Sorani Olive Leaf Extract as a Natural Antioxidant in Butter and Ghee: Kinetic Modelling, Phenolic Stability, and Radical Scavenging Mechanisms

• Alaa Abdul Karim Majeed

  Author

Lipid oxidation is identified as the main culprit of the short shelf life of dairy products, particularly in Iraq, where butter and ghee are usually kept at room temperature (about 20–25ºC) and kept under summer conditions where temperature rises above 40ºC. Based on the assumption, the objective of the current study was to find out the effectiveness of seven secoiridoid, phenylethanoid, and flavonoid phenolics derived from Sorani olive leaf ethanolic extract (OLE) in slowing the lipid oxidation process through radical scavenging and metal-chelation in accordance with Arrhenius first-order kinetics. The objectives included comparison of three extraction techniques, verification of phenolics quantification results of HPLC-ESI-MS/MS (ICH Q2(R1)), characterization of the fatty acid composition, effectiveness of the OLE (200–600 mg /kg) in comparison with BHT and rosemary extract during the time period of seven weeks at temperatures equal to 4 °C, 25 °C, and 40 °C, calculation of Arrhenius parameters and Q₁₀, observation of the kinetics of phenolics elimination, and sensory characteristics.

TPC, TFC, DPPH, FRAP and metal-chelation activities were tested; in addition, a complete validation of HPLC-ESI-MS/MS was carried out. Fatty acids composition was defined using GC-FID analysis. The peroxide level, TBARS, p-anisidine value, Totox and acid value were measured on a weekly basis through applying linear mixed models.

The subsequent extraction with ethanolic solution (EA) produced the highest TPC (48.7 mg GAE/g dw) and DPPH IC₅₀ value equal to 18.4±0.6 µg/mL. HPLC-ESI-MS/MS allowed discovering seven types of phenolics (the recovery rate was equal to 94.2-98.7%, RSD <4.5%), particularly oleuropein (42.3%) and hydroxytyrosol (18.6%) were identified as the most abundant ones. The value of activation energy increased from 58.4 to 84.1 kJ/mol when the OLE concentration was equal to 600 mg/kg (there were no significant differences with the value of activation energy for the BHT). Q₁₀ decreased from 2.4 to 2.0. The analysis showed that after seven weeks spent at the temperature of 4 °C, 74.3% of oleuropein was preserved.

Sorani OLE (600 mg/kg) can provide the same protective effect due to radical scavenging, Fe²⁺ chelation, and lipoxygenase inhibition, which creates conditions for its practical application in rural areas of Iraq under conditions of ambient temperature.

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