Zein Particles Research Articles

Quercetagetin-Loaded Zein-Propylene Glycol Alginate Ternary Composite Particles Induced by Calcium Ions: Structure Characterization and Formation Mechanism.

The complexation of zein and propylene glycol alginate (PGA) was confirmed to improve the entrapment efficiency and loading capacity of quercetagetin (Q) in our previous study. The present work focused on the influence and induction mechanism of calcium ions on structures of Q-loaded zein-PGA ternary composite particles. The incorporation of Ca2+ resulted in the formation of aggregates with a large dimension between zein particles, led to obvious conformational, secondary, and tertiary structural changes of zein, and caused the disappearance of crystalline structure of zein. PGA exhibited a fine filamentous network structure and became much thicker and stronger in the presence of Ca2+. The presence of Q promoted the affinity and binding capacity of Ca2+ to zein and PGA. An interwoven network structure with enhanced firmness and density was observed in Q-loaded zein-PGA composite particles, leading to improved thermal stability. Three potential mechanisms were proposed to explain the structural characteristics induced by Ca2+, including particle-particle collision for zein particles, chain-chain association for PGA molecules, and simultaneous cross-linking coupled with aggregating for Q-loaded zein-PGA composite particles.

Preparation, characterization and stability of curcumin-loaded zein-shellac composite colloidal particles.

Curcumin-loaded zein-shellac composite particles were prepared by the antisolvent co-precipitation method. The encapsulation efficiency of curcumin was significantly improved from 82.7% in zein particles to 93.2% in zein-shellac complex particles. The result of differential scanning calorimetry suggested that curcumin in the polymeric matrix was in an amorphous state. Fourier transform infrared spectroscopy analysis revealed that curcumin had non-covalently interacted with zein and shellac, mainly through hydrogen bonding and hydrophobic interaction. Aggregates in irregular shapes, with large sizes, were found by atomic force microscopy, and conglutination, integration or fusion of different entities into network structures occurred at a high level of shellac. At the mass ratio of zein to shellac of 1:1, curcumin in the complex particles exhibited improved photochemical and thermal stability. Curcumin-loaded zein-shellac complex particles allowed the controlled release of curcumin in both PBS medium and simulated gastrointestinal fluids.

Continuous production of core-shell protein nanoparticles by antisolvent precipitation using dual-channel microfluidization: Caseinate-coated zein nanoparticles

Antisolvent precipitation is commonly used to fabricate protein nanoparticles using a simple batch method that involves injecting a protein-solvent mixture into an antisolvent. In this study, the potential of producing core-shell protein nanoparticles by antisolvent precipitation using a continuous dual-channel microfluidization method was investigated. The solvent phase (zein in ethanol) and antisolvent phase (casein in water) were made to impinge on each other at high velocity, which generates intense shear, turbulent, and cavitation forces that ensure thorough mixing and breakup of the phases. Relatively small core-shell protein nanoparticles (d<125nm) could be produced using this method when the conditions were optimized. The mean particle diameter decreased with increasing antisolvent-to-solvent ratio, increasing homogenization pressure, increasing ethanol content in the solvent phase, and decreasing zein content in the solvent phase. Depending on the processing conditions employed, zein particles in the range of about 120nm to over 1000nm could be produced. The operating conditions were further optimized to increase the final zein concentration and decrease the organic solvent content while still obtaining small particles. The surface potential of the core-shell protein nanoparticles went from positive at low pH to negative at high pH, with a point of zero charge around pH5. Electron microscopy indicated that the protein particles formed had a roughly spherical shape. The results suggest that the dual-channel microfluidizer could be used to continuously form protein nanoparticles by antisolvent precipitation. Nevertheless, when the microfluidization method was compared with the simple batch method the size of the particles produced under similar conditions were fairly similar.

Binary Complex Based on Zein and Propylene Glycol Alginate for Delivery of Quercetagetin.

