Physicochemical properties of chitosan-based emulsions containing Ocimum gratissimum essential oil prepared by multifrequency ultrasound-assisted homogenization technique

The objective of this study is to investigate the optimal ultrasonic power for producing microemulsions with Ocimum gratissimum L. essential oil and to evaluate their physicochemical properties. The effects of three powers (125 W, 250 W, 375 W) on chitosan-based Ocimum gratissimum L. essential oil emulsion were examined by multi-frequency ultrasound-assisted homogenization. The results indicated that the physicochemical properties of chitosan-based Ocimum gratissimum L. essential oil emulsion were optimized under ultrasonic-assisted homogenization of three frequencies (20, 28, and 40 kHz combined) at 125 W for 15 min. Compared to the control group, significant reductions in particle size were observed in the emulsion treated with 125 W multi-frequency ultrasound (average particle size was 1.87 ± 0.01 μm; zeta potential was 13 ± 0.53 mV). Furthermore, the stability and antioxidant activity of the emulsion showed marked improvements (the scavenging rates of DPPH and ABTS increased to 87.57% and 81.71%, respectively). In addition, scanning electron microscopy and confocal laser scanning microscopy images revealed that 125 W multi-frequency ultrasonic-assisted homogenization emulsion droplets were evenly distributed and exhibited the highest encapsulation effect. These findings provide valuable insights into developing food-grade chitosan-based emulsions containing Ocimum gratissimum L. essential oil for functional food production. Graphical abstract