Stabilization of Pickering emulsions using starch nanocrystals treated with alkaline solution

Physicochemical properties and antibacterial property of pickering emulsion stabilized by smart Janus nanospheres

In this study, responsive Janus nanospheres were prepared by grafting LMA and DMAEMA monomers on both sides of SiO2 nanospheres using the Pickering emulsion stencil method and RAFT polymerization. The successful synthesis was verified through infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), scanning electron microscopy (SEM) characterizations. Subsequently, Pickering emulsion was formulated using Janus nanospheres as emulsifiers. The particle size of the emulsion droplets was systematically investigated by manipulating factors such as pH, nanosphere dosage, water to oil ratio, and oil phase polarity. Notably, the Pickering emulsion exhibited responsive properties to pH, temperature, and CO2. Furthermore, Janus nanospheres exhibited excellent emulsification property for real oil phases, including canola oil, kerosene, gasoline, and diesel oil. Building upon this, a smart antibacterial Pickering emulsion was developed using Janus nanospheres, and its inhibition rate against E. coli could reach 100% within 4 h, which would be beneficial for its application in the food field.

The Effect of Acid Hydrolysis on the Pickering Emulsifying Capacity of Tartary Buckwheat Flour

The effect of sulfuric acid hydrolysis on the Pickering emulsifying capacity of Tartary buckwheat flour (TBF) rich in starch was evaluated for the first time. The results indicate that the sulfuric acid concentration and hydrolysis time had a significant impact on the Pickering emulsifying capacity of acid-hydrolyzed Tartary buckwheat flour (HTBF). A low sulfuric acid concentration (1-2 mol/L) could reduce the particle size of HTBF, but it also decreased the Pickering emulsifying ability. At a sulfuric acid concentration of 3 mol/L, appropriate treatment time (2 and 3 days) led to particle aggregation but significantly improved wettability, thereby resulting in a rapid enhancement in emulsifying capacity. Under these conditions, the obtained HTBF (HTBF-D2-C3 and HTBF-D3-C3) could stabilize medium-chain triglyceride (MCT)-based Pickering high-internal-phase emulsions (HIPEs) with an oil-phase volume fraction of 80% at the addition amounts (c) of ≥1.0% and ≥1.5%, respectively. Its performance was significantly superior to that of TBF (c ≥ 2.0%). Furthermore, at the same addition amount, the droplet size of HIPEs constructed by HTBF-D3-C3 was smaller than that of HTBF-D2-C3, and its gel strength and microrheological performance were also superior to those of HTBF-D2-C3, which was attributed to the higher wettability of HTBF-D3-C3. The findings of this study can facilitate the in-depth application of Tartary buckwheat and provide references for the development of novel Pickering emulsifiers.

Differences in the Chromogenic Effect of Corn Starch and Potato Starch on Paprika Red Pigment and Structural Characterisation

The present study aims to investigate the chromogenic effect and the interaction between starch-pigment complexes of corn starch (CS) and potato starch (PS) complexed with paprika red pigment. Compared to PS, CS showed 12.5 times higher adsorption capacity for paprika red pigment. Additionally, the a* value of CS-P (26.90 ± 0.23) was significantly higher than that of PS-P (22.45 ± 1.84), resulting in a corn starch-paprika red pigment complex (CS-P) with a more intense red colour. The addition of paprika red pigment significantly decreased the particle size and porosity of CS by 48.14 ± 5.29% and 17.01 ± 3.80%, respectively. Conversely, no significant impact on PS was observed. Additionally, the Fourier transform infrared (FT-IR) spectroscopy results revealed that the starch molecules and paprika red pigment were bound to each other through strong hydrogen bonds. X-diffraction (XRD) results indicated that the starch-paprika red pigment complexes have a V-shaped structure. Furthermore, the relative crystallinity of the complexes between starch and red pepper pigment showed an increasing trend, however, the relative crystallinity of CS increased significantly by 11.77 ± 0.99-49.21 ± 3.67%. Consequently, the CS-P colouring was good.

