pH Cycling Method Research Articles

Effect of Heat Treatment Combined with TG Enzyme Cross-Linking on the Zein-Pea Protein Complex: Physicochemical and Gel Properties.

Plant proteins have the advantages of low cost and high yield, but they are still not comparable to animal proteins in processing due to factors such as gelation and solubility. How to enhance the processing performance of plant proteins by simple and green modification means has become a hot research topic nowadays. Based on the above problems, we studied the effect of gel induction on its properties. In this study, a pea protein-zein complex was prepared by the pH cycle method, and the effects of different induced gel methods on the gel properties of the complex protein were studied. The conclusions are as follows: All three gel induction methods can make the complex protein form a gel system, among which the gel strength of heat treatment and the TG enzyme-inducted group is the highest (372.84 g). Through the observation of the gel microstructure, the gel double network structure disappears and the structure becomes denser, which leads to a stronger water-binding state of the gel sample in the collaborative treatment group. In the simulated digestion experiment, heat treatment and enzyme-induced samples showed the best slow-release effect. This study provides a new method for the preparation of multi-vegetable protein gels and lays a theoretical foundation for their application in food processing.

Fabrication and characterization of W1/O/W2 double emulsions stabilized with Pleurotus geesteranus protein particles via one-step emulsification

In this study, Pleurotus geesteranus protein isolate (PPI) with low solubility in water was fabricated into nanoparticle (PPIP) that can be uniformly dispersed in pH 7.0 aqueous solution using pH cycle method. PPIP with a zeta potential of −19.21 mV had a mean size of 250.53 nm and two main peaks in particle size distribution profile. This was consistent with the TEM results, which existed both as individual particles and as particle aggregates. The main force responsible for maintaining the structure of protein particles was hydrogen bonding. Interestingly, these protein particles were successfully utilized to fabricate W1/O/W2 double emulsions using one-step homogenous emulsification, and the formation and properties of PPIP-stabilized W1/O/W2 double emulsions were significantly influenced by the protein particle concentration, oil content, and salt concentration in W2 continuous phase. Specifically, higher particle concentration and salt concentration caused a reduction in the number of W1/O droplets and the size of oil droplets. Conversely, an increase in oil content increased the number of W1/O droplets primarily due to the augmentation in the size of oil droplets. The gel strength of double emulsions was enhanced with particle concentration and oil content, as this led to the formation of stronger particle networks and droplet networks. While an opposite phenomenon was found in increasing salt concentration in W2 continuous phase, possibly resulting from the disruption of the ordered gel network. These findings not only provide new food-grade emulsifiers for W1/O/W2 double emulsions, but also broaden the application of edible mushroom proteins in food industry.

Effect of protein-based nanoencapsulation on viability of probiotic bacteria under hostile conditions

ABSTRACT The present study aimed to evaluate the effect of the incorporation of protein-based nanoencapsulation on the viability and stability of probiotic Lactobacillus rhamnosus in digestion conditions and model food. In the study’s first phase, protein-based nanoparticles were prepared by the pH cycling method, and then the probiotic, Lactobacillus rhamnosus, was nano-encapsulated. Two types of proteins, namely, whey protein and zein protein, were used to encapsulate probiotics individually. The obtained nano-encapsulated probiotics were characterized by performing particle size, SEM, FTIR, and in vitro assay was performed. Then, free and nano-encapsulated probiotics were added to the model food (yogurt) and analyzed for microbiological and sensory evaluation. Nanoencapsulation with both types of proteins significantly (p < .05) improved the stability and viability of Lactobacillus rhamnosus. The particle size for whey and zein nano-encapsulated probiotics ranged between 96 and 100 nm. The encapsulation efficiency for whey and zein nanoparticles was recorded at 96% and 87%, respectively. SEM images for both zein and whey nanoparticles showed their irregular spherical structure. FTIR spectra suggested that the mechanism of entrapment involved in water-insoluble or physical properties was mostly responsible for the generated loaded nanoparticle. In vitro analysis illustrated that whey nanoencapsulation showed the highest viability in SGC and SIC, followed by zein nanoencapsulation and free probiotics showed the minimum viability. Protein nanoencapsulation also significantly affected the sensory properties of food products. Conclusively, the nanoencapsulation of probiotics using protein nanoparticles helps prolong the viability and stability of probiotics under-simulated gastrointestinal digestion conditions and in yogurt.

