Rheological fingerprinting and tribological assessment of high internal phase emulsions stabilized by whey protein isolate: Effects of protein concentration and pH

Structure-property relationship of pea protein microgels as fat analogues in Pickering oil-in-water emulsions: effect of salt addition

BACKGROUND

The design of plant-based microgels provides a platform for food ingredients to enhance palatability and functionality. This work aimed to explore the modifying effect of salt addition (KCl) on the structure of pea protein microgel particles (PPI MPs), on the interfacial adsorption and characteristics of formed emulsions as fat analogues.

RESULTS

Salt addition (0-200 mmol L-1) promoted a structural transformation from α-helix to β-sheet, increased the surface hydrophobicity (from 1160.8 to 2280.7), and increased the contact angle (from 56.73° to 96.47°) of PPI MPs. The electrostatic shielding effect led to the tighter packing of MPs with irregular structures and lowered the adsorption energy barrier. Notably, salt-treated PPI MPs could adjust their adsorption state at the interface. The discernible adsorption of PPI MPs with 200 mmol L-1 salt addition that possessed enhanced anti-deformation ability dominated the interfacial stabilization, whereas a relatively rougher stretched continuous interfacial film formed after spreading and deformation of 0 mmol L-1 MPs. A tribological test suggested that emulsion stabilized by MPs at 0 (0.0053) and 80 mmol L-1 (0.0068) had similar friction coefficients to commercial mayonnaise (0.0058), whereas a higher salt concentration (200 mmol L-1) lowered its oral sensation due to the adsorption layer and enhanced the resistance to droplet coalescence during oral processing.

CONCLUSION

Salt could be a modifier to tune the structure of microgels, and further promote the formation and attributes of emulsions. This study would improve application attributes of PPI MPs in the design of realistic fat analogues. © 2024 Society of Chemical Industry.

Effect of ultrasound synergistic pH shift modification treatment on Hericium erinaceus protein structure and its application in 3D printing

This study investigates the effects of ultrasound synergistic pH shift modification on the structural and functional properties of Hericium erinaceus (HE) proteins. The modification resulted in significant changes in the molecular structure of HE proteins, including increased solubility (49.69 % at pH 1.5 and 61.30 % at pH 12.5), enhanced surface hydrophobicity (from 721.00 to 3377.00), and the exposure of free sulfhydryl groups, which rose from 9.3 μmol/g in the control to 19.9 μmol/g at pH 12.5. The modification also led to a reduction in particle size, improving oil-holding capacity and foaming properties, with foaming stability increasing from 10.5 % to 60.3 % at pH 12.5. Furthermore, the emulsification activity was significantly enhanced (187.5 % at pH 12.5). Rheological analysis revealed that ultrasound-modified proteins exhibited improved flow stress and gelation properties, with a shear recovery rate of 65.71 %. In 3D printing applications, the modified HE proteins demonstrated better printability, structural stability, and mechanical integrity, attributed to the enhanced molecular interaction and gelation properties. These findings suggest that ultrasound-assisted pH shift modification effectively alters the structure and functionality of HE proteins, making them suitable for use as a versatile raw material in food applications, particularly in 3D food printing.

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.

Effect of a collagen peptide-fish oil high internal phase emulsion on the printability and gelation of 3D-printed surimi gel inks

The effect of a high internal phase emulsion (HIPE) on three-dimensional-printed surimi gel inks was studied. Increasing the concentration of collagen peptide decreased the particle size of HIPE droplets and improved the viscoelasticity and stability. For example, when the collagen peptide concentration was 5 wt%, the viscoelasticity of the HIPE was high, as indicated by the presence of small and uniform particles, which formed a monolayer in the outer layer of the oil droplets to form stable a HIPE. A HIPE was used as the filling material to fill the surimi gel network, which reduced the porosity of the network. Surimi protein and peptides have dual emulsifying effects on the stabilization of oil. After adding the emulsion, the texture, gel properties and rheological properties of the surimi were reduced, and its printing adaptability was improved. This study provides new ideas for the production of surimi and its application in 3D printing.

