Low Foam Research Articles

Inorganic Salts as Chemical Foam Suppressors

Can the foamability of surfactant aqueous solutions be controlled chemically? Well-known antifoams can prevent foaming by inducing the coalescence of the bubbles, but can the surfactants be deactivated chemically? If yes, how does this affect the surface tension of their aqueous solutions and their foaming capacity? To shed a light on these fundamental questions, we chose a well-known surfactant containing in its molecule a sulfate group (Sodium dodecyl sulfate, SDS) and mixed it with BaCl2, (the solubility of BaSO4 is 0.245 mg/100 mL water, T = 20 °C), Pb(NO3)2 (the solubility of PbSO4 is 40.4 mg/100 mL water, T = 25 °C) and FeCl3 (the solubility of Fe2(SO4)3 is 25.6 g/100 mL water, T = 20 °C) at different molar ratios (MXn/SDS): 1/2, 1/1, 2/1, 4/1. The results were surprising: in the case of BaCl2, despite being in stoichiometric molar ratio with SDS (BaCl2 + 2SDS -> Ba(DS)2 + 2 NaCl), or in excess of BaCl2, which should convert the whole amount of SDS into a sediment, the surface tension value remained significantly lower than that of the single surfactant. At the same time, foamability was either low or absent. It therefore appears that all of the surfactants should be converted into a sediment with very small solubility, but the low surface tension indicates the opposite. The lack of foamability indicated the opposite of that opposite. With Pb(NO3)2 and FeCl3, the results are even stranger. The surface tension values are substantially smaller than those of the single surfactants, and at the same time, low foamability or lack of foamability was observed. It appears that the surfactant exists and at the same time does not exist in the aqueous solution. Where is the truth? Future studies will shed a light.

Digital foam index for evaluating fly ash air entrainer interactions

Real-time evaluation of fly ash and air-entrainer (AEA) interaction was performed by acquiring and analyzing videos of the evolving foam layer in cement-fly ash-water mixtures using the foam index test. This modified foam index test or digital foam index, defines two fundamental parameters linked to foam generation and stability, and thus can be used to improve concrete air-entrainment for freeze-thaw durability. The AEA dosage required to produce a metastable foam is defined as foam stability dosage, whereas the incremental AEA dosage beyond the foam stability dosage to achieve a foam layer covering the entire container surface is termed foam efficiency dosage, and the summation of these dosages is the traditional foam index. The foam stability and efficiency dosages are independent parameters as a vinsol resin-based AEA had a higher foam efficiency dosage but a lower foam stability dosage than a sulfonate–based AEA.

Synthesis and characterization of antibacterial and low‐temperature resistant slow rebound polyurethane foams

AbstractSlow rebound polyurethane foam (SPUF) has been widely used due to its advantages such as sound insulation, energy absorption, and good tactile sensation. However, SPUF is prone to harden at low temperature, and its application in medical equipment and households requires significant antibacterial properties. In this paper, self‐made silicone modified polyethylene glycol (Si‐APEG) and graphene oxide supported allicin (Alc@GO) were prepared and used as low‐temperature resistant agent and antibacterial agent, respectively. Low‐temperature resistant polyurethane foam (LSPUF) and antibacterial LSPUF (ALSPUF) were prepared respectively with water as foaming agent. The morphology of ALSPUF was observed by scanning electron microscope. Properties studied include apparent core density and porosity, mechanical properties including tensile strength, 40% compressive hardness, and rebound resilience, as well as low‐temperature resistance. Effects of Si‐APEG content on the structures and properties were analyzed and the LSPUF with an Si‐APEG content of 10 wt.% showed the best comprehensive performance. Therefore, ALSPUFs with Si‐APEG content of 10 wt.% and Alc@GO content of 0–3 wt.% were prepared. The addition of Alc@GO increased the antibacterial ratio significantly without obvious effect on the structure and mechanical properties of LSPUF. The antibacterial ratio of ALSPUF reached 99.07% at a Alc@GO content of 2.5 wt.% and testing time of 60 min. This work provides an effective and feasible method for the preparation of ALSPUF which can be widely used in medical devices and households.Highlights Silicone modified polyether is a suitable low‐temperature resistant agent for PU foam. Allicin supported on GO provides good antibacterial property for PU foam. ALSPUF has better mechanical properties than SPU.

