Increased Foam Stability Research Articles

Formation and characterization of microemulsion with novel anionic sodium N-lauroylsarcosinate for personal care

Microemulsions are unique clear systems comprising of oil, water, surfactant and cosurfactants that offered stimulating perspectives in various applications. The purpose of these study was to create a microemulsion using novel amino acid based anionic sodium N-lauroylsarcosinate (SNLS) surfactant for application in personal care formulations. Triglyceride oils such as caprylic acid, oleic acid and carboxylic acid ester isoamyl acetate were used as oil phase, while short chain alcohols like propanol and butanol were used as cosurfactants. The gradual variations happening in the microstructure of the microemulsions were explored via several complementary characterization techniques. Phase diagrams constructed with or without cosurfactants and using different ratio of surfactant/ cosurfactant (Smix) showed that largest microemulsion region was observed only in the presence of cosurfactant and from Smix of 1:1. Solubility of SNLS in pure water is around 30 wt%, which upsurges in presence of propanol or butanol up to around 85 wt%. This leads to increase in microemulsion region in phase diagram with increasing solubility of oils in the SNLS solution. Microemulsions were relatively stable at an ambient temperature of 27 °C. The optical microscopy, electrical conductivity and viscosity measurement were performed to examine the microstructural changes within the microemulsion region. Three different phases such as water in oil (w/o), bicontinuous, and oil in water (o/w) microemulsion were observed. Foaming behavior specifies increased foam stability of SNLS in the presence of certain amount of oils. Dynamic light scattering study supports the well-defined microemulsion stability even after the manifold dilution. The results obtained from this study may have implications for the developments of an appropriate tactic to prepare stable microemulsion from SNLS which could be exceedingly favorable for personal care formulations.

Structure and rheology of foams stabilized by lupin protein isolate of Lupinus.angustifolius

Plant-based protein sources play an important role in sustainable human nutrition but often lack in attractivity compared to animal-derived food products. Aerating is commonly used to increase the appeal of foods and may also improve acceptance for plant-based proteins in consumers' diets. We investigated structure and rheology of foams made from lupin protein isolate. Foamability and foam stability were determined from manual shaking tests. Gas volume fraction, bubble size, yield stress and shear modulus of the foams were determined during aging of pneumatically created foams. The impact of temperature pretreatment, pH and ionic strength on protein size distribution and conformation as well as surface activity in the aqueous solutions was characterized, and its effect on foaming behavior and foam properties is discussed. All foams were stable for at least 1 h. Heat induced denaturation of proteins did not alter foam characteristics much. Foaming capacity, however, strongly increased with increasing pH or ionic strength, but again gas volume fraction and bubble size were hardly affected. Foam rheology was shown to correlate not only to gas volume fraction, bubble size, and interfacial tension but also to the protein solutions’ interfacial elasticity. Protein aggregation decreased foamability but reduced drainage and hence increased foam stability. Blocking of drainage pathways by precipitated aggregates trapped in Plateau channel nodes was evidenced in endoscopic video observations. A “plant milk” made from lupin protein isolate, carboxymethyl cellulose as thickener, and emulsified sunflower oil yielded similar foam volume and texture as cow milk when prepared in a commercial whipper.

A novel strategy to fabricate stable oil foams with sucrose ester surfactant

HypothesisCan a mixture of sucrose ester surfactant in vegetable oil be aerated to yield stable oleofoams? Is foaming achievable from one-phase molecular solutions and/or two-phase crystal dispersions? Does cooling a foam after formation induce surfactant crystallisation and enhance foam stability? ExperimentsConcentrating on extra virgin olive oil, we first study the effect of aeration temperature and surfactant concentration on foamability and foam stability of mixtures cooled from a one-phase oil solution. Based on this, we introduce a strategy to increase foam stability by rapidly cooling foam prepared at high temperature which induces surfactant crystallisation in situ. Differential scanning calorimetry, X-ray diffraction, infra-red spectroscopy, surface tension and rheology are used to elucidate the mechanisms. FindingsUnlike previous reports, both foamability and foam stability decrease upon decreasing the aeration temperature into the two-phase region containing surfactant crystals. At high temperature in the one-phase region, substantial foaming is achieved (over-run 170%) within minutes of whipping but foams ultimately collapse within a week. We show that surfactant molecules are surface-active at high temperature and that hydrogen bonds form between surfactant and oil molecules. Cooling these foams substantially increases foam stability due to both interfacial and bulk surfactant crystallisation. The generic nature of our findings is demonstrated for a range of vegetable oil foams with a maximum over-run of 330% and the absence of drainage, coalescence and disproportionation being achievable.

