Formation and characterisation of high-internal-phase emulsions stabilised by high-pressure homogenised quinoa protein isolate

Fabrication and characterization of acidic high internal phase emulsion gels stabilized solely by wheat gluten for plant-based mayonnaise

Plant-based diets are currently gaining more popularity as a means of reducing the environmental footprint and promoting human health. Herein, plant protein-based acidic high internal phase emulsion gels (HIPE gels) were fabricated via a facile one-pot approach using wheat gluten (WG) solely. Pre-dissolving WG in edible vinegar-water solution was contributed to the fabrication of stable emulsion gels. Factors that affect the structure and performance of plant proteins as HIPE gels stabilizers were investigated. The results indicated that the stable HIPE gels could be formed with a vinegar concentration between 5 % and 20 % and a WG concentration of 1.0 %-7.5 % only. Microscopy images reveal that a collaboration of the soluble protein molecules adsorption and protein aggregate Pickering stabilization at oil-water interface, which was turned to form stable HIPE gels. In addition, the resulted HIPE gels exhibited shear thinning behavior, viscoelastic features, and good thixotropic recovery, which provide a similar perceived texture and sensory property for formulating egg-free mayonnaise. These findings provide a useful approach to construct HIPE-based softs from low-cost wheat gluten for preparing plant-based mayonnaise.

Replacing the animal fat in Bologna sausages using high internal phase emulsion stabilized with lentil protein isolate (Lens culinaris)

High internal phase emulsions (HIPEs) are promising techniques that can replace saturated fat in food without reducing the product's texture, sensory attributes, water-holding capacity, and cooking loss. In the current investigation, 100% pork back fat was replaced by HIPEs formed with lentil protein isolate (LPI) in Bologna sausages. HIPEs were prepared by 25% LPI dispersion (2, 4, 6, and 8%, w/w) and 75% (w/w) soybean oil. HIPEs with higher LPI concentration (4, 6, and 8%, w/w) showed lower droplet size, firmer appearance, and better rheology behavior than 2% LPI. The concentrations LPI (2%, 4%, 6%, and 8%, w/w) led to increased moisture in sausages (FH2, FH4, FH6, and FH8, respectively) compared to the FC. These LPI levels resulted in sausage values for pressed juice similar to the FC and lower energy values than sausages with soybean oil (FO) and pork back fat (FC). Besides, these LPI concentrations (4%, 6%, and 8%, w/w) resulted in a lower oil oxidation level in sausages with HIPEs (FH4, FH6, and FH8, respectively) compared to the control sausage formulation with pork back fat (FC). Bologna sausages elaborated with HIPEs showed emulsion stability values higher than 97%, without significance difference between them. The texture and sensory properties of sausages made with HIPEs were comparable to those made with pork back fat. HIPEs may improve the oxidation stability of the Bologna sausages. These results highlight the effectiveness of HIPEs structured with lentil protein in successfully substituting pork back fat in Bologna sausages with a better nutritional appeal.

Development of Oleogel-in-Water High Internal Phase Emulsions with Improved Physicochemical Stability and Their Application in Mayonnaise

Egg-free mayonnaise is receiving greater attention due to its potential health benefits. This study used whey protein isolate (WPI) as an emulsifier to develop high internal phase emulsions (HIPEs) based on beeswax (BW) oleogels through a simple one-step method. The effects of WPI, NaCl and sucrose on the physicochemical properties of HIPEs were investigated. A novel simulated mayonnaise was then prepared and characterized. Microstructural observation revealed that WPI enveloped oil droplets at the interface, forming a typical O/W emulsion. Increase in WPI content led to significantly enhanced stability of HIPEs, and HIPEs with 5% WPI had the smallest particle size (11.9 ± 0.18 μm). With the increase in NaCl concentration, particle size was increased and ζ-potential was decreased. Higher sucrose content led to reduced particle size and ζ-potential, and slightly improved stability. Rheological tests indicated solid-like properties and shear-thinning behaviors in all HIPEs. The addition of WPI and sucrose improved the structures and viscosity of HIPEs. Simulated mayonnaises (WE-0.3%, WE-1% and YE) were then prepared based on the above HIPEs. Compared to commercial mayonnaises, the mayonnaises based on HIPEs exhibited higher viscoelastic modulus and similar tribological characteristics, indicating the potential application feasibility of oleogel-based HIPEs in mayonnaise. These findings provided insights into the development of novel and healthier mayonnaise alternatives.

