Food-related nanoemulsions: Fabrication approaches, characterization methods, and emerging applications

Nanoemulsions are thermodynamically metastable but kinetically durable colloidal carriers with droplet sizes typically below 500 nm, capable of encapsulating lipophilic bioactive compounds to enhance their solubility, storage stability and in vivo bioavailability. Their small droplet size provides a large specific surface area, high encapsulation efficiency, and improved oral bioavailability, thereby alleviating the poor water solubility and oxidative degradation of polyphenols, essential oils, and fat-soluble compounds. This review provides an overview of two mainstream fabrication routes of food-grade nanoemulsions, namely high-energy and low-energy emulsification, and compares their operating principles, production costs, industrial scalability, and inherent limitations. Common characterization techniques for particle size, surface charge, microstructure, rheological properties, and biological activity are discussed, with a comparative analysis of their respective detection advantages and applicable scenarios. Recent research advances over the past five years (alongside foundational references for technical background) in food-related applications are summarized, covering three core directions: food quality preservation, biodegradable active packaging, and nutrient-fortified functional foods. Critical research gaps in current studies are highlighted, including insufficient systematic in vivo safety data and limited industrial-scale validation of natural pigment delivery systems, particularly regarding long-term stability during processing and storage. Furthermore, targeted future research priorities centered on green low-cost fabrication, all-natural emulsifier development, and stimulus-responsive delivery system construction are proposed. This review aims to provide theoretical insights and technical guidance for accelerating the translation of nanoemulsion platforms toward sustainable health-promoting food applications.