Multiscale Microstructure, Composition, and Stability of Surfactant/Polymer Foams.

Inclusion of polymer additives is a known strategy to improve foam stability, but questions persist about the amount of polymer incorporated in the foam and the resulting structural changes that impact material performance. Here, we study these questions in sodium dodecyl sulfate (SDS)/hydroxypropyl methylcellulose (HPMC) foams using a combination of flow injection QTOF mass spectrometry and small-angle neutron scattering (SANS) measurements leveraging contrast matching. Mass spectrometry results demonstrate polymer incorporation and retention in the foam during drainage by measuring the HPMC-to-SDS ratio. The results confirm a ratio matching the parent solution and stability over the time of our measurements. The SANS measurements leverage precise contrast matching to reveal detailed descriptions of the micellar structure (size, shape, and aggregation number) along with the foam film thickness. The presence of HPMC leads to thicker films, correlating with increased foam stability over the first 15-20 min after foam production. Taken together, mass spectrometry and SANS present a structural and compositional picture of SDS/HPMC foams and an approach amenable to systematic study for foams, gathering mechanistic insights and providing formulation guidance for rational foam design.

CO2 mobility reduction using foam stabilized by CO2- and water-soluble surfactants

Foam can reduce CO2 mobility to improve the sweep efficiency during injection into subsurface geological formations for CO2 storage and enhanced oil recovery. However, CO2 foams are thermodynamically unstable, so they must be stabilized. Surfactants are often used to generate and stabilize foams in porous media and can be soluble in the aqueous phase, or in the CO2 phase. Aqueous- and CO2-soluble surfactants must be characterized for their ability to reduce CO2 mobility and stabilize foam at reservoir conditions. In addition, numerical models are necessary to predict and evaluate the effect of foam for field-scale applications and require empirical data obtained from core-scale flooding experiments. This study presents a series of steady-state foam co-injections with dense phase CO2 and either aqueous- or CO2-soluble surfactant solutions at varying CO2 flow velocities and CO2 fractions. One anionic water-soluble surfactant, which is considered a benchmark foam stabilizer, and five partially CO2-soluble non-ionic surfactants were investigated. Gamma ray attenuation was used to accurately monitor in-situ saturations during steady-state co-injections. The primary objective was to determine the steady-state foam characteristics of the different surfactants by evaluating the mobility reduction factor (MRF) and the limiting water saturation where foam abruptly collapses (Sw∗). All of the tested surfactants generated foam and reduced CO2 mobility by more than three orders of magnitude. The anionic surfactant increased foam stability at lower water saturations, compared to the non-ionic surfactants, which resulted in lower residual water saturations and increased pore volume available for CO2 storage. Core flooding results provided input into a local-equilibrium foam model. The fitted foam model reproduced the experimental results for the anionic surfactant and for three of the five non-ionic surfactants. The two latter non-ionic surfactants violated model assumptions because non-monotonic water saturation changes were observed, an effect not accurately captured by local-equilibrium foam models. However, the modelling work elucidated subtle experimental trends and demonstrated the applicability of the dataset as input into implicit-texture local-equilibrium foam models.

Improving foam stability and lautering conditions

How to increase foam stability without adding foam stabilizers? As we published earlier, there was more than a sufficient amount of foam stabilizing substances in beer, but these must not be pushed out of the beer surface by foam negative substances. There are several separation steps in a brewing process: lautering, trub separation, and beer filtration; all of these can also separate foam negative substances. This short article discusses how a pH during sparging can influence foam stability. It seems that the lower the pH, the fewer foam negative substances are carried over to the following production steps of a brewing process.

