Effects of Oil Properties on Stability Behavior of High-Energy-Density Fat Emulsions

Abstract

Foods for special medical purposes play a critical role in clinical nutritional support, especially oil-in-water emulsions characterized as having high energy density, which could provide efficient energy for patients with insufficient intake or those requiring fluid restriction. The included oil types are the critical determinants of emulsion stability, which, in turn, governs digestive behavior, absorption efficiency, and ultimate bioavailability of the delivered nutrients. However, such emulsions face stability challenges during storage and application. In the present study, high-energy-density fat emulsions formulated with six typical oils, which contained 50% oil content, were prepared and systematically analyzed in terms of their particle size, zeta potential, microstructure, centrifugal stability, multiple light scattering, and rheological properties. The results indicated that oils with medium-chain fatty acids, due to their compact molecular structure and low viscosity, facilitated the formation of finer droplets and promoted the orderly arrangement of phospholipids at the interface of the emulsion system, leading to the formation of a dense, elastic interfacial layer and a gel network structure. Its marked shear-thinning characteristic and lowest frequency dependence contributed to desirable processing and storage stabilities. In contrast, long-chain triacylglycerols, especially those enriched with monounsaturated and saturated fatty acids, tended to form rigid but insufficiently elastic interfacial layers, which were unfavorable for resisting coalescence and phase separation induced by external forces. Highly unsaturated oils, on the contrary, exhibited medium levels for emulsion stability. Further analysis of the relationship between the physicochemical properties of oils and the characteristics of emulsions revealed that fatty acid species in the oil phase were the key determinants of emulsification behavior. It was therefore speculated that oils rich in medium-chain fatty acids with a moderate degree of unsaturation, especially including selected ω-3 and ω-6 fatty acids, could improve emulsion stability and fatty acid balance synchronously. This study provides a theoretical basis and technical support for the formulation design and stability control of high-energy-density fat emulsions.