzymes involved in oxidative spoilage. This is why it extends the shelf life of canned and packaged foods.

Chelating agent. Citric acid binds metal ions like iron and copper. Free metal ions catalyze oxidation reactions that cause rancidity and color loss. By tying up those metals, citric acid protects fats from going rancid and prevents color changes in cut fruit and packaged vegetables. This is the same reason lemon juice prevents avocado from browning.

Acidity regulator. Many food processes work better at a specific pH. Citric acid is used to adjust pH in beverages, jams, and canned foods for both safety (botulism risk decreases sharply below pH 4.6) and consistency.

Emulsification support. Citric acid doesn’t emulsify on its own, but it helps stabilize emulsions by chelating metal ions that would otherwise break them down. This is relevant in products like soy lecithin-stabilized emulsions.

The Mold Allergy Concern

The claim that citric acid causes reactions in people with mold allergies circulates widely online. Let’s be precise about what the evidence actually shows.

Mold allergy is a hypersensitivity reaction to mold proteins or spores. The allergens are specific proteins produced by molds like Aspergillus, Alternaria, or Cladosporium.

After the citric acid purification process, the Aspergillus niger mold is removed. Residual proteins, if any, are present in trace amounts well below what would typically trigger an IgE-mediated allergic response.

A small number of published case reports describe adverse reactions attributed to citric acid (Bukan et al., 2002 is one cited example), but these are poorly documented. They don’t clearly distinguish between reactions to citric acid itself versus other ingredients in the same product. The reactions described also don’t follow the typical pattern of IgE-mediated mold allergy.

The FDA, EFSA, and JECFA have all reviewed citric acid extensively. None of them flag the mold production method as a meaningful allergen concern for people with mold allergies.

This doesn’t mean no one ever reacts to citric acid-containing products. It means that if they do, citric acid specifically is an unlikely culprit compared to other ingredients. If you’ve noticed a pattern of reactions to processed foods, working with an allergist to identify the actual trigger is more useful than eliminating citric acid.

Citric Acid vs. Lemon Juice: Does the Source Matter?

Chemically, no. Citric acid is citric acid whether it came from a lemon or a fermentation tank. The molecule has the same structure, the same properties, and behaves identically in your body.

Nutritionally, lemon juice contains vitamin C, flavonoids, and other compounds that citric acid powder doesn’t. Those are genuinely different. But if the question is whether fermentation-derived citric acid is somehow less safe or more problematic than citrus-derived citric acid, the answer is no.

Regulatory Status

Citric acid has FDA GRAS status and is approved as a food additive in essentially every country with food safety regulations. The EU classifies it as E330. JECFA has reviewed it multiple times and established no numerical ADI, meaning evidence of harm at any reasonable dietary level is absent.

It’s also in the same metabolic cycle your cells run on. Your liver is processing citrate right now.

Practical Context

Most people consuming a Western diet get citric acid from dozens of sources daily. The amounts are generally small relative to what your metabolism produces internally. Citric acid is one of the better-understood food additives precisely because the molecule is so biologically fundamental.

Compare citric acid to sodium benzoate, which has specific chemical concerns (benzene formation) under certain conditions. Citric acid doesn’t carry equivalent concerns. It doesn’t react with other common food ingredients to form harmful compounds. It doesn’t accumulate in tissue. Its metabolic fate is just to be burned as fuel like any other tricarboxylic acid.

The “natural vs. manufactured” frame applied to citric acid misses the point. The processing method doesn’t change the molecule.