Preparation and Properties of Walnut Protein Isolate-Whey Protein Isolate Nanoparticles Stabilizing High Internal Phase Pickering Emulsions

To enhance the functional properties of walnut protein isolate (WalPI), hydrophilic whey protein isolate (WPI) was selected to formulate WalPI-WPI nanoparticles (nano-WalPI-WPI) via a pH cycling technique. These nano-WalPI-WPI particles were subsequently employed to stabilize high internal phase Pickering emulsions (HIPEs). By adjusting the mass ratio of WalPI to WPI from 9:1 to 1:1, the resultant nano-WalPI-WPI exhibited sizes ranging from 70.98 to 124.57 nm, with a polydispersity index of less than 0.326. When the mass ratio of WalPI to WPI was 7:3, there were significant enhancements in various functional properties: the solubility, denaturation peak temperature, emulsifying activity index, and emulsifying stability index increased by 6.09 times, 0.54 °C, 318.94 m2/g, and 552.95 min, respectively, and the surface hydrophobicity decreased by 59.23%, compared with that of WalPI nanoparticles (nano-WalPI), with the best overall performance. The nano-WalPI-WPI were held together by hydrophobic interactions, hydrogen bonding, and electrostatic forces, which preserved the intact primary structure and improved resistance to structural changes during the neutralization process. The HIPEs stabilized by nano-WalPI-WPI exhibited an average droplet size of less than 30 μm, with droplets uniformly dispersed and maintaining an intact spherical structure, demonstrating superior storage stability. All HIPEs exhibited pseudoplastic behavior with good thixotropic properties. This study provides a theoretical foundation for enhancing the functional properties of hydrophobic proteins and introduces a novel approach for constructing emulsion systems stabilized by composite proteins as emulsifiers.

High-pressure microfluidization enhanced the stability of sodium caseinate-EGCG complex-stabilized fish oil emulsion

Improving the emulsion-stabilizing effect of protein by chemical or physical modification has been paid much attention recently. Here, sodium caseinate (CS) was treated by high-pressure-microfluidization (HPM) under 0-100 MPa, and was further complexed with (-)-epigallocatechin-3-gallate (EGCG) to form an excellent emulsifier that stabilized fish oil emulsions. Results showed that HPM treatment (especially 80 MPa) significantly changed the secondary structure of CS, and 80 MPa-PCS-EGCG had the best emulsifying and antioxidant activities. In addition, after HPM treatment and EGCG bonding, CS formed a thicker interface layer on the surface of oil droplets, which could better protect the fish oil from the influence by oxygen, temperature and ion concentration. Moreover, the fish oil emulsion stabilized by PCS-EGCG complex significantly delayed the release of free fatty acids subjected to in vitro digestion. Conclusively, HPM-treated CS-EGCG complex could be a potential emulsifier to improve the stability of fish oil emulsions.

Rheology and stability mechanism of pH-responsive high internal phase emulsion constructed gel by pea protein and hydroxypropyl starch

There is an increasing demand for stable, highly viscoelastic, and printable emulsion gels based on pea protein (PeaP) as a substitute for animal fat. In this article, a simple pH modulation strategy was applied to regulate high internal phase (HIPE) gels prepared from PeaP and hydroxypropyl starch (HPS). The results showed that the interfacial tension of PeaP decreased from 11.9 to 7.1 mN/m at 5% PeaP and from 9.9 to 6.3 mN/m at 10% PeaP with increasing pH from 7 to 11. The incorporation of HPS improved the strength and physical stability of the HIPE gel. HIPE gels showed the best three-dimensional printing ability at pH 11. The main mechanism of HIPE gels at pH 3 was hydrophobic interaction, while electrostatic interaction dominated at pH 7, 9, and 11. This study may provide insights into the development of PeaP-based HIPE gels as a printable fat alternative.

Perilla seed oil high internal phase emulsion improve the gel properties of myofibrillar protein

The effects of perilla seed oil high internal phase emulsions stabilized by pea protein (PP-PSO HIPEs) on the gel properties and conformation of myofibrillar protein (MP) gels were investigated. The results showed that the PP-PSO HIPEs with 4.0 % (w/v) PP formed stable HIPEs with low droplet size and good viscoelasticity. The addition of PP-PSO HIPEs (5.0 % - 15.0 %) could significantly improve the MP gel properties (P < 0.05), while the addition of 10.0 % PP-PSO HIPEs showed the highest gel strength and water holding capacity. Otherwise, the MP gels with 10.0 % PP-PSO HIPEs showed higher proportions of immobile water (PT22) and lower proportion of free water (PT23), and the Raman spectra suggested that the content of α-helix decreased, while the content of β-sheet increased (P < 0.05), thus facilitating the formation of better gel properties. Therefore, the addition of PP-PSO HIPEs is a potential alternative for developing fat-reduced meat products.

