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Vitamin D 3 stability has been a concern in the functional food industry. Protein conjugated with saccharides showed potential for an improvement in vitamin D 3 stability. Novel and sustainable proteins, such as cricket protein, are of interest worldwide. Therefore, this research examined the utilization of cricket protein-fructooligosaccharide (FOS) conjugates formed through the Maillard reaction as a delivery system for vitamin D 3 in an oil-in-water (O/W) emulsion. O/W emulsions with vitamin D 3 stabilized by cricket protein powder (CP), cricket protein-FOS mixture (CPM), and cricket protein-FOS conjugates (CPF) with varying concentrations (0.3%, 0.5%, and 1.0% w/v). All emulsions had di-modal distributions with mean particle size diameters (D [4,3]) between 4.17 and 12.62 μm. The CPF emulsion had larger particle size diameters (8.46–12.62 μm) but less span value (3.26–4.76) when compared with CP and CPM (4.17–5.88 μm, 4.87–6.38). The storage stability of emulsions and vitamin D 3 release (4 °C, 0–30 days) was improved by conjugated products. The CPF-stabilized vitamin D 3 emulsions exhibited enhanced vitamin D 3 bioaccessibility (37–54%), surpassing that of CP (27–34%) and CPM (32–37%). Furthermore, CPF showed superior vitamin D 3 stability during in vitro gastrointestinal digestion. The concentration required for 50% inhibition of cell viability of CP, CPM, CPF, and CPF-vitamin D 3 emulsion was 0.643, 0.552, 0.474, and 0.229 mg/mL, respectively, indicating low cytotoxic activity. These findings validate the effectiveness of cricket protein-FOS conjugates, particularly at a 1% (w/v) concentration, in improving the release of vitamin D 3 in emulsion-based delivery systems and their potential for fortifying functional food products. [Display omitted] • Conjugated cricket protein (CPF) improved vitamin D 3 stability in O/W emulsion. • Several types and concentrations of cricket protein were tested for vitamin D 3 stability. • CPF-stabilized vitamin D 3 emulsions enhanced vitamin D 3 bioaccessibility. • CPF showed superior vitamin D 3 stability during in vitro gastrointestinal digestion. • Low cytotoxic activity of CPF-vitamin D 3 emulsion. [ABSTRACT FROM AUTHOR]

Abstract In this study, zein colloidal particles were self-assembled in aqueous ethanol through thermal treatment at 70 °C. The effect of heating, ethanol ratio and initial protein content on the physiochemical characteristics of zein nanoparticles were investigated. Thermal treatment was a necessary step to prepare nanoparticles with finer size and more homogenous distribution. The particle size decreased from 443.3 to 185.5 nm with initially ethanol concentration from 55% to 90% (v/v), whereas was inversely proportional to increased zein concentration (ranging from 125.6 to 199.1 nm for 20–100 mg/mL zein). The thermal treatment along with ethanol removal during zein nanoparticle generation induced the re-distribution of amino acid residues on the particle surface as indicated by the Raman spectroscopy and internal sulfhydryl groups determination. To further improve the stability and functional properties of these nanoparticles, gum arabic and sodium alginate were deposited as a secondary layer on zein nanoparticles mainly driven by electrostatic attraction. Sodium alginate at a polysaccharide/protein weight ratio of 1:10 showed the best improvement on the pH and ionic stability. The findings of this research provide a promising strategy and basic knowledge on optimizing zein-based delivery systems for food and pharmaceutical applications. Graphical abstract Image 1 Highlights • Zein nanoparticles were self-assembled by a combination of antisolvent process and thermal treatment. • Thermal treatment was a necessary step to prepare nanoparticles with fine size and homogenous distribution. • Polysaccharide composite nanoparticles showed good re-dispersibility after freeze-drying. • Alginate/zein composite nanoparticles had better stability against pH change and ionic strength. [ABSTRACT FROM AUTHOR]

Abstract In this study, the gelatin/zein nanofibers were electrospun and then cross-linked by glucose via Maillard reaction. The morphology observations showed that the average diameter of the cross-linked gelatin/zein nanofibers decreased with the increasing weight ratio of zein. FTIR results indicated that gelatin and zein molecules were homogenously dispersed within the fibers, and the Maillard reaction occurred between the proteins and glucose. The addition of zein affected the mobility of the gelatin chains, leading to the decreased denaturation temperature. The cross-linked fibers with a 1:1 gelatin/zein ratio showed the most hydrophobic surface (water contact angle of 134°), and comparable mechanical properties to the cross-linked gelatin nanofibers, while a higher ratio of zein (more than 50%) resulted in the decreased elastic modulus. The L929 cell cytotoxicity test suggested that the cross-linked gelatin/zein nanofibers exhibited good biocompatibility and non-cytotoxicity. Graphical abstract Image 1 Highlights • The gelatin/zein nanofibers were cross-linked with glucose by Maillard reaction. • The nanofiber morphology was maintained after cross-linking. • The cross-linked nanofibers showed good water resistance, and tunable wettability and mechanical properties. • The cross-linked nanofibers are biocompatible and non-cytotoxic. [ABSTRACT FROM AUTHOR]

Abstract The present work aims to prepare and stabilize zein colloidal nanoparticles using soluble soybean polysaccharide (SSPS) as a stabilizer. A simple antisolvent precipitation method was used to fabricate the zein/SSPS composite nanoparticles at pH 4.0. The results showed that the SSPS-stabilized zein nanoparticles (size around 200 nm, PDI below 0.2) did not aggregate or precipitate at pH 2.0–8.0. And they were also relatively stable for elevated ionic strength and high temperature. Affected by the SSPS coating, the surface hydrophobicity of the zein nanoparticles decreased over a wide pH range. Conditions of forming zein/SSPS nanoparticles were successfully used to encapsulate hydrophobic quercetin (Q). The encapsulation efficiency was greatly improved to 82.5% after SSPS coating, compared to 59.2% for the zein without coating. Besides, the photochemical stability and ABTS+ scavenging ability of Q in zein/SSPS composite nanoparticles were significantly enhanced. This study demonstrates that these composite nanoparticles can be used as all-natural delivery systems for bioactive molecules in food and pharmaceutical formulations. Graphical abstract Image 1 Highlights • Zein nanoparticles were prepared using SSPS as a stabilizer. • SSPS could stabilize zein nanoparticles in pH range 2.0–8.0. • The "core-shell" structure formed between zein and SSPS. • Surface hydrophobicity of zein nanoparticles decreased due to the coating of SSPS. • Quercetin was efficiently encapsulated and protected by composite nanoparticles. [ABSTRACT FROM AUTHOR]

In this study, caseinate-stabilized zein particles (zein-Cas) were developed at neutral pH to encapsulate fucoxanthin (FX) using a simple antisolvent precipitation method. Fluorescence results indicated that zein or Cas interact with fucoxanthin by hydrophobic contacts with a binding constant magnitude of 10 5  M −1 . The presence of proteins resulted in altering the FX precipitates from irregular shape to spherical shape at higher zein proportions, as confirmed by transmission electron microscopy. The average particle size of FX-loaded zein-Cas particles was below 150 nm (100 to 130 nm) with negative surface charge (−30 to −35 mV). The encapsulated FX showed higher stability, antioxidant activity and antiproliferative activity than free FX. Besides, the bioaccessibility of encapsulated FX was appreciably higher than it was not encapsulated. These results demonstrated that FX-loaded zein-Cas nanoparticles could enable the application of FX in functional foods and beverages, as well as in pharmaceutical products. [ABSTRACT FROM AUTHOR]

