Rheological Behavior and Structural Evolution of Capillary Suspensions in Food Systems: Droplet Deformation...

Solid fats are integral to numerous food products, influencing melting behavior, imparting viscoelasticity, and shaping sensory characteristics such as mouthfeel and spreadability. However, their typically high levels of saturated fatty acids (SFA) and industrial trans fatty acids (TFA) have prompted efforts to develop healthier lipid formulations that preserve essential functional properties. In this study, we explored capillary suspension-based structuring as a strategy to transform liquid vegetable oils into plastic fats. Specifically, octenyl succinate starch (OSA-starch) particles were dispersed within a primary oil phase and linked by liquid bridges, formed from a minor fraction of an immiscible secondary liquid. We systematically varied the proportions of particles, primary liquid, and secondary liquid to assess their effects on structural development and rheological behavior. Rheological analysis revealed significant formulation-dependent changes in yield stress and a consistent two-step yielding response. Based on these findings, we propose a "liquid-bridge stretching" hypothesis to explain the observed yielding behavior and employ stepwise regression analysis to develop an empirical predictor for the fluid-gel transition (with R² > 0.98). Our results enhance our mechanistic understanding of fluid-gel transitions in capillary suspensions and underscore their promise in creating healthier, tunable lipid systems.