Unlocking the potential of sustainable chemicals in mineral processing: Improving sphalerite flotation using amphiphilic cellulose and frother mixtures

The transition towards cleaner production of primary minerals demands technologies that improve productivity while lowering their environmental impact. The present study explores a novel approach to support this transition by partially substituting a commercial froth stabilization reagent in mineral froth flotation (DowFroth200) with an amphiphilic cellulose derivative (namely, hydroxypropyl methyl cellulose) that is nontoxic, biodegradable and can be produced from sustainable sources. The performance of the cellulose-frother mixture is explored using sphalerite as case study.In the first place, the interaction between the two frother molecules was studied from the perspective of two-phase foam characteristics. The use of the polymer-surfactant (PS) mixture studied reported an increased foam stability and small bubble sizes, attributed to a combination of liquid film drainage prevention and steric effects of cellulose macromolecules. As a result, when used as frothers in the flotation of sphalerite, the PS-mixture exhibited a robust behavior resulting in advantages such as: i) improved separation efficiencies; ii) consistent recovery values, even under highly alkaline pH, iii) maintaining high recoveries when the collector dosage was reduced down to 25% of typical values used in the industry; and iv) faster flotation kinetics. The results obtained aim to demonstrate that properly designed green chemical systems can have a positive impact in the mining sector.

Synergistic Effect between Surfactant and Nanoparticles on the Stability of Foam in EOR Processes

Summary The major challenge in enhanced oil recovery (EOR) by gas injection is poor volumetric sweep efficiency, mainly due to the high gas mobility and reservoir heterogeneity. Injecting gas as a foam increases sweep efficiency, but maintaining foam stability within the reservoir remains a challenge. This research evaluates the synergistic interaction of one type of nanoparticle and a surfactant to increase foam stability, using the concentration ratio of the two components to tune the affinity of the nanoparticle for the gas/liquid interface. We test the capability of the synergistic two-component system to stabilize methane foam and compare it with foam stabilized by surfactants only. A key distinction is the foam stability upon contact with oil, and we explain the observations in static and dynamic conditions. Foam stability was measured in both static (bubble structure) and dynamic (flow through porous media) conditions. In the static test, foam is generated by the shaking method, and foam texture (bubble size and shape) and the decay of foam height with time are indicators of foam stability. To test static stability in the presence of oil, heavy oil is injected into the foam/liquid interface. In dynamic tests, foam is pregenerated before flowing at elevated pressures into sandpacks containing various oil saturations. Normalized pressure gradient and apparent viscosity are the indicators of foam stability and effectiveness for improving oil recovery. The extent to which nanoparticles are covered with surfactant governs the foam stability, in both static and dynamic conditions. Static foam is stable in the presence of oil only if the nanoparticles are partially covered by the surfactant. In the dynamic test, foam stabilized with only the surfactant collapses in the porous media when oil is present. Nanoparticles alone could not generate foam regardless of the presence of oil or salinity, but foam stabilized with nanoparticles partially covered by surfactant is stable in the presence of both residual and initial oil, and foam apparent viscosity could reach up to 400 cp at residual heavy oil condition. In both static and dynamic conditions, nanoparticles completely covered with a bilayer of surfactant do not stabilize foam in the presence of oil. Partially covered nanoparticle foam also demonstrated salt tolerance in both static and dynamic tests, and foam apparent viscosity can reach up to 200 cp with high salinity and residual heavy oil presented. Thus, at appropriate surface coverage, the combination of nanoparticles and surfactant is more effective than either stabilizer alone. The result shows that interaction of surfactant and nanoparticles is important in foam stability in the porous media with oil. In particular, this interaction is synergistic at certain coverage. This type of synergy can provide much more robust mobility control for EOR processes involving gas injection.