Waxy maize starch incorporated (-)-epigallocatechin-3-gallate can stabilize emulsion gel and improve antioxidant activity

A food-grade emulsion gel was stabilized using waxy maize starch (WS) incorporated (-)-epigallocatechin-3-gallate (EGCG) at different ratio (from 5 % to 20 %, w/w). The microstructure, rheological behavior, physical stability and antioxidant activity of emulsion gels were investigated using confocal laser scanning microscopy (CLSM), cryo-scanning electron microscopy (cryo-SEM), and rheometer, etc. The results suggested that incorporated EGCG obviously affected the spatial configuration of WS hydrogel. The WS/EGCG hydrogels presented an excellent lipophilic capacity characterized by tightly adhering to linseed oil droplets in the emulsion gels. Moreover, the viscosity, viscoelasticity and physical stability of the emulsion gels stabilized by the WS/EGCG hydrogel matrices were significantly enhanced. The emulsion gel stabilized by the WS/EGCG hydrogel matrix (15 % EGCG) had long-term emulsifying stability because its emulsified phase volume fraction (77.14 %) remained stable for 30 days. Compared with typical natural and synthetic antioxidants in food and pharmaceutical processing, the emulsion gels stabilized by the WS/EGCG hydrogel matrices showed significant stronger DPPH (97.45 %) and ABTS•+ (97.97 %) free radical scavenging activity. These results demonstrate that WS/EGCG hydrogels can not only be used in food-grade matrix materials to stabilize emulsion gels but also improve the antioxidant activity of the emulsion gels.

Starch nanoparticles as a new ice crystal nucleator in Lactobacillus bulgaricus CICC 6097 cryoprotection

This work aimed at studying the cryoprotective effect of starch nanoparticles (SNPs) as ice nucleators on Lactobacillus bulgaricus CICC 6097 and exploring the protective mechanism. SNPs with a diameter of 363 nm were obtained, which possessed special properties to enhance ice nucleation and blunt ice crystals edges, and can be wrapped around the surface of bacteria form a protective barrier, thus maintaining the integrity of cell membranes and improving the survivability of L. bulgaricus CICC 6097 from 36.09% to 75.56%. However, SNCs solution formed ice crystals with obvious spikes during freezing, which was harmful to bacteria survival. Therefore, SNPs addition is a possible strategy for increasing viable cell counts during freezing. To the best of our knowledge, this report is the first to demonstrate the cryoprotective effect of ice nucleator on lactic acid bacteria.

Polysaccharide-based nanoassemblies: From synthesis methodologies and industrial applications to future prospects

Polysaccharides, due to their remarkable features, have gained significant prominence in the sustainable production of nanoparticles (NPs). High market demand and minimal production cost, compared to the chemically synthesised NPs, demonstrate a drive towards polysaccharide-based nanoparticles (PSNPs) benign to environment. Various approaches are used for the synthesis of PSNPs including cross-linking, polyelectrolyte complexation, and self-assembly. PSNPs have the potential to replace a wide diversity of chemical-based agents within the food, health, medical and pharmacy sectors. Nevertheless, the considerable challenges associated with optimising the characteristics of PSNPs to meet specific targeting applications are of utmost importance. This review provides a detailed compilation of recent accomplishments in the synthesis of PSNPs, the fundamental principles and critical factors that govern their rational fabrication, as well as various characterisation techniques. Noteworthy, the multiple use of PSNPs in different disciplines such as biomedical, cosmetics agrochemicals, energy storage, water detoxification, and food-related realms, is accounted in detail. Insights into the toxicological impacts of the PSNPs and their possible risks to human health are addressed, and efforts made in terms of PSNPs development and optimising strategies that allow for enhanced delivery are highlighted. Finally, limitations, potential drawbacks, market diffusion, economic viability and future possibilities for PSNPs to achieve widespread commercial use are also discussed.

Synthesis and characterization of sago starch nanocrystal laurate as a food grade particle emulsifier

Starch nanocrystals (SNCs) are tiny particles that possess unique qualities due to their small size, such as increased crystallinity, thin sheet structure, low permeability, and strong resistance to digestion. Although sago starch nanocrystals (SNCs) are naturally hydrophilic, their properties can be modified through chemical modifications to make them more versatile for various applications. In this study, the esterification process was used to modify SNCs using lauroyl chloride (LC) to enhance their surface properties. Three different ratios of LC to SNC were tested to determine the impact on the modified SNC (mSNC). The chemical changes in the mSNC were analyzed using FTIR and ¹H NMR spectroscopy. ##The results showed that as the amount of LC increased, the degree of substitution (DS) also increased, which reduced the crystallinity of the mSNC and its thermal stability. However, the esterification process also improved the hydrophobicity of the SNC, making it more amphiphilic. The emulsification capabilities of the mSNC were investigated using a Pickering emulsion, and the results showed that the emulsion made from mSNC-1.0 had better stability than the one made from pristine SNC. This study highlights the potential of SNC as a particle emulsifier and demonstrates how esterification can improve its emulsification capabilities.