Cell topology during coarsening of simulated three-dimensional dry liquid foams.

Cell topology provides a deep insight into the structure of dry liquid foams. This paper analyses the cell topology of simulated 3-dimensional monodisperse dry liquid foams through the process of coarsening, where gas slowly diffuses through the cell interfaces. The coarsened foams are polydisperse, yet show a difference in cell types to annealed, low energy foams of comparable polydispersity. These two types of foams are analysed using average face degree of the cells and a measure of combinatorial roundedness, a new concept from combinatorial topology. We see that the spectrum of cell types changes drastically through the evolution of the foam via coarsening, from cells with a face degree between 12 and 14, with many 4-, 5-, and 6-side faces, to a combination of very large cells with many faces alongside a high frequency of tetrahedra and other cells with low face degree. These results demonstrate the insight that topological methods can give into foams and other complex structures.

Research on compound amidohydroxysulfobetaine foamer for high-temperature and high-salinity clastic reservoirs

A high-quality foaming agent should exhibit excellent solubility in formation water and strong foaming ability, while also meeting the requirements of stability under high-temperature and high-salinity conditions, as well as low adsorption capacity. This study explores the potential of amidohydroxysulfobetaine surfactant as a foaming agent in sandstone reservoirs under specific reservoir conditions of 110 ℃ and 25.0×104 mg/L salinity. The findings indicate that compounding EHSB with a small amount of LHSB to form LA13 significantly reduces the Krafft point of EHSB. Furthermore, LA13 demonstrates outstanding solubility in 25.0×104 mg/L brine and exhibits an overall adsorption capacity on quartz sand surfaces lower than 0.6 mg/g when its concentration is below 1.0 wt%. Performance evaluation of bulk foam for LA31 at concentrations ranging from 0.05 wt% to 0.4 wt% suggests that using a foaming agent concentration of 0.05 wt% results in relatively low foaming volume and foam decay half-life; however, consistent foaming performance is observed across other concentrations, leading to highly stable foam due to the compound system's higher surface dilational modulus being the primary factor contributing to foam stability. Flow experiments reveal that the foam generated in cores with permeabilities of 46.5 mD, 185.5 mD, 632.0 mD, and 2005.3 mD exhibits a high resistance factor when the concentration of LA13 exceeds 0.1 wt%, while also demonstrating commendable gas-channeling regulation capability. Therefore, it is recommended to use LA13 as a foaming agent for field applications when its concentration surpasses 0.1 wt%. Additionally, comparing the mobility of foam formed by concentrations of 0.1 wt% and 0.2 wt% LA13 in cores with varying permeabilities shows that LA13 exhibits selective mobility regulation specifically in cores with permeabilities lower than 632.0 mD.

Enhancing bioactive compounds retention in pomegranate juice powder through foam mat drying

AbstractThe effect of addition of whey protein isolate (WPI; 0%, 5%, 7.5% and 10%) and carboxy methyl cellulose (CMC; 0%, 0.25%, 0.5% and 0.75%) was studied for its foaming properties and stability in pomegranate juice (PJ). High‐quality powders can be produced from fruit juices and heat‐sensitive food items using foam mat drying (FMD). The PJ foam with 10% WPI, a foaming agent, and 0.25% CMC, a stabilizer had high foam expansion (FE) (455.28%) and low foam density (FD) (0.2030 g/cc) and foam drainage volume (FDV) (20.10 mL). The PJ foam was subjected to different drying temperatures (50, 60 and 70°C) and thickness (3 and 6 mm). The drying temperature of 60°C and foam thickness of 3 mm were found to be the acceptable drying conditions based on drying time (180 min) and retention of bioactive compounds. At optimum drying conditions, the retention of phenols, anthocyanin, ascorbic acid, and antioxidant capacity was 97.86%, 83.90%, 77.29%, and 87.11%, respectively. The sensory evaluation of the reconstituted foam mat dried pomegranate juice powder (FPJP) showed lower overall acceptability scores than fresh juice (FJ), but the overall acceptability of the powder dried at optimum drying conditions was within liking limits (>6). FPJP has an amorphous nature with a particle size of 3564 nm and a porous and irregular structure. Bioactive compounds in FPJP were studied after 8 months of storage, with higher retention of bioactive compounds in refrigerated conditions.Practical applicationThe studies revealed that foam mat drying is suitable for the pomegranate juice which has high moisture and sugar content. It requires shorter drying time of 180 min. for drying up to moisture content of 4% (db). The foam mat dried juice powder obtained at optimum drying conditions has retained higher bioactive compounds and has higher sensorial acceptability when compared with the other treatment combinations. This drying process requires low initial investment and can easily be scaled up to the commercial level thus making it profitable business venture. Further, higher storage stability up to 8 months, low volume and consequent low transport cost improves the technical and financial viability of the process in industrial application. The Foam mat dried pomegranate juice developed can be used in many food products such as reconstituted beverages, ice creams, confectioneries, etc.

