Citric Acid Without Citrus: How Black Mold Turns Corn Starch Into a Cheap Food Additive
Citric acid, traditionally extracted from citrus fruits and used as a natural food preservative, has completely been replaced by a laboratory-produced alternative made from corn starch and black mold. This industrial substitute costs up to 80% less to produce. Scientific tests have detected toxic contaminants in finished fermentation-produced citric acid, including substances associated with kidney damage, liver toxicity, and cancer, raising serious questions about food safety.
Introduction: The Ingredient Behind a Familiar Name
During the 18th century, food was largely prepared and preserved in households using traditional ingredients such as salt, vinegar, sugar, honey, along with the natural acidity of citrus fruits. Unlike citric acid, which could be used in relatively small quantities with less impact on a food's original flavor, many of these traditional preservatives required larger amounts and significantly altered its taste.
In 1784, Swedish chemist Carl Wilhelm Scheele isolated citric acid from lemon juice. As food production became increasingly industrialized during the 19th century, citric acid became a commercially valuable preservative, leading to large-scale extraction from citrus fruits. By the early 20th century, manufacturers began replacing natural citrus extraction with a cheaper process using black mold (Aspergillus niger), fundamentally changing how citric acid was produced.
The name suggests a natural connection to lemons, limes, and other citrus fruits. Yet 99% of the commercially manufactured citric acid is not extracted from citrus fruit.
Instead, it is produced through industrial fermentation using microorganisms, particularly Aspergillus niger, a species of fungus commonly known as black mold.
The process is efficient, inexpensive, and capable of producing large quantities of citric acid throughout the year. These economic advantages have allowed industrial fermentation to almost completely replace natural citrus extraction, accounting for approximately 99% of global citric acid production.
Citric Acid Production and Consumption in the United States
The United States manufactures and imports hundreds of millions of pounds of citric acid annually. According to the U.S. International Trade Commission (USITC), domestic production is concentrated among three manufacturers:
Archer Daniels Midland (ADM) — Southport, North Carolina
Cargill — Eddyville, Iowa
Primient — Dayton, Ohio
U.S. Production and Consumption — 2024
According to IndexBox market data published February 25, 2026:
Category | Annual quantity |
Domestic production | 511 million pounds |
Imports | 375 million pounds |
Exports | −51 million pounds |
Total U.S. consumption | 836 million pounds |
The figures cover citric acid and related citrate ingredients. Quantities are rounded.
Where Citric Acid Is Used
Applying the 63% food-and-beverage allocation discussed earlier to total U.S. consumption produces the following breakdown:
Application | Share | Annual quantity |
Food and beverages | 63% | 527 million pounds |
Cleaning products, pharmaceuticals, cosmetics, and other industrial uses | 37% | 309 million pounds |
Total | 100% | 836 million pounds |
Approximately 527 million pounds of citric acid are used annually in food and beverages consumed by Americans—equivalent to 1.44 million pounds every day.
Beyond Manufacturing Efficiency: The Hazards of Fungal Fermentation
How Commercial Citric Acid Is Manufactured
Most commercially manufactured citric acid is produced through industrial fermentation using the fungus Aspergillus niger, commonly known as black mold. Corn starch is a common raw material, particularly in the United States.
The manufacturing process follows these principal steps:
Corn starch extraction: Corn is processed to separate its starch from the grain's other components.
Conversion into glucose: Enzymes break down the corn starch into glucose, a sugar that serves as food for the fungus.
Preparation of the fermentation mixture: The glucose solution is combined with water and nutrients, then introduced into industrial fermentation equipment.
Introduction of black mold: Selected strains of Aspergillus niger are added to the glucose mixture.
Fungal fermentation: Under controlled temperature, acidity, oxygen, and nutrient conditions, the fungus consumes glucose and produces citric acid, which accumulates in the fermentation liquid.
Removal of fungal material: The liquid is filtered to separate the fungal biomass and other solids from the citric-acid-containing solution.
Citric acid recovery and purification: Manufacturers recover the acid using methods that may include chemical precipitation, filtration, solvent extraction, activated carbon treatment, and ion exchange. The particular combination depends on the manufacturing process.
Crystallization and drying: The purified citric acid is concentrated, crystallized, dried, and packaged as the familiar white crystalline powder used by food manufacturers.
