ANTIOXIANT ACTIVITY OF SOME SUPPLEMENTARY PHENOLIC COMPOUNDS TO CORN OIL UNDER HIGH TEMPERATURE CONDITIONS

The effect of some phenolic compounds on the oxidative
stability of corn oil during heating at 60, 100 and 180ºC was
investigated. This investigation was to search for the most potent
antioxidants under high temperature conditions and the relationship
between their potency and their chemical structures. Progression of
oxidation status was monitored by measurement of peroxide,
anisidine, totox values and TBARS content. The Rancimat test was
also used to assess the stability of the oil containing phenolic
compounds at 100ºC. Results clearly revealed that all of TBHQ,
DTBHQ and Gentisic acid (2,5-DHBA) were the most effective
antioxidants at elevated temperatures (60, 100, and 180oC). The
Rancimat test was found to confirm these results at 100oC. The
efficacy of these compounds was higher than that of the commonly-
used food antioxidants e.g. BHT, BHA and α-tocopherol. The
superiority of these compounds mainly due to the presence of two
hydroxyl groups in para position in their structures. Although other
phenolic compounds contain the same structural features e.g. 2,5-
DHAc and quinizarin, they exhibited prooxidant activity. This may be
attributed to the existence of carbonyl group which was found to
accelerate markedly the lipid oxidation process through its
electrophilic activity feature. The chemical structure of potent
antioxidants at high temperatures must be containing two hydroxyl
groups in ortho or para position of its benzene ring and the meta
position must be free of them or carbonyl group(s)