Limonene is a kind of widely used flavor oil, susceptible to degradation with the loss of lemon-like odors and the formation of off-flavors. This study aimed to develop a novel structurally well defined zein-based core-shell microencapsules loaded with limonene for limonene protection and controllable release. The microencapsules were fabricated using a two-step heterogeneous precipitation process, with the shell being formed by direct zein precipitation on the oil-water interface and growing along with the water addition driven by hydrophobic interaction. The formation of core-shell microencapsules occurred at the limonene/zein ratio around 2.0 with D 4,3 close to 10 μm and shell thickness about 25 nm, while the smaller self-assembled zein particles could be formed at the ratio of 0.1 and 5.0, suggesting that the mass ratio of core to shell affected the formation of encapsulation and the shell thickness could be controlled. An interior rough and porous shell of the microencapsules was also observed. Sodium caseinate (SC) was adsorbed onto hydrophobic zein surface by electrostatic interaction, contributing to a hydrophilic interface and improving the re-dispersibility of the freeze-dried powder in water. The release rate of limonene in the burst release phase from zein-SC microencapsules was significantly lower than that of whey protein isolate (WPI)-stabilized emulsion, and tended to be gradual in the sustained phase, followed the zero order kinetics. The limonene retention rate of the microencapsules was higher than that of the WPI-stabilized emulsion during an acceleration storage condition, attributing to the solid barrier of the zein-SC shell of the microencapsules. High linear relationship (R 2  > 0.96) between limonene retention rate and storage time in both microencapsules and WPI-stabilized emulsion was observed, suggesting potential controllability of limonene degradation. The ability to design the natural biopolymer-based colloidal microcapsules with slow-release and oxidation prevention of the unstable flavor oils opens a new opportunity in a stable dispersions in aqueous foods. [ABSTRACT FROM AUTHOR]

This research evaluated the potential of zein-caseinate composite nanoparticles (zein-CAS NPs) as a carrier for water-insoluble bioactive food factors using curcumin (CUR) as a probe compound, and assessed its in-vitro impact using the cultured Caco-2  cells. CUR-loaded zein-CAS NPs were synthesized using a low-energy liquid-liquid dispersion method, and the obtained nanoparticles had a spherical shape with an average diameter of 187.16 nm, a narrow size distribution (polydispersity index of 0.13) and a negative surface charge of −36.43 mV. High encapsulation efficiency of CUR at 95.55% and a desirable re-dispersibility in water were also achieved, and the encapsulated CUR was in an amorphous form, as examined by differential scanning calorimetry analysis. Fourier transform infrared analysis revealed that hydrogen bonding and hydrophobic attraction were the major interactions between CUR and the zein-CAS NPs. The in-vitro release profile showed a sustained release of CUR in simulated gastric and intestinal fluids up to 72 h at 37 °C, without any burst effect. Furthermore, compared with free CUR, CUR-loaded zein-CAS NPs improved the stability of CUR against UV irradiation and thermal treatment. The cellular studies showed that, compared with free CUR, CUR-loaded zein-CAS NPs with the same CUR concentration exhibited greater bioavailability. These data suggested a possible utilization of zein-CAS NPs in improving water solubility, shelf stability, bioavailability and activity of lipophilic bioactive food factors. [ABSTRACT FROM AUTHOR]

Zein is a hydrophobic protein and is conventionally prepared as dispersible nanoparticles with the anti-solvent precipitation method. The dispersion stability of zein nanoparticles can be enhanced after adsorbing with a biopolymer such as sodium caseinate (NaCas). In our previous work, self-assembled nanocomplexes of zein and NaCas were formed after a pH-cycle from neutral to pH 11.5 and then to pH 7.0 using HCl. This pH cycle method eliminates the use of alcohol but is time-consuming during titration. The objective of the present work was to compare properties of dispersions with different mass ratios of zein:NaCas at pH 7.5 after the pH cycle and acidification with D-glucono-delta-lactone (GDL) or HCl. Compared with the HCl method, zein nanoparticles prepared with GDL had a smaller mean hydrodynamic diameter (64.3 vs. 134.8 nm) and a narrower distribution measured in dynamic light scattering, which was further confirmed in scanning electron microscopy. The different particle size distributions resulted in stable and unstable zein dispersions of the GDL and HCl treatments, respectively, after storage at 4 °C for 30 days. The incorporation of NaCas greatly reduced the turbidity of zein nanoparticle dispersions and zein-NaCas nanocomplex dispersions prepared with GDL exhibited better storage stability than those prepared with HCl. Based on fluorescence and FTIR spectroscopy, similar nanoparticle formation mechanisms were observed for GDL and HCl treatments. Hydrolysis of GDL resulted in uniform distribution of hydroniums to induce more nuclei for growth into more abundant and homogeneous zein nanoparticles than the HCl treatment. Therefore, GDL can be used to further improve the scalability of producing nanoparticles to make use of zein for various applications. [ABSTRACT FROM AUTHOR]

In this study, zein-propylene glycol alginate (PGA) composite nanoparticles were fabricated by emulsification-evaporation method, and their potential to be a delivery vehicle for β-carotene was investigated. The results showed that different PGA levels resulted in various structural characteristics, physicochemical stability and properties of in vitro simulated gastrointestinal digestion of β-carotene loaded zein-PGA composite nanoparticles. The analyses of fluorescence spectrum, circular dichroism and fourier transform infrared spectroscopy revealed that electrostatic interaction, hydrogen bonding and hydrophobic attraction played important roles in the formation of composite nanoparticles. The β-carotene entrapped in nanoparticles was amorphous, confirmed by differential scanning calorimetry. The improved physicochemical stability and the sustained release of β-carotene in nanoparticles proved the potential of zein-PGA composite nanoparticles as an excellent vehicle to deliver β-carotene in food system. [ABSTRACT FROM AUTHOR]

Propolis is a natural resinous mixture from many plant materials, buds, and exudates and is rich in polyphenols with several health beneficial properties. However, its application in food products and pharmaceuticals is hindered because of its low water solubility, undesirable sensorial characteristics and limited bio-accessibility. Here, we originally report the design and synthesis of food-grade colloidal nanoparticles as propolis carriers to enhance its oral bioavailability. Propolis was encapsulated into heat-denatured zein with carboxymethyl chitosan (CMCS) coating by acid-induced aggregation. Calcium cross-linking provided the best controlled release of propolis and improved encapsulation efficiency. The complex nanoparticles prepared under optimized conditions were spherical in shape with a Z-average diameter of ∼156 nm and zeta potential of ∼ -30 mV. Encapsulation efficiency (EE) and loading content (LC) of propolis in heat-denatured zein/CMCS nanoparticles reached∼83% and∼13.83%, respectively. Fourier transform infrared (FTIR) indicated that hydrogen bonds, electrostatic and hydrophobic interactions were the major forces responsible for nanoparticle formation. The in vitro antioxidant activity of propolis encapsulated in nanoparticles was considerably stronger than that of propolis dispersed in water. This new approach of fabricating propolis-loaded heat-denatured zein/CMCS nanoparticle provides a promising strategy with high yield and is non-toxic with improved water solubility, antioxidant activity and sustained release of propolis. [ABSTRACT FROM AUTHOR]