Curcumin-encapsulated hydrophilic gelatin nanoparticle to stabilize fish oil-loaded Pickering emulsion

Herein, pH-cycle method was explored to prepare curcumin-encapsulated hydrophilic bovine bone gelatin (BBG/Cur) nanoparticle and then the obtained nanoparticle was applied to stabilize fish oil-loaded Pickering emulsion. The nanoparticle had a high encapsulation efficiency (93.9 ± 0.5 %) and loading capacity (9.4 ± 0.1 %) for curcumin. The nanoparticle-stabilized emulsion had higher emulsifying activity index (25.1 ± 0.9 m2/g) and lower emulsifying stability index (161.5 ± 18.8 min) than BBG-stabilized emulsion. The pH affected the initial droplet sizes and creaming index values of the Pickering emulsions: pH 11.0 < pH 5.0 ≈ pH 7.0 ≈ pH 9.0 < pH 3.0. Curcumin provided obvious antioxidant effect for the emulsions, which was also dependent on pH. The work suggested pH-cycle method could be used to prepare hydrophobic antioxidant-encapsulated hydrophilic protein nanoparticle. It also provided basic information on the development of protein nanoparticles for Pickering emulsion stabilization.

Fabrication of zein-based hydrophilic nanoparticles for efficient gene delivery by layer-by-layer assembly

As a natural biological macromolecule, zein has broad application prospects in drug delivery due to its unique self-assembly properties. In this work, zein/sodium alginate (Zein/SA) nanocomposites were prepared by a pH-cycle method, Then Zein/SA/PEI (ZSP) nanocomposites were prepared by efficient layer-by-layer assembly method, ZSP nanocomposite of higher transfection performance was further labeled by folic acid (FA). After characterizing the physicochemical properties of ZSP by various methods, the potential of ZSP as a gene delivery vehicle was explored in vitro. The results showed that ZSP had good dispersibility and stability, the diameter distribution was in the range of 124–203 nm, and it had a typical core-shell structure, which could effectively condensate DNA and protect it from nuclease hydrolysis. ZSP exhibited proton buffering capacity similar to PEI, lower cellular toxicity, lower protein adsorption and erythrocyte hemolysis effect than PEI. ZSP/pDNA complexes could be taken up by cells and exhibited higher transfection efficiency than PEI/DNA complexes at the same weight ratio. The transfection efficiency of the complex in HeLa and 293T cells can be improved by FA labeling, especially in HeLa cells. These results provide new perspective for the design and development of efficient zein-based gene delivery systems.

Sodium alginate/gum arabic/glycerol multicomponent edible films loaded with natamycin: Study on physicochemical, antibacterial, and sweet potatoes preservation properties

Sweet potato (Ipomonea batatas Lam) is easily damaged due to its thin skin, which is limited in shelf life and causes enormous economic losses in the food industry. A new type of safe, non-toxic, and edible antibacterial functional film was developed with sodium alginate (2.5 %), gum arabic (1 %), glycerol (2 %), and natamycin as an antimicrobial agent in this study. The physical and antibacterial properties of films, such as thickness, chromaticity, water vapor permeability, tensile strength, and elongation at break, were studied. Furthermore, the antibacterial film was applied in the preservation of sweet potatoes. The results showed that natamycin emulsion had good compatibility with sodium alginate. Besides reducing the transparency of the composite membrane, the mechanical properties, barrier properties, and thermal stability of the composite film were significantly enhanced by the addition of natamycin prepared by a pH-cycle method. When the concentration of natamycin in the membrane solution reached 40 μg/mL or more, the antibacterial film had a noticeable inhibitory effect on the growth of molds, and yeasts, significantly enhancing the bacteriostatic effect of the base film. During the sweet potatoes storage, the water content, total starch content, Vc content, and flavonoid glycoside content of sweet potato showed a downward trend. However, the treatment of antibacterial film containing natamycin could slow down the physiological and quality changes of sweet potatoes during conventional storage, and the sweet potatoes still had good processing quality after 120 days of storage.

