Lissajous Plots Research Articles

Emulsions co-stabilized by Polygonatum sibiricum saponin and soy protein isolate: Physical stability, interaction mechanism, interface behavior

This study investigates the interaction mechanism between Polygonatum sibiricum saponin (PSS) and soy protein isolate (SPI) to enhance the stability of oil-in-water emulsions, laying the foundation for an efficient PSS delivery system. Initially, we evaluated the stability of oil-in-water emulsions with various PSS concentrations (0.1%, 0.2%, 0.3%, 0.5%, and 1% w/w). Results indicated that PSS enhances emulsion stability by increasing absolute zeta potential, reducing average particle size, and improving resistance to external factors. Notably, concentrations of 0.3%, 0.5%, and 1% (w/w) PSS show significant improvements in emulsion stability (p < 0.05). Subsequently, we elucidated the mechanism by which PSS enhances stability. Our findings reveal that PSS interacts with SPI, inducing structural modifications in SPI and expanding its hydrophobic regions. Additionally, PSS forms SPI-PSS complexes through hydrogen bonding with aromatic amino acid residues in SPI, thereby reducing interfacial tension and maintaining stable viscoelasticity. Comparative analysis of Lissajous plots identifies the optimal PSS to SPI ratio as 0.3% (w/w) each, resulting in a resilient interface film formed by numerous SPI-PSS complexes capable of withstanding compression or extension. Overall, our study underscores the efficacy of PSS in navigating the emulsion system and collaborating with SPI to stabilize emulsions.

Mechanism of sodium alginate synergistically improving foaming properties of pea protein isolate: Air/water interface microstructure and rheological properties

The synergistic effect of polysaccharides plays a crucial role in regulating the foaming properties of protein based aerated foods. In this study, the synergistic improvement mechanism of pea protein isolate (PPI)-sodium alginate (SA) composite on the foaming performance was determined through multi-component interaction, air/water interface adsorption behavior and foam properties. The results of interactions between PPI and SA indicated that SA and PPI could form smaller and more stable soluble composite through hydrogen bonding, hydrophobic interactions, and electrostatic interactions. The α-helix content of PPI significantly decreased, and PPI exhibited a more flexible secondary structure. In depth research on the air/water interfacial behavior and interfacial microstructure through adsorption kinetics, surface dilatational rheology and Lissajous plots indicated that the PPI-SA composite could accelerate the adsorption process, constructing a highly viscoelastic interface mainly based on elasticity. The results of foam properties showed soluble PPI-SA composite could prepare smaller and more dense foam with thicker and smoother interface film, which was beneficial to the foam stability. The results of small amplitude oscillatory shear and large amplitude oscillatory shear suggested that foam prepared by soluble PPI-SA composite showed stronger ability to resist deformation whether in linear or nonlinear viscoelastic region, revealing the good mechanical properties of these foam under extreme processing conditions and feasibility to improve the quality of aerated food. When the mass ratio of PPI/SA was 1:0.3, the foam properties was strongest. When the mass ratio of PPI/SA exceeded 1:0.3, insoluble substances appeared in the composite system, which was disadvantageous to foam properties and deformation resistance. Therefore, the complexation of PPI and SA was an effective way to improve the air/water interface and foaming properties of PPI, providing theoretical guidance for targeted regulation of the foaming properties of protein based aerated foods.

Non-Oxidative Coupling of Methane via Plasma-Catalysis Over M/γ-Al2O3 Catalysts (M = Ni, Fe, Rh, Pt and Pd): Impact of Active Metal and Noble Gas Co-Feeding

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al2O3 are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C2+ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:{\ ext{m}\ ext{o}\ ext{l}}_{\ ext{C}{\ ext{H}}_{4}}^{-1}$$\\end{document} and from 9 to 4.7 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ ext{M}\ ext{J}\\:\ ext{m}\ ext{o}{\ ext{l}}_{{\ ext{C}}_{2+}}^{-1}$$\\end{document}. Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing.