Propylene glycol alginate (PGA) was found to be able to dissolve in aqueous ethanol solution and applied to interact with zein to form a noncovalent binary complex by the antisolvent coprecipitation method at pH 4.0. Quercetagetin (Q) was employed to explore the Q-delivery potential of Zein-PGA binary complex. A fruit tree-like microstructure was observed for Zein-PGA binary complex as its "branches" were closely adsorbed by zein particles. A solid sponge-like entity was formed after lyophilization of Zein-PGA binary complex colloidal dispersion. A synergistic effect was found between zein and PGA on improving the entrapment efficiency and loading capacity of Q. The incorporation of Q at a high concentration induced a significant effect on the tertiary structure of zein. Electrostatic attraction, hydrogen bond, and hydrophobic effects were mainly involved in the interactions between zein and PGA. Schematics with four possible structures were proposed to explain the formation mechanism of composites.

Interaction and formation mechanism of binary complex between zein and propylene glycol alginate

The anti-solvent co-precipitation method was used to fabricate the zein-propylene glycol alginate (PGA) binary complex with different mass ratios of zein to PGA (20:1, 10:1, 5:1, 2:1 and 1:1) at pH 4.0. Results showed that attractive electrostatic interaction between zein and PGA occurred and negatively charged binary complex with large size and high turbidity was formed due to the charge neutralization. Hydrogen bonding and hydrophobic effects were involved in the interactions between zein and PGA, leading to the changed secondary structure and improved thermal stability of zein. Aggregates in the irregular shape with large size were obviously observed in the AFM images. PGA alone exhibited a fine filamentous network structure, while zein-PGA binary complex showed a rough branch-like pattern and the surface of “branch” was closely adsorbed by lots of spherical zein particles. Q in zein-PGA binary complex dispersions presented the improved photochemical and thermal stability. The potential mechanism of a two-step process was proposed to explain the formation of zein-PGA binary complexes.

Preparation of Edible Zein Hybrid Particles and Its Controlled Release Behaviors

A kind of novel hybrid particles (ZCa: Zein/CaCO3) for delivering water-soluble drugs have been prepared by solvent-nonsolvent phase separation method. The obtained ZCa hybrid particles were characterized by DLS, FT-IR spectra and SEM. ZCa hybrid particles have favorable dispersibility. The particle size and shape could be controlled by Zein/CaCO3 mass ratio, with the average size of ZCa hybrid particles being close to 200 nm. Using RB as water-soluble model drug, drug loading and release behaviors of ZCa hybrid particles were investigated. Compared with the pure zein particles, the encapsulation efficiency of ZCa was enhanced obviously, which reached 75.7%. The release ratio of RB in RB@ZCa could be controlled by pH value and by the content of CaCO3. ZCa was also applied to carry and release Dox, anticancer drug, and the cumulative release ratio of Dox@ZCa was obviously enhanced. The cumulative release ratio of Dox@ZCa reached 89 %. ZCa hybrid particles are a promising candidate in nutraceuticals and drugs delivery system. Keywords: Biocompatible polymers, Zein-based hybrid particles, edible drug carrier, calcium carbonate, zein, controllable release.

Colloidal zein particles at water-water interfaces

We synthesize colloidal zein particles using the anti-solvent precipitation method and study particle behavior at water-water interfaces. When added to phase-separating aqueous mixtures of fish gelatin and dextran, particles accumulate at the interface. In order to explain the mechanism of particle accumulation at the water-water interface, we investigate how zein particles interact with polymers (i.e. fish gelatin and dextran). We show that both polymers adsorb similarly on particle surface, which can explain why particles form contact angles close to 90°. Moreover, we show that particle accumulation is accompanied by aggregation. Those aggregates are able to arrest the late stage of the demixing process of the emulsion by the formation of a stable particle-rich layer at the water-water interface. This layer is referred as a ‘foam-like layer’ due to its morphology similar to that of a wet (non-drained) foam, and contains droplets of one phase, surrounded by particle-stabilized lamellae of the other phase.

