INHIBITED OXIDATION OF LIPIDS .2. COMPARISON OF THE ANTIOXIDATIVE PROPERTIES OF SOME HYDROXY DERIVATIVES OF BENZOIC AND CINNAMIC-ACIDS

The antioxidative properties of p-hydroxy-benzoic acid, vanillic acid, syringic acid, 3,4-dihydroxy-benzoic acid, p-coumaric acid, ferulic acid, sinapic acid and caffeic acid in lard autoxidation at 100-degrees-C are compared. The effect of phenolic acids is investigated within the concentration range 0.02 - 0.20 wt %. It is proved that the derivatives of the benzoic acid have weaker inhibiting properties than is the case of the corresponding analogues of the cinnamic acid due to the more active participation of the inhibitor in the elementary reactions of propagation and initiation of the radical chain process. The activity (a complex parameter demonstrating the efficiency and strength of the antioxidant) of the phenolic acids investigated decreases in the sequence: caffeic acid > 3,4-dihydroxy-benzoic acid > sinapic acid > syringic acid > ferulic acid > p-coumaric acid > vanillic acid. The increase in concentration of the acids investigated is most advisable in the case of sinapic, syringic and ferulic acids which are not consumed in side reactions.