Overview of foam system: Natural material-based foam, stabilization, characterization, and applications

Classification of surfactants and admixtures for producing stable aqueous foam

Surfactants and foam have captured the interest of researchers worldwide due to their unique behavior of surface activity, the dynamic nature of foam formation, and simultaneous destruction. The present review focuses on the surfactants' classification, surfactant-solvent interaction, foam formation, characteristics, and a range of admixtures to enhance the foam performance. Although surfactants have been researched and developed for decades, recently, their sustainability has been given special attention. One such aspect is the development of green foaming agents from natural and renewable sources and assessing their suitability for different applications. Further, widely researched parameters are the type of surfactant, surfactant concentration, surfactant-solvent interaction, and foam production method on the foamability of a surfactant solution and related foam characteristics, including stability and texture. However, still, there is no rule to predict the best foam. Another vital concern is the non-standardization of foam assessment methods across industries and regions. Recently, research has progressed in identifying suitable admixtures for foam performance enhancement and utilizing them to produce stable foams for application in enhanced oil recovery, drug delivery, and manufacturing of aerated food products and foamed concrete. Although foam stabilization using various admixtures has been recognized well in the literature, the underlying mechanism requires further research. The interaction of surfactant and admixtures in solution is complicated and requires more research.

Effects of ultrasound and thermal treatment on the interaction between hyaluronic acid and lactoferrin: Preparation, structures and functionalities

Complexes of polysaccharides and proteins have superior physicochemical and functional properties compared to single proteins or polysaccharides. In this study, lactoferrin-hyaluronic acid (LF-HA) complexes were prepared by both ultrasonic and thermal treatment. Appropriate preparation conditions, including ultrasonic and thermal treatment conditions, have been established. The complexes formed by different methods were structurally characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis, fourier transform infrared spectroscopy, and circular dichroism spectroscopy. Ultrasound formed non-covalent binding, while thermal treatment generated covalent bonding, altering the structure of LF. The LF-HA complexes showed improved heat stability, foaming stability, emulsifying activity and antioxidant capacity, but deceased foaming ability. Iron binding ability could only be improved by HA through thermal treatment. Moreover, the in vitro digestibility of LF-HA complexes decreased to below 80 % compared to LF.

Recent advances in nanomaterial-stabilized pickering foam: Mechanism, classification, properties, and applications

Pickering foam is a type of foam stabilized by solid particles known as Pickering stabilizers. These solid stabilizers adsorb at the liquid-gas interface, providing superior stability to the foam. Because of its high stability, controllability, versatility, and minimal environmental impact, nanomaterial-stabilized Pickering foam has opened up new possibilities and development prospects for foam applications. This review provides an overview of the current state of development of Pickering foam stabilized by a wide range of nanomaterials, including cellulose nanomaterials, chitin nanomaterials, silica nanoparticles, protein nanoparticles, clay mineral, carbon nanotubes, calcium carbonate nanoparticles, MXene, and graphene oxide nanosheets. Particularly, the preparation and surface modification methods of various nanoparticles, the fundamental properties of nanomaterial-stabilized Pickering foam, and the synergistic effects between nanoparticles and surfactants, functional polymers, and other additives are systematically introduced. In addition, the latest progress in the application of nanomaterial-stabilized Pickering foam in the oil industry, food industry, porous functional material, and foam flotation field is highlighted. Finally, the future prospects of nanomaterial-stabilized Pickering foam in different fields, along with directions for further research and development directions, are outlined.

Advances in guided bone regeneration membranes: a comprehensive review of materials and techniques

Guided tissue/bone regeneration (GTR/GBR) is a widely used technique in dentistry to facilitate the regeneration of damaged bone and tissue, which involves guiding materials that eventually degrade, allowing newly created tissue to take its place. This comprehensive review the evolution of biomaterials for guided bone regeneration that showcases a progressive shift from non-resorbable to highly biocompatible and bioactive materials, allowing for more effective and predictable bone regeneration. The evolution of biomaterials for guided bone regeneration GTR/GBR has marked a significant progression in regenerative dentistry and maxillofacial surgery. Biomaterials used in GBR have evolved over time to enhance biocompatibility, bioactivity, and efficacy in promoting bone growth and integration. This review also probes into several promising fabrication techniques like electrospinning and latest 3D printing fabrication techniques, which have shown potential in enhancing tissue and bone regeneration processes. Further, the challenges and future direction of GTR/GBR are explored and discussed.

