Influence of calcium ions on the stability, microstructure and in vitro digestion fate of zein-propylene glycol alginate-tea saponin ternary complex particles for the delivery of resveratrol

Abstract

Calcium ions (Ca2+) can alter the molecular structure of proteins and polysaccharides through electrostatically binding to negatively charged groups. In this study, the zein-propylene glycol alginate (PGA)-tea saponin (TS) ternary complex particles induced by different Ca2+ levels (1–10 mM) were fabricated and characterized for the delivery of resveratrol. Fluorescence spectrum and circular dichroism analysis were applied to investigate the effect of Ca2+ on the micro-environment and secondary structure of zein in the complex particles. The hydrogen bonds, hydrophobic effects and electrostatic interactions contributed to the formation of the complex particles. Environmental stability evaluation showed that the stability of the complex particles and retention rate of resveratrol were enhanced by the addition of Ca2+ at the lower concentration (≤4 mM). Besides, the level of Ca2+ could modulate the digestion behavior of the complex particles and achieve the better sustained-release of resveratrol at the Ca2+ level of 2 mM. However, the aggregation of complex particles occurred through bridging flocculation induced by the high level of Ca2+ (>6 mM). These results indicated that Ca2+ induction has a great potential for the fabrication and application of food-grade complex particles loaded with nutraceuticals.