The Interaction between Zein and Lecithin in Ethanol-Water Solution and Characterization of Zein-Lecithin Composite Colloidal Nanoparticles.

Lei Dai,Di Wang,Cuixia Sun,Yanxiang Gao,Leonardo Fraceto

doi:10.1371/journal.pone.0167172

Abstract

Lecithin, a naturally small molecular surfactant, which is widely used in the food industry, can delay aging, enhance memory, prevent and treat diabetes. The interaction between zein and soy lecithin with different mass ratios (20:1, 10:1, 5:1, 3:1, 2:1, 1:1 and 1:2) in ethanol-water solution and characterisation of zein and lecithin composite colloidal nanoparticles prepared by antisolvent co-precipitation method were investigated. The mean size of zein-lecithin composite colloidal nanoparticles was firstly increased with the rise of lecithin concentration and then siginificantly decreased. The nanoparticles at the zein to lecithin mass ratio of 5:1 had the largest particle size (263 nm), indicating that zein and lecithin formed composite colloidal nanoparticles, which might aggregate due to the enhanced interaction at a higher proportion of lecithin. Continuing to increase lecithin concentration, the zein-lecithin nanoparticles possibly formed a reverse micelle-like or a vesicle-like structure with zein in the core, which prevented the formation of nanoparticle aggregates and decreased the size of composite nanoparticles. The presence of lecithin significantly reduced the ζ-potential of zein-lecithin composite colloidal nanoparticles. The interaction between zein and lecithin enhanced the intensity of the fluorescence emission of zein in ethanol-water solution. The secondary structure of zein was also changed by the addition of lecithin. Differential scanning calorimetry thermograms revealed that the thermal stability of zein-lecithin nanoparticles was enhanced with the rise of lecithin level. The composite nanoparticles were relatively stable to elevated ionic strengths. Possible interaction mechanism between zein and lecithin was proposed. These findings would help further understand the theory of the interaction between the alcohol soluble protein and the natural small molecular surfactant. The composite colloidal nanoparticles formed in this study can broaden the application of zein and be suitable for incorporating water-insoluble bioactive components in functional food and beverage products.

Highlights

Food macromolecules and small molecular compounds are usually used to fabricate foodgrade colloidal structures such as colloidal nanoparticles, complexes, and microcapsules, which show good potential for applications in food and beverage industries [1].Zein, the major storage protein of corn, is generally regarded as safe (GRAS) food ingredient by the US Food and Drug Administration and it is a hydrophobic protein which can be solubilized in high concentration ethanol aqueous solutions (60–90%) but insoluble in water [2]
Because of the difference in soluble characteristics, zein can be converted into spherical colloidal nanoparticles by the antisolvent precipitation method, which makes it to be an ideal delivery system for drugs and micronutrients in food, pharmaceutical and biotechnological products [3,4]
The Polydispersity Index (PDI) values of zein-lecithin colloidal nanoparticles were decreased after adding lecithin

Summary

Introduction

Food macromolecules and small molecular compounds are usually used to fabricate foodgrade colloidal structures such as colloidal nanoparticles, complexes, and microcapsules, which show good potential for applications in food and beverage industries [1].Zein, the major storage protein of corn, is generally regarded as safe (GRAS) food ingredient by the US Food and Drug Administration and it is a hydrophobic protein which can be solubilized in high concentration ethanol aqueous solutions (60–90%) but insoluble in water [2]. Because of the difference in soluble characteristics, zein can be converted into spherical colloidal nanoparticles by the antisolvent precipitation method, which makes it to be an ideal delivery system for drugs and micronutrients in food, pharmaceutical and biotechnological products [3,4]. Based on this property, zein has been widely used to fabricate colloidal delivery systems for encapsulation of nutraceuticals and functional ingredients such as lutein [5], curcumin [5,6,7] and quercetin [8]. A combination of lecithin and Pluronic F68 was reported to stabilize the zein nanoparticles [12]

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