Ability of Phenolic Acids to Protect a-Tocopherol

The ability of phenolic acids (gallic, gentisic, protocatechuic, syringic, vanillic, ferulic, caffeic, and sinapic; 600 mg/kg) to protect a-tocopherol was tested during the heating of sunflower oil on a hot plate set at 180°C and was compared with the ability of these phenolic acids to slow down the formation of polymerised triacylglycerols (TAG) in the same conditions. The half-life of a-tocopherol (calculated as the time needed for the a-tocopherol content to decrease to 50% of the original value) was extended significantly by gentisic, caffeic, and gallic acids (from 1.16 h to 1.77 h, 1.78 h, and 2.26 h, respectively), while the formation of polymerised TAG was slightly suppressed only by gallic acid.