Whey protein isolate—low methoxyl pectin coacervates as a high internal phase Pickering emulsion stabilizer

Efficacy of almond gum for coacervation with whey protein isolate- optimization, functionality and characterization: A comparison with high-methoxyl pectin

Complex coacervates of whey protein isolate (WPI) and two polysaccharides (almond gum (AG) and high methoxyl pectin (HMP)) under the different pHs (2.5-6.0) and biopolymer mass ratios (1:1-6:1) were prepared to achieve the maximum coacervate yield (CY). The optimum pH and mixing ratio to obtain the maximum CY of WPI-AG (75.93 %) and WPI-HMP (53.0 %) coacervates were 4.3 and 2:1, and 3.5 and 3:1, respectively. Although higher serum layers in emulsions stabilized by WPI-AG/HMP coacervates were detected at the 90 °C, remarkable heat stability under processing temperatures was obtained in ex-situ emulsions with both complex coacervates. Significantly more cold-storage and ionic stabilities were observed for emulsions formulated with WPI-AG than WPI-HMP. Peak shifts in FTIR spectra in the WPI-AG coacervate compared to the individual WPI and AG biopolymers revealed strong electrostatic interactions between these biopolymers. The absence of crystalline peaks for AG and HMP in X-ray diffraction (XRD) spectra confirmed the complexation of AG and HMP with WPI. Thermogravimetric and microstructural analyses showed that porous, loose mesh-like WPI-AG coacervates had superior thermal stability and structural integrity compared to WPI-HMP coacervates and individual biopolymers, which evidenced a more gradual weight loss pattern. WPI-AG coacervates would be promising for efficient emulsion-based delivery systems.

The present state and future outlook of pectin-based nanoparticles in the stabilization of Pickering emulsions

The stabilization of Pickering emulsions using micro/nanoparticles has gained significant attention due to their wide range of potential applications in industries such as cosmetics, food, catalysis, tissue engineering, and drug delivery. There is a growing demand for the development of environmentally friendly micro/nanoparticles to create stable Pickering emulsions. Naturally occurring polysaccharides like pectin offer promising options as they can assemble at oil/water interfaces. This polysaccharide is considered a green candidate because of its biodegradability and renewable nature. The physicochemical properties of micro/nanoparticles, influenced by fabrication methods and post-modification techniques, greatly impact the characteristics and applications of the resulting Pickering emulsions. This review focuses on recent advancements in Pickering emulsions stabilized by pectin-based micro/nanoparticles, as well as the application of functional materials in delivery systems, bio-based films and 3D printing using these emulsions as templates. The effects of micro/nanoparticle properties on the characteristics of Pickering emulsions and their applications are discussed. Additionally, the obstacles that currently hinder the practical implementation of pectin-based micro/nanoparticles and Pickering emulsions, along with future prospects for their development, are addressed.

Novel Pickering emulsion stabilized by glycosylated whey protein isolate: Characterization, stability, and curcumin bioaccessibility

Pickering emulsions prepared from protein-polysaccharide complexes have attracted increasing attention. In this study, whey protein isolates (WPI) were modified with oligochitosan using transglutaminase (TGase)-type to fabricate Pickering emulsions, and loaded with curcumin. The curcumin/protein ratio of 1:25 and oil phase fraction (φ = 17 %) are the most optimal condition for emulsions stabilization, and particle size of glycosylated WPI emulsion was 31.70 μm. Glycosylated WPI emulsion had the highest encapsulation efficiency (96.64 %) of curcumin. Microstructure analysis showed that glycosylated WPI had small droplets covered by dense interface layers. The modified WPI emulsions exhibited optimal emulsifying properties and emulsion stability, which effectively inhibited the premature water-oil stratification in emulsion. In vitro digestion results showed that WPI-oligochitosan complexes enhanced curcumin bioaccessibility (40.34 %). The antioxidant activity of glycosylated WPI emulsions was significantly increased. The results of this study provide helpful references for applying glycosylated WPI-stabilized Pickering emulsions, which can be used as transport carriers of curcumin.

