Nedjalka Vl. Yanishlieva

Effect of lipid unsaturation on the antioxidative activity of some phenolic acids

Antioxidative properties ofp-hydroxybenzoic, vanillic, syringic, 3,4-dihydroxybenzoic,p-coumaric, ferulic, sinapic and caffeic acids were studied in the concentration range 0.02–0.20 wt% during autoxidation at 100°C of lard and sunflower oil methyl esters (MEL and MESO, respectively). In both lipid systems, the derivatives of benzoic acid had weaker inhibiting properties than did the corresponding analogues of cinnamic acid. The effectiveness and strength of the antioxidative action were considerably lower in the lipid system MESO, which was rich in linoleic acid and was more easily oxidized. Thep-hydroxybenzoic, vanillic, syringic andp-coumaric acids in this system exercised no inhibiting effect. We established that the molecules of the investigated phenolic acids initiated the chain radical process of autoxidation, and the formed antioxidant radicals propagated the chains as a result of the reaction with the lipid substrate. These reactions proceeded at a higher rate in MESO than in MEL.

Antioxidative activity of phenolic acids on triacylglycerols and fatty acid methyl esters from olive oil

The autoxidation of kinetically pure triacylglycerols and methyl esters of olive oil (TGOO and MEOO) in the presence of four different concentrations of p-coumaric, ferulic and caffeic acids at 100 °C was studied. It was established that effectiveness and strength of the phenolic acids were greater in MEOO than in TGOO. In both lipid substates the molecules of phenolic acids participate in one side-reaction (with hydroperoxides). The rate constants of this reaction in TGOO and in MEOO are practically the same. The phenolic acids take part in chain initiation. The rate of this reaction for ferulic and caffeic acids has equal values in TGOO and in MEOO, whereas for p-coumaric acid it is twice as high in TGOO than in MEOO. The radicals of the phenolic acids participate in one reaction of chain propagation (with the lipid substrate) both in triacylglycerols and in methyl esters of olive oil. Comparison with the data published recently for sunflower oil triacylglycerols and methyl esters demonstrates the strong influence of the unsaturation type and degree of the lipid system on the kinetics and mechanism of the antioxidative action of the phenolic acids.

Kinetics of inhibited oxidation of lipids in the presence of 1-octadecanol and 1-palmitoylglycerol

The kinetics of initiated oxidation of sunflower oil methyl esters at 50°C in the presence of the phenolic inhibitorp-methoxyphenol are investigated. It is established that addition of 0.1 M 1-octadecanol and of 0.1 M 1-palmitoylglycerol leads to a 1.5- or 2.3-fold decrease of the rate constant of chain termination on the inhibitor, which proves the blocking of its effect due to the formation of a complex based on a hydrogen bond. The stronger effect of 1-palmitoylglycerol is explained by the presence of two hydroxyl groups in its molecule.

Method of obtaining native powdered sunflower lecithin

Thermal dehydration treatment of sunflower sludge leads to a significant deterioration of the quality of the product obtained. A combined scheme is suggested for simultaneous dehydration and fatremoval from sunflower sludge at room temeperature.