Improvements in gelatin cold water solubility after electrospinning and associated physicochemical, functional and rheological properties

A major limitation of gelatin feedstocks for industrial food and pharmaceutical applications is the lack of solubility at room temperature, necessitating use of drum/dry blending processes, combined with additives. Herein, electrospinning is investigated as an alternative route for producing cold water soluble 100% gelatin feedstock in place of powders. The physicochemical, rheological and functional properties of electrospun gelatin and an industrially available gelatin powder feedstocks were compared. Optimal conditions for producing gelatin nanofiber sheets were found to be 25% (w/v) polymer concentration in a binary solvent system of acetic acid: water (3:1 v/v), a spinning voltage of 25 kV, a flow rate of 0.5 ml/h and a tip-to-collector distance of 150 mm. The production of nanofibers from gelatin powder did not change the nature of the material. The glass transition temperature of gelatin nanofibers was lower than gelatin powder. Conversion of gelatin powder into nanofiber sheets also increased the dissolution rate in water at ambient temperature and promoted emulsion and foam forming ability, as well as increasing foam stability. Loss tangent measurements revealed that the gel formed by the gelatin nanofibers could be characterized as a weak gel. No difference was observed in the Young's modulus of samples made from gelatin nanofibers and powder, and the 0.2% (w/v) gelatin nanofiber sample yielded a higher viscosity than the 0.1% (w/v) concentration. Gelatin nanofibers have promising potential to be used as feedstock in food technology when cold water solubility and improved control of physical, functional and textural properties are required.

A Review of Sclerosing Foam Stability in the Treatment of Varicose Veins.

Varicose veins are common clinical entities. Foam sclerotherapy is a minimally invasive and simple procedure; however, the side effects, efficacy, and stability of sclerosing foam are not ideal. To summarize the current studies on sclerosing foam stability and promote foam sclerotherapy development. We reviewed the literature before June 2018 and included only representatives studies on sclerosing foam stability. We summarized the foam half-life time (FHT) of polidocanol (POL) under 17 preparation conditions and the FHT of sodium tetradecyl sulfate under 21 preparation conditions. The preparation conditions included various combinations of temperature, liquid-gas ratio, preparation method, etc. RESULTS: The FHT of POL varied between 40 and 4,000 seconds under different conditions. The FHT of sodium tetradecyl sulfate varied from 25.7 to 390 seconds. The higher the drug concentration, the lower the temperature required to increase foam stability. The addition of surfactant greatly increased foam stability. For different gas compositions, the FHT sequence was as follows: CO2 < CO2 + O2 < O2 < air. Foam stability can be improved by changing the preparation conditions; therefore, the role of surfactants and predictive methods for FHT are worth investigating further.

Enzymatic cross-linking of pectin in a high-pressure foaming process.

The enzyme laccase is a copper-containing oxidoreductase with the ability to oxidize a wide range of substrates, such as ferulic acid. Thus, the ferulic acid-containing sugar beet pectin (SBP) can be cross-linked through laccase-mediated oxidation. As cross-linking increases viscosity, it could be applied to stabilize SBP-containing foams. In this study, laccase-mediated cross-linking of SBP was investigated under conditions of a high-pressure foaming process. Shear, presence of CO2, and pressure were simulated in a rheometer equipped with a high-pressure cell. At rest, addition of laccase to SBP solution led to the formation of a stiff gel. Application of shear upon mixing of laccase and SBP solution decreased the storage modulus with increasing shear duration and shear rate. This can be attributed to the formation of a fluid gel. However, when shear was stopped before all available ferulic acid groups were cross-linked, a stronger and more coherent network was formed. Pressure exerted by CO2 did not affect cross-linking. Additionally, this approach was tested in a stirred high-pressure vessel where SBP was foamed through CO2 dissolution under pressure and shear followed by controlled pressure release. While pure SBP foam was highly unstable, addition of laccase decelerated collapse. Highest stability was reached when laccase and SBP were mixed prior to depressurization. At the point of foam formation, the continuous phase was thereby viscous enough to increase foam stability. At the same time, continuation of cross-linking at rest caused gel templating of the foam structure.