Formation and characterization of the binary complex between zein and propylene glycol alginate at neutral pH

The effects of propylene glycol alginate (PGA) at different concentrations on the physical, conformational, thermal and morphological characteristics of zein particles were explored at pH 7.0. Results showed that the size of zein particles increased from nano-scale to micron-scale with the increasing proportion of PGA incorporation, consequently leading to greatly raised turbidity of zein colloidal dispersions. There was a large increase in fluorescence intensity of zein in the presence of PGA, indicating conformational change of zein. Results of X-ray diffraction and Fourier transform infrared spectroscopy revealed that the binary complex between zein and PGA was successfully generated due to the non-covalent interaction forces, mainly including hydrogen bonds and hydrophobic effects. The presence of PGA enhanced the physical and thermal stability of zein colloidal particles. The clumps and irregularly-shaped aggregates with large diameters were observed after the interaction between zein and PGA at mass ratios of 2:1 and 1:1. Findings in this work may help further understand the interaction theory between negatively charged proteins and polysaccharides and provide new insights into for the development of potential carriers for bioactive compounds in food system.

Zein-based colloidal particles for encapsulation and delivery of epigallocatechin gallate

Zein, a water insoluble plant protein from a renewable natural source, has been identified as a highly promising material for the production of protein-based colloidal particles for the encapsulation of lipophilic compounds. However, the encapsulation of hydrophilic, water-soluble, bioactive molecules within zein colloidal particles is still unexplored. We show that the encapsulation of epigallocatechin gallate (EGCG) is strongly limited by the weak physical interactions occurring with the zein matrix during the precipitation phase. We demonstrate that the use of sodium caseinate, as a colloidal stabilizer to coat the zein particles, enables the modulation of the encapsulation efficiency and functionality of zein colloidal particles for EGCG delivery. In particular, coated zein particles exhibit a larger size, opposite surface charge and significantly different antioxidant activity, owing to the localization of EGCG affected by the different extent of interaction of EGCG with zein and sodium caseinate. Remarkably, particle formulation also tunes the release rate of EGCG during in vitro digestion and modulates the rate of fat digestion, through the combination of the Pickering emulsion stabilization effect and EGCG interaction with lipase enzyme. Zein-based colloidal particles constitute hence remarkable systems for the tunable and multi-functional delivery of EGCG.

Fabrication and characterization of Pickering emulsions and oil gels stabilized by highly charged zein/chitosan complex particles (ZCCPs)

Herein, we reported a facile method to fabricate ultra-stable, surfactant- and antimicrobial-free Pickering emulsions by designing and modulating emulsions’ interfaces via zein/chitosan colloid particles (ZCCPs). Highly charged ZCCPs with neutral wettability were produced by a facile anti-solvent procedure. The ZCCPs were shown to be effective Pickering emulsifiers because the emulsions formed were highly resistant to coalescence over a 9-month storage period. The ZCCPs were adsorbed irreversibly at the interface during emulsification, forming a hybrid network framework in which zein particles were embedded within the chitosan network, yielding ultra-stable food-grade zein/chitosan colloid particles stabilized Pickering emulsions (ZCCPEs). Moreover, stable surfactant-free oil gels were obtained by a one-step freeze-drying process of the precursor ZCCPEs. This distinctive interfacial architecture accounted for the favourable physical performance, and potentially oxidative and microbial stability of the emulsions and/or oil gels. This work opens up a promising route via a food-grade Pickering emulsion-template approach to transform liquid oil into solid-like fats with zero trans-fat formation.

Enzymatically triggered release of dye model compounds from zein particles

A responsive release system consisting of biocide encapsulated by the hydrophobic protein zein was investigated, in which a biocide will be released if growth of micro-organisms occurs. Because biocide release is difficult to detect, a model system using dyes with different size, polarity and charge was developed first to study the applicability of the zein matrix as an enzyme triggered responsive release system. The responsive release efficiency was highest for dyes with a positive charge, that have limited flexibility and the possibility of aromatic interactions with the matrix. The positively charged dyes showed a larger effect than negatively charged dyes. Additives were shown to enhance the release efficiency of the system. The most efficient release system combines the dye methyl violet with the additive oleic acid. These compounds interact to form a larger, more hydrophobic moiety. A plasticizing effect is thought also to be important, since even without clear specific interactions between dye and additives, release properties are enhanced. The charge of the additives seemed to be more important than their size, and both hydrophobic and ionic interactions were shown to play a role.

