Citric Acid in Food: Is the FDA-Approved Preservative Actually Natural?

What is citric acid and what does it do in food?

Citric acid is a weak organic acid (C₆H₈O₇) that occurs naturally in citrus fruits — lemons contain roughly 47–48 g/L of citric acid. In food manufacturing, it functions as an acidulant (lowering pH), a flavor enhancer (providing tartness), an antioxidant (chelating metal ions that would otherwise accelerate oxidation), and a preservative (inhibiting microbial growth at low pH). It is one of the most widely used food additives in the world.

The FDA granted citric acid GRAS status under 21 CFR 184.1033, which means it is considered safe for use in food under conditions of intended use with no specified maximum level in most applications. EFSA likewise confirms no safety concern at current use levels, noting citric acid is completely metabolized via the Krebs cycle — a normal part of human cellular energy production.

You can find it on the label of preservatives in carbonated beverages, canned tomatoes, frozen foods, candy, salad dressings, processed cheeses, and hundreds of other product categories. It also appears in pharmaceuticals, cosmetics, and household cleaning products.

How commercial citric acid is actually made

Before 1923, citric acid was extracted from citrus fruit juice — primarily Sicilian lemons. That changed when American chemist James Currie demonstrated that the mold Aspergillus niger could produce citric acid efficiently from sugar substrates. By the 1940s, fermentation had entirely displaced fruit extraction as the dominant production method. Today, global production exceeds 2 million metric tons per year, almost all of it via Aspergillus niger fermentation.

The process involves fermenting a glucose or sucrose solution — typically derived from corn starch, sugar cane molasses, or sugar beet — with a strain of Aspergillus niger under controlled conditions. The mold secretes citric acid into the medium. The acid is then filtered, purified, and crystallized. Regulatory standards require the final product to meet strict purity specifications; the mold itself does not appear in the finished citric acid.

You can read the additive profile for the organism used in this process here: Aspergillus niger (fermentation production).

The 2018 Toxicology Reports study and the sensitivity question

A 2018 case series published in Toxicology Reports(Sweis & Cressey) documented inflammatory and musculoskeletal symptoms in individuals who consumed products containing manufactured citric acid. The authors hypothesized that the reactions were not to citric acid itself — which is metabolically inert at food doses — but to trace residues of Aspergillus niger proteins or fermentation byproducts that survived purification.

Important caveats: this was a small case series, not a controlled clinical trial. The authors did not establish causality, only temporal association. No regulatory agency — FDA, EFSA, or Health Canada — has changed its position on citric acid safety based on this publication. The study has been cited in allergy literature as warranting further research, not as evidence of a confirmed hazard.

True IgE-mediated allergy to citric acid is considered extremely rare. Sensitivity reactions to citric acid-containing products are more plausible if mold allergens are present — though the commercial purification process is designed to eliminate them. Consumers who suspect a reaction should consult an allergist, not self-diagnose based on ingredient labels alone.

Is "citric acid" on a label the same as the acid in lemons?

Molecularly, yes. The citric acid molecule (C₆H₈O₇) produced by Aspergillus niger fermentation is chemically identical to the citric acid in a lemon. The difference is in the production process and what may accompany the molecule.

Food marketing frequently implies citric acid comes from citrus fruits — through imagery, naming, or proximity to fruit claims. This is misleading. The FDA does not require manufacturers to disclose the production method for citric acid, so "citric acid" on a label gives no indication of whether it was extracted from fruit (essentially never, at commercial scale) or produced by mold fermentation (essentially always).

This is worth understanding when evaluating FDA GRAS determinations more broadly — GRAS status covers the substance, not the production method.

Dental erosion: the documented concern

The one area of consensus concern around citric acid is dental erosion. Multiple peer-reviewed studies confirm that citric acid at concentrations found in soft drinks and sour candies demineralizes tooth enamel with repeated exposure. This is not unique to citric acid — any acidic substance below pH 5.5 can erode enamel — but citric acid is particularly erosive because it also chelates calcium from the enamel surface.

The American Dental Association links frequent consumption of acidic beverages (those containing citric, phosphoric, or tartaric acid) to increased erosion risk. This is a dose-frequency issue: occasional consumption poses minimal risk; multiple acidic drinks per day, especially sipped slowly, poses documented risk to dental health.

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