Starch physical treatment, emulsion formation, stability, and their applications

Pickering emulsions are increasingly preferred over typical surfactant-based emulsions due to several advantages, such as lower emulsifier usage, simplicity, biocompatibility, and safety. These types of emulsions are stabilized using solid particles, which produce a thick layer at the oil-water interface preventing droplets from aggregating. Starch nano-particles (SNPs) have received considerable attention as natural alternatives to synthetic stabilizers due to their unique properties. Physical formulation processes are currently preferred for SNP production since they are environmentally friendly procedures that do not require the use of chemical reagents. This review provides a thorough overview in a critical perspective of the physical processes to produce starch nano-particles used as Pickering emulsion stabilizers, fabricated by a 2-step process. Specifically, the reviewed physical approaches for nano-starch preparation include high hydrostatic pressure, high pressure homogenization, ultrasonication, milling and antisolvent precipitation. All the essential parameters used to evaluate the effectiveness of particles in stabilizing these systems are also presented in detail, including the hydrophobicity, size, and content of starch particles. Finally, this review provides the basis for future research focusing on physical nano-starch production, to ensure the widespread use of these natural stabilizers in the ever-evolving field of food technology.

Synthesis, characterization, DFT studies, and adsorption properties of sulfonated starch synthesized in deep eutectic solvent

In this study, sulfonated starch (SS) was successfully synthesized using sulfamic acid as a sulfonating agent in a deep eutectic solvent (DES). Four-factor and three-level orthogonal experiments were conducted to determine the optimal preparation conditions, which were found to be a molar ratio of starch to urea of 1:20, a reaction temperature of 90 °C, a reaction time of 5 h, and a stirring speed of 200 rpm. The sulfonation reaction mechanism was extensively studied using various techniques, including Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, molecular weight, particle distribution, X-ray photoelectron spectroscopy, scanning electron microscopy, and DFT calculations. The results showed that the sulfonation reaction slightly damaged starch granules, occurred on the surface of starch granules, and on the O6 atoms of the glucose unit. SS exhibited a wide pH range of application (5-10), a fast adsorption rate (400 s to reach adsorption equilibrium), and a high adsorption capacity (118.3 mg/g) under optimal conditions. The adsorption process of SS for methylene blue followed the pseudo-first-order kinetic model and was consistent with the Langmuir model, which was endothermic and spontaneous. The adsorption process was attributed to hydrogen bonding and electrostatic interactions.

Chestnut Starch Nanocrystal Combined with Macadamia Protein Isolate to Stabilize Pickering Emulsions with Different Oils

This study investigated the formation and molecular interaction mechanism of chestnut starch nanocrystal (SNC)/macadamia protein isolate (MPI) complexes and their application in edible oil-in-water Pickering emulsion (PE). SNC/MPI complexes were characterized by scanning electron microscopy and particle size analyzer. The PEs stabilized by SNC/MPI complexes were characterized by confocal laser scanning microscopy and rheological measurement. The results showed that hydrogen bonds between the two particles significantly affected the secondary structure and assembly of SNC/MPI complexes at the oil/water interface. The optimal mass ratio of SNC to MPI in the complexes with the best stability was determined as 20:1. The formation of edible oil-in-water PEs stabilized by SNC/MPI complexes significantly improved the oxidative and storage stability of different edible oils (olive oil, walnut oil, edible tea oil, and macadamia oil). These different edible oil-in-water PEs stabilized by SNC/MPI could be used as effective carriers of quercetin with their loading rates higher than 93%.