Two-step sequential cross-linking of sugar beet pectin for transforming zein nanoparticle-based Pickering emulsions to emulgels

Nanosized (<100nm) zein spheres were employed for fabrication of a series of fish O/W Pickering emulsions. Although surface tension measurement informed the high potency of zein particles for interfacial adsorption, the prepared emulsions destabilized shortly. Electrostatic deposition of sugar beet pectin onto zein particles interfacial layer at pH 4.0 increased significantly the emulsion stability which was attributed to enhanced steric and electrostatic repulsions based on ζ-potential measurements. Pectin enrichment also increased the viscosity of the continuous phase of emulsion. Injection of the oxidative enzyme laccase into the pectin-enriched emulsion to cross-link the feruloyl-bearing pectin molecules and the subsequent addition of CaCl2 to set ion-mediated cross-linkages between carboxyl groups of pectin chains transformed Pickering emulsions to emulgels. The higher the pectin content, the shorter was the gelation time of emulsions. The obtained emulgels were self-standing and became harder along with increasing pectin content.

Self-assembly of zein microspheres with controllable particle size and narrow distribution using a novel built-in ultrasonic dialysis process

Zein microspheres with controllable particle size and narrow size distribution were self-assembled using a novel built-in ultrasonic dialysis process (BUDP). The effects of different variables on the microstructures of obtained zein particles were investigated using an OA16 (45) orthogonal experimental design. The results showed that zein particles prepared by the BUDP possessed a spherical morphology with mean particle size (Dp50) from 431.2±69.6nm to 2335±406.1nm under different process parameters. Zein microspheres prepared at optimized conditions presented much smaller particle size and narrower size distribution (Dp50=398.2±41.3nm) than those obtained without ultrasound (Dp50=1776±1181.1nm). FT-IR, 1H NMR, XRD, TG and DSC characterization results showed that the chemical structure, crystal structure and thermal behavior of the zein microspheres obtained by BUDP were similar with raw zein and that prepared without ultrasound. The ultrasound power and zein concentration were the most important process parameters affecting particle formation. The formation mechanisms of zein microspheres and the influence mechanisms of the operating parameters were discussed in detail. Also, a semi-empirical model was developed for predicting particle size. Furthermore, curcumin was encapsulated into zein microspheres using BUDP, and curcumin-loaded zein microspheres sustained curcumin release rate successfully in vitro.

Synthesis and characterization of silver/zein nanocomposites and their application

Zein nanoparticles were prepared by the liquid‐liquid dispersion method. The particles were used as templates for growing silver nanoparticles by reduction of silver ions using gamma radiation. The dynamic light scattering and transmission electron microscopy (TEM) results indicated that the obtained zein nanoparticles have spherical shape with a homogeneous particle size distribution and an average particle size of 60 nm. The factors affecting the silver nanoparticle deposition on zein nanoparticles were studied. Among these factors, irradiation dose, silver ion concentration, and zein polymer content were evaluated. The formation of the nanocomposite was detected using UV–vis spectroscopy and TEM. The surface plasmon resonance peak was found to be sensitive to the concentration of the zein and AgNO3 solutions. A blue shift was observed as the zein content was increased, while a red shift took place upon increasing the AgNO3 concentration. The TEM imaging indicated that the silver particles are nanosized, spherical in shape and adsorbed on the surface of zein particles. The Zein/silver nancomposites were applied for the antimicrobial test against E. coli and found to have high antibacterial activity. POLYM. COMPOS., 38:E9–E15, 2017. © 2015 Society of Plastics Engineers