The composite fibrous films were developed from zein and poly(lactic acid) (PLA) by incorporating carvacrol at three different concentrations (5, 10 and 20%) using electrospinning. The morphology and size of fibers obtained from both zein and PLA were affected by the level of the incorporated carvacrol. The Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) results showed that carvacrol was encapsulated in electrospun zein and PLA fibers. The antioxidant activity of carvacrol loaded zein fibers ranged from 62 to 75%, while antioxidant capacity of PLA fibers varied from 53 to 65% for 5–20% carvacrol content. The composite fibrous films showed a sustained diffusion controlled release behavior. Preliminary studies on whole wheat bread samples showed that carvacrol loaded electrospun zein and PLA fibers are able to preserve bread samples, indicating that they are good candidates for active food packaging applications to extend the shelf life of whole wheat bread. [ABSTRACT FROM AUTHOR]

In the present work, the influence of hydrophobicity of zein/tannic acid complex particles (ZTPs) on the rheological behavior of ZTP-stabilized emulsion gels is described. The hydrophobicity of the particles was controlled by the incorporation of different amounts of hydrophilic tannic acid, while retaining a similar particle size. The resulting ZTPs with varying hydrophobicity were successfully used to form emulsion gels with similar oil droplet size. With a decrease in the hydrophobicity of ZTPs, the storage modulus (G′) of emulsion gels increased, while tan δ and the frequency dependence decreased, indicating the formation of a stronger gel network. The crossover strain, γ co , increased with a decrease in the hydrophobicity of ZTPs, indicating the gel network becomes more resistance against breakdown. In all cases, G′ increased in a power-law manner with an increase in protein concentration (G' ∼  c p n ) and oil content (G' ∼  φ m ). The exponent n and m decreased with decreasing particle hydrophobicity, indicating that hydrophobic interactions between particles within the particle network in the continuous phase and the oil droplets provide a relatively larger contribution to the gel strength for emulsion gels stabilized by ZTPs with higher hydrophobicity. Increasing the oil polarity provided a lower gel strength for emulsions stabilized by particles with high hydrophobicity, while it increased the gel strength for particles with low hydrophobicity. The results show that the rheological behavior of ZTP-stabilized emulsion gels can be tuned by changing the particle hydrophobicity and oil polarity, which provide interesting features for various applications in the food industry. [ABSTRACT FROM AUTHOR]

The objective of this study was the development of zein based antilisterial films that contain a consumer-controlled and pH-triggered release mechanism for lysozyme (LYS). For this purpose, composite films were formed by mixing hydrophobic zein with hydrophilic soy protein isolate (SPI) or lentil protein isolate (LPI). Active property of films was formed by maintaining 30 to 50% of total LYS in free form (LYS free ). On the other hand, the pH-triggered release mechanism was formed by exploiting attractive charge-charge interactions between LYS (pI: 11.4) and SPI or LPI (pI values ≈ 4.5), and binding remaining LYS (LYS bound ) in film matrix. The pH-triggered release mechanism of composite films worked in buffers that had pHs varying between 4.3 and 7.3. The composite films bound majority of LYS between pH 5.3 and 7.3, but they released LYS at pH ≤ 4.5. The pH-triggered release of LYS was achieved with zein-LPI films activated by acidification in packed cold-stored beef, lamb and smoked salmon. The zein-SPI films performed pH-triggered LYS release in packed food with the exception of packed smoked salmon. The LYS free and LYS bound released from pH-triggered films showed antimicrobial activity on Listeria innocua . Consumer-controlled release mechanisms enable increasing antimicrobial stress over pathogens during transfer from market to home and cold storage at home. Thus, such films could initiate personalized packaged food to help risk management of susceptible individuals. [ABSTRACT FROM AUTHOR]

Protein nanoparticles can be used to encapsulate, protect, and deliver hydrophobic bioactive agents however, they are often unstable to environmental stresses. In this study, the impact of electrostatic deposition of a biopolymer coating (alginate/gelatin) on the physicochemical and functional properties of curcumin-loaded zein nanoparticles was determined. The pH stability of the zein nanoparticles was greatly improved by the biopolymer coatings, with a 7:3 w/w alginate-to-gelatin ratio being the most effective at inhibiting particle aggregation from pH 3 to 7. The optimized biopolymer-coated nanoparticles remained stable to aggregation during long-term storage, and were resistant to heat treatment at 80 °C for up to 40 min in 10% aqueous sucrose solutions (pH 4.5). The in vitro bioaccessibility of curcumin was appreciably higher (22.4%) when it was encapsulated within biopolymer-coated zein nanoparticles than when it was not encapsulated (<8%). This effect was mainly attributed to the ability of the nanoparticles to inhibit curcumin degradation and increase curcumin solubility within the simulated gastrointestinal tract (GIT). The in vitro antioxidant capacity of curcumin after exposure to the simulated GIT was also greatly improved by encapsulation within the nanoparticles, as demonstrated by much stronger ABTS + · radical scavenging and ferric ion reducing power. These results suggest that biopolymer-coated zein nanoparticles may be an effective oral delivery system for curcumin that could be used in functional foods or beverages. [ABSTRACT FROM AUTHOR]

In this work, the gelatin/zein nanofibers by hybrid electrospinning were fabricated. The morphology observations by field emission scanning electron microscopy showed that the diameter of gelatin/zein nanofibers was significantly increased with the increasing gelatin ratio. The results of Fourier transform infrared spectroscopy and differential scanning calorimetry indicated that gelatin and zein strongly interacted via hydrogen bonding. The homogeneous mixing resulted in the crystalline structure for the gelatin/zein nanofiber at a 1:1 wt ratio, which showed a hydrophobic surface (water contact angle of 118°). The mechanical tests showed that the gelatin/zein nanofibers with weight ratios of 1:3 and 1:2 gave rise to much higher elongation at break of 87.9% and 69.0%, indicating good deformability and flexibility. In contrast to the pure gelatin or zein nanofibers, the gelatin/zein fibers preserved the 3D porous structures after immersed in water or ethanol for 24 h. [ABSTRACT FROM AUTHOR]