Comparison of Approaches for Assessing Linearity of Impedance Measurements

There are two experimental methods available to assess the linearity of electrochemical impedance measurements. Observation of current as a function of potential, known as Lissajous plots, provides an instantaneous visual representation of the data.1 Deviation from an elliptical shape suggests a perturbation amplitude that is too large, resulting in nonlinear impedance data. A second approach is to measure, along with the fundamental, the higher harmonics of the measurement signal. Under potentiostatic control, the harmonics of current that exceed the noise level suggest nonlinear behavior. These harmonics may be expressed in terms of a frequency-dependent total harmonic distortion, THD, written as the ratio between the sum of the root mean square of the harmonic magnitude and fundamental frequency magnitude for electrochemical applications.The impedance was measured for a model system consisting of a Pt disk immersed in an electrolyte containing 0.01 M potassium ferricyanide, 0.01 M potassium ferrocyanide, and 1 M KCl. Measurements were performed using a Gamry Reference 3000 with THD measurement enabled and disabled. Low-frequency (10 mHz) Lissajous plots were recorded to facilitate comparison of the two methods for assessing linearity. The impedance measurements with THD enabled or disabled were in good agreement, including the frequency-dependent stochastic error structure, the shapes of Lissajous curves, and the values of the impedance. Both the low-frequency THD and the low-frequency Lissajous plots gave similar sensitivity to nonlinear behavior. Perturbation amplitudes of 1, 5, and 10 mV rms yielded elliptical Lissajous plots with THD values on the order of the background noise. Interestingly, the THD for the 10 mV perturbation was slightly above the background noise with a value of 0.01 (or 1 % of the fundamental). Perturbation amplitudes of 20, 60, and 100 mV rms yielded both non-elliptical Lissajous plots and low-frequency THD values much larger than the background noise.The regression of the measurement model 2 to the imaginary part of the impedance was applied to assess the consistency of the measured data to the Kramers-Kronig relations.3 Data measured at amplitudes of 1, 5, 10, and 20 mV rms were found to be consistent with the Kramers-Kronig relations, and data collected with amplitudes of 60 or 100 mV rms were found to be inconsistent with the Kramers-Kronig relations. As the measurement with a 20 mV rms amplitude was found to be nonlinear by observation of non-elliptical Lissajous plots and a THD of 4.2% at a frequency of 10 mHz, the post-measurement analysis of consistency with the Kramers-Kronig relations was found to be less sensitive than experimental observation of Lissajous plots and calculation of THD. Comparison of Lissajous plots to THD values suggests that experiments with THD less than 1% of the fundamental may be considered to be linear.

Nonlinear viscoelasticity of Melaleuca alternifolia essential oil Pickering emulsion stabilized with cellulose nanofibrils

Pickering emulsions are suitable technological approaches to stabilize the bioactive compounds of essential oils (EOs) with economic interests for the pharmaceutical, cosmetic and food industries using atoxic and renewable stabilizers, such as cellulose nanostructures. The Melaleuca alternifolia essential oil (MaEO) is recognized for its pronounced antimicrobial performance, which has attracted your interest in developing eco-friendly antiseptic products. In this contribution, we report the nonlinear viscoelasticity behavior of MaEO-in-water Pickering emulsions stabilized by cellulose nanofibrils (CNF) using Large Amplitude Oscillatory Shear (LAOS) tests. The rheological characterizations by Fourier Transform (FT) rheology spectroscopy and Lissajous plots enabled the correlation of the viscous and elastic behaviors with the physical processes involving the deformation of the emulsion. Also, the internal structure of the emulsion was elucidated by fluorescence optical microscopy. Several findings relative to the effects of the shear deformation amplitude over the nonlinear viscoelasticity of the emulsified system are reported here, which are essential to the industrial processes used to develop technological products.