Effect of fish sperm deoxyribonucleic acid encapsulation on stability, bioaccessibility, redispersibility, and solubilization of curcumin

Curcumin is a member of the polyphenol family with various functionalities. Its application as a functional food, however, is currently limited by the low stability, bioaccessibility, redispersibility, and solubilization. The purpose of the study is to explore the fish sperm deoxyribonucleic acid encapsulation to solve these challenges of curcumin. Curcumin was encapsulated by fish sperm deoxyribonucleic acid using a pH cycle method. The fish sperm deoxyribonucleic acid-to-curcumin mass ratio was inversely proportional to the mean size and positively related to the encapsulation efficiency, the highlight of which is the high loading capacity. Fish sperm deoxyribonucleic acid/curcumin, that amorphous, presented sphere mainly driven by hydrogen bonding and hydrophobic effects. It was stable at pH 2.5–8.0 due to its high surface charges, stable after heating at 80, 115, and 120 °C respectively, and slow the curcumin degradation during storage. NaCl had basically no effect on its stability. It improved bioaccessibility to 58.07 μg/ml due to its structural integrity in the stomach. Furthermore, it exhibited excellent redispersibility and solubilization after freeze-drying. Based on the obtained results, pH cycle fish sperm deoxyribonucleic acid encapsulation is an effective strategy to improve the stability, bioaccessibility, redispersibility, and solubilization of curcumin. This study provides new ideas for the wide application of functional food ingredients assisted by biopolymers.

Chitosan-induced biomodification on demineralized dentin to improve the adhesive interface.

ObjectivesMetalloproteinase-inhibiting agents, such as chitosan, can prevent collagen degradation in demineralized dental substrates, thereby improving the adhesive interface. This study evaluated the bond strength (BS) and chemical and morphological characterization of the adhesive interface after applying chitosan solution to demineralized dentin.Materials and MethodsThe 80 third molars were selected. Forty teeth underwent caries induction using the pH cycling method. The teeth were divided according to the treatment: distilled water (control) and 2.5% chitosan solution. The surfaces were restored using adhesive and composite resins. Half of the specimens in each group were aged, and the other half underwent immediate analyses. The teeth were sectioned and underwent the microtensile bond strength test (µTBS), and chemical and morphological analyses using energy-dispersive spectroscopy and scanning electron microscopy, respectively. Data analysis was performed using 3-way analysis of variance.ResultsFor µTBS, sound dentin was superior to demineralized dentin (p < 0.001), chitosan-treated specimens had higher bond strength than the untreated ones (p < 0.001), and those that underwent immediate analysis had higher values than the aged specimens (p = 0.019). No significant differences were observed in the chemical or morphological compositions.ConclusionsChitosan treatment improved bond strength both immediately and after aging, even in demineralized dentin.

Effect of silver diamine fluoride, potassium iodide, and glutathione on micro-shear bond strength of glass ionomer cement to caries affected dentine.

Silver diamine fluoride (SDF, 38%) is an efficient topical fluoride used to arrest dental caries though it causes black staining of both teeth and restoration. The application of potassium iodide (KI) after SDF reduces the stain, but the color change is only temporary. An alternative method suggested is by mixing glutathione (GSH) with SDF, which preserves the silver ions of SDF within the solution. Hence, the purpose of this in vitro study was to evaluate the microshear bond strength (μSBS) of glass ionomer cement (GIC) to caries affected dentin (CAD) pretreated with SDF/KI/GSH. Thirty dentine slices of 2 mm thickness from human permanent upper premolars were demineralized using pH cycling method to mimic CAD. They were allocated to three groups of 10 each and treated with SDF, SDF-KI (SDF followed by KI), SDF + GSH (SDF mixed with GSH), respectively. Specimens were bonded with GICs. The μSBS was assessed using a universal testing machine and the data obtained were analyzed using one-way ANOVA and Tukey's post hoc test. The μSBS (mean ± standard deviation) values for groups SDF, SDF-KI, and SDF + GSH were 4.81 ± 2.026, 5.78 ± 1.809, 8.18 ± 2.828 megapascal respectively. Group 3 showed significantly better bond strength compared to groups 1 and 2. In group 2, the addition of KI showed better bond strength when compared to group 1, but the difference was not statistically significant. Pretreatment of teeth with GSH along with SDF application showed significantly better bond strength of GIC to CAD compared to SDF and SDF-KI.

Green-step fabrication of gliadin/sodium caseinate nanogels for methotrexate release, cytotoxicity and cell phagocytosis

In this study, a simple and green approach was developed to produce novel nanoparticles (NPs) via the pH-cycle method of gliadin (Gli) NPs and sodium caseinate (CAS). The nanogels could be used as a carrier for the antitumor agent, methotrexate (MTX). The Gli/CAS nanogels (ratio 1:1) exhibited a spherical shape with diameters of approximately 146 nm, polydispersity index of 0.19 and ζ-potential of−23 mV. The loading capacity of MTX in the nanogels reached 27.35%. MTX release from MTX-Gli/CAS nanogels was in a pH-dependent manner, and MTX was released at a quicker rate at pH 5.0 than at pH 7.2. MTT assay indicated that the MTX-Gli/CAS nanogels effectively killed cancer cells in vitro. Cytotoxicity analysis revealed that the Gli/CAS NPs demonstrated good biocompatibility. Meanwhile, the MTX-loaded nanogels could be effectively endocytosed by HepG2 cells and enhance cancer cell apoptosis. Thus, they could be used as a new carrier of anticancer drugs. The high MTX payload and pH-dependent drug release rendered Gli/CAS nanogels as an efficient carrier for MTX. The nanogels possibly have a great potential in the development of a new nanocarrier for anti-cancer drug delivery with a simple spot step.

