Formation of short chain volatile organic acids in the automated AOM method

The end point in the automated AOM stability test for fats is related to the rapid production of volatile acids at the end of the induction period and usually measured by conductivity of an aqueous solution of the exit gases. It has been postulated that the reaction involves the transitory presence of a diperoxide which decomposes into two aldehydes and formic acid. The volatile acids produced by several oils were composed mainly of formic acid and significant amounts of acetic acid. In addition, acids with three or more carbon atoms, including propionic, butyric and caproic, were detected. It was found that the temperature of the water in the receiving jars was important in relation to retention of the formic acid. At temperatures above 20 C significant losses may occur. The relationships between peroxide value of the oils, the conductivity of the exit gas solutions and the organic acid content was investigated for the following fats and oils: sunflower, canola, olive, corn, peanut and soybean oil, triolein, lard and butterfat.