Smart antimicrobial system based on enzyme-responsive high methoxyl pectin-whey protein isolate nanocomplex for fresh-cut apple preservation

The increase in pectin methylesterase (PME) activity on fresh-cut apple surface can smartly trigger the controlled release of bactericidal agents encapsulated within intelligent responsive Pickering emulsions. In this study, we developed a PME-responsive nanocomplex (W-H-II) to stabilize Pickering emulsion containing thyme essential oil (TEO), preserving fresh-cut apples. W-H-II, formed by heat-induced whey protein isolate (WPI) and high methoxyl pectin (HMP) (pH 4.5, 85 °C, 15 min, WPI:HMP ratio 1:2), exhibited good pH stability due to the stabilizing effects of hydrophobic, hydrogen bonding, and electrostatic interactions. The presence of PME triggered the demethylation of HMP within W-H-II, conferring PME response characteristics. Subsequently, a bacteriostasis experiment with pectinase-producing Bacillus subtilis provided evidence of PME-triggered TEO release from W-H-II-stabilized Pickering emulsion. Furthermore, microscopy techniques were employed to verify the demulsification behavior of the emulsion when PME activity ranged from 0.25 to 2.50 U mL-1. Finally, the PME-responsive TEO Pickering emulsion effectively preserved fresh-cut apples. Stored for 6 days at 5 °C and 10 °C, as the PME activity on the apple surface increased, the decay rate of the coated group was 0 %, with a total colony count below 3.0 log CFU g-1. This study introduces a novel intelligent preservation strategy for storing fresh-cut apples.

Segregative phase separation of gelatin and tragacanth gum solution and Mickering stabilization of their water-in-water emulsion with microgel particles prepared by complex coacervation

This study aimed to investigate the segregative interaction of gelatin (G) and tragacanth gum (TG) and the stabilization of their water-in-water (W/W) emulsion by G-TG complex coacervate particles. Segregation was studied at different pHs, ionic strengths and biopolymer concentrations. Results showed that incompatibility was affected by increasing the biopolymer concentrations. So, three reigns were demonstrated in the phase diagram of the salt-free samples. NaCl significantly changed the phase behavior via enhancement of self-association of polysaccharide and changing solvent quality due to the charge screening effect of ions. The W/W emulsion prepared from these two biopolymers and stabilized with G-TG complex particles was stable for at least one week. The microgel particles improved emulsion stability by adsorption to the interface and creating a physical barrier. A fibrous and network-like structure of the G-TG microgels was observed by scanning electron microscopy images suggesting the Mickering emulsion stabilization mechanism. It was confirmed that the bridging flocculation between the microgel polymers led to phase separation after the stability period. Biopolymer incompatibility investigation is a useful tool to obtain beneficial knowledge for preparation new food formulation, especially no contain oil emulsions for low- calorie diets.

Protein-Based High Internal Phase Pickering Emulsions: A Review of Their Fabrication, Composition and Future Perspectives in the Food Industry

Protein-based high internal phase Pickering emulsions (HIPEs) are emulsions using protein particles as a stabilizer in which the volume fraction of the dispersed phase exceeds 74%. Stabilizers are irreversibly adsorbed at the interface of the oil phase and water phase to maintain the droplet structure. Protein-based HIPEs have shown great potential for a variety of fields, including foods, due to the wide range of materials, simple preparation, and good biocompatibility. This review introduces the preparation routes of protein-based HIPEs and summarizes and classifies the preparation methods of protein stabilizers according to their formation mechanism. Further outlined are the types and properties of protein stabilizers used in the present studies, the composition of the oil phase, the encapsulating substances, and the properties of the constituted protein-based HIPEs. Finally, future development of protein-based HIPEs was explored, such as the development of protein-based stabilizers, the improvement of emulsification technology, and the quality control of stabilizers and protein-based HIPEs.

Emulsion Gels Formed by Electrostatic Interaction of Gelatine and Modified Corn Starch via pH Adjustments: Potential Fat Replacers in Meat Products

The application of emulsion gels as animal fat replacers in meat products has been focused on due to their unique physicochemical properties. The electrostatic interaction between proteins and polysaccharides could influence emulsion gel stability. This study aimed to evaluate the physicochemical properties of emulsion gels using starch and gelatin as stabilizers, promoting electrostatic attraction via pH adjustment. Three systems were studied: emulsion gel A (EGA) and emulsion gel B (EGB), which have positive and negative net charges that promote electrostatic interaction, and emulsion gel C (EGC), whose charge equals the isoelectric point and does not promote electrostatic interactions. There was no significant difference in proximate analysis, syneresis and thermal stability between samples, while EGA and EGB had higher pH values than EGC. The lightness (L*) value was higher in EGA and EGB, while the yellowness (b*) value was the highest in EGC. The smaller particle size (p < 0.05) in EGA and EGB also resulted in higher gel strength, hardness and oxidative stability. Microscopic images showed that EGA and EGB had a more uniform matrix structure. X-ray diffraction demonstrated that all the emulsion gels crystallized in a β′ polymorph form. Differential scanning calorimetry (DSC) revealed a single characteristic peak was detected in both the melting and cooling curves for all the emulsion gels, which indicated that the fat exists in a single polymorphic state. All emulsion gels presented a high amount of unsaturated fatty acids and reduced saturated fat by up to 11%. Therefore, the emulsion gels (EGA and EGB) that favored the electrostatic protein-polysaccharide interactions are suitable to be used as fat replacers in meat products.

