Active packaging systems designed to effectively deliver bioactive compounds to foods have been developed to maintain product quality and are the major subject of research. We developed humidity-responsive active packaging films by emulsifying lemongrass essential oil (LEO) and mixing the emulsion with polyvinyl alcohol (PVA). Because many factors affect release behavior, application-specific design is required. Among these factors, we compared release behavior across emulsifiers. Of four emulsifiers, two were mixed at controlled ratios to adjust the hydrophilic–lipophilic balance (HLB), and the amount of LEO released at each relative humidity (RH) was measured. Based on this data, we evaluated correlations between HLB, surface loading with LEO release behavior. Correlation coefficient between HLB value and LEO release behavior were 0.67 at 30% RH, 0.54 at 60% RH, and between surface loading value and LEO release behavior were 0.50 at 30%RH, 0.24 at 60% RH. In RH 90%, most of the LEO are released, so they are not significantly affected by these factors. When surface loading was expressed as moles of emulsion per unit area (mol·m⁻²) rather than mass per unit area (g·m⁻²), its correlation with release strengthened, correlation coefficients of 0.77, 0.55, and 0.34 respectively. To interpret these results, we modeled the droplet interface as a geodesic sphere with equilateral triangle, placing emulsifier molecules at the centers of the faces’ incircles, and quantified several geometric parameters under this assumption. It suggests that larger intermolecular spacing lowers emulsion stability, facilitating droplet coalescence and collapse. These results identify a new factor that can serve as an additional stability index along with HLB and surface-loading values.

Conference Theme: Physical properties of food hydrocolloids for enhanced product development