Surface-active Polysaccharides Research Articles

Preparation of maltodextrin stabilized α-tocopherol nanoemulsions using solvent-displacement technique.

α-Tocopherol nanoemulsions were prepared in current research using various proportions of Polysorbate 20 and maltodextrin as binary stabilizer mixtures through solvent-displacement technique. The effects of maltodextrin proportion in stabilizer mixture, on physicochemical characteristics of gained nanoemulsions, namely average particle size, polydispersity index (PDI), zeta potential, conductivity, invitro antioxidant activity, invitro cellular uptake and their rheological parameters were studied. The results show that using maltodextrin, as surface active biopolymer, together with Polysorbate 20, as small molecular stabilizer, could improve the characteristics of nanoemulsions considerably. The studied characteristics of all prepared shear-thinning (pseudo-plastic) nanoemulsions were well fitted to maltodextrin proportions via various polynomial models using regression statistical analysis. Thus, applying the surface active polysaccharides as stabilizer, in nanoemulsion formulations, and tuning its proportions to general used small molecular emulsifiers, can develop more desired functional lipid such as α-tocopherol nanoemulsions for various water-based food and pharmaceutical uses.

Effect of different surface active polysaccharide derivatives on the formation of ethyl cellulose particles by the emulsion-solvent evaporation method

This paper aims at a better understanding of the systematic production of the ethyl cellulose (EC) particles by using an emulsification-solvent evaporation method in the presence of different polysaccharide derivatives. In particular, the role of different surface active polymers i.e. one ionic—carboxymethyl cellulose, one nonionic—hydroxyethyl cellulose, and two amphiphilic—high molecular weight methyl cellulose and low molecular weight methyl cellulose on EC particle formation was investigated. We have established how individual surface active polysaccharides with varying concentration from 0.1 to 3.0 wt% affect particle size and its distribution, particle shape, surface charge, and particle surface morphology. The interdependencies between surfactant nature and concentration at constant processing parameters and the subsequent nano- to micro-particle characteristics are discussed. It was determined that the particle size, surface morphology, supramolecular structure and surface properties of EC particles, prepared by an emulsion evaporation method can be effectively controlled by the type and concentration of used polysaccharide surfactant yielding spherical particles sizes from 170 nm to the micrometer level with smooth particle surfaces or remarkably a wrinkled surface morphology or “particle on particle” structures.Graphical abstract

Comparative interfacial in vitro digestion of protein and polysaccharide oil/water films

The behaviour of proteins (β-lactoglobulin (βlg) and soy protein isolate (SPI)) and a surface active polysaccharide (hydroxypropylmethylcellulose, HPMC) o/w interfacial films under simulated gastrointestinal conditions using the interfacial tensiometer Octopus were compared and related to the performance of the emulsions (using the same emulsifiers) under in vitro digestion.The evolution of interfacial tension (γ) was used to investigate the effect of gastrointestinal fluids on o/w interfacial films. Clear differences were observed among these emulsifiers. During the gastric phase, HPMC showed the lowest change in γ values as compared to protein films. The most important changes occurred during the intestinal stage where it was observed an important decrease of γ associated with the rapid penetration of BS, followed by a lower rate of decrease attributable to the accumulation of FFA at the interface. In the last stage, the subphase was exchanged by buffer alone, to remove the reversibly adsorbed digestion products. SPI formed the most resistant interface to the remotion of digestion products, followed by HPMC and finally by βlg. The results agree with the degree of lipolysis reported for the emulsions stabilized by these emulsifiers, which suggest that lipid digestion could be modulated by the ability of emulsifiers to prevent the BS activity (to adsorb at the O/W interface or remove the inhibitory digestion products from the interface). Thus, emulsifiers-BS interactions appears as a key factor in controlling the lipolysis.