Soft gliadin nanoparticles at air/water interfaces: The transition from a particle-laden layer to a thick protein film

HypothesisProtein-based soft particles possess a unique interfacial deformation behavior, which is difficult to capture and characterize. This complicates the analysis of their interfacial properties. Here, we aim to establish how the particle deformation affects their interfacial structural and mechanical properties. ExperimentsGliadin nanoparticles (GNPs) were selected as a model particle. We studied their adsorption behavior, the time-evolution of their morphology, and rheological behavior at the air/water interface by combining dilatational rheology and microstructure imaging. The rheology results were analyzed using Lissajous plots and quantified using the recently developed general stress decomposition (GSD) method. FindingThree distinct stages were revealed in the adsorption and rearrangement process. First, spherical GNPs (∼105 nm) adsorbed to the interface. Then, these gradually deformed along the interface direction to a flattened shape, and formed a firm viscoelastic 2D solid film. Finally, further stretching and merging of GNPs at the interface resulted in rearrangement of their internal structure to form a thick film with lower stiffness than the initial film. These results demonstrate that the structure of GNPs confined at the interface is controlled by their deformability, and the latter can be used to tune the properties of prolamin particle-based multiphase systems.

Measurement of thoraco-abdominal synchrony using respiratory inductance plethysmography: technical aspects and a proposal to overcome its limitations

ABSTRACT Background Thoraco-abdominal asynchrony (TAA) is usually assessed by respiratory inductance plethysmography. The main parameter used for its assessment is the calculation of the phase angle based on Lissajous plots. However, there are some mathematical limitations to its use. Research design and methods Sequences of five breaths were selected from a) normal subjects, b) COPD patients, both at rest and during exercise, and c) patients with obstructive apnea syndrome. Automated analysis was performed calculating phase angle, loop rotation (clockwise or counterclockwise), global phase delay and loop area. TAA severity was estimated quantitatively and in subgroups. Results 2290 cycles were analyzed (55% clockwise rotation). Phase angle ranged from −86.90 to + 88.4 degrees, while global phase delay ranged from −179.75 to + 178.54. Despite a good correlation with global phase delay (p < 0.01, ANOVA test), phase angle and loop area were not able to correctly classify breaths with severe deviation and paradoxical movements (p=ns, Bonferroni post hoc test). Conclusions Global phase delay covers the whole spectrum of TAA situations in a single value. It may be a relevant parameter for diagnosis and follow-up of clinical conditions leading to TAA. Clinical trial registration The trial from which the traces were obtained was registered at ClinicalTrials.gov ;(identifier: NCT04597606).

Comparison of Approaches for Assessing Linearity of Impedance Measurements

Electrochemical impedance spectroscopy experiments are inherently nonlinear for systems affected by faradaic reactions. The methods used to determine whether an experiment is sufficiently linear include observation of current as a function of potential, known as Lissajous plots, measurement of total harmonic distortion, and post-experiment assessment of consistency with the Kramers–Kronig relations. An experimental approach is employed to compare sensitivity of these methods to determination of nonlinear response in electrochemical impedance measurements. The Lissajous figures showed linear behavior for a total harmonic distortion equivalent to 1 percent of the fundamental; whereas, the measurement model analysis revealed nonlinear behavior only for larger perturbation amplitudes.

Effect of Applied AC Voltage on the Performance of Non-Faradaic Impedimetric Biosensors