A High Andean Hydrocolloid Extracted by Microatomization: Preliminary Optimization in Aqueous Stability

Aqueous suspensions rely on electrostatic interactions among suspended solids, posing a significant challenge to maintaining stability during storage, particularly in the food and pharmaceutical industries, where synthetic stabilizers are commonly employed. However, there is a growing interest in exploring new materials derived from natural and environmentally friendly sources. This study aimed to optimize the stability parameters of a novel Altoandino Nostoc Sphaericum hydrocolloid (NSH) extracted via micro atomization. Suspensions were prepared by varying the pH, gelatinization temperature and NSH dosage using a 23 factorial arrangement, resulting in eight treatments stored under non-controlled conditions for 20 days. Stability was assessed through turbidity, sedimentation (as sediment transmittance), ζ potential, particle size, color and UV-Vis scanning. Optimization of parameters was conducted using empirical equations, with evaluation based on the correlation coefficient (R2), average relative error (ARE) and X2. The suspensions exhibited high stability throughout the storage period, with optimized control parameters identified at a pH of 4.5, gelatinization temperature of 84.55 °C and NSH dosage of 0.08 g/L. Simulated values included turbidity (99.00%), sedimentation (72.34%), ζ potential (-25.64 mV), particle size (300.00 nm) and color index (-2.00), with simulated results aligning with practical application. These findings suggest the potential use of NSH as a substitute for commercial hydrocolloids, albeit with consideration for color limitations that require further investigation.

Formulations and assessments of structure, physical properties, and sensory attributes of soy yogurts: Effect of carboxymethyl cellulose content and degree of substitution

Soy yogurts present challenges, including absence of tender and slipperiness mouthfeel, and poor stability. This study aimed to investigate the impacts of carboxymethyl cellulose (CMC) with degrees of substitution of 0.7 (CMC0.7) and 1.2 (CMC1.2) at concentrations ranging from 0 % to 1.1 % on the stability, microstructure, rheology, tribology, and mouthfeel of soy yogurts. As the CMC concentration increased from 0 % to 0.3 %, soy yogurts displayed a coarser microstructure, decreased stability, and increased gel strength. As the concentration of CMC further increased from 0.5 % to 1.1 %, soy yogurts exhibited trends of a smoother microstructure, increased stability, and softer gel strength. Notably, soy yogurts with CMC0.7 demonstrated a superior water holding capacity (WHC) than soy yogurts with CMC1.2. Tribological measurements indicated that soy yogurts with CMC0.7 at a 0.7 % concentration had the lowest coefficient of friction (COF) value among most sliding speeds, showing a 23 % reduction compared to soy yogurts without CMC at a sliding speed of 10 mm/s. Moreover, sensory evaluation showed that soy yogurts with CMC0.7 at a 0.7 % concentration had the highest total score in mouthfeel evaluation. Therefore, the addition of CMC0.7 within the concentration range of 0.5 % to 1.1 % may produce stable and delicate yogurts.

Composite formation of whey protein isolate and OSA starch for fabricating high internal phase emulsion: A comparative study at different pH and their application in biscuits

The composites formed by whey protein isolate (WPI) and octenyl succinate anhydride (OSA)-modified starch were characterized with a focus on the effect of pH, and their potential in fabricating high internal phase emulsions (HIPEs) as fat substitutes was evaluated. The particles obtained at pH 3.0, 6.0, 7.0, and 8.0 presented a nanosized distribution (122.04 ± 0.84 nm-163.24 ± 4.12 nm) while those prepared at pH 4.0 and 5.0 were remarkably larger. Results from the shielding agent reaction and Fourier transform infrared spectroscopy (FT-IR) showed that the interaction between WPI and OSA starch was mainly hydrophobic at pH 3.0-5.0, while there was a strong electrostatic repulsion at pH 6.0-8.0. A quartz crystal microbalance with dissipation (QCM-D) study showed that remarkably higher ΔD and lower Δf/n were observed at pH 3.0-5.0 after successive deposition of WPI and OSA starch, whereas slight changes were noted for those made at higher pH values. The WPI-OSA starch (W-O) composite-based HIPEs made at pH 3.0 and 6.0-8.0 were physically stable after long-term storage, thermal treatment, or centrifugation. Incorporation of HIPE into the biscuit formula yielded products with a desirable sensory quality.