Polyvinyl alcohol as foaming agent in foam formed paper

The use of polyvinyl alcohol (PVOH or PVA) as a foaming agent in foam formed paper was investigated. Polyvinyl alcohol is a linear, nonionic water-soluble polymer. It has hydrophobic and hydrophilic parts that give it a surface-active character. PVOH is mainly characterized by degree of hydrolysis and molar mass. Degree of hydrolysis is given as mol-% hydroxyl groups on the polymer. Molar mass is measured indirectly by measuring the viscosity of a 4% PVOH solution. The results show that the degree of hydrolysis of PVOH had a strong effect on the foamability of PVOH. Foamability decreased strongly when the degree of hydrolysis increased from 88 to 98 mol-%. The effect of molar mass on foamability was weaker. We saw an increase in foam stability and bubble size with increasing molar mass, but we did not see any effect on maximum air content. PVOH dosage needed to reach &gt;70% air content (Φ) varied from 2 g/l up to 10.5 g/l, and the lowest addition levels of PVOH needed were achieved with a low molar mass PVOH with a low degree of hydrolysis. The best strength properties were achieved when using fully hydrolyzed PVOH as the foaming agent. Strength properties (both in- and out-of-plane) of samples made using PVOH were better than those made using an anionic foaming agent (sodium dodecyl sulfate, SDS). By adding PVOH binder fibers to the pulp, we were able to further enhance the strength properties of paper and board.

Synergistic effects of nanoparticles and surfactants on n-decane-water interfacial tension and bulk foam stability at high temperature

The synergistic effects of nanoparticles and surfactants on decane-water interfacial tension, and bulk foam stability at high temperature was investigated in this study. The interfacial properties were determined using a spinning drop interfacial tensiometer while the foam stability was evaluated from the normalized foam height. The extent of interaction between nanoparticles and surfactants was estimated from the hydrodynamic nano-aggregate sizes and zeta potential values. The foam microscopic images and the bubble morphology were examined to elucidate the mechanisms of foam stabilization by nanoparticles. Results clearly showed that nanoparticles-Triton X-100 mixed system demonstrated the smallest aggregate sizes in bulk solution and considerable reduction in water/n-decane interfacial tension. Significant reduction in interfacial tension and increased foam stability occurred due to electrostatic interaction between the charged surfaces of the nanoparticles and surfactant head-groups. However, influence of electrostatic attraction was found to be dominant over the influence of electrostatic repulsion in promoting foam stability and reducing interfacial tension. The most stable foam was generated by titanium dioxide (TiO2) nanoparticles and cetyltrimethylammonium, bromide (CTAB), while the least stable foam was generated in presence of multi-walled carbon nanotubes and triton X-100. Possible reasons and mechanisms for these observations were suggested. The destabilizing influence of high temperature on foam stability was significant, however, CTAB-foam stability increased by 160% and 440% in presence of silicon dioxide (SiO2) and TiO2 nanoparticles at 80 °C. This phenomenon can be attributed to the moderate adsorption and aggregation of surface-active complex at the gas-liquid interface of the foam and Plateau borders.

Effect of Newtonian and non-Newtonian viscosifying agents on stability of foams in enhanced oil recovery. Part I: under bulk condition

Foams show poor stability in enhanced oil recovery applications and stimulation processes in oil-well operations of oil fields. This paper presents a laboratory study to investigate the effect of Newtonian and non-Newtonian viscosity enhancement materials on improving the stability of foams at bulk conditions. For this goal, glycerol and hydrolyzed polyacrylamide (HPAM) were utilized to enhance the viscosity of foaming agents, which were composed of α-olefin sulfonate surfactant and salinity. To this end, a comparative study of the foam stability in surfactant solution containing different percentages of glycerol, HPAM polymer and a mixture of polymer with glycerol was undertaken. In a foam stability analysis, which was examined in the absence of an oleic phase, several characteristics such as foam volume evolution, foam half-decay time and a liquid fraction of foam were measured over a wide range of concentrations. Evaluating the conductivity and volume of injected gas during foam generation and foam decay provided the foam capacity and the maximum density parameters to characterize the foamability and stability of the generated foam in more detail. The results of bulk foam experiments indicated that polymer and glycerol could either increase or reduce the foamability, but both materials substantially increased foam stability within a certain range of concentrations. This could be explained by increasing the viscosity of the liquid phase of foam in the lamellae that attributed to decreased velocity of liquid drainage from the foam structure. Two regimes of foam drainage and coalescence demonstrated a different behavior for the same viscosity of solutions containing either glycerol or HPAM polymer. The solutions containing glycerol exhibited a small but sharp decay right after stopping the sparging gas, while for high polymer concentrations this did not happen.

