Sequential solidification of zein and sodium alginate within confined templates: Fabrication of food-grade Janus particles

Janus particles exhibit immense potential for applications in the food industry, such as in interfacial stabilization and targeted delivery. However, their practical application is limited by the prevalent issues in existing fabrication methods, including low throughput, poor controllability, and the use of non-food-grade materials. To address the issues, this study developed a sequential solidification strategy based on the confined templates of zein/sodium alginate Janus droplets for the controllable preparation of food-grade Janus particles. The core of this strategy lied in the sequential in-situ solidification of the two independent compartments within the Janus droplet, without disrupting their anisotropic structure. First, the zein compartment within Janus droplets was solidified through riboflavin/hydrogen peroxide/UV-induced tyrosine cross-linking. Subsequently, the sodium alginate compartment within Janus droplets was cross-linked via an external gelation method mediated by calcium chloride droplets. This sequential solidification process successfully replicated the intricate structure of the Janus droplets into solid particles. Furthermore, a gradient energy input method was employed to reduce the Janus droplets to the nanoscale, thus providing ideal nanoconfined templates for the formation of Janus nanoparticles. Therefore, the size of food-grade Janus particles can be directly controlled by the size of confined templates. This work not only develops an efficient and controllable method to fabricate food-grade Janus particles, but also paves the way for their application in food systems.