Electrochemical impedance spectroscopy based non-faradaic biosensors are promising low-cost and rapid detection tool for a variety of biomarkers. Unlike faradaic impedimetric biosensors, non-faradaic impedimetric biosensors are redox-free and do not require the use of three electrodes. Instead, two electrodes are enough to carry out biosensing using non-faradaic biosensors. Commonly used AC perturbation during non-faradaic impedimetric biosensors is 10 mV to maintain the linearity of the electrochemical biosensor. In this work, we investigated the effect of different AC voltages (10, 50, 100, 200, 400, 800 and 1600 mV) on bare gold interdigitated electrodes (Au-IDEs). As the AC voltage increased, the capacitance and phase of bare Au-IDEs increased whereas the impedance decreased. At 800 and 1600 mV, non-linear effects started to appear on the Lissajous plots. Then, the effect of all the AC voltages except 800 and 1600 mV on the performance of fully functionalized non-faradaic LDL-cholesterol sensors were investigated. Increasing the AC voltage resulted in better limit of detection and change in capacitance. However, it also resulted in larger change in capacitance due to testing against negative (control samples). The reported study can be useful for the future development of non-faradaic impedimetric biosensors for the detection of different biomarkers and to achieve different limits of detection as per the application requirements.

Modulation of molecular state and air-water interface adsorption behavior of ovalbumin via interference with its surrounding charge distribution

Herein, pH combined with ionic strength was employed to modulate the charge distribution around ovalbumin molecules, and the whole process (from the water phase to the interface) of film formation and stabilization of ovalbumin at the air-water interface was further analyzed. As the pH continuously rose above the isoelectric point, the molecular surface charge increased. More cations, however, reduced the surface charge through the electrostatic shielding effect. The pH and cationic strength were shown to have a remarkable effect on the aggregate size. Intrinsic fluorescence and excitation emission matrix spectroscopy indicated that the migration of tryptophan and tyrosine was accompanied by a change in the backbone structure and rearrangement of the hydrophilic/hydrophobic side chains. Interfacial adsorption kinetic analysis revealed that low pH and ionic strength generally favored the adsorption and stabilization of ovalbumin. Lissajous plots confirmed that stronger intra-interfacial interactions and viscoelastic-like solid interfaces would be generated under the above conditions. Interfacial dilatational rheology analysis illustrated that in most cases, the interfacial film formed by ovalbumin was dominated by an elastic response and produced a nonlinear viscoelastic response under strain. Overall, the combined effect of low pH (pH 5.0) and ionic strength (25 mmol/L and 50 mmol/L) on the surface charge resulted in superior foam capacity (60.00% for pH 5.0 and 50 mmol/L) and stability (97.87% for pH 5.0 and 25 mmol/L). This study detailed the mechanism by which charge influenced the molecular and interfacial properties of ovalbumin, leading the way for the development of protein-based foam systems.

Utility of Lissajous Plots for Electrochemical Impedance Spectroscopy Measurements: Detection of Non-Linearity and Non-Stationarity

Correct interpretation of Electrochemical Impedance Spectroscopy (EIS) data is bound to the linearity and stationarity of the measurement. Current-Potential traces, also known as Lissajous figures for EIS measurements, contain valuable information regarding the linearity and the stationarity of the obtained data. Here, the behavior of the Lissajous figures is analyzed for various scenarios. The Lissajous analysis is shown to be helpful in the determination of the linearity and the stationarity of the data, especially for situations where Kramers-Kronig compatibility tests fail. The averaging of the Lissajous plots is shown to change the EIS results for non-linear and non-stationary systems. Further, the analysis of the Lissajous figures in the frequency domain by means of Fourier transforms is found to be very useful in differentiating between the non-linear and the non-stationary behaviors in the obtained data. The effect of averaging the Lissajous figures is also shown to make a difference when the system is non-stationary.

Effect of isomalt on rheological, mechanical, and textural properties of reduced-sugar aerated coatings made with egg white protein

The aim of this work was to investigate the effect of sucrose replacement by isomalt on rheological, mechanical, and textural properties of aerated coatings made with egg white protein. Novel results, useful to control the manufacture and performance of reduced-sugar meringue-type confectionery coatings, were obtained. Liquid full-sugar samples (powdered sucrose and egg white protein) were prepared by whisking. Liquid reduced-sugar samples were made by replacing 20% and 40% of sucrose by isomalt. Dry discs (3.74 cm diameter) were obtained by heat-treatment (105 °C for 1 h). The analysis of small and large oscillatory shear behaviour (by strain-stress Lissajous plots) and flow curves (by Cross model) of liquid samples were performed. Double uniaxial compression tests were done to obtain mechanical and textural properties of dry discs. The main physical properties and bubble size distributions were also analysed. The partial sucrose replacement by isomalt influenced the behaviour of the studied aerated coatings.