Polysaccharide-Based Nanoparticles as Pickering Emulsifiers in Emulsion Formulations and Heterogenous Polymerization Systems

Bio-based Pickering emulsifiers are a nontoxic alternative to surfactants in emulsion formulations and heterogenous polymerizations. Recent demand for biocompatible and sustainable formulations has accelerated academic interest in polysaccharide-based nanoparticles as Pickering emulsifiers. Despite the environmental advantages, the inherent hydrophilicity of polysaccharides and their nanoparticles limits efficiency and application range. Modification of the polysaccharide surface is often required in the development of ultrastable, functional, and water-in-oil (W/O) systems. Complex surface modification calls into question the sustainability of polysaccharide-based nanoparticles and is identified as a significant barrier to commercialization. This review summarizes the use of nanocelluloses, -starches, and -chitins as Pickering emulsifiers, highlights trends and best practices in surface modification, and provides recommendations to expedite commercialization.

Recent Developments in the Formulation and Use of Polymers and Particles of Plant-based Origin for Emulsion Stabilizations

The main scope of this Review was the recent progress in the use of plant-based polymers and particles for the stabilization of Pickering and non-Pickering emulsion systems. Due to their availability and promising performance, it was discussed how the source, modification, and formulation of cellulose, starch, protein, and lignin-based polymers and particles would impact their emulsion stabilization. Special attention was given toward the material synthesis in two forms of polymeric surfactants and particles and the corresponding formulated emulsions. Also, the effects of particle size, degree of aggregation, wettability, degree of substitution, and electrical charge in stabilizing oil/water systems and micro- and macro-structures of oil droplets were discussed. The wide range of applications using such plant-based stabilizers in different technologies as well as their challenge and future perspectives were described.

Eco-friendly and superhydrophobic nano-starch based coatings for self-cleaning application and oil-water separation

High-performance nano-based superhydrophobic coatings have attracted tremendous attention in a wide range of sectors. As a biodegradable and low-cost natural polymer, starch nanoparticles (SNPs) exhibit significant potential for use in many advanced materials. However, nano-starch based superhydrophobic coatings have not yet been reported. Herein, SNPs/polydimethylsiloxane composites were applied to fabricate these coatings using an environmentally friendly approach. The coating exhibited superhydrophobic (water contact angle >152.0° and sliding angle <9.0°) and self-cleaning properties owing to the hierarchical micro and nanostructures formed by coralloid SNP aggregates combined with the low surface energy of the PDMS covering. Meanwhile, the strong adhesion of PDMS and chemical bonding of SNPs with PDMS endowed the coatings with mechanical and chemical robustness. The excellent oil-water separation abilities of the coating were also comprehensively confirmed. This coating shows the potential application in the development of eco-friendly self-cleaning materials and oily wastewater treatment.

Nanostarch: Preparation, Modification, and Application in Pickering Emulsions

Nanostarch, as a food-grade Pickering emulsion stabilizer, has attracted wide attention owing to its biodegradability, nontoxicity, small size, and large specific surface area. In this review, the preparation, modification, and application of Pickering emulsions incorporating nanostarch are described. At present, methods for nanostarch preparation mainly include acid hydrolysis, acid hydrolysis combined with other treatments, nanoprecipitation, ultrasonication, ball milling, and cross-linking. Nanostarch is a promising Pickering emulsion stabilizer, and its emulsifying ability of nanostarch is significantly improved by hydrophobic modification. The hydrophobicity, charge, size, and content of nanostarch affect the emulsion stability. Future developments in this area of research include the efficient and environmentally friendly preparation of nanostarch as well as the control of its hydrophobicity via modification. Future studies should focus on the digestibility and storage stability of Pickering emulsions stabilized by nanostarch under different conditions.

Oil-in-water Pickering emulsion stabilization with oppositely charged polysaccharide particles: chitin nanocrystals/fucoidan complexes

BACKGROUND

Chitin nanocrystals (ChN) are insoluble particles that can be used as stabilizers for Pickering emulsions. Their unique cationic properties and antibacterial activity have generated considerable interest among researchers. However, ChN have remained largely underexplored. Furthermore, the droplets of the emulsions stabilized by ChN are as large as 10-100 μm, and their physical stability requires further improvement. Some studies have shown that the spontaneous reaction of oppositely charged particles can effectively stabilize the emulsions. Positively charged ChN and negatively charged fucoidan (F) were therefore compounded to stabilize Pickering emulsions, and the stability of these emulsions was analyzed qualitatively.