Formulation and Evaluation of Toothpaste Combining Clove Flower Extract (Syzygium aromaticum L.) and Chamomile Flower Essential Oil (Matricaria chamomilla)

Introduction: Herbal remedies like clove and chamomile have been traditionally used for their potential oral health benefits. This study aimed to formulate and evaluate a toothpaste combining clove flower extract (Syzygium aromaticum L.) and chamomile flower essential oil (Matricaria chamomilla) for its efficacy in promoting oral hygiene. Methods: Clove flower extract was obtained through ethanol extraction, while chamomile essential oil was procured commercially. Various toothpaste formulations (F1-F3) were prepared with varying concentrations of the herbal extracts, alongside a control formulation (F0) without the extracts. The formulations underwent comprehensive evaluation, including organoleptic assessment, pH determination, homogeneity testing, and foam height analysis. Additionally, antimicrobial activity against common oral pathogens (Streptococcus mutans and Staphylococcus aureus) was assessed using the agar well diffusion method. Results: All formulations (F0-F3) exhibited acceptable organoleptic properties, pH levels within the safe range for oral use, and homogeneity. However, foam height varied among formulations, with F1-F3 showing lower foam compared to the control (F0). Notably, F2 and F3 demonstrated significant antimicrobial activity against both S. mutans and S. aureus, suggesting their potential in combating oral pathogens. Conclusion: The combination of clove flower extract and chamomile essential oil in toothpaste formulations holds promise for enhancing oral hygiene due to their antimicrobial properties. Further research is warranted to optimize foam height and explore the long-term clinical effects of this herbal toothpaste.

Aggregation Behavior and Application Properties of Novel Glycosylamide Quaternary Ammonium Salts in Aqueous Solution.

Amidation of lactobionic acid with N,N-dimethylaminopropyltriamine was conducted to obtain N-(3'-dimethylaminopropyl)-lactamido-3-aminopropane (DDLPD), which was quaternized with bromoalkanes of different carbon chain lengths to synthesize double-stranded lactosylamide quaternary ammonium salt N-[N'[3-(lactosylamide)]propyl-N'-alkyl] propyl-N,N-dimethyl-N-alkylammonium bromide (CnDDLPB, n = 8, 10, 12, 14, 16). The surface activity and the adsorption and aggregation behaviors of the surfactants were investigated via equilibrium surface tension, dynamic light scattering, and cryo-electron microscopy measurements in an aqueous solution. The application properties of the products in terms of wettability, emulsification, foam properties, antistatic, salt resistance, and bacteriostatic properties were tested. CnDDLPB exhibited a low equilibrium surface tension of 27.82 mN/m. With an increase in the carbon chain length, the critical micellar concentration of CnDDLPBD decreased. Cryo-electron microscopy revealed that all products except C8DDLPB formed stable monolayer, multi-layer, and multi-compartmental vesicle structures in an aqueous solution. C14DDLPB has the best emulsification performance on soybean oil, with a time of 16.6 min; C14DDLPB has good wetting and spreading properties on polytetrafluoroethylene (PTFE) when the length of carbon chain is from 8 to 14, and the contact angle can be lowered to 33°~40°; CnDDLPB has low foam, which is typical of low-foaming products; C8DDLPB and C10DDLPB both show good antistatic properties. C8DDLPB and C14DDLPB have good salt resistance, and C12DDLPB has the best antimicrobial property, with the inhibition rate of 99.29% and 95.28% for E. coli and Gluconococcus aureus, respectively, at a concentration of 350 ppm.

