Preparation and characterization of zein-kappa carrageenan complex for encapsulation of saffron, and in vitro controlled release study

Abstract

The bioactive compound crocin in saffron is chemically unstable and prone to environmental degradation. An encapsulation system is required to improve its stability, bioavailability, and therapeutic effects. Current methods are often challenged with problems such as rapid release, poor stability, and low encapsulation efficiency. This study provides a new approach for encapsulating saffron extract using complex coacervation method, using zein and kappa carrageenan (KCG) as shell material. The zeta potential and turbidity measurement results indicated that a pH of 3.0 and a zein:KCG ratio of 14:1 were the optimum conditions for zein-KCG complex coacervate formation. The encapsulation efficiency (EE) of freeze-dried saffron extract (FSE) increased under these conditions, and it was found that the EE depended on the ratio between the core (FSE) and the shell (zein:KCG coacervates). The highest encapsulation efficiency, 71.53 ± 2.76%, was obtained at a core-to-shell ratio of 1:2. The size of microcapsules increased from 1.25 μm to 2.82 μm after crosslinking with tannic acid (TA). The thermal properties of the microcapsules improved with crosslinking with TA, and FTIR analysis provides further evidence of electrostatic interactions between zein and KCG and hydrogen bond formation between FSE and the shell. Additionally, the microcapsules (non-crosslinked and crosslinked) remained stable in acidic conditions and demonstrated slow release in the gastrointestinal system.