Interfacial moduli at large strains and stability of emulsions stabilised by plant proteins at high bulk shear rates

For several commercial plant-protein stabilisers, we investigated how surface shear and dilatational properties affect dynamic emulsion stability under high bulk shear conditions. Potato protein isolates Potato-1 (rich in patatin) and Potato-2 (rich in protease inhibitors) showed a stiffer, more solid-like response than soy and pea protein isolates in large amplitude oscillatory surface shear. Soy protein isolates had the weakest interfaces and showed a more liquid-like behaviour. Potato-2 had the highest stiffness and most brittle interface in large amplitude oscillatory dilatational deformations. It also showed more significant softening, evident from both the shear and dilatational Lissajous plots. Only the Potato-1-stabilised emulsion was stable against coalescence at high bulk shear (although that emulsion was unstable against flocculation because of its low zeta potential). The low stiffness imparted to the interface by the pea and soy protein isolates was not suitable for preparing emulsions with high dynamic stability. In the linear regime, both Potato-1 and Potato-2 produced interfaces with similar surface shear moduli, and in dilatation, Potato-2 gave a higher modulus. The lower stability of the Potato-2 emulsions appears to be linked to the higher brittleness and stronger softening effect for increasing deformation amplitude. Both in surface shear and dilatation, the maximum linear strain for the Potato-1-stabilised interface is larger. The lower maximum linear strain and stronger softening effect at high deformations for Potato-2 may have resulted in more disruption of the interfacial microstructure, and this induced (partial) coalescence.

Role of oil polarity on myofibrillar protein emulsions stability: A multi-scale research

The oil polarity was hypothesized to significantly influence the microscopic conformation of interfacial myofibrillar protein (MP) and thus the mesoscopic interfacial rheology of MP film, which ultimately tuned the macroscopic stability of MP-stabilized emulsions. In this research, the inner mechanism was revealed hierarchically based on emulsions multi-scale properties, by a combination of in vitro interfacial concentration measurement, dynamic interfacial tension measurement and interfacial dilatational rheology (highlighting Lissajous plots). Then, the above conclusion was verified through in silico molecular dynamic simulation. At macroscopic level, the light scattering results showed that emulsion prepared with higher polarity oil exhibited higher physical stability. This could be explained from the mesoscopic perspective that: (1) the adsorption dynamics of MP was faster (though lower diffusion rate, but higher penetration and rearrangement rate) on the higher polarity interface, which decreased interfacial tension more efficiently; (2) adsorption ratio, surface load and desorption ratio indicated that ‘multilayer interfacial film’ was formed by loosely-bound MP on the lower polarity interface, which decreased the effective interfacial coverage to impair emulsions stability; (3) Lissajous plots showed that interfacial structure with higher stability against large deformation was formed on the higher polarity oil interface. Finally, the microscopic molecular mechanism for explaining the above findings was revealed by in silico molecular dynamic simulation: though MP was less unfolded on the higher polarity interface leading to weaker intermolecular hydrophobic interactions, this compact molecular structure with stronger intramolecular rigidity predominantly contributed to steadier interfacial film structure. This multi-scale study provides a deep insight into the inner relationship between oil polarity and emulsions stability.