Stabilization of oil-in-water high internal phase emulsions with octenyl succinic acid starch and beeswax oleogel

High internal phase emulsions (HIPEs) based on beeswax (BW) oleogels and octenyl succinic acid starch (OSA starch) were prepared by a facile one-step method. Effects of the oleogelation of internal phase on the formation, stability and functionality of the HIPEs were investigated. OSA starch absorbed at the interface allowed high surface charge (|ζ| > 25 mV) of the droplets, and small droplet size (d ≈ 5 m). Microstructural observation suggested that the HIPEs were of O/W type with droplets packed tightly. With the increase in BW content (0-4 %), the particle size (4-7 μm) and ζ-potential (-25 ~ -30 mV) of the HIPEs were first decreased and then increased. Stability analysis revealed that the addition of BW effectively improved emulsion stability against centrifugation, freeze-thawing, changes in pH and ionic strength, and the HIPE with 2 % BW presented the best stability. Rheological tests indicated that the HIPEs with higher content of BW exhibited higher storage modulus, solid-like properties, and shear thinning behaviors. Creep-recovery results implied that the oleogelation enhanced the structure of HIPEs and improved the deformation resistance of the systems. When subjected to light and heat, oleogel-in-water HIPEs showed advantages in protecting β-carotene from degradation, and β-carotene in the HIPEs with 2 % BW had the lowest degradation rate. These findings suggested that gelation of oil phase could improve the stability of HIPEs and the encapsulation capability, which would be meaningful for the development of novel healthy food.

Thermo-induced changes in the structure of lentil protein isolate (Lens culinaris) to stabilize high internal phase emulsions

This study aims to assess the impact of heat treatment on the emulsifying properties of lentil protein isolate (LPI) dispersion to produce high internal phase emulsions (HIPEs). The heat-treated LPI dispersion was characterized by size, turbidity, solubility, zeta potential, free sulfhydryl group, electrophoresis, differential scanning calorimetry, circular dichroism, Fourier transforms infrared spectroscopy and intrinsic fluorescence. HIPEs were produced with 25% of LPI dispersion (2%, w/w) and soybean oil (75%) using a rotor-stator (15,500 rpm/1 min). HIPEs were evaluated for their droplet size, zeta potential, centrifugal stability, microscopy, appearance, Turbiscan stability, and rheology over 60 days (25 °C). Heat treatment reduced the size of LPI, resulting in increased turbidity, solubility, and exposure of hydrophobic groups. HIPEs produced with heat-treated LPI at 70 °C (HIPE70) and 80 °C (HIPE80) for 20 min exhibited lower droplet sizes, increased stability, reduced oil loss, and a homogeneous appearance compared to HIPE produced with untreated LPI (HIPEc). In addition, HIPE70 and HIPE80 displayed resistance to shear stress, higher apparent viscosity, and increased storage modulus than HIPEc. HIPEs produced with heat-treated LPI were stable, suggesting that the treatment was efficient for improving the functional properties of the protein and the possibility of future research focusing on fat substitutes in food applications.

High Internal Phase Emulsions Stabilized by Pea Protein Isolate Modified by Ultrasound Combined with pH-Shifting: Micromorphology, Rheology, and Physical Stability

In this study, the interfacial behavior of high internal phase emulsions (HIPEs), stabilized by ultrasound combined with pH-shifting modified pea protein isolate (MPPI), was investigated, and its emulsification process and stabilization mechanism were discussed. The effects of MPPI concentration on the micromorphology, droplet size, rheology, and stability of HIPEs were investigated. As the MPPI concentration increased, the appearance of HIPEs gradually changed from a relatively fluid state to a plastic solid-like state with detailed texture. There occurred a gradual decrease in droplet size, the cohering of an orderly and tight arrangement, in addition to the formation of a bilayer elastic interface layer. The macro- and microrheological assessments confirmed that the apparent viscosity, storage modulus, elasticity index, and macroscopic viscosity index increased gradually. Furthermore, it was demonstrated that 5 wt% MPPI-stabilized HIPEs had the potential to be used as 3D printing inks. Stability evaluation showed that the TURBISCAN stability index decreased and centrifugal stability increased. The appearance and microstructure remained highly stable after heating at 80 °C for 30 min and storage at 4 ℃ for 90 days. These findings confirm that MPPI improves the rheological behavior and stability of HIPEs by modulating the interfacial adsorption and network structure.