How foam stability against drainage is affected by conditions of prior whey protein powder storage and dry-heating: A multidimensional experimental approach

In the present work, we investigated the effects of powder dry-heating parameters on whey protein foams stability, especially against drainage.To this aim, whey protein isolate solutions were prepared at various pH (3.5, 5.0, 6.5), with or without a prior dialysis step to reduce the lactose content, freeze-dried, adjusted to various levels (0.12, 0.23, 0.52) of powder water activity aw and dry-heated at 70 °C for up to 125 h. Protein solutions were then reconstituted at pH 7.0 and foams prepared by air bubbling.An original approach was followed to study the foam stability against drainage, involving monitoring of the liquid fraction as a function of both height in the foam column and time, and analysing the whole set of time and height liquid fraction profiles using multivariate statistics.The effects of dry-heating parameters were markedly interdependent, resulting in complex effects on foam stability. However, the results suggest that dry-heating at pH 3.5 increased foam stability. Moreover, the aw adjustment step, though consisting in a two-week pre-conditioning at room temperature, also had a significant effect on the foam stability, of the same order of magnitude as dry-heating effects.

Investigation of foaming causes in three mesophilic food waste digesters: reactor performance and microbial analysis

Foaming negatively affects anaerobic digestion of food waste (FW). To identify the causes of foaming, reactor performance and microbial community dynamics were investigated in three mesophilic digesters treating FW. The digesters were operated under different modes, and foaming was induced with several methods. Proliferation of specific bacteria and accumulation of surface active materials may be the main causes of foaming. Volatile fatty acids (VFAs) and total ammonia nitrogen (TAN) accumulated in these reactors before foaming, which may have contributed to foam formation by decreasing the surface tension of sludge and increasing foam stability. The relative abundance of acid-producing bacteria (Petrimonas, Fastidiosipila, etc.) and ammonia producers (Proteiniphilum, Gelria, Aminobacterium, etc.) significantly increased after foaming, which explained the rapid accumulation of VFAs and NH4+ after foaming. In addition, the proportions of microbial genera known to contribute to foam formation and stabilization significantly increased in foaming samples, including bacteria containing mycolic acid in cell walls (Actinomyces, Corynebacterium, etc.) and those capable of producing biosurfactants (Corynebacterium, Lactobacillus, 060F05-B-SD-P93, etc.). These findings improve the understanding of foaming mechanisms in FW digesters and provide a theoretical basis for further research on effective suppression and early warning of foaming.

Nanotechnology for improved CO2 utilization in CCS: Laboratory study of CO2-foam flow and silica nanoparticle retention in porous media

Underground CO2 storage may reduce anthropogenic CO2 emissions, but suffer from detrimental flow instabilities mainly from development of viscous fingers and density segregation that arise at larger scales. Suggested approaches to mitigate reduction in CO2 utilization include mobility control, conformance modifications and CO2 thickeners, where CO2 foams have been shown as one of the most promising techniques. We present laboratory results that study foam generation and flow by adding hydrophilic silica nanoparticles during co-injection with liquid CO2 in sandstone core plugs to reduce CO2 mobility. Nanoparticle retention characteristics in the porous media is essential to CO2-foam flow strategies: high degree of retention may, in addition to reducing foamability, be detrimental to fluid injectivity if particle accumulation reduce the formation fluid flow capacity near the injection well. Retention was 401μg/g, in the lower range of reported literature values for aqueous surfactants, suggesting that nanoparticles to a large degree remain at the CO2-brine interface to stabilize foam when flowing through the porous medium. Elution, recovery of nanoparticles from the pore space by re-mobilization, was 79μg/g. Hence, 20% of retained nanoparticles were re-mobilized, and will contribute positively in a field application to increase foam stability further from the injection well. An apparent foam viscosity hysteresis related to the average gas saturation was observed when drainage-like (increasing gas fractions) and imbibition-like (decreasing gas fractions) injection strategies were compared. Nanoparticle-stabilized foam was also compared with surfactant-stabilized foam and the following main differences were observed: 1) maximum surfactant-stabilized foam apparent viscosities occurred at fg=0.9, compared with nanoparticle-stabilized foam with fg=0.7 (drainage-like) and fg=0.35 (imbibition-like); 2) without the presence of oil surfactant-stabilized foam have a higher (three orders of magnitude) apparent viscosity compared with nanoparticle-stabilized foam; 3) shear-thinning behavior was observed with surfactant-stabilized foam, whereas close to Newtonian behavior was observed with nanoparticle-stabilized foam; 4) no hysteresis was observed with surfactant-stabilized foams, whereas a clear hysteresis was observed with nanoparticle-stabilized foam.