Interfacial and foaming properties of soluble lupin protein isolates: Effect of pH

Lupins are rich in proteins (∼40%) and fibers (∼40%), and have been widely used for animal feed, but limitedly for human consumption due to the presence of alkaloids. Due to their high protein content, lupins have a high potential to be used as protein sources in diverse food manufacturing processes, including emulsion and foam stabilization. However, the interfacial properties of lupin protein isolates (LPI), especially their performance at different pH values, are not well understood so far. Here, we systematically investigated the air-water interfacial and foaming properties of the soluble fraction of LPI at pH 7.0, pH 6.0, pH 4.0, and pH 3.5. We observed that LPI at pH 4.0 (LPI-4) and pH 3.5 (LPI-3.5) adsorbed faster at the air-water interface than at pH 7.0 (LPI-7) and pH 6.0 (LPI-6) due to a smaller particle size and higher surface hydrophobicity of LPI-4 and LPI-3.5. This resulted in a higher foam overrun of LPI-4 and LPI-3.5 (300% and 331%, respectively). The air-water interfaces formed by LPI at different pH values were dramatically different in terms of interfacial structure and mechanical properties. LPI-4 and LPI-3.5 formed stiff and solid-like interfaces, leading to higher foam stability. In contrast, for LPI-7 there were clearly more protein aggregates at the interface, and this structure was weaker and less stretchable in response to shear and dilatational deformation, causing lower foam stability. LPI-6 also showed weaker air-water interfaces and thus formed less stable foams. Overall, LPI at acid pH (3.5 and 4) has a better performance in foam stabilization than at a pH close to neutral (6 and 7). Our results suggest that LPI can be potentially used as a plant-based clean-label additive in the production of foam-based food products in acidic environments.

Submerged fermentation of lentil protein isolate and its impact on protein functionality, nutrition, and volatile profiles.

Fermentation of pulses as a clean processing technique has been reported to have a favorable impact on the functional and nutritional quality of the starting materials. Compared to commonly fermented pulses such as peas and chickpeas, limited information is available on the effect of fermentation on lentils, especially when using a high protein isolate (>80% protein) as compared to seeds or flours. Therefore, in the present work, lentil protein isolate was used as a feedstock for submerged fermentation with Aspergillus niger, Aspergillus oryzae, or Lactobacillus plantarum. After 48h, the samples showed increased protein content with enhanced solubility and oil-holding capacity. Controlled fermentation, as opposed to spontaneous fermentation, maintained the high foaming capacity; however, all fermented samples had lower foam and emulsion stabilizing properties and reduced water-holding capacity compared to the control. The fermented proteins were also less digestible, possibly due to an increase in phenolics and saponins. New volatile compounds were identified in fermented samples that show promise for improved sensory attributes. Significant differences were observed in specific quality attributes depending on the microbial strain used. Further research is required to better understand the fermentative metabolism of microbial communities when provided high-protein lentil ingredients as growth substrates. PRACTICAL APPLICATION: Fermented lentil protein isolate has promising flavor profiles that may improve its sensory properties for food application.

