Aqueous foams require stabilizers to be generated and to prevent their rapid destruction. Beside synthetic surfactants or polyelectrolytes, natural stabilizers can be used to produce and stabilize foams. Up to now, these are mostly of animal origins. Here, we present some new results obtained with two plant-based compounds. The first one is a powder of pea peptides. The second is a filtration permeate obtained during the industrial treatment of soybean. Together with studies of their composition, we have investigated the foamability of these solutions at different concentrations. We have used three different generation techniques to tune the foam parameters, and then studied the stability and aging of the obtained foams. These results are then compared to the ones of egg white and standard surfactant solutions. In parallel, we have performed complementary experiments at the scale of a single solution-air interface. Two different opposite behaviors are evidenced, in terms of foamability and stability, with a strong impact of the foaming process. Finally, we studied mixtures of these compounds, showing that the macroscopic features can be smoothly tuned by mixing these plant-based products, allowing us to better identify the balance between the role of the chemical composition, the concentration and the process of gas incorporation.

In recent years, water pollution has become a critical issue due to population growth and rapid industrialization, with profound consequences for both environmental and public health. Among the key contributors are phenolic compounds, including bisphenol A, catechol, hydroquinone, and resorcinol, which are classified as priority pollutants. These substances exert harmful effects even at low concentrations, driving increasing research efforts focused on understanding their molecular interactions, monitoring their occurrence in wastewater, and developing sustainable strategies for their detection and removal. In particular, catechol is extensively used in a wide range of industrial processes, yet its cellular effects and mechanisms of action remain poorly characterized. To address this gap, lipid monolayers were used as membrane models, for investigating specific interactions with external agents at the molecular level. Two systems were designed to evaluate the role of physical phase heterogeneity: one in a pure liquid-condensed phase and another exhibiting a coexistence between liquid-condensed and liquid-expanded phases. The effects of catechol exposure were assessed through compressibility measurements (π-A isotherms) and Atomic Force Microscopy (AFM) imaging. The results demonstrate that catechol induces marked alterations in the lipid monolayer, increasing disorder within the liquid-condensed phase and reducing its relative proportion in favour of the liquid-expanded phase. Such perturbations in lipid phase organization suggest that catechol may compromise membrane functionality, with potential implications for essential biological processes and disease mechanisms. These findings provide a promising basis for further investigations into the mechanisms underlying catechol-membrane interactions.

Despite its low purity (70 %), technical grade oleylamine OlA is widely used for AuNPs synthesis as it allows to reach a narrow size distribution. We synthesized AuNPs in technical grade OlA and then investigated the formation of films from these particles at the air-water interface. A specific centrifugation procedure was applied to control the amount of ligand before spreading. The compression isotherms for various gold/OlA ratios, and the morphology of the film were monitored during compression, using Brewster Angle Microscopy (BAM), Atomic Force Microscopy (AFM) and transmission electron microscopy (TEM). This multiscale analysis reveals that the ligand impurities segregate within the film, forming domains of distinct heights at the mm scale, like a 2D-foam. The AuNPs form clusters within the boundaries between the domains. Ligand segregation is also observed at the mu m scale, with the formation of patches of different heights. Most surprisingly, we observe a population of ultrasmall AuNPs after deposition at the interface.

Sustainable incentives foster the use of plant-based ingredients as emulsifiers, but their composition, functionality and interfacial properties deserve more attention. A recent study highlighted high contents of endogenous phospholipids in pea protein isolate (PPI) and the potential of high-pressure homogenization (HPH) to release submicron lipid structures in aqueous suspensions. These findings raised the pivotal question of the interfacial properties of this widespread ingredient, suggesting a competition between proteins and phospholipids for interfacial adsorption. Dilatational interfacial rheology measurements were conducted using either the soluble fraction of the ingredient as such, lipids extracted from PPI, or purified pea proteins (7S). Oscillatory deformations of the oil-water interfacial layers were analyzed using Lissajous plots, which substantiated the interactions between proteins and lipids by deciphering their respective contributions. The formation of mixed interfacial films according to the protein-to-lipid ratio was demonstrated, with a prevalent influence of pea lipids on the rheological signature of the films. Atomic force microscopy confirmed the formation of mixed interfacial films where lipid domains coexist with protein aggregates. These insights advance the current knowledge regarding the complexity and functionality of plant protein ingredients, which is important to promote the rational formulation of plant-based food products.