Nanoencapsulation of apigenin with whey protein isolate: Physicochemical properties, in vitro activity against colorectal cancer cells, and bioavailability

Incorporating lipophilic phytochemicals with anti-cancer activities in functional beverages requires an appropriate nanoencapsulation technology. The present objective was to encapsulate apigenin with whey protein isolate (WPI) utilizing a pH-cycle method and subsequently characterize physicochemical properties, the in vitro anticancer activities against human colorectal HCT-116 and HT-29 cancer cells, and the in vivo bioavailability. Up to 2.0 mg/mL of apigenin was nanoencapsulated with 1.0 mg/mL WPI, with an encapsulation efficiency of up to 98.15% and loading capacity of up to 196.21 mg/g-WPI. Nanodispersions were stable during storage, and apigenin became amorphous after encapsulation. Nanoencapsulation and in vitro digestion did not reduce the anti-proliferative activity of apigenin. Nanoencapsulation of apigenin enhanced the cellular uptake, the pro-apoptotic effects, and the bioavailability in the mice's blood and colon mucosa when comparing to the unencapsulated apigenin. Therefore, the present work may be significant to incorporate lipophilic phytochemicals in functional beverages for disease prevention.

Study on the physicochemical and emulsifying property of proteins extracted from Pleurotus tuoliensis

Food-derived Pickering emulsifiers, particularly proteins, are environmentally friendly and receive considerable attention for the edibility. In this study, Pleurotus tuoliensis protein was extracted at pH 7 (P. tuoliensis albumin, PTA) and pH 9.5 (P. tuoliensis protein isolate, PTPI). PTA and PTPI contained sufficient essential amino acids for humans, but low solubility. Therefore, the pH-cycle method was applied to improve the dispersity. Compared with PTA-NP (PTA nanoparticle), PTPI-NP (PTPI nanoparticle) had smaller particle size, higher surface hydrophobicity and wettability. The advantage in particle size and surface hydrophobicity not only made PTPI-NP show faster adsorption behavior at the oil-water interface at 0.1 mg/mL, but also kept the droplet size of PTPI-NP stabilized emulsions more similar at various oil contents (0.1–0.5). After 30 d storage, the creaming and oiling off behavior of PTA-NP and PTPI-NP stabilized emulsions were unchanged. These results showed that P. tuoliensis protein, especially PTPI, could be used as natural emulsifiers in food industry.

Fabrication and characterization of curcumin-loaded nanoparticles using protein from brewers’ spent grain

Using plant-derived proteins as delivery materials to encapsulate lipophilic bioactive compounds is of great interest. Three protein fractions from brewers’ spent grain (BSG) were extracted by the alkaline or alcoholic method with different procedures, and their potential to encapsulate curcumin was evaluated by preparing composite nanoparticles stabilized by lecithin using a pH-cycle method. The three protein fractions showed considerably different encapsulation properties. The particle size and entrapment efficiency varied from 173 to 306 nm and 21.2% to 83.9%, respectively. Compared with the other two fractions, the one extracted with 55% (v/v) ethanol showed better encapsulation performance. Curcumin after encapsulation exhibited an enhanced UV light and thermal stability while its antioxidant activity maintained. These results suggested that BSG protein could be a promising delivery material to encapsulate the water-insoluble bioactive compounds.