Recently, Pickering emulsions have attracted extensive interests due to their advantages of “surfactant-free” and sustained delivery for bioactives. However, developing natural, biodegradable and food grade nanoparticles as Pickering emulsion stabilizers face new challenges. In this study, zein/gum arabic (GA) complex colloidal nanoparticles (ZGAPs) were prepared with a core-shell structure through hydrogen bonding and electrostatic interactions. The mean size of ZGAPs was larger than that of zein nanoparticles, and the zeta potential reversed from positive to negative, further confirming that GA molecules adsorbed onto the surface of zein nanoparticles. The three-phase contact angle ( θ o/w ) of zein nanoparticles was around 133.75°. After addition of GA, the θ o/w of ZGAPs was adjusted to 88.95° closing to neutral wettability. This result indicated that ZGAPs could be developed as effective Pickering emulsifiers. Confocal laser scanning microscope images evidenced that ZGAPs formed a densely packed layer at the surface of oil droplets, which provided compact barriers of the droplets against coalescence and Ostwald ripening. At constant particle concentrations, the oil volume fraction significantly influenced the droplet sizes and rheological properties of Pickering emulsions. The droplet size and emulsified phase volume fraction of Pickering emulsions were increased with the rise of oil fraction. Consequently, Pickering emulsion gels were successfully fabricated at a higher oil fraction φ ≥ 0.5, which exhibited a long-term storage stability. These findings would provide a potential way of producing Pickering emulsion gels, which showed the advantages of both emulsions and gels, and could become novel and effective delivery systems of bioactives. [ABSTRACT FROM AUTHOR]

In this study, the gelatin, zein, and gelatin/zein films were fabricated by electrospinning and solvent casting, respectively. Scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy and water contact angle measurements were performed to characterize the morphology, molecular interactions, thermal behavior, and surface hydrophilicity of the electrospun and casted films. Results showed that the zein particles prevented the gelatin chains from aggregating intra-molecularly in the casted films due to heterogeneous mixing, while strong hydrogen bonding was formed in the nanofibrous film as a result of homogeneous mixing. Interestingly, the gelatin/zein nanofibrous film had a hydrophobic surface (water contact angle of 118.0°), while the casted gelatin/zein film had a hydrophilic surface (water contact angle of 53.5°). The confocal laser scanning microscopy observations suggested that the zein particles were well dispersed in the gelatin network to maintain the nanofibrous structures after immersion in water or ethanol, leading to the improved solvent resistance. [ABSTRACT FROM AUTHOR]

In this study, pectin was applied as a carbohydrate-based coating to improve physicochemical stability of sodium caseinate/zein (CZ) complex protein nanoparticles. Pectin coating was achieved via a pH- and heating-induced facile electrostatic adsorption process. The effect of pectin coating was tested on two different nanoparticle structures, i.e. solid and hollow CZ nanoparticles. The inter- and intra-molecular interactions between proteins and pectin were characterized by Fourier transform infrared and fluorescence spectroscopy. Pectin coating significantly improved the stability of nanoparticles under gastrointestinal conditions, showing minimal change in particle size and polydispersity. Our results showed that pectin coating not only significantly increased the capability of protein nanoparticles to encapsulate curcumin and but also provided sustained release under gastrointestinal conditions. Pectin-coated CZ nanoparticles demonstrated exceptional stability by maintaining their morphology before and after freeze-drying. Therefore, pectin coating is an effective strategy to potentially realize practical applications of protein nanoparticles as oral delivery vehicles. [ABSTRACT FROM AUTHOR]

Zein films loaded with 5 or 10% of Zataria multiflora Boiss. essential oil (ZEO) were successfully obtained. Migration of antimicrobial carvacrol and thymol, major components of ZEO, was monitored at different temperatures and with different food simulants, and apparent diffusion was calculated. Antimicrobial properties of the films were assayed in vapour phase and liquid medium. The results showed that films containing 5% ZEO achieved reductions of 1.18 log and 1.14 log against L. monocytogenes and E. coli , respectively, and the log reduction value increased to 2.16 log and 2.65 log for films with 10% ZEO. However, the films lacked antimicrobial activity when tested in vapour phase. Finally, thin zein films loaded with 10% ZEO were successfully applied as a coating on PP bags. The effectiveness of the active bags was tested in a more complex medium than liquid bacterial growth media, that is cow's milk inoculated with the above microorganisms. This work offers a successful approach on the use of zein proteins for active food packaging. [ABSTRACT FROM AUTHOR]

Zein nanoparticles (ZNPs) suspended in water were produced by the antisolvent precipitation method and combined with ι-carrageenan (ι-CGN) suspended in sodium phosphate buffer in order to evaluate the ability of the negatively-charged ι-CGN to stabilize ZNPs against flocculation and gravitational separation. Physical stability of 0.01% ZNP (w/v) dispersions with 0%–0.02% ι-CGN (w/v) was observed during storage at 4 °C and during centrifugation. Colloidal properties of the particles during storage, such as hydrodynamic radius, turbidity, and ζ-potential were characterized at pH values above pH 5. At pH 5, ZNPs were present as small aggregates with an average hydrodynamic radius of approximately 500 nm, and at higher pH values these aggregated further so that the average size was greater than 1000 nm. Addition of sufficient ι-CGN to achieve a ZNP:ι-CGN weight ratio less than or equal to 10:1 prevented aggregation in the pH range of 5.25–6.75 and limited aggregation at pH 7.0 (average particle radius of 200–400 nm). Enhanced stability was attributed to the adhesion of ι-CGN to the nanoparticle surface, as the ZNPs surface charge became significantly negative with introduction of ι-CGN. These particles remained stable for up to 30 days with significantly lower turbidity and greater resistance to gravitational separation when compared to ZNPs alone. Characterization of ZNPs with an atomic force microscope showed that the particles possessed a nearly spherical geometry with a Young's modulus of ∼100 MPa, neither of which was significantly altered after addition of interactive ι-CGN. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Interparticle forces that govern the assembly of particles adsorbed at fluid interfaces determine the rheology and microstructure of particle laden interface. In this study, natural small molecule, tannic acid (TA), was used to modify particle-particle interactions and assembly behaviors of food grade hydrophobic protein particle (zein nanoparticle) at air-water interface. For bare zein particle (ZP), the rapid adsorption and high interparticle forces led to the low coverage and formation of large ZP aggregates at the interface. The hydrogen-bonding of TA weakened the particle hydrophobicity and thus interparticle forces at fluid interfaces. Therefore, the adsorption process and assembly rate of ZTP at the interface obviously reduced, which also provided enough time for ZTP to rearrange into orderly interfacial networks. Furthermore, the Lissajous plots of surface pressure versus deformation are used to understand the surface rheological response to large mechanical deformation in terms of interfacial microstructure. The rheological response of interface stabilized by ZTP showed strain hardening during extension and strain softening during compression. These findings indicate that the interfacial rheology and microstructure of zein particle-laden interface can be tuned by changing the TA content. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the release kinetics and antibacterial activities of curcumin (CUR) loaded in zein (zein-CUR) electrospun fibers towards Escherichia coli ( E. coli , 8099) and Staphylococcus aureus ( S. aureus , ATCC 6538). CUR was successfully loaded in zein fibers by electrospinning technique, and the encapsulation efficiency was close to 100% and the encapsulated CUR still retained its antioxidant capacity. The morphology and size of fibers strongly depended on CUR contents. The interaction between CUR and zein matrix was confirmed to be hydrogen bonding, and the addition of CUR caused a slight increase in the T g of zein matrix. The electrode process of CUR electrooxidation was diffusion-controlled and could be preceded by chemical reaction. The predominant release of CUR from fibers was Fickian diffusion, and First-order model and Hixson-Crowell model could well describe this diffusion behavior. The zein-CUR fibers showed good antibacterial activity towards S. aureus and E. coli , and the inhibition efficiency increased with the increase of CUR contents. However, the antibacterial activity towards S. aureus was better than that towards E. coli . The study displayed that the zein-CUR fibers might have potential as a promising material for antimicrobial applications to inhibit bacterial growth and propagation in active food packaging. [ABSTRACT FROM AUTHOR]