The resulting citric acid has the same molecular formula (C₆H₈O₇) and chemical structure as citric acid naturally found in lemons and other citrus fruits. However, while natural citric acid is extracted directly from citrus juice, commercially manufactured citric acid is produced by fermenting sugars with black mold (Aspergillus niger), followed by chemical processing and purification. This manufacturing process introduces different contamination concerns, including residual fungal metabolites, mycotoxins, and processing chemicals that must be removed from the finished ingredient.
The concern is not the citric acid itself, which is chemically identical regardless of its origin, but the toxic contaminants that can arise during black-mold fermentation and remain in the finished ingredient despite purification.
Toxic Contaminants in Finished Citric Acid: What the Research Reveals
The central food-safety concern surrounding citric acid manufactured through black-mold fermentation is whether toxic substances produced during fermentation survive purification and remain in the finished ingredient, and in what quantities.
A 2011 scientific investigation confirmed that strains of Aspergillus niger used in citric acid manufacturing produced mycotoxins, including fumonisin B₂ and ochratoxin A, under laboratory conditions. These substances are associated with serious health hazards, including kidney toxicity and possible carcinogenic effects.
In April 2026, the European Food Safety Authority (EFSA) reported measurable mycotoxin contamination in a finished citric acid preparation manufactured using Aspergillus niger for animal-feed applications. Laboratory testing identified the following concentrations:
Type of Mycotoxin | Highest reported concentration | Principal health concern |
Citrinin | 470.9 µg/kg | Kidney toxicity |
Deoxynivalenol (DON) | 248.0 µg/kg | Vomiting, gastrointestinal and immune effects |
Ochratoxin A | 8.2 µg/kg | Kidney damage and possible carcinogenicity |
Aflatoxins B1 and B2 | 1.4 µg/kg combined | Liver toxicity and cancer risk |
These toxins were detected in the finished ingredient, after manufacturing and purification—not merely in the fermentation mixture.
Citrinin and ochratoxin A are particularly concerning because of their toxic effects on the kidneys. Severe kidney damage can progress to kidney failure, requiring dialysis or transplantation. Aflatoxin B1 is also a recognized human carcinogen, primarily associated with liver cancer.
How Much Contamination Survives Purification?
The available investigations do not establish what percentage of each toxin survives industrial purification. Determining that requires measuring toxin concentrations before and after purification in the same production batches.
The 2026 EFSA findings establish that measurable contamination was present in the finished preparation. They do not establish the removal efficiency of the manufacturing process or the prevalence of comparable contamination in food-grade citric acid.
What Limits Apply in the United States?
The FDA recognizes citric acid as Generally Recognized as Safe (GRAS) under 21 CFR § 184.1033.
However, that regulation does not specify numerical limits for citrinin, ochratoxin A, fumonisins, or deoxynivalenol in finished citric acid. Although the FDA establishes contaminant limits for certain food products, no corresponding citric-acid-specific numerical limits have been identified in the cited federal requirements.
The unresolved questions are therefore straightforward: What quantities of these toxins are permitted in finished food-grade citric acid, and what testing requirements ensure that manufacturers meet those limits?
The 2026 EFSA assessment could not establish the safety of the particular finished citric acid preparation it examined.
The evidence establishes that toxic fungal contaminants can be present in finished fermentation-produced citric acid. It does not establish how frequently this occurs in commercial food-grade production or how effectively manufacturers remove each toxin.
The issue is not the citric acid molecule. It is the presence of toxic contaminants in the finished ingredient, the effectiveness of their removal, and the standards used to protect consumers.
Sources:
Our Position: Is the Risk Worth Taking?
The detection of kidney-damaging mycotoxins in a finished fermentation-produced citric acid preparation raises serious questions about the purity of this widely used food ingredient. The extent of contamination across the American food supply remains unknown, and the available evidence does not establish how effectively these toxins are eliminated during commercial purification.
We consider accepting this uncertainty an unnecessary gamble, particularly when kidney health is at stake. Until manufacturers and food-safety regulators provide independently verifiable testing results, clear contamination limits, and evidence that finished food-grade citric acid meets those standards, we recommend limiting consumption of foods and beverages containing commercially manufactured citric acid wherever practical.
Consumers should not be expected to rely on blind faith where transparent evidence of product purity is needed.
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