Abstract
The aqueous citric acid solution was added into the vegetable oils (cotton seed oil, soya-been oil) and heated to 180°240°C, and analysed by paper-chromatography with chloroform-acetic acid-water solvent (volume ratio 30 : 15 : 1.2).
Authors confirmed that citric acid is decomposed to citraconic anhydride through aconitic and itaconic acids by heating at 180°C for 30min. At 240°C, citric acid was disappeared after 10min heating and only small quantity of citraconic anhydride was detected after 30min heating. No citric acid was detected after 30min heating at the condition of deodorization for oil purification (210°C, 23mmHg, steam blowing).
The stabilities were tested by A.O.M. for the oil added with citric acid before and after the deodorization. The A.O.M. stability was higher for the oil added the acid after the deodorization, and when it is added before, it is necessary to restrict the duration time of the deodorization within 30min because citraconic anhydride formed by the decomposition has no antioxidant effect.