Mung bean protein as a promising biopolymeric vehicle for loading of curcumin: Structural characterization, antioxidant properties, and in vitro release kinetics

Mung bean protein was used to load curcumin by conventional (simple complexation of protein with curcumin) and pH-shifting (based on the pH-dependent solubility of curcumin and un/re-folding of mung bean protein structure) methods. The maximum encapsulation efficiency was obtained as 91.03% for pH-cycle method and 3.60% for conventional method in the curcumin concentration of 1.0 mg/mL (curcumin to protein ratio of 1:20). The formation of hydrophobic interactions and hydrogen bonding between curcumin and mung bean proteins was confirmed by fluorescence spectroscopy and Fourier transform infra-red analysis. The results of XRD and DSC analysis also showed that the crystallinity of curcumin was decreased by loading into the mung bean proteins. The curcumin-mung bean protein complexes showed significantly improved anti-radical activity and reducing power. The curcumin release was studied under simulated gastrointestinal condition and the release mechanism was predicted. The results showed a non-Fickian diffusion or anomalous transport for sample formed by pH-shifting approach and super case II transport relaxation release for sample produced by the conventional method. This study also showed that the complexation of curcumin with mung bean protein by pH-shifting method significantly decreased its sedimentation in a model beverage during 30 days of storage.

An In-Vitro Comparative Evaluation of Pre-treatment With Nano-Silver Fluoride on Inhibiting Secondary Caries at Tooth Restoration Interface.

Introduction and aimDental caries is the global burden worldwide and has a negative effect on the quality of life. Restorative materials in pediatric dentistry have shown satisfactory properties; however, the highest failures are still reported due to the occurrence of secondary caries. The article aims to assess the effectiveness of pre-treatment with nano-silver fluoride (NSF) in inhibiting secondary caries at the tooth restoration interface.Materials and methodsForty tooth specimens were prepared from 20 newly extracted human premolar teeth by sectioning the tooth mesiodistally. Class V cavities were prepared on each specimen at enamel dentin junction. Specimens were randomly distributed into four groups (n=10): 1) glass ionomer cement (GIC) restoration, 2) composite restoration 3) NSF pre-treatment + GIC restoration, 4) NSF pre-treatment + composite restoration. After sterilization, specimens were subjected to artificial caries formation by pH cycling method for 14 days. Specimens were sectioned and mounted to evaluate the demineralization by using the Vickers microhardness test. Outer lesion depth was measured at the tooth restoration interface on digital radiographs. Data was analyzed using Student unpaired t-test, one-way ANOVA, and Tukey honestly significant difference (HSD) post hoc test.ResultsThe mean microhardness value of pre-treated GIC and composite group with NSF was more than the non-treated NSF group, with a significant difference at the enamel, indicating lesser demineralization. Outer lesion depth was lesser in the pre-treated group showing better tooth restoration integrity with a statistically significant difference between the groups.ConclusionPre-treatment with NSF is beneficial in increasing the resistance of GIC and composite resin restoration to secondary caries formation.

Fabrication and characterization of oil-in-water emulsions stabilized by macadamia protein isolate/chitosan hydrochloride composite polymers

To utilize macadamia protein isolate (MPI) from macadamia oil production waste, the emulsifying capacity of macadamia protein isolate (MPI) was investigated. MPI-chitosan hydrochloride (CHC) composite polymer (MCCP) was designed and fabricated using a two-step pH cycling method. The particle size, zeta potential, and stability of MCCPs with different CHC-to-MPI ratios were examined. MCCP fabricated with 20% CHC-to-MPI ratio was selected for emulsion preparation based on its particle size. MCCP stabilized emulsions better than either MPI alone or MPI mixed with CHC. Confocal laser scanning microscopy images proved that MCCP formed a layer on the surface of oil droplets. The surface loading and microstructure of the emulsion suggested that MCCPs stabilize the emulsion through a percolating network structure. The stability of the emulsions increased with increased MCCP concentration and oil fraction. Higher viscosity was also observed with higher MCCP concentration and oil fraction. The stability of the emulsion was then evaluated under different pH values and ionic strengths. Overall, this study successfully fabricated the composite polymers with MPI and CHC, and emulsions stabilized by the composite polymers. It provided a potential application of MPI in novel foods for individuals with vegetarian or Kosher requirements.

Synthesis and characterization of strontium fluor-hydroxyapatite nanoparticles for dental applications

