Kinetic Analysis of High-Temperature Sunflower Oil Peroxidation Inhibited by the Major Families of Phenolic Antioxidants Unveils the Extraordinary Activity of 1,4-Hydroquinones

Peroxidation of vegetable oils represents a major problem for the food and biodiesel industries, and it is greatly accelerated by oil degree of unsaturation and by temperature increase. Phenols represent the most common additives used to counteract oil peroxidation, however clear structure-activity relationships at high temperatures are not available. We report, herein, a kinetic study of O-2 consumption during spontaneous peroxidation of sunflower oil at 130 degrees C in the presence of 18 antioxidants belonging to the main families of natural and synthetic phenols, including alpha-tocopherol, alkylphenols (BHT, BHA), hydroquinones (TBHD), catechols (quercetin, catechin) and gallates. Results show that TBHQ provide the best protection in terms of induction period (IP) duration and O-2 consumption rate. EPR spectroscopy demonstrated that the inhibition activity is negatively correlated to the stability of the phenoxyl radical of the antioxidant (A(center dot)), suggesting that chain propagation with linoleate (RH) moieties A(center dot) + RH -> AH + R-center dot decreases the efficacy of those antioxidants forming persistent A(center dot) radicals. These results provide important information to optimize the antioxidant activity of phenols and of novel phenol-based materials.

Automated summary

The peroxidation of vegetable oils is a significant issue for the food and biodiesel industries, especially when the degree of unsaturation and temperature increase. Using phenols as additives is a common method to prevent oil peroxidation, but their effectiveness at high temperatures is not well understood.