Enhancing the Stability of Soybean Oil: Using Endogenous Phenolic Compounds Additive and Carnosic Acid Plus Carnosol

This study aims to investigate the stability of soybean oil (SO) using natural antioxidants─specifically inherent and added tocopherols, alongside carnosic acid and carnosol from rosemary (Salvia rosmarinus) acetone extracts. By employing a series of selective oxidation assays, we determined that the strongest synergistic effect of the antioxidant combination was achieved with a 1.5:1 ratio of tocopherol to carnosic acid plus carnosol. Furthermore, this combination was tested in SO, as evidenced by various metrics such as the induction period (IP) value, peroxide value (PV), free fatty acids (FFA), kinetic parameters, and antioxidant depletion tracking. The findings highlight the potential of natural antioxidants as a viable strategy for food preservation, emphasizing their bioavailability and overall benefits. The kinetic changes of antioxidants during thermal oxidation in soybean oil revealed that their interaction involved the regeneration of tocopherol by carnosic acid, which degrades into a carnosol.