Process optimization and characterization of hydrolysate from underutilized brown macroalgae (Padina tetrastromatica) after fucoidan extraction through subcritical water hydrolysis

The growing demand for macroalgal biomass as a source of proteins, peptides, and amino acids is garnering attention for their biological and functional properties. This study depicts the use of emerging green techniques, i.e. subcritical water, to hydrolyze protein from Padina tetrastromatica. The biomass was treated with subcritical water at varying temperatures between 100 and 220 °C for 10-40 min at a biomass to water proportion of 1:50 (w/v) and pressure of 4.0 MPa. The optimum conditions for recovering the maximum protein (127.2 ± 1.1 mg g-1), free amino acids (58.4 ± 1.0 mg g-1), highest degree of hydrolysis (58.8 ± 1.2 %) and low molecular weight peptides (<650 Da) were found to be 220 °C for 10 min. The amino acid profiling of the hydrolysate revealed that it contains 45 % essential amino acids, with the highest concentration of methionine (0.18 %), isoleucine (0.12 %) and leucine (0.10 %). It was found that the hydrolysate contains phenolics (23.9 ± 1.4 mg GAE g-1) and flavonoids (1.23 ± 0.1 mg QE g-1), which are largely responsible for antioxidant activity. The hydrolysate effectively inhibits acetylcholinesterase and α-amylase in vitro, with IC50 values of 17.9 ± 0.1 mg mL-1 and 16.0 ± 0.5 %, respectively, which can help prevent Alzheimer's disease and diabetes mellitus. Consequently, this study reveals that utilizing eco-friendly subcritical water hydrolysis method, 79 % of the protein was recovered from P. tetrastromatica, which might be an effective source of bioactive peptides in various nutraceutical, pharmaceutical and cosmeceutical applications.

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

Foam, as a structured multi-scale colloidal system, is becoming increasingly popular in food because it gives a series of unique textures, structures, and appearances to foods while maintaining clean labels. Recently, developing green and healthy food-grade foaming agents, improving the stability of edible foams, and exploring the application of foam structures and new foaming agents have been the focus of foam systems. This review comprehensively introduces the destabilization mechanisms of foam and summarizes the main mechanisms controlling the foam stability and progress of different food-grade materials (small-molecular surfactants, biopolymers, and edible Pickering particles). Furthermore, the classic foam systems in food and modern cuisine, their applications, developments, and challenges are also underlined. Natural small-molecular surfactants, novel plant/microalgae proteins, and edible colloidal particles are the research hotspots of high-efficiency food-grade foam stabilizers. They have apparent differences in foam stability mechanisms, and each exerts its advantages. However, the development of foam stabilizers remains to be enriched compared with emulsions. Food foams are diverse and widely used, bringing unique enjoyment and benefit to consumers regarding sense, innovation, and health attributes. In addition to industrial inflatable foods, the foam foods in molecular gastronomy are also worthy of exploration. Moreover, edible foams may have greater potential in structured food design, 3D/4D printing, and controlled flavor release in the future. This review will provide a reference for the efficient development of functional inflatable foods and the advancement of foam technologies in modern cuisine.

Investigating the physicochemical properties and air-water interface adsorption behavior of transglutaminase-crosslinking rapeseed protein isolate

Improving the technical functionality to adapt to the application of complex food systems is an important challenge for the development of plant protein ingredients. Herein, the correlation between the physicochemical properties and interfacial adsorption behavior of rapeseed protein isolate (RPI) at the air-water interface after transglutaminase (TG) treatment was investigated. The results of cross-linking degree, Fourier transform infrared spectroscopy (FTIR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the TG enzyme was able to catalyse cross-linking between lysine and glutamine residues of RPI. The foaming capacity of RPI was enhanced from 120 % to 150 % after TG cross-linking 5 h, whereas the average size (210-219 nm) of the RPI determined by dynamic light scattering did not change significantly. Besides, the hydrophobicity tended to increase overall under the enzyme treatment, while the surface electrostatic potential decreased. The former indicates the unfolding of the protein and reduces the kinetic barriers to protein adsorption at the air-water interface, with a consequent increase in disulfide bonding and surface pressure. Furthermore, as the enzyme treatment time increased, a significant increase in protein content of foam by 33.86 %. These findings provide novel insight into the foaming mechanism of TG cross-linking RPI.

Topical foam as a promising carrier system for active pharmaceutical ingredients: review of clinical studies

Skin disorders are preferentially treated by topical administration of medicines or cosmetics because of the possibility of local action. However, a great concern is the delivery of topical actives with effective penetration through the stratum corneum to ensure the desired effect. Considering the search for a carrier system that allows the penetration/permeation of active pharmaceutical ingredients through this structure, searching for effective topical pharmaceutical forms is needed. Foams have been widely studied over the years due to their high capacity to favor the active to overcome the cutaneous barrier and because this form of presentation has ease of application and high acceptability by users. The objective of this review was to analyze the potential of foam as a topical pharmaceutical form for treating skin disorders, upon clinical cases reported in the literature. Foam presents technical advantages when compared to other conventional topical pharmaceutical forms due to its fast action, high tolerance, and safety, with reduction or total remission of adverse events. Regarding the patient, foam increased the rate of adherence to the treatment. Therefore, it is concluded that foam is an effective, secure, and stable topical presentation form for carrying active pharmaceutical ingredients and widely accepted by patients.