Temperature Dependent Dynamic Response of Open-Cell Polyurethane Foams

BackgroundPolyurethane foams have many uses ranging from comfort fitting seats and shoes to protective inserts in helmets and sports equipment. Current military helmet designs employ foam pads of varying densities and bulk material properties to help absorb energy from impacts ranging from quasi-static to ballistic level strain-rates.ObjectiveThis study aims to analyze the thermomechanical uniaxial compression behavior of a high density liner foam pad and a low density liner foam pad used in the Advanced Combat Helmet. These experiments were conducted under strain-rates of 102\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^2$$\\end{document} s-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document} and under temperature conditions ranging from -20 to 40 °C. This temperature range was chosen to simulate desert and arctic conditions, with a strain-rate regime chosen to represent loads that would occur often throughout the life of the helmet, such as drops, bumps from riding in a vehicle, or heavy collisions from falling.MethodMultiple experimental apparatuses were used in this study, including a Shimadzu TCE-N300 thermostatic chamber (used to create the varying temperature environments) and a custom-built drop-test system (used to induce intermediate strain-rates). Every experiment was paired with two accelerometers and a high speed camera used for Digital Image Correlation (DIC) to analyze sample deformation and resultant acceleration. The foam’s mechanical response and energy absorption properties were investigated from the measured stress-strain curves. Additionally, each foam composition was analyzed with X-ray computed micro-tomography (XCT) to investigate microstructure properties pre and post-mortem.ResultsResults show that temperature decreased the energy absorption of the low density composition by 48% ± 5% as temperature changed from -20 °C to 40 °C, while energy absorption increased by 53% ± 16% for the high density composition over the same temperature.ConclusionA comparison between the loading response and the material’s density characteristics revealed that the foam’s mechanical properties are heavily dependent on strain-rate applications, as well as environmental factors including temperature. Several important characteristics surrounding each foam composition’s deformation mechanics and damage tolerance as a result of temperature are discussed.

Melting and crystallization temperatures, foaming, and fluid-induced crystallization of poly (ε-caprolactone) in compressed CO2 and N2

Melting and crystallization temperatures of poly(ε-caprolactone)(PCL) exposed to CO2 and N2 have been evaluated at pressures up to 125 bar using High Pressure Torsional Braid Analysis. It is shown that in contrast to CO2, exposure to high pressure N2 does not lead to a significant depression of Tm or Tc. Instead, these transition temperatures tend to increase in nitrogen, reflecting more of a hydrostatic pressure rather than a solvent effect. Another factor that may play a role is the fluid-induced crystallization which tends to increase the melting temperature. By conducting foaming at properly selected temperatures along the rigidity reduction paths which are scaled with respect to the melting temperatures in CO2 or N2, foams with low bulk foam densities of about 0.2 g/cm3 could be generated in CO2 at 100 bar and in N2 at 200 bar.

Development of a friction factor correlation applicable to both wet and dry foam flow in circular vertical pipes

BackgroundFoam flow, distinguished by its low density and extensive specific surface area, is employed for the cleaning of plant systems. However, its dual nature as a gas-liquid mixture and a non-Newtonian fluid complicates the prediction of the frictional pressure drop. MethodsThis study constructed a laboratory-scale experimental setup to illustrate the upward flow behavior of aqueous foam in a vertical circular pipe, capturing the foam flow using a high-speed camera. Utilizing the collected data and images, a model was developed for the friction factor to predict the frictional pressure drop of the foam flow, under the assumption that the foam flow is a non-Newtonian, quasi-homogeneous, steady, and fully developed laminar flow. Significant findingsWet foam, characterized by small, uniformly distributed spherical bubbles, is observed at lower foam quality levels. In contrast, dry foam, marked by a larger mean bubble diameter, non-uniform bubble distributions, and slugs, is observed at higher foam quality levels. A notable inflection point in the frictional pressure drop is observed during the transition from wet to dry foam within a vertical pipe. The foam regime and frictional pressure drop characteristics of the foam flow show limited sensitivity to surfactant concentration within the experimental range. A correlation for friction factors, applicable to both wet and dry foam flows in vertical circular pipes, was developed based on the Reynolds number, exhibiting a prediction error of 23.6 %.

Optimization of microalgae protein extraction from Scenedesmus obliquus and investigating its functional properties

The objective of this work was to evaluate alkaline treatment with enzymatic approaches for the optimal extraction of proteins from Scenedesmus obliquus microalgae. The experiments were designed with an emphasis on the alkaline treatment period and the enzyme-to-substrate ratio utilizing response surface methodology (RSM) with central composite design (CCD). Higher enzyme concentrations led to better extraction rates and efficiency, according to the findings. Cellulase demonstrated extraction efficiencies between 16.88% and 21.42%, but the multi-enzyme complex had efficiencies ranging from 15.28% to 27.87%. With an extraction rate of 19.13%, alkaline treatment was less advantageous than enzymatic treatment due to its longer procedure. Microalgal proteins' functional characteristics were also looked at. These proteins demonstrated foaming capacity, oil absorption, and emulsification ability, making them suitable alternatives to animal proteins in food systems such as egg white and soybean. Although microalgal protein powder had lower foam capacity (20%), stability (25%), fat absorption capacity (124%), and emulsification ability compared to egg white powder, it still exhibited favorable functional properties, highlighting its potential for various food applications. Further enhancement of the functional properties can be achieved by optimizing the environmental conditions during extraction.

