Butyric acid (4 carbon atoms), from Greek word βούτυρος, meaning butter, was discovered by Lieben and Rossi in 1869.
It is a saturated fatty acid (no double bond so in shorthand 4:0) member of sub-group called short chain fatty acids (SCFA), up to 6 carbon atoms.
Molecular weight: 88.10512 g/mol
Molecular formula: C4H8O2
IUPAC name: butanoic acid
CAS registry number: 107-92-6
In purified form, it is a colorless oily liquid soluble in water, with melting point at -7.9 °C (17.78 °F; 265.25 K) and boiling point at 163.5 °C (326.3 °F; 436.65 K) at 760 mmHg.
Food sources of butyric acid
It occurs as glycerol ester in animal fats like those present in butter (it makes up 3-4 percent of butter fat), Parmigiano and other cheeses and plant oils.
The unpleasant odor of rancid butter is due to hydrolysis, and subsequent liberation, of this acid from glycerol.
Akoh C.C. and Min D.B. “Food lipids: chemistry, nutrition, and biotechnology” 3th ed. 2008
Chow Ching K. “Fatty acids in foods and their health implication” 3th ed. 2008