A green and kinetic method for measuring emulsion stability based on image analysis: ImageScan

Emulsions in the food, cosmetics, and pharmaceutical industries are thermodynamically unstable. Conventional methods, including turbidimetric and TurbiScan assays, for evaluating emulsion stability are often time-consuming and reliant on expensive equipment. This study aimed to develop and validate a cost-effective, green, and rapid image-based method for assessing emulsion stability, as an alternative to costly conventional methods. Commercial emulsifiers DATEM, DMG, SSL, DMGX, and PG95S were evaluated at concentrations of 0.5% and 0.25% w/w. Emulsions were prepared and immediately afterward monitored for 10 hours using a desktop scanner. Gray Value Profiles (GVP) were analyzed using ImageJ to track changes in the emulsion layers. An image-based stability index (ISI), analogous to the Turbiscan Stability Index (TSI), was developed. Half-life parameter was derived from ISI modeling at different time points (0, 1, 2, 4, 6, 8, and 10 h). Due to the kinetic nature of the method, validation was performed against a turbidimetric kinetic assay using a spectrophotometer that provides a Half-life Time parameter (HLT). Average Half-life values for lower/high concentrations were: 1.779/2.191 (DATEM), 1.973/2.252 (DMG), 1.640/1.828 (SSL), 1.986/2.440 (DMG), 1.662/1.913 (PG95S). Average HLT values for lower/high concentration were: 264.812/354.240 (DATEM), 391.749/546.102 (DMG), 269.205/293.535 (SSL), 375.234/550.129 (DMG), 266.358/389.764 (PG95S). Half-life was significantly correlated with HLT from a reference turbidimetric method (r = 0.9019, p < 0.05). Moreover, the Bland-Altman analysis showed that the differences between the emulsion stability measurements by turbidimetric and ImageScan methods were within a 95% agreement limit. ImageScan method allows for the identification of destabilization layers by GVP and provides results comparable to Turbiscan, with significant cost advantages as well as obtaining a kinetic parameter for comparison. The proposed method offers simple and scalable solutions for emulsion stability evaluation, providing real-time, objective stability assessments for both industrial and research applications.