Antioxidant and antimicrobial properties of thyme essential oil encapsulated in zein particles

AbstractZein has been used successfully for encapsulation of functional foods. Thyme essential oil was encapsulated in zein particles by liquid‐liquid dispersion method. Functional properties of thyme essential oil can be enhanced by encapsulation technology. Based on the SEM images, size of the particles was in micron scale. A centrifugation step was applied to separate encapsulated particles during production. This treatment caused some differences in structural and functional properties. The highest encapsulation efficiency value of 97.02 % was achieved at 503 × g for 10 min centrifugation. Interaction time between samples and DPPH radicals was extended by encapsulation. Advantage of encapsulation in terms of antioxidant actions was highlighted by Rancimat test. A fast release rate of thyme essential oil encapsulated in zein was observed in triacylglycerols media. Antimicrobial activity of encapsulated thyme essential oil was lower than that of free form in 24 h incubation. A better encapsulation efficiency rate was obtained compared to reported values. Rancimat test can be effectively used to measure antioxidant activity when essential oils are used as antioxidants in encapsulated form. A fast release rate of thyme essential oil encapsulated in zein was observed in TAGs media. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Encapsulation of resveratrol in biopolymer particles produced using liquid antisolvent precipitation. Part 2: Stability and functionality

Resveratrol is a polyphenol that is believed to have beneficial effects on human health. However, its low water-solubility and poor chemical stability hamper its use as a functional food ingredient. The goal of this study was to assess the effect of resveratrol encapsulation within biopolymer particles on its UV-induced isomerization and the effect of particle structure on particle stability to environmental stresses and redispersion of powdered particles. Biopolymer particles were formed by antisolvent precipitation of hydrophobic proteins (zein or gliadin) and coated with hydrophilic copolymers (pectin or sodium caseinate). The stability and functionality of bare zein and gliadin particles (0.5% (w/v) in suspension) were compared to zein and gliadin particles coated with sodium caseinate (1.0% (w/v)) or pectin (0.1% (w/v)), respectively. Resveratrol was encapsulated at a concentration of 250 mg/l and the effect of particle structure on resveratrol UV-stability was monitored. The suspensions of coated particles were physically stable after being held at temperatures up to 90 °C (30 min). Both bare protein particles and pectin coated gliadin nanoparticles aggregated when increasing the ionic strength, while sodium caseinate coated zein particle suspensions remained stable. The pH stability of the particle suspensions was related to the isoelectric point of the nanoparticles. After freeze-drying, only the sodium caseinate coated zein nanoparticles could be fully redispersed in water. All particle formulations protected resveratrol against UV-light to some extent. However, resveratrol was best protected when encapsulated in sodium caseinate-coated zein particles. In conclusion, these particles seem promising encapsulation systems to stabilize resveratrol upon supplementation to functional foods.

Fabrication and characterization of zein–bioactive glass scaffolds

Plant proteins show advantages over animal-based proteins for biomaterial applications attributable to their ease of availability and suitable biodegradability. In this study, composite foams based on zein and 45S5 bioactive glass (BG) particles were produced through salt leaching for potential applications in bone tissue engineering (BTE) applications. Different characterization techniques were used including scanning electron microscopy for morphological and microstructural analysis, ATR-FTIR spectroscopy and X-ray diffraction for composition characterization and mechanical tests. Zein–BG composite scaffolds demonstrate enhanced bioactivity with a compressive modulus and strength around 5·7 MPa and 1·9 MPa, respectively. Zein–BG composite scaffolds constitute a new bioactive material with potential applications in BTE.

