THE EFFECT OF CITRIC ACID UPON THE OXIDATION OF PEANUT OIL AND OF THE METHYL ESTERS DERIVED FROM PEANUT OIL

Abstract

Addition of 0.005–0.500% citric acid to refined peanut oil caused a marked retardation of the oxygen absorption by the oil at 100 °C. Conversely, oxygen absorption was accelerated by the addition of from 0.11 to 10.00 p.p.m. iron in the form of iron stearate. When iron and citric acid were added together, the accelerating effect of iron on oxidation was overcome when the molar ratio of citric acid to iron was about 23:1; with higher concentrations of citric acid, oxidation was retarded still further.With distilled methyl esters of the fatty acids of peanut oil, further purified by passage through a column containing activated carbon, citric acid addition alone had only a small effect. Addition of iron caused acceleration of oxygen absorption which was compensated for by suitable addition of citric acid. Addition of hydroquinone caused a retardation of oxygen absorption, and still further retardation occurred when citric acid and hydroquinone were added together. It was concluded that citric acid has the properties of both a metal deactivator and a synergist, but does not in itself function as an antioxidant.