Propionic Acid
The short version
A short-chain fatty acid antifungal — the parent of calcium propionate, naturally produced in Swiss cheese.
It's widely considered safe at the amounts used in food, so we mark it green. The Safety section below has the details.
Where it comes from
First identified in 1844 as a fatty acid degradation product. Naturally produced by Propionibacterium during the fermentation of Swiss cheese — responsible for the characteristic flavor. Industrially produced by ethylene carbonylation.
How it's used
Used as a free acid in bread and baked goods to inhibit mold, often interchangeable with calcium propionate (E282). Effective antifungal at low concentrations (0.1–0.3%). Does not interfere with yeast activity.
Safety profile
No ADI assigned by JECFA. Considered safe at food levels. Naturally produced in the human gut by fermentation of dietary fiber. Some anecdotal reports of migraines or irritability at very high industrial exposure.
Physical & chemical properties
Colorless oily liquid with pungent rancid odor. Miscible with water. Weak acid (pKa 4.87). Most effective as antifungal in protonated form at low pH.
Regulation worldwide
Permitted globally for bakery products. Specific EU max levels by product category.
Educational information only. Not medical or dietary advice.