Being biocompatible, bioactive, having low solubility in a wet environment and showing similarities to mineral part of hard tissue in human's body, hydroxyapatite has so many applications in dentistry and related hard tissue concerns. Fluoride ion being found in bone and enamel can be joined to hydroxyapatite and reduce solubility and also hold biocompatibility relatively like hydroxyapatite. Playing main role in bone regeneration, strontium can be used partially or totally to treat biomaterials and increase biocompatibility and bioactivity. In this study hydroxyapatite and strontium hydroxyapatite were synthesized by chemical precipitation of different percentages of strontium by which substitutes calcium. Additionally, Fluoride was incorporated into the apatite structure, using pH-cycling method and producing Strontium- Fluoride hydroxyapatite. Diammonium phosphate, calcium nitrate, strontium nitrate and sodium fluoride were starting materials and solution of sodium hydroxide and nitric acid were used to control pH. Accordingly, synthesized nano-powders characterized by XRD, FTIR, F-selective electrode, inductively coupled plasma spectroscopy and SEM. Subsequently, biological assessment of fluoride's and strontium's influence on the proliferation and differentiation of MG63 cell line was conducted by MTT and ALP tests. Results of XRD and FTIR showed that nano-crystals of HA, SrHA, FHA and F-SrHA were successfully achieved by this method. SEM images revealed that prepared crystalline powders morphology was nano-size and spherical. Biocompatibility also approved by MTT tests. Also, since the process of calcification of hard tissues (bones and teeth) is effected by alkaline phosphatase enzyme (ALP), the influence of both alone and combined fluoride and strontium on cell differentiation was investigated. Consequently, results represent the ability of these elements to enhance remineralization of tooth enamel.

Magnesite formation through temperature and pH cycling as a proxy for lagoon and playa paleoenvironments

Incorporating magnesium into the carbonate structure is difficult at low temperatures. However, Veitsch-type anhydrous magnesites (MgCO3) are found in evaporative environments without the typical hydrothermal conditions associated with magnesite formation. To address the disconnect, this study refined a temperature and pH cycling method to achieve up to 91 mol% MgCO3 of (Mg,Ca)CO3 carbonates without exceeding 40 °C. Individual parameters were tested to develop a novel simultaneous growth and replacement mechanism for magnesite formation. The experimental conditions ideal for magnesite growth match very well with an evaporative/lagoonal/playa geologic setting: small thermal mass for daily temperature swings, algal mass for pH control, and a solution highly concentrated in Mg2+ with high Mg:Ca ratios. Additionally, this study suggests the inclusion of dissolved silica in the system may play an important, but previously unacknowledged, catalytic role in the development of magnesium bearing carbonates. Finally, a high mol% MgCO3 carbonate precursor, such as the one produced in this study, is needed for the diagenetic alteration towards pure magnesite.

Entrapment of β-carotene and zinc in whey protein nanoparticles using the pH cycle method: Evidence of sustained release delivery in intestinal and gastric fluids

Nanoparticles prepared from whey protein isolates were used for the entrapment and sustained delivery of β-carotene and Zn ions. The loaded whey protein nanoparticles were prepared using the pH cycle method at an aggregation pH value of 6 and 22 h of ageing time in the presence of Ca ions. The size, morphology, stability and release profiles of the loaded nanoparticles were evaluated at neutral and acidic conditions. Results suggested whey protein nanoparticles entrapped around 97% of the β-carotene and 33% of the Zn ions in spherical compact structures. The retention of β-carotene in prepared nanoparticles at different time points was significantly higher (P < 0.05) relative to the controls. FT-IR data suggested that physical interactions were primarily involved in the entrapment process. The formulated nanoparticles showed higher cargo release profiles reaching 70% after 24 h in neutral conditions even in the presence of proteolytic enzymes.

Properties of Ternary Biopolymer Nanocomplexes of Zein, Sodium Caseinate, and Propylene Glycol Alginate and Their Functions of Stabilizing High Internal Phase Pickering Emulsions

A pH-cycle method based on preparing an alkaline solution of zein followed by neutralization with an acid can be used to prepare zein nanoparticles. In the present work, partial alkaline hydrolysis of propylene glycol alginate (PGA) to a lower pH was studied to prepare binary zein-PGA nanocomplexes and ternary complexes with additional sodium caseinate (NaCas). 0.5% or more PGA was sufficient to reduce the pH to 7.5 or lower, eliminating the need for titration, and resulted in simultaneous nanocomplex formation. The addition of NaCas into alkaline zein-PGA solution resulted in smaller complexes with all biopolymers, whereas adsorption on binary zein-PGA complexes was observed when NaCas was added into the neutral zein-PGA dispersions. The formation of nanocomplexes involved with hydrophobic and electrostatic attractions and hydrogen bonds and was further affected by the amount of NaCas. The ternary nanocomplexes with equal masses of zein and NaCas had an excellent capacity to prepare gel-like Pickering emulsions with as much as 80% v/v oil with characteristics suitable for texture modification and delivery systems of bioactive compounds in food and consumer products. Therefore, PGA can be used to possibly scale-up the pH-cycle method to produce zein-based nanoparticles with unique functional properties.