This study investigated the interactions of zein with (−)-epigallocatechin gallate (EGCG), quercetagetin (Q) and chlorogenic acid (CA) in ethanol-water solution (70%, v/v). Zein-polyphenol conjugates and mixtures were characterized in terms of their physical, structural, thermal, and morphological properties, as well as their antioxidant activity. The formation of zein-polyphenol conjugates was verified using GPC, SDS-PAGE and grafting efficiency determination. Zein interacted more strongly with EGCG and Q than with CA. The polyphenols could form both covalent and non-covalent complexes with zein, and their structural and functional properties depended on the nature of the complexes formed. Covalent zein–EGCG complex exhibited higher thermal stability and stronger antioxidant activity than non-covalent ones. The morphology of zein nanoparticles formed when the alcohol was evaporated also depended on the nature of the interaction and polyphenol type. This study provides useful information for the design of zein-based colloidal delivery systems for encapsulation and protection of bioactive components. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Sodium carbonate was proposed as a sacrifice template and tannic acid was used as a natural cross-linker to prepare hollow zein nanoparticles (HZN/T). The formulation of nanoparticles, including the amount of water, zein and sodium carbonate, were optimized by surface response methodology (Box-Behnken design). The optimized HZN/T exhibited a small dimension of 87.93 nm with a PDI of only 0.105 and a zeta potential of −39.70 mV, indicating the nanoparticles were homogenous and formed stable colloidal dispersion. Then curcumin was used as a model lipophilic nutrient to explore the encapsulation and delivery potentials of HZN/T, in comparison with hollow zein nanoparticles without tannic acid (HZN/NT) and solid zein nanoparticles with tannic acid (SZN/T) prepared under the same conditions. Generally, the encapsulation efficiency of HZN/T or HZN/NT was significantly higher than that of SZN/T. Interestingly, encapsulation of curcumin dramatically increased particle size of SZN/T by 50 nm, while it did not induce any expansion of the dimension of HZN/T due to its hollow structure. The molecular interactions between curcumin and zein nanoparticles were investigated by Fourier transform infrared spectroscopy and fluorescent spectrophotometer. The in vitro stability and release profile of nanoparticles were evaluated under the simulated gastrointestinal conditions. Although all types of zein nanoparticles showed a sustained release of curcumin, cross-linking via tannic acid played an important role to make zein nanoparticles more resistant against simulated intestinal digestion. Therefore, compared with traditional SZN/T, the HZN/T developed in this study has promising features as a potential oral delivery system for lipophilic nutrients/drugs. [ABSTRACT FROM AUTHOR]

Novel antimicrobial biopolymer films based on the incorporation of ethyl-N α -dodecanoyl- l -arginate hydrochloride (LAE) in zein matrices were manufactured and characterized as materials for LAE controlled released applications such as active food packaging. Characterization of the films’ functional properties revealed that incorporation of LAE (5 and 10%) in the biopolymer matrix did not cause substantial changes in morphological, optical, thermal, mechanical and barrier properties. As the mechanism of action of these films is mainly based on release of the antimicrobial, this process was characterized when the active biofilms were exposed to three food simulants (water, 3% acetic acid, and 10% alcohol) at three temperatures (4, 23, and 37 °C). The data obtained revealed that, with the exception of exposure to water at 4 °C which achieved a release of more than 80% of the LAE incorporated, the agent was almost completely extracted in all conditions. Release of LAE was faster at higher temperatures, and the diffusion coefficient values varied according to the Arrhenius law, and increased with temperature. Antibacterial activity of films was assayed against Listeria monocytogenes and Escherichia coli . Zein films with 5% LAE produced 2.02 and 3.07 log reduction against L. monocytogenes and E. coli , respectively, after 5 days of storage at 4 °C. Greater antibacterial activity was observed with films containing 10% LAE (5 log reduction) at 37 °C. This work highlighted that LAE incorporation in a packaging film constructed with renewable polymer materials offers an interesting and efficient hurdle for control of bacterial contamination in foods. [ABSTRACT FROM AUTHOR]

Polysaccharide−protein complexes can be used to improve the physical stability of oil-in-water emulsions. The purpose of this study was to investigate the effects of concentration of citrus pectin, zein and oil as well as order of mixing on physical properties and stability of emulsions stabilized by pectin–zein complexes. Emulsions containing oil phase (5–30% w/w rice bran oil) and aqueous phase (0.5–2% w/w pectin, adjusted to pH 4) were prepared by mechanical homogenizer. The zein concentration (0.001–0.5% w/w) was added in either primary or secondary emulsification step. The obtained emulsions were then assessed by measuring droplet size, zeta potential, microstructure, apparent viscosity, and emulsion stability after storage at ambient temperature and under environmental stress conditions. Using 1.5% w/w pectin could produce the stable emulsions with low percent creaming index, at the oil concentration of 15 and 20% w/w. Moreover, the stable emulsions could be formed when the zein was added after pectin adsorption (secondary emulsification) but not when it was added together with pectin. This was attributed to electrostatic attraction between cationic groups on zein molecules and anionic groups of pectin on the droplet surface. We also found that pectin−zein stabilized emulsions were much more stable than emulsions stabilized by pectin or zein alone. The stability of emulsions also increased as zein concentration was increased. The results suggested that the pectin–zein complexes could be used to improve the physical stability of oil-in-water emulsions, especially the formulations with a high volume fraction of oil. [ABSTRACT FROM AUTHOR]

In this work, we developed multilayer bacterial cellulose (BC)-zein films based on the strong BC film as the outer layers and the electrospun zein fibers as the inner layer, to improve the water resistance properties of hydrophilic BC films. The water resistance properties were evaluated by dynamic water absorption measurement and mung beans storage test. The obtained results showed that the incorporation of electrospun zein fibers made the relatively thin and flexible multilayer films become stiffer, while the zein interlayer did not markedly affect the thermal stability and surface properties of films. Compared to pure BC films, the BC-zein films exhibited significantly better water resistance properties, especially under longer zein deposition time (90 and 120 min). This improvement could be mainly due to the inherent hydrophobicity of zein protein. These findings provide the possibility of adopting a multilayer film strategy for the development of BC packaging films with enhanced water resistance properties by incorporating a high barrier interlayer of electrospun zein fibers. [ABSTRACT FROM AUTHOR]