Naturally occurring protein/polysaccharide hybrid nanoparticles for stabilizing oil-in-water Pickering emulsions and the formation mechanism

In this study, we reported for the first time that the natural protein/polysaccharide hybrid nanoparticles (PPH NPs) with a diameter of ∼ 129 nm, originating from Lactobacillus plantarum fermented cheese whey, could act as green-based NPs for stabilizing Pickering emulsions. Characterizations of PPH NPs showed that the negative-charged PPH NPs were composed of ∼ 37.7% total protein and ∼ 7.3% polysaccharide bearing several functional groups, such as -OH, -NH, -COOH, etc.; and displayed excellent emulsifying capacity in preparing oil-in-water Pickering emulsions. The obtained emulsions exhibited gel-like behavior with excellent stability against the variation of pH, ionic strength, and temperature. Confocal observations showed that PPH NPs effectively adsorbed and anchored at the oil-water interface, thus creating the steric hindrance to inhibit droplet coalescence. This research is of importance in developing novel and biocompatible Pickering stabilizers with outstanding performance, as well as enable a versatile design of stable Pickering emulsions suitable for food industries.

Preparation of powdered oil by spray drying the Pickering emulsion stabilized by ovalbumin - Gum Arabic polyelectrolyte complex

The suitability of the perilla seed oil Pickering emulsion stabilized by the ovalbumin (OVA) - gum Arabic (GA) polyelectrolyte complex for spray drying was investigated and the resultant powder was characterized. The OVA - GA complex conferred enhanced stability to the emulsion than OVA, GA, and their mixture. The viscosity of the Pickering emulsion was highly sensitive to stabilizer concentration and that fabricated by 2% OVA - GA complex showed acceptable viscosity and powder yield. The Pickering emulsion was more effective in preventing oil leakage during spray drying than the OVA-stabilized emulsion and the resultant powder possessed an oil content of up to 77.7%. Besides, the spray-dried Pickering emulsion powder showed greater rehydration and better flowability than that of the OVA-stabilized emulsion powder. Hence, the Pickering emulsion stabilized by the OVA - GA polyelectrolyte complex is promising as a novel feed for the production of oil powders by spray drying.

Formation, Structure and stability of high internal phase Pickering emulsions stabilized by BSPI-C3G covalent complexes

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The HIIPPE was stabilized by BSPI-C3G covalent particles.

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HIPPEs stabilized with 74% (v/v) oil phase fraction have a stable gel-like state.

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HIPPEs stability was the best with the 3 % (w/v) BSPI-C3G particle concentration.

Food-grade high internal phase Pickering emulsions (HIPPEs) are stabilized by protein-based particles, which have attracted extensive attention due to their good gel-like structure. The black soybean isolate protein/cyanidin-3-O-glucoside (BSPI-C3G) covalent particles were used as a particulate emulsifier to form stable HIPPEs with oil phase fractions (74 % v/v) and low particle concentrations (0.5 %–3 % w/v) The particle size distribution and microstructure demonstrated that the BSPI-C3G covalent particles acted as an interfacial layer and surrounded the oil droplets. As the concentration of BSPI-C3G particles increased from 0.5 % to 3 %, the droplet size, elasticity, antioxidant capacity of the heated or stored HIPPEs more stable. So, the HIPPEs had the best stability with the BSPI-C3G particle at 3 % (w/v) concentration. These findings may extend the application of BSPI and C3G in foods and provide the guidelines for the rational design of food-grade HIPPEs stabilized by protein/anthocyanin complexes.

Construction of high internal phase Pickering emulsions stabilized by bamboo fungus protein gels with the effect of pH

This study is a contribution to explore natural protein sources as high internal phase Pickering emulsions (HIPPEs) stabilizers and to achieve full utilization of biological resources. Bamboo fungus proteins were obtained by alkaline extraction and subsequently transformed into protein gels by enzymatic cross-linking method. 1% (w/v) of bamboo protein gel particles (BGPs) were used to stabilize high HIPPEs (φ = 80%) using a one-step homogenization method. At pH 3, 9 and 11, BGPs could produce stable, gel-like oil/water HIPPEs with excellent storage stability. In contrast, at pH 5 and 7, stable HIPPEs could not be formed, which might be attributed to the variation of contact angle and electrostatic repulsion of BGPs. Structure analysis indicated that HIPPEs with gel-like structures were mainly stabilized by physical barriers and electrostatic repulsion. The present study is expected to provide new insight on comprehensive utilization of fungi sources.

