Formation and Stability of Food Emulsions: A Review through the Lens of the Oil Phase.

Abstract

Emulsions serve vital roles in the food industry, including structural design and delivery of functional components. As thermodynamically unstable systems, emulsions undergo various destabilization processes over time. Therefore, understanding the instability mechanisms of emulsions and how to combat them have been long-term research topics. Although extensive research has focused on the impacts of the aqueous phase and emulsifiers on emulsion stability, the regulatory role of the oil phase has long been undervalued, and the underlying mechanisms remain to be fully elucidated. This review mainly summarizes the influence of the oil phase on the formation and stability of food emulsions based on reported research, aiming to provide useful principles and rational references for future research. We focus on destabilization phenomena and mechanisms, as well as the effects of the physicochemical properties of the oil phase, including polarity, carbon chain length, degree of unsaturation, oxidation state, and other physical attributes such as density, viscosity, and water solubility. From a multi-scale perspective, we discuss the mechanisms by which the oil phase regulates emulsion formation and stability, including the adsorption kinetics, interfacial thickness, and interfacial rheological properties of emulsifiers, as well as the droplet size distribution and zeta potential of emulsions. In addition, the adaptability of various emulsifiers with specific oil phases is discussed, with emphasis on challenging systems including volatile essential oils, oxidation-prone polyunsaturated lipids, and aerated emulsions. This review highlights the pivotal role of the oil phase and provides a theoretical basis for the rational design and quality control of food emulsions.