Impact of hydroxypropylmethylcellulose on whey protein concentrate spread film at the air–water interface: Structural and surface dilatational characteristics

Abstract The static (film structure and elasticity) and dynamic features (surface dilatational properties) of whey protein concentrate (WPC) spread films at the air–water interface, as influenced by three commercial hidroxypropylmethycelluloses (HPMC), i.e., E4M, E50LV and F4M, were studied, at 20 °C, pH 7 and I = 0.05 M. To this end a fully automated Wilhelmy-type film balance was used. The results showed a significant influence exerted by HPMC surface active polysaccharides on the WPC film structure. After the polysaccharide addition in the aqueous subphase the π-through area isotherms changed, especially for the highest molecular weight HPMC, as the time increased. Moreover, the presence of HPMC also decreases the surface modulus and the relative viscoelasticity of the WPC protein films. These results can be interpreted in terms of the ability of the polysaccharides to absorb at the air–water interface by itself, penetrate into the spread protein film due to its surface activity and increasing surface pressure. The existence of limited thermodynamic compatibility between the protein and HPMC, occurring in the aqueous phase and at the air–water interface, could be the cause of the observed phenomena, which in turn would be determined by the molecular properties of the cellulose derivative. As mixtures of proteins and polysaccharides are often used in many technological applications, the results presented here should help to improve the processes involved in the formation and stabilization of complex colloidal formulations like foams and emulsion based on these biopolymers.

Competitive adsorption behavior of β-lactoglobulin, α-lactalbumin, bovin serum albumin in presence of hydroxypropylmethylcellulose. Influence of pH

The interfacial properties at the air–water (A/W) of each individual whey proteins (β-lactoglobulin, β-lg; α-lactalbumin, α-la; bovin serum albumin, BSA), and their mixtures with a surface-active polysaccharide, hydroxypropylmethylcellulose (HPMC) were studied at pH 3 or 6. The interfacial films were studied by measurement surface pressure (π) isotherms and dynamics of adsorption. At equilibrium proteins surface activity was affected by pH only at low concentrations (below 1·10−2 % wt/wt), due to their pH-dependent conformational changes. HPMC resulted less surface active at pH 3 (below 1·10−4 % wt/wt concentration) that at pH 6. On kinetic studies (π–t), the behavior of β-lg, HPMC and BSA did not change with pH but α-la presented a higher surface activity at pH 3 than 6, even on saturating bulk concentrations. Mixtures of β-lg or BSA with HPMC showed a behavior in between that of single components revealing a net competence for the interface but the mixture α-la and HPMC at pH 6 showed an enhance adsorption. Rheological studies (surface dilatational elastic, Ed, over time) presented the major differences for pHs evaluated. The α-la formed extremely viscoelastic films at pH 6.0, while at pH 3 has the lowest Ed value. β-lg and HPMC films were more viscoelastic at pH 6, being Ed protein film higher. Finally, BSA presented the lowest viscoelastic films without differences between both pHs. For mixtures: i) at pH 6 β-lg/HPMC mixture Ed was dominated by HPMC; at pH 3.0, Ed begins dominated by HPMC, reaching an intermediate value; ii) α-la/HPMC mixture formed more viscoelastic films at pH 6.0 with an intermediate Ed value, while at pH 3.0 the Ed is dominated by protein; iii) BSA/HPMC mixture presented a similar trend in Ed behavior at both pHs.

On the chemical dynamics of extracellular polysaccharides in the high Arctic surface microlayer

Abstract. The surface microlayer (SML) represents a unique system of which the physicochemical characteristics may differ from those of the underlying subsurface seawater (SSW). Within the Arctic pack ice area, the SML has been characterized as enriched in small colloids of biological origin, resulting from extracellular polymeric secretions (EPS). During the Arctic Summer Cloud Ocean Study (ASCOS) in August 2008, particulate organic matter (POM, with size range > 0.22 μm) and dissolved organic matter (DOM, < 0.22 μm, obtained after filtration) samples were collected and chemically characterized from the SML and the corresponding SSW at an open lead centered at 87.5° N and 5° E. Total organic carbon was persistently enriched in the SML with a mean enrichment factor (EF) of 1.45 ± 0.41, whereas sporadic depletions of dissolved carbohydrates and amino acids were observed. Monosaccharide compositional analysis reveals that EPS in the Arctic lead was formed mainly of distinctive heteropolysaccharides, enriched in xylose, fucose and glucose. The mean concentrations of total hydrolysable neutral sugars in SSW were 94.9 ± 37.5 nM in high molecular weight (HMW) DOM (> 5 kDa) and 64.4 ± 14.5 nM in POM. The enrichment of polysaccharides in the SML appeared to be a common feature, with EFs ranging from 1.7 to 7.0 for particulate polysaccharides and 3.5 to 12.1 for polysaccharides in the HMW DOM fraction. A calculated monosaccharide yield suggests that polymers in the HMW DOM fraction were scavenged, without substantial degradation, into the SML. Bubble scavenging experiments showed that newly aggregated particles could be formed abiotically by coagulation of low molecular weight nanometer-sized gels. Aerosol particles, artificially generated by bubbling experiments, were enriched in polysaccharides by factors of 22–70, relative to the source seawater. We propose that bubble scavenging of surface-active polysaccharides could be one of the possible mechanisms for the enrichment of polysaccharides in the high Arctic open lead SML.

