Enhancing the quality and oxidative stability of sunflower oil during thermal treatment with an ultrasound-extracted pomegranate flower (Punica granatum L.) extract

Introduction This study investigated the effect of ultrasound assisted pomegranate flower ( Punica granatum L .) extract (DPF) on the oxidative stability of sunflower oil during intermittent heating. Dried pomegranate flowers were extracted using 80% aqueous ethanol in an ultrasonic bath, yielding a phytochemically rich extract characterized by high levels of total phenolics (267.36 ± 4.19 mg GAE/g DW), flavonoids (84.56 ± 2.43 mg QE/g DW), and ellagitannins such as punicalagins and ellagic acid. The extract exhibited strong in vitro antioxidant activity in the DPPH radical scavenging assay. Methods Sunflower oil was fortified with DPF extract at concentrations of 400, 800, 1,600, and 2,400 μg/g oil, with 200 μg/g BHT as a synthetic reference. All samples were heated at 180 ± 5°C for 2 h daily over 5 consecutive days. The oil's oxidative stability was assessed by monitoring physicochemical indices including refractive index, viscosity, acid value, peroxide value, iodine value, total polar compounds (PCC), polymer content (PC), and thiobarbituric acid (TBA) value. Results and discussion Results demonstrated that DPF incorporation significantly enhanced the oil's thermal oxidative stability in a dose dependent manner. Higher concentrations (1,600 and 2,400 μg/g oil) provided superior protection across all parameters, often outperforming 200 μg/g oil BHT. The oil enriched with 2,400 ppm DPF proved most effective, it best preserved the iodine value while mitigating increases in refractive index, viscosity, acid value, peroxide value, PCC, PC, and TBA value. The findings indicate that ultrasound extracted pomegranate flower antioxidants, particularly at 2,400 μg/g oil, can serve as a potent natural alternative to synthetic antioxidants, effectively prolonging the frying life and maintaining the quality of sunflower oil under repeated thermal stress.