Comparison between Quinoa and Quillaja saponins in the Formation, Stability and Digestibility of Astaxanthin-Canola Oil Emulsions

Saponins from Quillaja saponaria and Chenopodium quinoa were evaluated as natural emulsifiers in the formation of astaxanthin enriched canola oil emulsions. The aim of this study was to define the processing conditions for developing emulsions and to evaluate their physical stability against environmental conditions: pH (2–10), temperature (20–50 °C), ionic strength (0–500 mM NaCl), and storage (35 days at 25 °C), as well as their performance in an in vitro digestion model. The emulsions were characterized, evaluating their mean particle size, polydispersity index (PDI), and zeta potential. Oil-in-water (O/W) emulsions were effectively produced using 1% oil phase and 1% emulsifier (saponins). Emulsions were stable over a wide range of pH values (4–10), but exhibited particle aggregation at lower pH, salt conditions, and high temperatures. The emulsion stability index (ESI) remained above 80% after 35 days of storage. The results of our study suggest that saponins can be an effective alternative to synthetic emulsifiers.

Research Progress of Food-Grade High Internal Phase Pickering Emulsions and Their Application in 3D Printing

High internal phase Pickering emulsion (HIPPE) is a type of emulsion stabilized by solid particles irreversibly adsorbed on an interfacial film, and the volume fraction of the dispersed phase (Φ) is larger than the maximum packing volume fraction (Φ_max). Proteins, polysaccharides, and their composite particles can be used as good particle stabilizers. The contact angle can most intuitively demonstrate the hydrophilicity and hydrophobicity of the particles and also determines the type of emulsions (O/W or W/O type). Particles' three-phase contact angles can be adjusted to about 90° by compounding or modification, which is more conducive to emulsion stability. As a shear thinning pseudoplastic fluid, HIPPE can be extruded smoothly through 3D printer nozzles, and its high storage modulus can support the structure of printed products. There is huge potential for future applications in 3D printing of food. This work reviewed the biomacromolecules that can be used to stabilize food-grade HIPPE, the stabilization mechanism of the emulsions, and the research progress of food 3D printing to provide a reference for the development of advanced food products based on HIPPE.

Impact of incorporations of various polysaccharides on rheological and microstructural characteristics of heat-induced quinoa protein isolate gels

This study aimed to investigate the properties of heat-induced gels (85 °C for 30 min) of quinoa protein isolate (QPI) in the presence and absence of various polysaccharides including guar gum (GG), locust bean gum (LBG), and xanthan gum (XG) at pH 7. For this purpose, samples with three gum concentrations (0.05, 0.1, and 0.2 wt%) at a fixed QPI concentration (10 wt%) and a fixed ionic strength (50 mM NaCl) were studied in terms of their gelation behaviour, small and large deformation rheological properties, water holding capabilities, and microstructural characteristics. Rheological measurements revealed that all polysaccharides incorporation could improve gel strength (complex modulus, G*) and breaking stress, accelerate gel formations, and more stiffer gels were obtained at greater polysaccharide concentrations. The XG exhibited the most gel strengthening effect followed by LBG and GG. Incorporation of 0.2 wt% XG led to a 15 folds increase in G* compared to the control. Confocal laser scanning microscopy observation revealed that the polysaccharides also altered gel microstructures, with the gels containing XG showing the most compact gel structures. The findings of this study may provide useful information for the fabrication of novel QPI based food gel products with improved texture.

Formation by high power ultrasound of aggregated emulsions stabilised with milk protein concentrate (MPC70)

In this work, oil-in-water emulsions stabilised by milk protein concentrate (MPC70) were investigated. The MPC70 concentration was kept constant at 5% (close to the protein content found in skim milk) and the oil volume fraction was varied from 20 to 65%. Sonication was performed at 20 kHz and at a constant power of 14.4 W for a total emulsion volume of 10 mL. Under certain oil concentration (≥35%) and sonication times (≥3s) the emulsion aggregated and formed high-viscosity pseudo plastic materials. However, the viscosity behaviour of the emulsion made with 35% oil reverted to that of a liquid if sonicated for longer times (≥15 s). Confocal laser scanning microscopy showed clearly that the oil droplets are aggregated under the sonication conditions and oil concentrations indicated above. An attempt to explain this behaviour through a simple model based on the bridging of oil droplets by the MPC70 particles and, taking into account the oil droplet and MPC70 particle sizes as well as the oil volume fraction, was made. The model fails to describe in details the aggregation behaviour of these emulsions, likely due to the inhomogeneous protein layer, where both free caseins and casein micelles are adsorbed, and to the packing of the oil droplets at concentrations ≤55%. Nonetheless, this work demonstrates the potential of ultrasound processing for the formation of dairy emulsions with tailored textures.