Long-term storage of colloidal solutions presents significant challenges in maintaining the physical and mechanical properties of manufactured products over extended periods. Ensuring stability is critical for agro-alimentary products, pharmaceutical formulations, and petroleum applications to preserve product quality and longevity during storage. Monitoring the stability of colloidal dispersions is essential for anticipating potential degradation over time. This study explores the evaluation of stability criteria using quasi-surface resonant analysis. Specifically, the zeta potential of colloidal solutions is investigated via resonant optical parameter, the Free Spectral Range (FSR), to distinguish between stable and unstable dispersions. For this purpose, sensors based on organic UV210 Micro-Resonators (MRs) were fabricated using deep UV photolithography. These MRs were integrated into an optical test platform, enabling real-time data collection with a spectrometer and dedicated MATLAB processing. The study focuses on black carbon nano powders dispersed in water and in water plus an anionic surfactant (Sodium Dodecyl Sulfate, SDS). The findings show that unstable solutions exhibit an increasing FSR over time, which is indicative of sedimentation, whereas stable dispersions maintain a constant FSR. These results are validated through complementary rheological and zeta potential measurements, establishing a clear correlation between FSR variations and colloidal dispersion stability. This study demonstrates the potential of resonant optical measurements as a novel tool for assessing colloidal dispersion stability, functioning as a "zetameter" on a surfacic platform.

Natural rubber originates from the coagulation of rubber particles (RP) from Hevea brasiliensis latex. The size distribution of Hevea RP is bimodal with the presence of small rubber particles (SRP) and large rubber particles (LRP). This study aims at getting a better understanding of the early coagulation steps of Hevea RP taking into account the particle size. SRP and LRP were obtained by centrifugation of freshly tapped ammonia-free latex from RRIM600 clone. Size and zeta potential measurements showed that both RP fractions were efficiently separated and stable in basic buffer. SRP and LRP dispersions were placed in a Langmuir trough and RP were let to adsorb at the air-liquid interface to form interfacial films. Surface tension and ellipsometry indicate that the formation kinetics and the stabilization of the film at the air-liquid interface are faster for SRP than LRP. Moreover, the arrangement of RP at the interface differs between SRP and LRP, as shown by Brewster angle microscopy, atomic force microscopy and confocal laser scanning microscopy. First, the RP membrane and cis-1,4-polyisoprene core spread at the air-liquid interface before clustering. Then, while the SRP fuse, the LRP keep their structure in individual particles in floating aggregate. The role of the non-isoprene molecules on the different organization of SRP and LRP films is discussed, the one of the two major RP proteins, SRPP1 (Small Rubber Particle Protein) and Rubber Elongation Factor (REF1) in the early coagulation steps.

Hypothesis: The interfacial behavior and properties of fluid films of both rubber particle (RP) fractions (i.e. small rubber particles (SRP) and large rubber particles (LRP)) from Hevea brasiliensis latex depends on the clone, and more specifically on the RP biochemical composition. Experiments: SRP and LRP fractions from two clones of Hevea brasiliensis (RRIM600 and PB235) were characterized: biochemical composition (protein, lipid, cis-1,4 polyisoprene chain), RP film formation kinetics at the air-liquid interface, organization of films and interfacial rheological properties. Findings: Both RP fractions from PB235 clone contain more lipids than the ones from RRIM600. Particle size influences all measured indicators in the same way for both clones: SRP adsorb faster, reach a higher surface pressure and display stronger viscoelastic response than LRP. SRP and LRP also show different organizations at various scales, as observed by Brewster angle and atomic force microscopies. For each RP fraction, the clone influences most indicators but with various tendencies. This study highlights the effect of the high lipid content of clone PB235, particularly neutral lipids, on film formation kinetics. The faster formation kinetics of films from clone PB235 is attributed to the saturation of the interface by lipids. SRP films from both clones have similar rheological responses with a strong viscous component, assigned to the complete destructuration of RP membrane and the spreading of the polymer chains. In contrast, LRP retain their individual particle topology thus limiting long-distance interactions at the interface.

Pancreatic lipase related-protein 2 (PLRP2) exhibits remarkable galactolipase and phospholipase A1 activities, which depend greatly on the supramolecular organization of the substrates and the presence of surfactant molecules such as bile salts. The objective of the study was to understand the modulation of the adsorption mechanisms and enzymatic activity of Guinea pig PLRP2 (gPLRP2), by the physical environment of the enzyme and the physical state of its substrate. Langmuir monolayers were used to reproduce homogeneous and heterogeneous photosynthetic model membranes containing galactolipids (GL), and/or phospholipids (PL), and/or phytosterols (pS), presenting uncharged or charged interfaces. The same lipid mixtures were also used to form micrometric liposomes, and their gPLRP2 catalyzed digestion kinetics were investigated in presence or in absence of bile salts (NaTDC) during static in vitro, so called "bulk", digestion.The enzymatic activity of gPLRP2 onto the galactolipid-based monolayers was characterized with an optimum activity at 15 mN/m, in the absence of bile salts. gPLRP2 showed enhanced adsorption onto biomimetic model monolayer containing negatively charged lipids. However, the compositional complexity in the heterogeneous uncharged model systems induced a lag phase before the initiation of lipolysis. In bulk, no enzymatic activity could be demonstrated on GL-based liposomes in the absence of bile salts, probably due to the high lateral pressure of the lipid bilayers. In the presence of NaTDC (4 mM), however, gPLRP2 showed both high galactolipase and moderate phospholipase A1 activities on liposomes, probably due to a decrease in packing and lateral pressure upon NaTDC adsorption, and subsequent disruption of liposomes.(c) 2023 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.