Biobased Immiscible Polylactic Acid (PLA): Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Blends: Impact of Rheological and Non-isothermal Crystallization on the Bead Foaming Behavior

Nowadays, bead foams are of great interest due to their high lightweight potential. The processing of such foams strongly depends on the crystallization and rheological behavior of the polymers used. By blending polymers, these properties can be tailored to obtain beaded foams with low density, small cell size and high cell density. As a bio-based polymer, PLA is of great interest due to its renewable carbon source. PLA suffers from its low thermal and rheological properties, which can be compensated by using blends. The correlation between the PLA/PHBV ratio and the rheological as well as the crystallization behavior was investigated. The use of PHBV as a minor phase significantly changes the rheological properties and increases the crystallization behavior of PLA. These findings were applied to the foam extrusion process to obtain low density bead foams. Bead foams with densities below 100 kg/m3, mean cell sizes below 50 µm and cell densities of 1 × 107 cells/cm3 were obtained.

Methane foam performance evaluation in fractured oil-wet carbonate systems at elevated pressure and temperature conditions

This study investigates the potential of foam flooding for enhanced oil recovery in oil-wet fractured systems under reservoir conditions. Two surfactants with distinct ionic properties were employed in combination with methane to generate foam via simultaneous injection into propped fractures, aiming to optimize the diversion of gas from fractures to the matrix for improved oil recovery. Core flooding experiments demonstrated the critical roles of total injection rate and foam quality in controlling foam performance. Increasing the total injection rate from 1 to 3 cm³/min enhanced foam generation rates and foam lamella stability, facilitating better interactions between fractures and the matrix. However, beyond an injection rate of 4 cm³/min, there was a decline in apparent viscosity and mobility reduction factor. Foam strength was directly proportional to higher foam quality within the 50 to 80% range, but beyond 85% foam quality, fluctuations in pressure drop signaled the formation of weaker, less stable foams. Micro-scale experiments validated these macroscopic findings, revealing that smaller bubbles were associated with higher flow rates and lower foam qualities. This research contributes valuable insights into both micro and macro-scale in-situ foam generation, which can inform the design and application of foam-based enhanced oil recovery methods in fractured reservoirs.

A new strategy to fabricate polyvinyl alcohol (PVA) foam with low thermal conductivity using PVA-citric acid solution in supercritical carbon dioxide

Polymer foams with low density have a great potential in the field of heat preservation due to good thermal insulation properties. In this work, a new method for the preparation of polyvinyl alcohol (PVA) foam with low density using PVA-citric acid (CA) solution based on supercritical carbon dioxide (scCO2) foaming technology was proposed. This approach introduced abundant water as co-blowing agent and utilized the crosslinking between CA and PVA to regulate the viscosity of solution, thereby the low density PVA foam with stable morphology was prepared. The effects of saturation time, PVA content, CA content, temperature and pressure on PVA foaming behavior were investigated. Meanwhile, the use of water as assistant solvent was explored to increase the co-blowing content and weaken the diffusion of water molecules to CO2 in the PVA-CA solution, which resulted in the successful fabrication of PVA foams with lower density and low thermal conductivity. The results showed that the minimum densities of PVA before and after addition of assistant solvent were 0.070 g/cm3 and 0.047 g/cm3, respectively. Moreover, PVA foam fabricated by the addition of assistant solvent showed the thermal conductivity of 29.68 mW/mK and the compression modulus of 2.21 MPa.

The structural characteristics and physicochemical properties of mung bean protein hydrolysate of protamex induced by ultrasound.

