Thyme Essential Oil Nanoemulsion Stabilized by Chitosan Nanoparticles for Potential Application in Food Preservation

The global demand for food has been increasing, presenting new challenges in meeting this demand. To address this growing need, the use of coating technology through nanoemulsions shows great potential. The use of thyme essential oil stabilized by chitosan nanoparticles offers a promising and sustainable approach for the development of edible coatings. Chitosan was extracted from shrimp shell waste and used to produce nanoparticles via the ionotropic gelation method, using sodium tripolyphosphate (TPP) as a crosslinking agent. To prepare the nanoemulsions, thyme essential oil was used as the dispersed phase, combined with an aqueous phase containing chitosan nanoparticles and Tween 80 as the emulsifier. Two techniques were employed to produce nanoemulsions: high-pressure homogenization and ultrasonication. Nanoemulsion formulations with different concentrations were prepared and characterized in terms of droplet size (Z-Average) and stability using dynamic light scattering (DLS). The average droplet sizes obtained were above 100 nanometers for samples produced via high-pressure homogenization and below 100 nanometers for those prepared using ultrasonication. Analysis of variance (ANOVA) confirmed that both the method (p = 0.002) and the oil phase concentration (p < 0.001) had statistically significant effects on droplet size. Regression analysis showed that oil concentrations below 2.0 g (w/w) increased droplet size, while concentrations above 4.0 g (w/w) significantly reduced it (p < 0.05). However, physical stability tests conducted at 5 °C for 30 days showed consistent values across both formulations, with only minor fluctuations, suggesting overall good stability.