Probing molecular mechanisms of emulsifier-modulated lipid crystallization via ultrasonic phase velocity

Lipid crystallization critically shapes food quality, yet its molecular regulation by emulsifiers remains poorly quantified. This study employs ultrasonic phase velocity, integrated with differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS), to elucidate sucrose fatty acid ester (SFE) modulation of hydrogenated coconut oil (HCO) crystallization. Compressibility drives acoustic responses, contributing ∼ 70 % to phase velocity changes versus ∼ 30 % from density. Phase velocity correlates strongly with crystallization enthalpy (R² > 0.99), detecting onset 15-30 min earlier than DSC. Three SFEs (C12:0, C18:0, C18:1) exhibit distinct mechanisms: laurate integrates into crystals, expanding lamellar structures; stearate forms pre-crystalline assemblies, delaying crystallization by up to 40 %; and oleate disrupts ordering with its bent structure. A three-regime model (breakpoints at 1.2 % and 3.8 %) explains 91 % of crystallization variance. These insights enable emulsifier selection for optimizing chocolate texture and spread stability, potentially reducing costs by 15-20 %, while establishing ultrasonic phase velocity as a precise (0.035 % resolution), non-destructive tool for real-time molecular monitoring in complex food systems.