Fabrication and Characterization of Zein Composite Particles Coated by Caseinate-Pectin Electrostatic Complexes with Improved Structural Stability in Acidic Aqueous Environments.

Yaqiong Zhang,Bo Wang,Liangli (Lucy) Yu,Boyan Gao,Yan Wu

doi:10.3390/molecules24142535

Abstract

Zein composite particles coated with caseinate-pectin electrostatic complexes (zein-caseinate-pectin particles) were fabricated using an electrostatic deposition and liquid-liquid dispersion method without heating treatment. Compared to zein particles coated only with caseinate, the acidic stability of zein-caseinate-pectin particles was greatly improved, and the particle aggregation was suppressed at pH 3–6, especially at pH values near the isoelectric point of caseinate (pH 4–5). Besides, desirable long-term storage stability and re-dispersibility were observed. Under different zein to curcumin (Cur) feeding ratios (10:1, 20:1, 30:1 and 40:1, w/w), the Cur-loaded zein-caseinate-pectin particles had a spherical shape with an average diameter ranging from 358.37 to 369.20 nm, a narrow size distribution (polydispersity index < 0.2) and a negative surface charge ranging from −18.87 to −19.53 mV. The relatively high encapsulation efficiencies of Cur (81.27% to 94.00%) and desirable re-dispersibility were also achieved. Fluorescence spectroscopy indicated that the encapsulated Cur interacted with carrier materials mainly through hydrophobic interactions. The in-vitro release profile showed a sustained release of Cur from zein-caseinate-pectin particles in acidic aqueous environment (pH 4) up to 24 h, without any burst effect. In addition, the encapsulation retained more ABTS•+ radical scavenging capacity of Cur during 4 weeks of storage. These results suggest that zein-caseinate-pectin particles may be used as a potential delivery system for lipophilic nutrients in acidic beverages.

Highlights

Zein is the major storage protein in corn with high hydrophobicity, desirable biodegradability and biocompatibility [1,2]
ABTS+ radical scavenging capacity of Cur during 4 weeks of storage. These results suggest that zein-caseinate-pectin particles may be used as a potential delivery system for lipophilic nutrients in acidic beverages
Since caseinate and pectin aqueous solutions have opposite net charges in the pH range of 3 to 4, pH 3.5 was chosen to facilitate the formation of caseinate-pectin electrostatic complexes

Summary

Introduction

Zein is the major storage protein in corn with high hydrophobicity, desirable biodegradability and biocompatibility [1,2]. Due to its high surface hydrophobicity, bare zein particles have relatively poor stability in aqueous systems and undesirable re-dispersibility after drying [7]. This problem can be partly overcome by coating zein particles with protein-based emulsifiers, such as β-lactoglobulin [8] and sodium caseinate [9]. Our previous study showed that zein-caseinate particles had desirable physical stability and re-dispersibility in a neutral aqueous environment, which may be due to the enhanced electrostatic and steric stabilization by caseinate molecules adsorbed on the surface of zein particles [10,11]. Zein-caseinate particles are still highly sensitive to aggregation at pH values near or below pH 4.6, the isoelectric point of the Molecules 2019, 24, 2535; doi:10.3390/molecules24142535 www.mdpi.com/journal/molecules

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