The effects of different heat-treated temperatures (75, 85 and 95 °C) and times (15, 30 and 45 min) on physical, structural, thermal and morphological characteristics of zein in ethanol-water solution were investigated. The result of particle size distribution suggested that the volume percentage of small zein colloidal nanoparticles (d < 200 nm) was increased from 87.9% to 98.2% after heat treatment at 75 °C for 15 min. Both of the fluorescence intensity and ultraviolet absorption of zein approached to the maximum value when zein solution was heated at 95 °C for 30 min. Differential scanning calorimetry thermograms implied that heat treatment enhanced the thermal stability of zein with the rise of denaturation temperature. The secondary structure changes of zein induced by heat treatment might be explained by a potential mechanism of three-step process, including partial protein folding, a larger extent unfolding and the formation of partial protein aggregates. In addition, heat treatment significantly modified the morphology of zein from the typical sphericity to distinct oval at 75 and 85 °C, as well as obvious dumbbell-like shape at 95 °C for 30 min. [ABSTRACT FROM AUTHOR]

Zein colloidal nanoparticles can adsorb at the oil–water interface to form Pickering emulsion. However, zein Pickering emulsion is usually not stable due to the poor wettability of zein colloidal nanoparticles. The objective of this study was to modify the surface of zein nanoparticles using sodium caseinate (NaCas) and assess the properties of zein/NaCas nanocomplexes and the resultant oil-in-water Pickering emulsions. One percent (w/w) of zein/NaCas colloidal nanocomplexes were formed, with the zein:NaCas ratios (w/w) ranging from 10:1 to 10:4 at pH = 3 by an ultrasound treatment. The zeta-potential of the zein/NaCas nanocomplexes showed altered surface charges, indicating that NaCas adsorbed on the surface of the zein colloidal nanoparticles. Three-phase contact angle measurements suggested that the original zein colloidal nanoparticles were preferentially wetted in water. The incorporation of 0.1%–0.2% (w/w) NaCas significantly enhanced its wettability in the oil, and intermediate wettability was achieved at a zein:NaCas ratio of 10:3. Confocal laser scanning microscope (CLSM) images showed that the incorporation of NaCas improved the interfacial coverage of the Pickering emulsions. When the zein:NaCas ratio ranged from 10:1 to 10:3, the interface was composed of zein/NaCas nanocomplexes. At a zein:NaCas ratio of 10:4, NaCas can competitively adsorbed to the interface and formed a hybrid interfacial structure. The Zein/NaCas nanocomplexes stabilized the Pickering emulsions and exhibited greater centrifugal stability than plain zein emulsions at most pHs and ionic strengths. The underlying mechanisms of the improved emulsion stability are discussed in this paper. This study explored a novel approach to stabilizing Pickering emulsions via the surface modification method using a food-grade protein. [ABSTRACT FROM AUTHOR]

In this study, whey protein isolate (WPI) based bio-nanocomposite films embedded with zein nanoparticles (ZNP) were prepared by solution casting. Nanoparticles were coated with sodium caseinate to obtain a uniform distribution in the films. The mechanical, water vapor barrier, surface wetting, morphological and viscoelastic properties of the films were investigated. The addition of ZNP significantly improved the water vapor barrier and mechanical properties of the WPI without adversely affecting the elongation of the films. Dynamical mechanical analysis and contact angle measurements revealed that upon addition of the nanoparticles, the fractional free volume and hydrophilicity of the WPI films decreased. Sodium caseinate containing both hydrophilic and hydrophobic groups created an efficient interface between the hydrophobic ZNP and hydrophilic WPI matrix, allowing for a homogeneous distribution of nanoparticles even at very high loading levels as evidenced by the scanning electron microscope (SEM) and atomic force microscopy (AFM) images. The WPI/ZNP nanocomposite films can potentially become effective food packaging materials. [ABSTRACT FROM AUTHOR]

Colloidal complexation of zein hydrolysate (ZH) with tannic acid (TA) and the possibility of using the ZH-TA complex to construct a nanoemulsion system for alga oil delivery were investigated. Turbidity and fluorescence titration measurements demonstrated the complexation of ZH with TA, which leads to the formation of ZH-TA complex. Isothermal titration calorimetry further confirmed the complexation between ZH and TA was driven by the non-covalent interaction (e.g. hydrophobic interaction and hydrogen bonding). The emulsifying activity of ZH was considerably improved after the complexation with TA, which was responsible for the fabrication of alga oil nanoemulsions ( d = 120 nm). The emulsions stabilized by the ZH-TA complex showed a remarkable physical stability and high alga oil encapsulation efficiency. More importantly, the complexation of ZH with TA also endowed ZH-TA complex with high antioxidative properties. The alga oil nanoemulsions stabilized by ZH-TA complex showed an increased oxidative stability with reduced lipid hydroperoxides and volatile hexanal compared with that of stabilized by ZH alone. This study demonstrated that ZH-TA complex could be employed as an emulsifier in constructing a physical stable nanoemulsion delivery system, and opens up the possibility of utilizing peptides–polyphenol complex as efficient emulsifiers to improve the oxidative stability of O/W nanoemulsions. [ABSTRACT FROM AUTHOR]

Water-insoluble zein (corn prolamins) has great potential for use as delivery systems. In this study, stable zein nanoparticle dispersions were produced using a pH-cycle method to form complexes with sodium caseinate (NaCas) without using an organic solvent. NaCas was mixed with zein at pH 11.5 and the subsequent neutralization to pH 7.0 enabled the co-assembly of zein and NaCas. The mean hydrodynamic diameter of spherical nanoparticles was smaller than 100 nm based on dynamic light scattering, scanning electron microscopy, and atomic force microscopy. The nanodispersions were stable during 30-day storage at 4 °C. The freeze-dried sample showed excellent re-dispersibility. The current study showed the promise of this novel method to prepare zein nanoparticles for applications such as delivery systems. [ABSTRACT FROM AUTHOR]

Electrospraying is a technique now applied for the production of food nanoparticles, nanofibres and nanocapsules, which could constitute a good alternative for the development of films. The goal of this work was to determine the electrospraying operation conditions and the zein concentration that would allow a film to be produced and also to evaluate the structural characteristics and barrier and thermal properties of films developed at different thicknesses. Results showed that films can be obtained by electrospraying, resulting possible to produce homogeneous films, without electrical arc formation during processing when using a 11.4% zein solution, an electrical voltage of 7.8–8.7 kV and a distance of 1.5 ± 0.5 cm between the nozzle and the deposit plaque. Regarding the effect of the production methods (electrospraying and casting) and the film thickness on film appearance, both variables had significant effect on colour parameters, observing a more yellowish colour (b* = 72.3 ± 6.8) and lower transparency (%T = 90.6 ± 0.21) at larger thicknesses (100 μm), and a smoother and more homogeneous surface (ESEM) when films were obtained by electrospraying. Water vapour permeability was only influenced by film thickness (1.51 × 10 −08 to 3.11 × 10 −08 g/s-m-Pa) in both methodologies. The glass transition temperatures (Tg) for electrospraying and casting films were different (222 °C and 231 °C respectively) and higher than that of zein powder (165 °C), indicating a possible change in the film structure due to the process. Under the process conditions tested in this work, electrospraying can be considered as an alternative technique to produce films. [ABSTRACT FROM AUTHOR]