Effect of simulated saliva on rheological and tribological properties of oleogel-in-water HIPEs during oral processing

HYPOTHESIS

High internal phase emulsions (HIPEs) have great potentials in the food industry to control fat consumption. Textural perception of HIPEs during oral processing is strongly influenced by saliva, which has not been systematically investigated. Therefore, we investigated the roles of saliva in the rheological and tribological properties of HIPEs during oral processing.

EXPERIMENTS

HIPEs (O/W) stabilized by oleogel and a protein were fabricated. Small (SAOS) and large (LAOS) amplitude oscillatory shearing measurements and tribological tests were performed, in combination with structural characterization of the emulsions.

FINDINGS

Particle size and CLSM observation indicated that saliva induced coalescence of droplets by weakening the interface and more EC resulted in faster clustering. SAOS tests revealed that emulsions mixed with saliva had weaker structural strength and lower resistance to deformation. Particularly in large deformation, the HIPEs mixed with saliva presented an acceleration in the droplet-droplet structure breakdown, which led to the pronounced strain-thinning behavior and energy dissipation. Tribological curves further revealed that the corporation of saliva contributed to the release of oil to reduce friction coefficient.

Tunable rheological properties of high internal phase emulsions stabilized by phosphorylated walnut protein/pectin complexes: The effects of pH conditions, mass ratios, and concentrations

The current study reported high internal phase emulsions (HIPEs) stabilized by phosphorylated walnut protein/pectin complexes (PWPI/Pec) and elucidated how their rheological properties were modulated by pH conditions, mass ratios, and concentrations of the complexes. At pH 3.0, the HIPEs stabilized by PWPI/Pec exhibited smaller oil droplet sizes, as well as higher storage modulus (G') and flow stress, in comparison to those stabilized by the complexes formed at pH 4.0-6.0. These observations can be directly linked to pH-dependent changes in particle size, surface hydrophobicity, and wettability of the PWPI/Pec complexes. Rheological analysis revealed that all generated HIPEs displayed weak strain overshoot behavior, irrespective of pH conditions. Notably, HIPEs stabilized by PWPI/Pec at mass ratios of 2:1 and 4:1 showed enlarged oil droplet sizes, lower G' and flow stress but higher flow strain with unaffected loss factor compared to those stabilized by PWPI/Pec 1:1. However, reducing the concentration of PWPI/Pec led to a simultaneous decrease in G', flow stress, and flow strain, along with a significant increase in the loss factor of the HIPEs. Furthermore, the HIPEs formed with 1% PWPI/Pec 1:1 at pH 3.0 demonstrated excellent stability against heat treatment and long-term storage. These results provide valuable insights into the modulation of rheological characteristics of HIPEs and offer guidance for the application of walnut protein-based stabilizers in HIPE systems.

High internal phase emulsions stabilized by alkaline-extracted walnut protein isolates and their application in food 3D printing

Alkaline-extracted walnut protein isolates showed relatively poor solubility and emulsifying properties in many previous studies. However, whether they can be used as potential emulsifiers to stabilize high internal phase emulsions (HIPEs) remains unknown. Herein, walnut protein isolates were prepared by alkaline extraction from walnut kernels with or without pellicles (named PAWPI and AWPI, respectively). PAWPI conjugated with pellicle polyphenols showed improved solubility and higher antioxidant capacity than AWPI. HIPEs were fabricated via a one-step method using AWPI or PAWPI as the sole protein emulsifier. HIPEs (oil fraction of 0.8, with 0.1% β-carotene) could be stabilized by PAWPI at a relatively low concentration of 0.2% (w/v), while at least 1% (w/v) AWPI was required to effectively stabilize HIPEs. HIPEs stabilized by PAWPI had smaller oil droplet sizes than those stabilized by AWPI. Rheological analysis indicated that PAWPI-stabilized HIPEs showed higher viscosity and better viscoelasticity than AWPI-stabilized HIPEs. Large-amplitude oscillation shearing analysis suggested that PAWPI-stabilized HIPEs were stiffer but more brittle than AWPI-stabilized HIPEs. Moreover, both PAWPI- and AWPI-stabilized HIPEs exhibited good storage stability and were relatively stable against heat treatment and ionic strength. PAWPI-stabilized HIPEs showed a higher protective capacity for encapsulated β-carotene than AWPI-stabilized HIPEs. In addition, PAWPI-stabilized HIPEs showed good 3D printability and could be used as a promising edible ink.