Effect of Storage Conditions on the Composition and Bioactivity of Freeze-Dried Lemongrass Oil Nanoemulsions Stabilized by Salt-Sensitive Cellulose Nanocrystals and Tween 80

Oil-in-water emulsions are widely used to enhance the solubility, stability, and bioactivity of essential oils in aqueous systems. Advancing the functionality and sustainability of these emulsions using renewable, eco-friendly ingredients remains an important research focus. This study developed and evaluated a lemongrass essential oil nanoemulsion stabilized by Tween 80, NaCl, and soybean stover-derived cellulose nanocrystals. After freeze-drying, the nanoemulsion was redispersed in water and analyzed for particle size, zeta potential, polydispersity index, and essential oil recovery. Freeze-drying led to significant bioactivity losses, with antifungal and antioxidant activities reduced by 77% and 31%, respectively. Antioxidant activity declined rapidly within the first two weeks of storage at room temperature but was not significantly impacted by light exposure. Storage conditions also altered the sample composition, with one new compound detected in samples stored without light exposure and eleven new peaks observed in light-exposed samples. This study provides insights into the effects of freeze-drying and storage on lemongrass essential oil-loaded nanoemulsion stabilized by Tween 80, NaCl, and cellulose nanocrystals. The findings highlight the challenges of preserving bioactivity and composition in lyophilized essential oil-loaded emulsions and suggest avenues for optimizing drying processes and formulations to improve storage stability and efficacy.