Lipid Degradation in Sunflower Oil in Water Nanoemulsion: Understanding the Kinetics and Role of Ultrasonication

This study has been undertaken to understand the impact of ultrasonication on the oxidative stability of nanoemulsions and evaluate the extent of degradation of oil via oxidation and hydrolysis during their formation. For the first time, the clear evidence of the oil degradation in ultrasonically prepared nanoemulsions is presented based on the change in the composition analysis over the period of nanoemulsion storage. In this work, the sunflower oil emulsions were prepared at different sonication conditions (power and energy) and using different emulsifiers (Tween 80/Span 80 and whey protein isolate). The oxidative kinetics were modeled by using a logistic equation approach to identify optimal sonication parameters. Results revealed that excessive ultrasonication, beyond a threshold power and energy density, led to a substantial increase in the peroxide value and rate of lipid oxidation during storage. Moreover, changing the emulsifier reduced lipid oxidation by 66% based on the peroxide value of the nanoemulsions. To validate the degradation of oil, the fatty acid profile of emulsified oil after one month of storage was analyzed. It was found that excessive sonication of the emulsion stabilized with Tween 80/Span 80 resulted in changes to the fatty acid composition, including an increase in the free fatty acid content, confirming both oxidative and hydrolytic degradation. Overall, the findings highlight the importance of limiting ultrasonic energy input and suggest the use of long-chain, protein-based emulsifiers to improve the oxidative stability and extend the shelf life of such prepared food-grade nanoemulsions.