The linear/nonlinear rheological behaviors of Pickering emulsion stabilized by Zein and Xanthan gum: Effect of interfacial assembly strategies

Protein/polysaccharide complexes have been widely used to fabricate Pickering emulsions, yet their linear and nonlinear rheological behaviors have received little attention. In this work, two interfacial assembly strategies of layer-by-layer (LBL) and directly mixed (DM) were employed to create zein (2%, 1%, w/v)/xanthan gum (XG) (0.8%, 0.4%, 0.2%, w/v) complex Pickering emulsions (oil phase: aqueous phase = 1:2). Both small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) behaviors were investigated. Results showed that regardless of interfacial assembly strategies, emulsions exhibited relatively smaller droplet size, but had higher viscosity and storage modulus (SAOS test) with XG concentrations at 0.8% (w/v). The steady shear test showed LBL emulsions had superior viscosity, with a minor difference between DM and LBL emulsions in the linear SAOS test. Both interfacial assembly strategies resulted in emulsions exhibiting a hysteresis loop and a thixotropic recovery rate above 85%. The Elastic/Viscous Lissajous plots revealed that the elasticity and stiffness were affected by interfacial assembly strategies. LBL emulsions showed a more pronounced secondary loop, accompanied by a greater thixotropic restructuring time scale. The micromorphology contributed to the diverse linear and nonlinear behaviors, with the zein-XG complex mixed layer coating the oil droplets in DM emulsions and XG being added to a previously zein-emulsified emulsion to form a multilayer in LBL emulsions. In addition, emulsions showed a well-distributed nature, with no oil-off phenomena observed during centrifugal, salt, and thermal treatments. Results illustrated the effect of interfacial assembly strategies on the linear/nonlinear rheological behavior of Pickering emulsion. Our study might be helpful in preparing Pickering emulsion as edible ink for 3D printing and as a fat replacer.

Improvement of 3D printing performance of pea protein isolate Pickering emulsion gels by regulating electrostatic interaction between protein and polysaccharide

3D food printing had attracted wide attention for its multiple advantages such as being able to customize food according to individual needs. In this study, plant-based edible inks suitable for 3D food printing applications were formulated using Pickering emulsion gels containing pea protein isolate (PPI) and flaxseed gum (FG). The effect of different electrostatic interaction between PPI and FG on the 3D printing performance, rheology properties and microstructure of emulsion gel inks were investigated in acidic (pH 3) and neutral (pH 7) environments, respectively. At pH 3, the inks showed good printing performance with the addition of FG at 0.5%, 0.7% and 0.9%, respectively. At pH 7, the inks at 0.5% had the best 3D printing performance. They demonstrated printing performance with precise shape, smooth surface and clear texture. The inks produced were soft matter solids with a storage modulus (G′) greater than the loss modulus (G″). According to Lissajous plots analysis, the addition of FG significantly improved the viscoelasticity, which was beneficial to improve the 3D printing performance of inks. These inks also exhibited good thermal stability. In addition, Cryo-SEM analysis showed that the inks had a striated structure at pH 3 but a honeycomb structure at pH 7 due to the difference in electrostatic interaction. And the honeycomb structure is more stable compared to the striated structure. This study showed that edible inks can be formulated from plant-derived ingredients, which may increase their application in the development of plant-based foods with improved properties using additive manufacturing processes.

A methodology for post-processing the four-point beam bending data and computing stiffness modulus using harmonic analysis

The computation of modulus of bituminous mixes from a beam bending test conforming to an undamaged yet steady state is not straightforward. The most widely used practice of choosing the 50th or 100th cycle, for modulus computation, does not ensure that the material response has reached a steady state, crossing the initial transient stage of drastic modulus reduction. In the current study, it is analytically shown that the material retardation time governs the attainment of a steady state response. The study proposes a methodology for post-processing the four-point beam bending test data so as to identify the cycles that could result in a sensible computation of material modulus. The experimental investigations involve four-point beam bending (4-PB) tests carried out on four bituminous mixes, prepared using an unmodified and three modified binders. The 4-PB tests are carried out at 20 oC, 10 Hz frequency at strain levels of 200, 400, 600 and 800 micro-strains. The harmonics of the input/output waveform has been used to identify the cycles that can be used for the computation of a material modulus, and the modulus is computed from the Lissajous plots (stress–strain plots) of the cycles prior to damage initiation. Based on harmonic analysis, the current study specifies a range of modulus for each mix at various strain levels, and the values are further compared with the modulus computed using the conventional post-processing procedure. It is observed that the conventional procedure of using the stiffness modulus at 100th cycle results in higher values of modulus than the ones computed using the proposed post-processing method, as a consequence of the transient response of the material before attaining a steady state.