The effects of glycerol on molecular mobility, oxygen diffusion and microstructure in amorphous zein matrix were studied using phosphorescence and atomic force microscopy (AFM). Films containing various amounts of glycerol (0, 5, 10, 20 and 30 wt%) were cast from solutions of 0.5% (w/v) zein in 70% ethanol/water (v/v). Erythrosin B (Ery B) phosphorescence was used to monitor the molecular mobility of these matrices over the temperature range from 0 to 100 °C. Analysis of Ery B emission peak frequency and bandwidth and intensity decay provided information about thermally-activated modes of molecular mobility in the matrices. Dipolar relaxation around the triplet state of Ery B was weakened and the extent of relaxation was decreased at low concentration glycerol (≤10%), indicating a role as antiplasticizer. The rate of non-radiative decay from the Ery B triplet state indicated that glycerol only performed as a plasticizer and increased the local mobility of the zein matrix at and above ∼20 wt %, while in films with glycerol at ≤20 wt % the local mobility remained nearly constant or only slightly increased compared with pure zein. Though transitioning from antiplasticizer to plasticizer at higher content, glycerol dramatically suppressed the oxygen permeability of the film in the whole concentration range tested. AFM images indicated that glycerol induced aggregation of zein complexes. These results indicate how the addition of glycerol to zein films could affect the physical properties, structure and thus functional properties in ways that influence their eventual use. [ABSTRACT FROM AUTHOR]

Core-shell biopolymer nanoparticles were prepared using antisolvent precipitation to form surfactant-stabilized zein core nanoparticles and then electrostatic deposition to form an alginate shell. The particle yield was relatively high (95%). The nanoparticles had a core diameter of about 80 nm, a shell thickness of about 40 nm, and an electrical charge of about −21 mV (pH 4.0). The amount of alginate required to saturate the surfaces of the zein nanoparticles was 2.0 mg/m 2 . The nanoparticle suspensions had relatively good stability to pH: the particles were stable to aggregation from pH 3 to 8, but aggregated at pH 2 due to loss of charge. They were also relatively stable to elevated ionic strengths: the particles were stable to aggregation up to 100 mM NaCl at pH 7.0 and up to 2.0 M NaCl at pH 4.0. The suspensions had good thermal stability at pH 7, i.e., no increase in particle size after heating at 90 °C for 120 min. Nevertheless, some particle growth was observed during heating at pH 4 for 2 h. The core/shell biopolymer nanoparticles fabricated in this study have potential to be used as nano-delivery systems for bioactive molecules in food and pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Zein is a group of alcohol-soluble maize proteins and is typically dissolved in 70–80% aqueous ethanol before dispersion into water to precipitate zein as nanoparticles, which can simultaneously encapsulate various lipophilic compounds co-dissolved in aqueous ethanol. However, strategies are needed to prevent the precipitation of hydrophobic zein nanoparticles at a wide pH range and the use of flammable ethanol in the industrial production. The objective of this work was to replace ethanol with nonflammable propylene glycol to prepare zein nanoparticles and stabilize nanoparticles using gum arabic (GA). Nanoparticles smaller than 200 nm were produced using a stir plate, and GA prevented their precipitation at pH 3.0–8.0. Both electrostatic and hydrophobic interactions contributed to the adsorption of GA on zein nanoparticles, with the former being more significant at a lower pH corresponding to a higher surface load. Encapsulation of peppermint oil in zein nanoparticle-GA complexes did not significantly change particle dimension and dispersion stability. The gradual release of peppermint oil from freeze-dried samples was observed at pH 2.0–8.0, reaching complete release in a shorter time at a lower pH. The established method may enable the preparation of stable zein nanoparticles for various applications in the food industry. [ABSTRACT FROM AUTHOR]

Background Oxidation of encapsulated bioactive compounds is a key challenge that limits shelf-life of bioactive containing products. The objectives of this study were to compare differences between the oxidative barrier properties of biopolymer particle based encapsulation system (zein colloidal particles) and oil-in-water emulsions and evaluate the impact of these differences on oxidative stability of encapsulated bioactives. Methods Both zein colloidal particles and oil-in-water emulsions were stabilized by casein protein. The oxidative barrier properties of the selected encapsulation systems were determined by measuring the permeation rate of peroxyl radicals and oxygen across the interface. Peroxyl radical permeation rates were correlated with stability of a model bioactive, curcumin and oxygen permeation rates were correlated with stability of another model bioactive, retinol. Results Radical permeation rate was significantly higher in oil-in-water emulsions compared to zein colloidal particles, indicating enhanced barrier property of zein colloidal particles against peroxyl radical induced oxidation. Consistent with these results, stability of curcumin encapsulated in zein colloidal particles was significantly higher compared to that in oil-in-water emulsions. Oxygen permeation measurements showed no significant differences in the barrier properties of both encapsulation systems against oxygen permeation. Consistent with these results, the oxidative stability of retinol was similar in both encapsulation systems. Conclusions The results of this study demonstrate the advantages of biopolymer particle based encapsulation system in limiting free radical induced oxidation of encapsulated bioactives and also demonstrate the ineffectiveness of both encapsulation systems in limiting oxygen permeation. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to improve the barrier ability of sodium caseinate (SC) films using corn zein via direct coatings and structural inversion approach. The effects of zein coatings on barrier properties (oxygen and water vapor) and surface properties (surface hydrophobicity, surface free energy and surface topography) of the films were extensively investigated. Zein coating via the structural inversion approach heightened surface hydrophobicity of SC films, and polar parameter (γ AB) of surface free energy (γ) decreased from 11.5 to 3.4 mJ/m2, whilst apolar parameter (γ LW) of γ increased from 25.3 to 32.1 mJ/m2. In contrast, direct coating of zein presented an opposite pattern. Zein coatings increased surface roughness of SC films, structural inversion approach led to apparent surface irregularities with high irregular projections, whereas the well-defined zein nanospheres were evenly distributed in film surface via direct depositing. Zein coatings produced via structural inversion approach enhanced the barrier of SC films against water vapor and oxygen, whereas the direct coating approach only decreased oxygen permeability (OP) of the films. The present data pointed to a possible arrangement and orientation of hydrophilic and hydrophobic moieties of zein on surface of SC films under different conditions. A schematic illustration of the formation pathway of zein coatings on SC films was proposed to relate it with barrier and surface properties of the films. [Copyright &y& Elsevier]