The limited physicochemical properties (such as low foaming and emulsifying capacity) of mung bean protein hydrolysate restrict its application in the food industry. Ultrasound treatment could change the structures of protein hydrolysate to accordingly affect its physicochemical properties. The aim of this study was to investigate the effects of ultrasound treatment on the structural and physicochemical properties of mung bean protein hydrolysate of protamex (MBHP). The structural characteristics of MBHP were evaluated using tricine sodium dodecylsulfate-polyacrylamide gel electrophoresis, laser scattering, fluorescence spectrometry, etc. Solubility, fat absorption capacity and foaming, emulsifying and thermal properties were determined to characterize the physicochemical properties of MBHP. MBHP and ultrasonicated-MBHPs (UT-MBHPs) all contained five main bands of 25.8, 12.1, 5.6, 4.8 and 3.9 kDa, illustrating that ultrasound did not change the subunits of MBHP. Ultrasound treatment increased the contents of α-helix, β-sheet and random coil and enhanced the intrinsic fluorescence intensity of MBHP, but decreased the content of β-turn, which demonstrated that ultrasound modified the secondary and tertiary structures of MBHP. UT-MBHPs exhibited higher solubility, foaming capacity and emulsifying properties than MBHP, among which MBHP-330 W had the highest solubility (97.32%), foaming capacity (200%), emulsification activity index (306.96 m2 g-1 ) and emulsion stability index (94.80%) at pH 9.0. Ultrasound treatment enhanced the physicochemical properties of MBHP, which could broaden its application as a vital ingredient in the food industry. © 2023 Society of Chemical Industry.

Foam fractionation Tags (F-Tags) enabling surfactant-free, activity-preserving recovery of enzymes

Enzymes have become important tools in many industries. However, the full exploitation of their potential is currently limited by a lack of efficient and cost-effective methods for enzyme purification from microbial production. One technology that could solve this problem is foam fractionation. In this study, we show that diverse natural foam-stabilizing proteins fused as F-Tags to β-lactamase, penicillin G acylase, and formate dehydrogenase, respectively, are able to mediate foaming and recovery of the enzymes by foam fractionation. The catalytic activity of all three candidates is largely preserved. Under appropriate fractionation conditions, especially when a wash buffer is used, some F-Tags also allow nearly complete separation of the target enzyme from a contaminating protein. We found that a larger distance between the F-Tag and the target enzyme has a positive effect on the maintenance of catalytic activity. However, we did not identify any particular sequence motifs or physical parameters that influenced performance as an F-tag. The best results were obtained with a short helical F-Tag, which was originally intended to serve only as a linker sequence. The findings of the study suggest that the development of molecular tags that enable the establishment of surfactant-free foam fractionation for enzyme workup is a promising method.Key points• Foam-stabilizing proteins mediate activity-preserving foam fractionation of enzymes• Performance as an F-Tag is not restricted to particular structural motifs• Separation from untagged protein benefits from low foam stability and foam washingsGraphical

Quasi-static three-point bending of sandwich panels with Miura-ori cores

Collapse mechanisms of sandwich panels with Miura-ori cores are analysed and classification of the deformation regimes under three-point bending is proposed. It is revealed that the homogenisation approach to the core material properties is not applicable to the deformation of panels with relatively strong origami cores due to the immediate simultaneous local deformations of the core and face sheets. To describe this deformation regime, an analytical model based on the development of new stationary hinge lines in Miura-ori cells and rigid motion rotation of the adjacent planes is proposed. The model pertains to a single degree-of-freedom model governed by the global bending angle of the panel. On the other hand, the homogenisation approach to the core material properties proved to be applicable to bending analysis of panels with relatively soft Miura-ori cores. This approach is used to analytically obtain the collapse load related to several deformation modes. Parametric FE analysis is conducted to further explore the deformation regimes of panels with different face sheet thicknesses.Experiments were conducted to validate the finite element studies and analytical models. A good agreement between the analytically predicted collapse forces and those obtained by the FE simulations is shown. Deformation mode maps are constructed based on the analytical and FE analyses in terms of the face sheet thicknesses and core strength.A brief comparison between the bending strength of sandwich panels with Miura-ori cores and panels with PVC and honeycomb cores is presented, demonstrating the superiority of the honeycomb cores loaded in the out-of-plane direction. On the other hand, the possibility of the development of high shear strains in metallic Miura-ori cores without damage gives them advantages compared to three-point bending of panels with low density PVC foam cores.