Preparation and Properties of High-Temperature-Resistant, Lightweight, Flexible Polyimide Foams with Different Diamine Structures

Polyimide foam (PIF) is a rising star in high-end applications such as aerospace thermal insulation and military sound absorption. However, the basic rule on molecular backbone design and uniform pore formation of PIF still need to be explored. In this work, polyester ammonium salt (PEAS) precursor powders are synthesized between alcoholysis ester of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDE) and aromatic diamines with different chain flexibility and conformation symmetry. Then, a standard "stepwise heating" thermo-foaming approach is used to prepare PIF with comprehensive properties. A rational thermo-foaming program is designed based on in situ observation of pore formation during heating. The fabricated PIFs have uniform pore structure, and PIF_BTDA-PDA shows the smallest size (147 μm) and narrow distribution. Interestingly, PIF_BTDA-PDA also presents a balanced strain recovery rate (SR = 91%) and mechanical robustness (0.051 MPa at 25% strain) and its pore structure maintains regularity after 10 compression-recovery cycles, mainly due to high rigidity of the chains. Furthermore, all the PIFs possess lightweight feature (15-20 kg∙m^-3), good heat resistance (T_g at 270-340 °C), thermal stability (T_5% at 480-530 °C), thermal insulation properties (λ = 0.046-0.053 W∙m^-1K^-1 at 20 °C, λ = 0.078-0.089 W∙m^-1K^-1 at 200 °C), and excellent flame retardancy (LOI > 40%). The reported monomer-mediated pore-structure control strategy can provide guidelines for the preparation of high-performance PIF and its industrial applications.

Physical treatment synergized with natural surfactant for improving gas-water interfacial behavior and foam characteristics of α-lactalbumin

The purpose of this study was to investigate effect of physical treatment (ultrasound, U/high pressure homogenization, H/combined treatment, UH or HU) and surfactant (Mogroside V, Mog) on air/water interface adsorption and foaming properties of α-lactalbumin (ALa). Firstly, the binding of Mog and all physical-treated ALa was a static quenching process. Mog had the greatest binding affinity for HU-ALa among all treated samples. U or H treatment could change surface hydrophobicity of ALa/Mog complex. Secondly, at the molar ratio (ALa:Mog) of 1:50, foaming ability (FA) of all ALa samples got the maximum. The sequence of FA in ALa and ALa/Mog complex was listed as follow: HU > U > H > UH. Moreover, foaming stability (FS) of HU-ALa was the highest, followed by H-ALa, U-ALa and UH-ALa. Meanwhile, low concentration Mog increased FS of ALa or UH-ALa, but it reduced FS of H-ALa, U-ALa and HU-ALa. Quartz crystal microbalance with dissipation monitoring (QCM-D) experiment indicated that ALa/Mog complex after U or H treatment was quickly absorbed at air/water interface, compared with the treated ALa, and HU-ALa/Mog had the largest frequency shift. In addition, HU-ALa had the thickest bubble membrane and the highest dissipation shift in all samples, indicating that the absorbed membrane thickness and viscoelasticity of samples was correlated with foam stability. Therefore, U and H treatment synergism with Mog was an effective approach to enhance foam properties of ALa, which indicated that HU-treated ALa/Mog complex could be viewed as the safe and efficient foaming agent applied in food processing.

Food aeration: Effect of the surface-active agent type on bubble deformation and break-up in a viscous Newtonian fluid: From single bubble to process-scale

Two continuous whipping devices, a rotor-stator (RS) and a narrow angular gap unit (NAGU), were used to produce aerated food with a 25% (v/v) gas fraction target. The liquid phase was a Newtonian model-solution containing 2% (w/w) of either whey proteins (WPC), sodium caseinate (SCN), or tween 20 (TW20). Strong differences emerged regarding gas incorporation and bubble size as a function of process parameters: namely, rotation speed and residence time. To improve understanding of the results obtained at pilot-scale, a second investigation consisting in the observation of the deformation and break-up of single gas bubbles has been undertaken using successively a Couette device and an impeller close to NAGU. For proteins, the observation of single bubble deformation and break-up showed that bubble break-up occurred by tip-streaming above a well-defined critical Capillary number Ca_c of 0.27 and 0.5 for SCN and WPC, respectively, whereas no break-up was observed with TW20 even though Ca reached 10. The poor foaming ability obtained with TW20 could be explained by a poor break-up mechanism, promoting coalescence and gas plugs at high shear instead of gas incorporation. Conversely, protein promote tip-streaming as the major break-up mechanism at low shear rate, explaining why rotation speed is not a key process parameter. Differences observed between SCN and WPC can be attributed to diffusion limitation for SCN when a much larger surface area is generated during aeration.