Abstract: Zein has been studied as a versatile food biopolymer to fabricate nanoparticles for encapsulating a large variety of bioactive compounds. Being water-insoluble prolamines, dispersing zein nanoparticles in aqueous systems is a challenge. Recently, sodium caseinate (NaCas) was observed to have improved the dispersibility of freeze-dried zein nanoparticles but not for spray-dried samples. In this paper, three different approaches were studied to produce spray-dried zein nanoparticles precipitated by dispersing aqueous ethanol solutions of zein into the aqueous phase. The control (S2) was produced by dispersing zein solution into NaCas dispersion without pH adjustment. The other two approaches involved conditions dissociating NaCas: adjusting NaCas dispersion to pH 11.0 (S5) or dissolving NaCas in heated zein solution before dispersing to a pH 8.0 buffer (S4). After hydrating the spray-dried powder, dispersions demonstrated varying turbidity and precipitation stability during storage. Entire NaCas was observed to have adsorbed on S2 zein nanoparticles, corresponding to bigger particles, higher turbidity and lower stability of dispersions than those of S4 and S5. Conversely, only κ-casein was on zein nanoparticles of S4 and S5, corresponding to a higher zein:casein mass ratio and higher surface hydrophobicity than that of S2. The best dispersibility was observed for S4 at pH 7.0 and 0–300 mM NaCl, with the smallest hydrodynamic diameter (∼125 nm), lowest turbidity, and without precipitation during 15-day refrigerated storage. Compositional analyses suggested that κ-casein in S4 was a part of zein nanoparticle matrices and was not detached by increased ionic strength during storage. Conversely, caseins detached from zein nanoparticles of S2 and S5, causing particle aggregation and precipitation. Additionally, the approach in S4 utilized less ethanol (50% v/v vs. 80% in the other two approaches) to dissolve zein. Our work is significant in fabricating delivery systems of bioactive compounds utilizing zein as a carrier biopolymer. [Copyright &y& Elsevier]

Abstract: In this work, multilayer structures based on polyhydroxybutyrate-co-valerate with a valerate content of 12% (PHBV12) containing a high barrier interlayer of electrospun zein nanofibers were developed. It was observed that the method used for the preparation of the outer PHBV12 layers affected their functional properties, since mechanical resistance increased and water vapour permeability and transparency decreased in the multilayer containing outer layers prepared by compression-moulding to a higher extent than for their counterparts obtained by casting. The addition of zein interlayer produced minimum changes in mechanical and optical film properties while the incorporation of the zein nanostructured interlayers significantly improved oxygen barrier properties of the multilayer films prepared by both processing technologies. However, the effect of the interlayer on the water vapour and limonene permeability depended on zein content. Thus, this approach provides an innovative way to develop fully renewable microbial biopolyester-based multilayer structures with enhanced barrier performance of significant interest in food packaging applications. [Copyright &y& Elsevier]

Abstract: In this work, novel materials with heat management properties have been developed by means of the encapsulation of a phase changing material (PCM) in a biopolymeric matrix using the electrospinning technique. This study optimizes the methodology to obtain micro-, submicro- and nanoencapsulation structures based on zein (a maize protein) and dodecane (a PCM paraffin which has a transition temperature at −10 °C). The results demonstrate that dodecane can be properly encapsulated in the zein matrix under different conditions, although the efficiency and, thus, the heat management properties of the structures developed, change according to the encapsulation morphology and the electrospinning parameters/configuration employed. These encapsulation technologies can be of interest in the food industry in order to develop new smart packaging materials with the ability to maintain temperature control, e.g. to preserve the cold chain. [Copyright &y& Elsevier]

Abstract: Nanoparticles with a compact spherical structure and a narrow size distribution were prepared from a zein protein polymer by electrohydrodynamic atomization. The effects of key parameters of the process (polymer concentration, flow rate and applied voltage) on the size and morphology of the particles was studied. Zein nanoparticles could be obtained from zein concentrations ranging from 2.5% to 15% (w/w). The sizes of these particles, ranging from 175 to 900 nm, increased with increasing polymer concentration. Compact nanostructures were obtained for 2.5% and 5% zein solutions whereas 10% and 15% solutions yielded collapsed and shrunken particles. Flow rate also exerted an effect, the lower the flow rate the smaller the nanoparticles. The morphology of the nanoparticles did not change after incorporating curcumin in proportions ranging from 1:500 to 1:10 (curcumin:zein), and the encapsulation efficiency was around 85–90%. Fluorescence microscopy images showed that the nanostuctures obtained took the form of matrix systems with the curcumin homogeneously distributed in the zein matrix. The curcumin remained in the amorphous state in the nanoparticle, as revealed by X-Ray diffractometry, evidencing intimate contact with the polymer. After three months of storage at 23 °C and 43% relative humidity in the dark, neither the size or the morphology of the nanoparticles had undergone significant changes, nor had the curcumin content altered. Thanks to encapsulation, the curcumin presented good dispersion in an aqueous food matrix: semi-skimmed milk. [Copyright &y& Elsevier]

Abstract: Viscoelastic properties of α-zein dispersed in aqueous ethanol were studied using oscillatory strain rheometry. In 55–80% v/v aqueous ethanol, zein was only partially soluble, forming a gel at a sufficiently high zein concentration. The strain dependence of the storage modulus and the loss modulus of gelled systems exhibited features characteristic to closely-packed swollen particles. Close-packing was found to occur at a lower zein concentration with increasing ethanol concentration as the threshold for gelation decreased from a zein concentration of ca. 29 to 20% w/v with increasing ethanol concentration from 55 to 80% v/v. A contrasting trend in the effect of the solvent quality was revealed at a constant zein concentration of 30% w/v, at which the storage modulus decreased from ca. 12,000–700 Pa with increasing ethanol concentration from 55 to 80% v/v. The two major factors determining viscoelastic properties of the partially solvated zein systems were identified to be: (1) the degree of dissolution of zein into the continuous phase that was negatively correlated with the volume fraction of the dispersed phase and positively correlated with the osmotic pressure of the continuous phase; and (2) the degree of swelling of partially solvated zein particles that was positively and negatively correlated with the volume fraction and the storage modulus of the dispersed phase, respectively. [Copyright &y& Elsevier]

Abstract: Cranberry procyanidins (CPs)-zein nanoparticles were fabricated using a modified liquid–liquid dispersion method. The CPs were purified using chromatographic methods and analyzed using HPLC equipped with a fluorescence detector (FLD) and mass spectrometer (MS). The purified CPs had a purity of 64.7% (w/w) and contained procyanidin oligomers (from dimers to decamers) and polymers, with polymers being the predominant component (38.7%, w/w). The particle size of the CPs-zein nanoparticles increased from 392 nm to 447 nm with the increase of the CPs-to-zein mass ratios from 1:8 to 1:2. Morphologically, the CPs-zein nanoparticles were spherical as observed by scanning electron microscopy (SEM). The loading efficiency of CPs in the CPs-zein nanoparticles decreased with an increase of CPs-to-zein mass ratios from 1:8 to 1:2, and ranged from 10% to 86%. The oligomers with higher degree of polymerization (DP) showed higher loading efficiency than the oligomers with lower DP, suggesting a greater binding affinity on zein proteins. The loading capacity of the CPs-zein nanoparticles fabricated using a high CPs-to-zein mass ratio (1:2) was significantly higher than those using a low mass ratio (1:8). Fourier transform infrared spectroscopy (FTIR) suggested that the primary interactions between the CPs and zein were hydrogen bond and hydrophobic interactions. Cell culture studies using human promyelocytic leukemia HL-60 cells showed that the CPs encapsulated in nanoparticles had decreased cytotoxicity compared to the CPs. [Copyright &y& Elsevier]