Novel Correlation of Peroxide/Conjugation Values for Vegetable Oils During Deep-Frying

The present work deals with the chemical properties of vegetable oils commonly used for deep-frying, for example, sunflower, corn, cotton, canola, and olive oils. Ten deep-frying cycles were carried out for 20 min each. Oil degradation was measured by peroxide values (PVs) and was highly correlated with the presence of conjugated-diene and conjugated-triene structures. Frying cycles caused two alternative reactions, which both impacted the PV. In one reaction, there was an increase in PV with the oxidation of the unsaturated bonds, and in the second stage, there was a decrease in the cleavage of the double-bond oxide. Additionally, the point of returns (PRs) and activation energy (Ea) were determined for the two stages. The PRs were eight cycles for olive and corn, five cycles for canola, four cycles for sunflower, and three cycles for cotton oil. In terms of ER, the olive and cotton oils had the highest ER and were most resistant to decomposition, and the associated activation energy formation of peroxide decomposition products. The corn oil was the least resistant to decomposition. In addition, this work demonstrated a novel analytical technique that showed the correlation between the total value of conjugated diene-triene structures and PV, using a titration method. The correlation was high confidence for the regression, recovery, and U⁹⁵. This significant correlation is useful for measuring the PV of oils subjected to other processes.