RESULTS

The results showed that the composite particles comprising two polysaccharides in a mass ratio of 1:1 and at a pH of 2 (ChN₁ -F₁ -pH 2) possessed the lowest sulfate content (20.1%) and almost zero potential (-3 mV), indicating a high degree of neutralization of the positively charged amino group in ChN and the negatively charged sulfate group in F. Meanwhile, ChN₁ -F₁ -pH 2 displayed a dense network structure that improved the dispersibility and wettability (contact angle = 9.3°). Fourier transform infrared spectroscopy results confirmed that ChN and F were effectively combined through electrostatic interaction or neutralization to produce a polyelectrolyte complex. Furthermore, the particle size of the Pickering emulsion stabilized by ChN-F was significantly reduced, and the maximum size did not exceed 10 μm; the physical and storage stability also improved. The ChN₁ -F₁ -pH 2 emulsion presented excellent storage stability; in particular, the emulsions stabilized by ChN₁ -F₁ -pH 5 and ChN₁ -F₁ -pH 6 exhibited excellent flocculation stabilities.

CONCLUSION

The size of the emulsion droplets stabilized by the oppositely charged polysaccharide particles (ChN-F complexes) reduced significantly. Furthermore, by changing the mass ratio and pH, the microstructure and binding degree of the complexes can be adjusted, thereby promoting their adsorption on the oil-water interface and improving the stability of the Pickering emulsion. © 2020 Society of Chemical Industry.

Formation and structural evolution of starch nanocrystals from waxy maize starch and waxy potato starch

The formation and structural evolution of starch nanocrystals from waxy maize starch (WMS) and waxy potato starch (WPS) by acid hydrolysis were studied. The relative crystallinity, the short-range molecular order, and the double-helix content of WMS and WPS increased significantly during the initial stage of acid hydrolysis, indicating that acid preferentially eroded the amorphous regions of starch granules. With time, there was increased destruction of lamellar structures, causing the granules to completely disintegrate to form nanocrystals. WMS and WPS displayed different hydrolysis mechanisms. WPS was more susceptible to acid hydrolysis than WMS, and WMS exhibited an endo-corrosion pattern and WPS showed an exo-corrosion pattern. WMS nanocrystals had a parallelepiped shape, and WPS nanocrystals were round. This difference in shape is likely due to the different packing configuration of double helices in native starches.

An Efficient Approach to Prepare Water-Redispersible Starch Nanocrystals from Waxy Potato Starch

Starch nanocrystals (SNCs) are a biodegradable polymer which has been widely studied and used in many fields. In this study, we have developed an efficient procedure for the preparation of SNCs. First, sodium hexametaphosphate (SHMP) and vinyl acetate (VAC) were used to modify waxy potato starch (WPS). Then, the modified starches were hydrolyzed with sulfuric acid to prepare SNCs. Results showed that SNCs prepared with modified starch had higher zeta potentials and better dispersion properties than the original starch. After modification, WPS still maintained its semi-crystalline structure, but the surface became rougher. SHMP-modified WPS showed a decrease in viscosity peak and an increase in gelatinization temperature. VAC-modified WPS showed increased swelling power. Additionally, SNCs prepared with VAC-modified WPS had better water redispersibility and dispersion stability than those from SHMP-modified starch—which will have broader application prospects in the field of safe and biodegradable food packaging.

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.

Food-Grade Pickering Emulsions: Preparation, Stabilization and Applications

In recent years, Pickering emulsions have emerged as a new method and have attracted much attention in the fields of food sciences. Unlike conventional emulsions, Pickering emulsions are stabilized by solid particles, which can irreversibly adsorb on the oil-water interface to form a dense film to prevent the aggregation of droplets. The research and development of food-grade solid particles are increasingly favored by scientific researchers. Compared with conventional emulsions, Pickering emulsions have many advantages, such as fewer using amounts of emulsifiers, biocompatibility and higher safety, which may offer feasibility to have broad application prospects in a wide range of fields. In this article, we review the preparation methods, stabilization mechanism, degradation of Pickering emulsions. We also summarize its applications in food sciences in recent years and discuss its future prospects and challenges in this work.