Synergies between plant antioxidant blends in preventing peroxidation reactions in model and food oil systems

A study was conducted to investigate the oxidative behavior of various mixt ures of rosemary, sage, and citric acid in a linoleic acid model system by oxygen consumption measurement and in a palm olein system by differential s canning calorimetry (DSC) analysis. Response surface methodology was used t o optimize the use of the mixtures. Results showed that rosemary and sage w ere two important factors for the protective index (PI). The two antioxidan ts were highly significantly (P < 0.001) in influencing PI values. There wa s a significant (P < 0.01) synergistic effect between rosemary and sage on PI values. Citric acid was also round to be significant (P < 0.05) for PI. With respect to onset time (T-o), all three antioxidants were significant ( P < 0.05). However, no significant interaction among antioxidants was found for T-o. Mathematical models for both PI and T-o could be developed with c onfidence. The R-2 values for PI and T-o were 0.992 and 0.926, respectively . A combination of 0.078% rosemary, 0.067% sage and 0.037% citric acid was the optimal combination for PI, whereas a combination of 0.068% rosemary, 0 .075% sage, and 0.039% citric acid was required to reach the optimal T-o va lue.