Encapsulation of resveratrol in biopolymer particles produced using liquid antisolvent precipitation. Part 1: Preparation and characterization

Several health-promoting effects have been ascribed to resveratrol, a polyphenol extracted from grape skins and other sources. Its utilization as a functional food ingredient, however, is compromised by its low water solubility, poor UV stability, and low oral bioavailability. The purpose of this study was to examine the possibility of encapsulating resveratrol in biopolymer particles to overcome these issues. The particles were produced by antisolvent precipitation of hydrophobic biopolymers (gliadin or zein) in the absence or presence of hydrophilic biopolymers (pectin or sodium caseinate). Bare gliadin and zein particles had mean particle diameters of 260 and 120 nm, respectively. Pectin was the best hydrophilic biopolymer for coating gliadin particles [0.1% (w/v) pectin on 0.5% (w/v) gliadin], whereas caseinate was the best for coating zein particles [1.0% (w/v) sodium caseinate on 0.5% (w/v) zein]. Resveratrol was encapsulated at a concentration of 250 mg/l with encapsulation efficiencies of 53% and 86% in coated gliadin and zein particles, respectively. Encapsulation efficiencies were higher for coated than bare particles. No covalent bonds were detected by FTIR between resveratrol and the proteins within the particles. Electron microscopy showed that bare particles had smooth surfaces with some evidence of aggregation, whereas coated particles had rougher surfaces surrounded by filaments or films, suggesting the presence of non-absorbed hydrophilic biopolymers. In conclusion, these particles seem promising encapsulation systems to enrich functional foods with resveratrol.

Gelation characteristics of the sugar beet pectin solution charged with fish oil-loaded zein nanoparticles

It is of interest to fabricate chemical- and sugar-free pectin gels by which nutraceuticals or nutraceutical-loaded particles are delivered to consumers. Fish oil, a well known source of omega-3 fatty acids, was encapsulated in zein via alcohol evaporation. The mean size of the core-free and fish oil-loaded zein particles was 69 and 83 nm, respectively. The oil-loaded zein nanoparticles were then inoculated into the sugar beet pectin solution that gelified subsequently by the action of the oxidative enzyme, laccase. It was found that nanoparticle charging and enzymatic oxidation of pectin solution changed the flow model of the solution from Newtonian to Power law. An initial gelation rate was estimated for laccase-injected pectin solutions by using the data obtained from small amplitude rheometry tests. Nanoparticle charging of pectin solution slowed down the gelation rate ∼26 folds and resulted in a much less firm final gel. Fourier transform infrared spectroscopy confirmed that ferulic acid residues of sugar beet pectin were oxidized by laccase, resulting in gel formation.

Pomegranate Seed Oil‐Loaded Particles of the Zein Cross‐Linked with Citric Acid

AbstractZein was cross‐linked chemically with citric acid in the presence of sodium hydroxide as the reaction catalyst. Water was then used to desolvate the zein and generate core‐free or pomegranate seed oil‐loaded particles. Mean size of the particles obtained from noncross‐linked and cross‐linked zein was 350 and 246 nm, respectively. Cross‐linking reaction caused an increase in the oil encapsulation efficiency. Scanning electron microscopy revealed the spherical morphology of particles. Fourier transform infrared (FTIR) spectroscopy confirmed the occurrence of chemical linkages between citric acid and zein. As well, it suggested that oil entrapment inside the zein particles was merely physical. Particulation of zein increased the upper limit of the glass transition phenomenon of biopolymer from 78C to ∼120C. The glass transition temperature (Tg) was also affected by the cross‐linking of zein and oil encapsulation. The amount of encapsulated oil released from particles via the peptic hydrolysis was lower for the cross‐linked sample.Practical ApplicationsMany biologically active ingredients including the pomegranate seed oil are extensively susceptible to oxidation, as well as, some are hydrolyzed considerably by enzymes leading to diminished bioactivity. Encapsulation of these hydrophobic cores within sub‐micron zein particles generated via desolvation with water (an easily scale‐up able method) leads not only to increased oxidative stability but also the wider application of core in aqueous foods. Citric acid‐mediated cross‐linking of zein molecules before the desolvation stage increased considerably the gastric digestion stability of particles, which assures that the encapsulated core may pass the stomach without being hydrolyzed with pepsin or acid. The particles prepared from the cross‐linked zein were also more heat resistant. This suggested that the particles can be heat‐treated to higher temperatures in food processing practices.