Recent progress in Pickering emulsions stabilised by bioderived particles

In recent years, the demand for non-surfactant based Pickering emulsions in many industrial applications has grown significantly because of the option to select biodegradable and sustainable materials with low toxicity as emulsion stabilisers. Usually, emulsions are a dispersion system, where synthetic surfactants or macromolecules stabilise two immiscible phases (typically water and oil phases) to prevent coalescence. However, synthetic surfactants are not always a suitable choice in some applications, especially in pharmaceuticals, food and cosmetics, due to toxicity and lack of compatibility and biodegradability. Therefore, this review reports recent literature (2018-2021) on the use of comparatively safer biodegradable polysaccharide particles, proteins, lipids and combinations of these species in various Pickering emulsion formulations. Also, an overview of the various tuneable factors associated with the functionalisation or surface modification of these solid particles, that govern the stability of the Pickering emulsions is provided.

Novel Fabrication of Zein-Soluble Soybean Polysaccharide Nanocomposites Induced by Multifrequency Ultrasound, and Their Roles on Microstructure, Rheological Properties and Stability of Pickering Emulsions

In this work, soluble soybean polysaccharides (SSPS) were employed together with multifrequency ultrasound to fabricate zein nanocomposites which were conducive to enhancing the stability of high internal phase emulsions (HIPEs). Compared with non-ultrasonic treated zein colloidal particle samples (132.23 ± 0.85 nm), the zein nanoparticles samples induced by dual-frequency ultrasound exhibited a smaller particle size (114.54 ± 0.23 nm). Furthermore, the particle size of the zein composite nanoparticles (256.5 ± 4.81) remarkably increased with SPSS coating, consequently leading to larger fluorescence intensity together with lower zeta-potential (-21.90 ± 0.46 mv) and surface hydrophobicity (4992.15 ± 37.28). Meanwhile, zein-SSPS composite nanoparticles induced by DFU showed remarkably enhanced thermal stability. Fourier transform infrared (FTIR) spectroscopy and Circular dichroism (CD) spectroscopy were also used to characterize zein-SSPS composite nanoparticles. The results confirmed that DFU combined with SSPS treatment significantly increased β-sheets (from 12.60% ± 0.25 b to 21.53% ± 0.37 c) and reduced α-helix content (34.83% ± 0.71 b to 23.86% ± 0.66 a) remarkably. Notably, HIPEs prepared from zein-SSPS nanocomposites induced by dual-frequency simultaneous ultrasound (DFU) at 40/60 kHz showed better storage stability. HIPEs stabilized by DFU induced zein-SSPS nanoparticles exhibited higher storage modulus (G') and loss modulus (G″), leading to lower fluidity, together with better stability contributing to the water-binding capacity and three-dimensional (3D) network structure of the HIPEs emulsion. The findings of this study indicate that this method can be utilized and integrated to further extend the application of zein and SSPS and explore HIPEs.

Effect of pH and Pea Protein: Xanthan Gum Ratio on Emulsions with High Oil Content and High Internal Phase Emulsion Formation

Electrostatic interaction between protein and polysaccharides could influence structured liquid oil stability when emulsification is used for this purpose. The objective of this work was to structure sunflower oil forming emulsions and High Internal Phase Emulsions (HIPEs) using pea protein (PP) and xanthan gum (XG) as a stabilizer, promoting or not their electrostatic attraction. The 60/40 oil-in-water emulsions were made varying the pH (3, 5, and 7) and PP:XG ratio (4:1, 8:1, and 12:1). To form HIPEs, samples were oven-dried and homogenized. The higher the pH, the smaller the droplet size (Emulsions: 15.60-43.96 µm and HIPEs: 8.74-20.38 µm) and the oil release after 9 weeks of storage at 5 °C and 25 °C (oil loss < 8%). All systems had weak gel-like behavior, however, the values of viscoelastic properties (G' and G″) increased with the increment of PP:XG ratio. Stable emulsions were obtained at pHs 5 and 7 in all PP:XG ratios, and at pH 3 in the ratio 4:1. Stable HIPEs were obtained at pH 7 in the ratios PP:XG 4:1, 8:1, and 12:1, and at pH 5 at PP:XG ratio 4:1. All these systems presented different characteristics that could be exploited for their application as fat substitutes.