The understanding and analyzing of solid particle behavior in a liquid is a challenge in numerous fields and engineering industry as the petroleum or the cosmetic one. It is indeed essential to know the behavior of soft matter process to avoid problems and ensure the product quality. This study presents the viscometer development working on a resonant optical signal principle by measuring the Free Spectral Range (FSR) parameter of a resonant optical mode during nanoparticles (NPs) sedimentation in a liquid which consists of a water/glycerol mixture. The photonic structure is composed of racetracks micro-resonators made of a UV210 polymer fabricated by deep-UV photolithography developed on an oxidated silicon layer to get a Si/SiO2 bi-layer. The chip is then integrated in an optical bench to track the evolution of the FSR during the complete sedimentation process. The resonant signal analysis established by an adapted signal processing of silica nanoparticles sedimentation in different water/glycerol concentrations allows us to determine stages and velocity rate of the sedimentation process to finally access to their viscosity. At the same time, measures are performed on a commercial mechanical rheometer so as to compare the dynamic evolution of their viscosity and their associated FSR. The plot of those data versus the glycerol concentration in water obviously shows a possible mathematical transformation between viscosity and FSR slope. There is therefore a good agreement between mechanical and resonant optical measures if we consider the dynamic evolution of both curves; so, this work proves the feasibility of an optical viscometer based on resonant signal.

Migration and sedimentation of solid particles in a liquid are physical phenomena involving accumulation of soft matter or decantation of fragmented matter. A thorough understanding together with relevant measurements are prerequisites regarding many fields, including medicine, galenic pharmacology, food processing, and the cosmetics industry. In this paper, we investigate the feasibility of monitoring and detecting the migration of a nanoparticle cloud with a resonant light probe. For this purpose, hybrid silicon/silica/UV210 organic integrated photonic racetrack resonators were patterned by thin film processes to be used as sensors measuring the outcome of the impact of a cloud of nanoparticles, the dynamic migration plus sedimentation phenomenon of the nanoparticle cloud in water. A broadband superluminescent diode has been used for the excitation. Then, the spectral characteristics of the resonant guided modes have been analyzed, considering the observed changes while tracking the free spectral range of the transduced comb spectra as a function of time. The way to operate can be summarized as follows: Solutions based on spherical silica nanoparticles of fixed size are prepared and subjected to rheological measurements to obtain their respective viscosities. Next, a millimeter tank filled with water is conveniently placed on the active surface of the sensing chip, prior to the addition of one of the previously mentioned solutions. The series of spectra are acquired during the whole migration sequence and the transduced optical signal is then directly processed and treated by a specific code operated in real time by way of Lagrange interpolation polynomials. Collected data are then compared to a simple theoretical model describing the sedimentation of a spherical particle in water (Stokes' law). Eventually, the implementation of the device in a characterization platform and the development of a specific protocol allows a global treatment, whose description is followed by discussions on measurements and data. Consequently, after the impact of the drop containing the nanoparticles, the monitoring of a first phase regarding their fast cloud migration into the global study volume (with flow of matter plus vortex) eventually followed by their slow sedimentation, can be detected using such a resonant light probe. The overall duration of the first phase associated with sedimentation velocities is in the order of a few tens of µm/min for particles with submicron diameters (several hundreds of nanometers); a first attempt of comparison of this first phase with the results of the classic Stokes model would give a convergence of the values reaching between 9 and 19% for the sedimentation rates.

Oil bodies (OB) are the natural form of energy storage in oilseeds. They consist of a triacylglyceride core stabilized by proteins (mainly oleosins) embedded in a phospholipid membrane. In some tree nut species, OB contain an important amount of polyunsaturated fatty acids that make them interesting food ingredients but prone to oxidation. Due to the growing interest in minimally-processed nut-based beverages, the understanding and the preservation of the physico-chemical properties of these lipoprotein assemblies are of great interest. In this context, previous interfacial studies have led to the proposition of a new model of adsorption for minimally-processed OB that is useful to design functional emulsion or foam in which OB act as emulsifiers. The objective of the present study was to determine the impact of processing and fat content on the physico-chemical behavior of tree nut-based matrixes. The interfacial and oxidative behaviors of minimally-processed isolated OB were compared with processed complex nut-based matrixes (i.e. beverages) of different fat content. Processing operations (heat-treatment, homogenization) affected OB interfacial properties and oxidative stability but fat content had even stronger impact on this last parameter, with more concentrated systems more stable to oxidation. The results underline the good physico-chemical stability of tree nut OB, and raise the interest of their use in the minimally-processed form to fully exploit their beneficial properties.