Characterization of the molar mass distribution of macromolecules in beer for different mashing processes using asymmetric flow field-flow fractionation (AF4) coupled with multiple detectors.

The macromolecular composition of beer is largely determined by the brewing and the mashing process. It is known that the physico-chemical properties of proteinaceous and polysaccharide molecules are closely related to the mechanism of foam stability. Three types of "American pale ale" style beer were prepared using different mashing protocols. The foam stability of the beers was assessed using the Derek Rudin standard method. Asymmetric flow field-flow fractionation (AF4) in combination with ultraviolet (UV), multiangle light scattering (MALS) and differential refractive index (dRI) detectors was used to separate the macromolecules present in the beers and the molar mass (M) and molar mass distributions (MD) were determined. Macromolecular components were identified by enzymatic treatments with β-glucanase and proteinase K. The MD of β-glucan ranged from 106 to 108g/mol. In addition, correlation between the beer's composition and foam stability was investigated (increased concentration of protein and β-glucan was associated with increased foam stability).

Foams Stabilized by In Situ-Modified Nanoparticles and Anionic Surfactants for Enhanced Oil Recovery

Foams have been widely used in oilfields for effective profile control and displacement. However, foams stabilized by surfactants lack long-term stability, especially in an oil reservoir. Here, we have studied the in situ modification of positively charged AlOOH nanoparticles via the adsorption of the anionic surfactant sodium dodecyl sulfate (SDS) and the characterization of foam stabilized by AlOOH nanoparticles in synergy with SDS under different conditions. Changes in the zeta potential and adsorption isotherm of the AlOOH nanoparticles confirmed their modification. The most stable foam was obtained with an SDS/AlOOH concentration ratio of 5:1; further increases of the SDS concentration led to a decrease and subsequent increase in foam stability. The relationships between the zeta potential, three-phase contact angle, nanoparticle aggregate size, and foam stability were comprehensively analyzed, revealing that foam stability was affected by all of these factors. We concluded that nanoparticles with pa...

Evaluation of structural characteristics determining surface and foaming properties of β-lactoglobulin aggregates

Due to its structural versatility and remarkable surface activity, β-lactoglobulin (β-Lg) is a prominent food structuring agent in both its native state and in the form of heat-induced aggregates. In this study, we considered the properties of soluble aggregates of pure β-Lg having a median diameter of 50nm. The behavior of the aggregates at the air/water interface has been probed as a function of pH, with the aim of evaluating the controversial role of surface charge in connection with the functionality of particle-stabilized foams. Based on these new experimental results, it would appear that charge shielding around the isoelectric point (pI) leads to significantly increased foam stability as compared to samples having a significant positive or negative zeta potential. Against expectations, however, maximum foam stability was not linked to minimum foam drainage. High foamability and foam stability have been found to correlate with maxima in the rates of initial surface pressure increase and with interfacial dilatational properties. Evidence for efficient stabilization of the air/water interface was also reflected in a small average bubble size and a low rate of mean bubble area increase for aggregates with pH∼pI. Information from additional comparative experiments on systems with native β-Lg enabled an evaluation of the significance of surface hydrophobicity and aggregate particle size in relation to the foaming properties.