Molecular Dynamics Simulation of the Synergistic Effect of Alkali/Surfactant/Polymer on the Formation and Stabilization of Water-Based Foam Systems

The stable maintenance effect of a chemical oil displacement agent on a foam liquid film usually creates problems with the oilfields surface system. To achieve comprehensive insights into the influence mechanism of these chemical agent components on the foam liquid film, an "SDBS/HPAM/OH^-" water-based foam simulation system and corresponding control systems were constructed by adjusting the categories and quantities of component molecules by molecular dynamics (MD) simulation. The simulated results indicated that the foam stability follows the order of "SDBS/HPAM/OH^-" system > "SDBS/HPAM" system > "SDBS" system. The smaller the inclination angle of the SDBS molecular tail chain, the greater the tendency of the SDBS molecular configuration to be "upright" at the gas-liquid interface, which is not conducive to preventing the aggregation and penetration of gas molecules at the gas-liquid interface. Although the presence of HPAM molecules can significantly enhance the stability of the liquid film by restricting the liquid film's drainage and the diffusion of gas molecules, the addition of HPAM molecules would weaken the formation ability of the foam liquid film. Through decreasing the aggregation of cations around the co-adsorption layer, OH^- not only enhances the interfacial activity of SDBS molecules, but also reduces the electrostatic repulsion between -COO^- groups on the HPAM molecular chain, which makes the foam more stable. With an increase in the pH, SDBS concentration, and HPAM concentration, the stability of foam liquid film was strengthened. These results are helpful in facilitating new insights into the formation and stabilization mechanism of water-based foams. In particular, they provide support for the development and application of new defoaming technologies.

Application of egg white hydrolysate (EWH) to improve frothing functionality of pasteurized liquid egg in large quantity production

Sterilized Liquid Eggs (SLE) are convenient for the baking process by minimizing the food safety risks of fresh eggs. Although these advantages were encouraging, the thermal effects of the pasteurization process had a negative impact on the functionality of the egg whites, thus making them unattractive to the food industry. Therefore, our previous study found that adding 1-5% egg white hydrolysate (EWH) contributed to the foaminess and stability in SLE. This primary purpose of this study was to confirm the feasibility of applying the optimum concentration of EWH for simultaneous evaluation and shelf life for batch production of SLE. The physical characteristics of the foam were analyzed by adding 1 ± 0.2% of EWH to SLE, and it was found that the foam with 1% EWH had better stability (low drainage), better viscosity, and similar distribution of foam bubbles size in the microstructure. No Salmonella infection has been found during the shelf life of 7 days. In addition, the highest overall acceptability has obtained using the large quantity produced SLE with 1% EWH to produce spoon cookies, followed by sensory evaluation. The cross-sectional height of the cookie and the distribution of holes in the structure were in line with those of the non-sterilized liquid egg white (NSLE). Hence, adding 1% EWH was found to the optimum concentration, which provides good foaming performance and stability of SLE. This study conveys a positive assessment to SLE producers and potential users, as it will increase their profitability economically while meeting the market challenges.

Preparation and characterization of high embedding efficiency epigallocatechin-3-gallate glycosylated nanocomposites

Glycosylated protein nano encapsulation was an efficient encapsulation technology, but its embedding rate for EGCG was not high, and the research on the embedding mechanism was relatively weak. Based on this, this study compared the embedding effect of glycosylated peanut globulin and glycosylated casein on EGCG. The embedding mechanism of EGCG with glycosylated protein was discussed by ultraviolet, fluorescence, infrared and fluorescence microscopy. Results revealed that the highest encapsulation efficiency of EGCG was 93.89 ± 1.11%. The neutral pH value and 0.3 mg/mL EGCG addition amount were suitable for EGCG glycosylated nanocomposites. The hydrogen bond between EGCG hydroxyl group and tyrosine and tryptophan of glycosylated protein is mainly non covalent. The encapsulation effect of EGCG glycosylated nanocomposites could be quenched by changing the polar environment and spatial structure of the group. The fluorescence characteristic and dispersibility of EGCG glycosylated peanut globin were higher than EGCG glycosylated casein. This study might provide a theoretical basis for EGCG microencapsulation technology and EGCG application in tea beverage and liquid tea food systems.