Zein-based colloidal particles for encapsulation and delivery of epigallocatechin gallate

Zein, a water insoluble plant protein from a renewable natural source, has been identified as a highly promising material for the production of protein-based colloidal particles for the encapsulation of lipophilic compounds. However, the encapsulation of hydrophilic, water-soluble, bioactive molecules within zein colloidal particles is still unexplored. We show that the encapsulation of epigallocatechin gallate (EGCG) is strongly limited by the weak physical interactions occurring with the zein matrix during the precipitation phase. We demonstrate that the use of sodium caseinate, as a colloidal stabilizer to coat the zein particles, enables the modulation of the encapsulation efficiency and functionality of zein colloidal particles for EGCG delivery. In particular, coated zein particles exhibit a larger size, opposite surface charge and significantly different antioxidant activity, owing to the localization of EGCG affected by the different extent of interaction of EGCG with zein and sodium caseinate. Remarkably, particle formulation also tunes the release rate of EGCG during in vitro digestion and modulates the rate of fat digestion, through the combination of the Pickering emulsion stabilization effect and EGCG interaction with lipase enzyme. Zein-based colloidal particles constitute hence remarkable systems for the tunable and multi-functional delivery of EGCG.