Effect of Deodorizing and Heating Conditions on the Content of Citric Acid and Its Decomposed Products in Edible Oils

Soybean oil containing 50 or 1000ppm of citric acid was treated under reduced pressure with various deodorizing conditions. Citric acid and its decomposed acids, i.e., aconitic, itaconic, and citraconic acids, in the deodorized oils were determined quantitatively by GLC. When 50ppm of citric acid was added, no other acid but citric acid was found. The amount of citric acid was decreased as deodorizing temperature was increased and the time was prolonged. Meanwhile 1000ppm of citric acid was added, besides considerable amount of the unreacted citric acid, small amount of aconitic and itaconic acids were found.Soybean oil comprising 50 or 1000ppm of citric acid was heated under atmospheric pressure with various conditions. The results were similar to those of deodorizing conditions. The formation of citraconic acid together with aconitic and itaconic acids was observed only when the oil containing 1000ppm of citric acid was heated at the higher temperature.These findings indicate that the synergistic effect of these decomposed acids from citric acid is negligible in commercial edible oils.