Surface dilatational and foaming properties of whey protein and escin mixtures

Saponins are naturally occurring components in plants, which have promising interface stabilising properties. In this work, we will focus on the saponin type called escin, which is known to form very strong viscoelastic interfacial layers at the air-water interface. The ability to form stiff interfaces can be advantageous for stabilising foams. The interfacial properties of escin were studied in mixtures with whey protein isolate (WPI). Understanding multicomponent systems is crucial in designing food products, containing both proteins and saponins. Pure WPI and escin, and WPI-escin mixtures at 7:1, 3:1, 1:1, and 1:3 (w:w, WPI:escin) ratio were evaluated for their interfacial properties using large amplitude oscillatory dilatation (LAOD). The responses to the deformations were highly non-linear and could only be assessed by plotting Lissajous plots of the surface stress signal versus deformation. Escin appeared to co-adsorb with WPI, leading to mixed interfaces. A small addition of escin, such as in the 7:1 or 3:1 (WPI:escin) ratios, already resulted in substantially stiffer interfacial layers compared to pure WPI. At higher escin content (1:1 and 1:3), escin completely dictated the mechanical properties of the interfaces, which resulted in stiff and glassy-like systems. The stiff interfacial layers of escin resulted in about three times more stable foams compared to pure WPI. We also observed higher foam stability for mixtures with higher escin contents. Escin is a promising natural and plant-based foaming ingredient, which can be mixed with whey proteins to create stable aerated systems.

Enhanced freeze-thawing stability of water-in-oil Pickering emulsions stabilized by ethylcellulose nanoparticles and oleogels

This study developed water-in-oil (W/O) Pickering emulsions stabilized by ethylcellulose (EC) nanoparticles and EC oleogels, which presented significantly improved freeze-thawing (F/T) stability. Microstructural observation suggested EC nanoparticles were distributed at the interface and within the water droplets, and the EC oleogel trapped oil in the continuous phase. Freezing and melting temperatures of water in the emulsions with more EC nanoparticles were lowered and the corresponding enthalpy values were reduced. F/T led to lower water binding capacity but higher oil binding capacity of the emulsions, compared to the initial emulsions. Low field-nuclear magnetic resonance confirmed the increased mobility of water but decreased mobility of oil in the emulsions after F/T. Both linear and nonlinear rheological properties proved that emulsions exhibited higher strength and higher viscosity after F/T. The widened area of the elastic and viscous Lissajous plots with more nanoparticles suggested the viscosity and elasticity of emulsions were increased.

Phase switching phenomenon in a system of three coupled DC glow discharge plasmas.

We report the first experimental observations of phase switching in a system of three coupled plasma sources. Two of the plasma sources are inductively coupled to each other while the third one is directly coupled to one of them. The coupled system acquires a frequency pulling synchronized state following which a transition occurs to a frequency entrainment state with an increase in the frequency of the directly coupled system. We also observe a sudden jump from a lower to a higher frequency entrainment state and a concomitant phase switching between the oscillations of the two directly coupled sources while the phase difference between the inductively coupled sources remains constant. These experimental findings are established using various diagnostic tools, such as the Fourier spectra, frequency bifurcation plots, Lissajous plots, and Hilbert transforms of the data. The experimental results are qualitatively modeled using three coupled van der Pol equations, in which two of them are environmentally coupled while the third one is directly coupled with one of them.