Nanostructures self-assembled from food-grade molecules with pH-cycle as functional food ingredients

Background: Food ingredients fabricated with materials science and engineering principles have unique functionalities serving various applications and purposes. With repeated warnings from energy consumption and environmental issues, scouting for environment-friendly, sustainable, and recyclable routes of preparing self-assembled nanostructures is imperative. Scope and approach: Food-grade molecules are abundant, renewable, biocompatible, biodegradable, and affordable, and can be used as building blocks to prepare materials for use as novel functional food ingredients. In this article, we review low-energy and organic solvent-free routes of producing self-assembled nanostructures by manipulating pH, i.e., the pH-cycle technology. The principles of forming nanostructures using the pH-cycle and the potential applications of these nanostructures are discussed. Key findings and conclusions: The pH-cycle technology utilizes pH-dependent intra- and intermolecular interactions to initially dissolve constituents to enable molecular contact, followed by spontaneous assembly as unique nanostructures tunable with processing parameters and formulations. The technology does not require sophisticated equipment, and implementation of mild reaction temperature and short exposure time minimizes possible chemical reactions at alkaline pH. These nanostructures physically self-assembled from food molecules can be used as novel food ingredients for applications such as delivery systems of bioactive compounds and edible coatings and packaging films to enhance food quality, safety, healthfulness, and sustainability.