Tannic acid multipoint crosslinked casein/chitosan microcapsules loaded with oregano essential oil for fruit preservation

Natural food preservatives composed of environmentally-friendly, non-toxic, and biodegradable components have gradually become excellent alternatives to traditional food preservatives. This study developed a fully biomass-based, non-toxic, and eco-friendly food preservation material by encapsulating oregano essential oil (OEO) in self-assembled casein (CA)/chitosan (CS) microcapsules crosslinked with tannic acid (TA) via multiple sites. OEO was successfully encapsulated with an efficiency of 92.5 %. Structural analysis revealed that TA crosslinking significantly altered the secondary structure of casein (increasing α-helix content) and enhanced thermal stability. In food-simulating media, the microcapsules exhibited sustained OEO release across four typical environments, confirming their potential for extensive food preservation applications. The microencapsulated emulsion exhibited prolonged antioxidant and antibacterial activities compared with free OEO. Fruit preservation tests verified that the emulsion effectively extended the shelf life of perishable fruits under ambient conditions. Notably, the use of food-grade materials and a TA-mediated multipoint cross-linking strategy not only enhanced microcapsule stability but also offers an innovative approach for developing safe and sustainable food preservatives.