Hydroxypropylmethylcellulose–β-lactoglobulin mixtures at the oil–water interface. Bulk, interfacial and emulsification behavior as affected by pH

In this work we have studied the bulk, interfacial and emulsification behavior of a surface-active polysaccharide, hydroxypropylmethylcelulose (HPMC) and β-lactoglobulin (βlg) mixtures at two pHs, 3 and 6. The absence of an increase of particle size or a modification of zeta potential in HPMC/βlg mixtures indicated that both biopolymers would not form complexes in the bulk at pH 6. The protein presented a positive charge at pH 3, which makes possible the formation of a weak complex with the HPMC. The interface was dominated by the protein, indicating the displacement of the less surface-active HPMC at pH 6. The interfacial pressure of the HPMC/βlg mixture at pH 3 failed in between the curves corresponding to the single components. βlg Complexation may decrease its availability to adsorb at the O/W interface, lowering the mixture interfacial pressure. A bimodal distribution was obtained in emulsions at pH 6 and their confocal images evidenced a strong flocculation, non-adsorbed HPMC would remain in the continuous phase, thus promoting depletion flocculation of oil droplets. At pH 3 the emulsion droplet size distribution curve was bimodal, indicating polidispersity. Nevertheless, a high stability to coalescence was observed. The mixed emulsion zeta potential is reduced in comparison with the protein alone, indicating complexation between βlg and HPMC. When analyzing the confocal microcopy images of recently prepared emulsions, no flocculation was observed.

Effects of soy protein hydrolysis and polysaccharides addition on foaming properties studied by cluster analysis

The objective of the work was to study foaming properties (foam overrun, drainage rate and collapse stability) of soy protein and their hydrolysates as affected by polysaccharides. As starting material a sample of commercial soy protein isolate was used (SP) and hydrolysates of 0.4, 5.0 and 5.2% degree of hydrolysis (DH) were produced by an enzymatic reaction. The polysaccharides added were xanthan, λ and κ-carrageenan, guar, locust bean gum and hydroxypropylmethylcelluloses as surface-active polysaccharides. The effect of polysaccharides addition on foaming properties depended in a complicated way on the degree of hydrolysis of protein, surface-activity of polysaccharide, concentration of both macromolecules, contribution of polysaccharide consistency to bulk viscosity and interfacial interactions between biopolymers. However, through cluster analysis the best combination of protein/polysaccharide to obtain defined foaming properties could be determined for an eventual industrial application.

Effect of dynamic high-pressure treatment on the interfacial and foaming properties of soy protein isolate–hydroxypropylmethylcelluloses systems

The objective of the work was to study the effect of dynamic high-pressure homogenization (HPH) on the interfacial and foaming properties of soy protein isolate (SP) and surface-active polysaccharides (E4M and E15) with different molecular weight. SP was dispersed with water (2% w/v) together with the polysaccharides (0.3% w/v) and subjected to high-pressure from 0 to 300 MPa, in 100 MPa intervals. After treatment, foam overrun by whipping method, viscosity, particle size distribution and surface pressure at 48 s of drop formation time, of systems were measured. The effect of HPH of these systems on foam overrun was not directly relation with the effect on the surface pressure at short adsorption time. The viscosity decrease may be explained some of the foaming results together with interfacial performance at longer adsorption time than 48 s which depend on the system and level of pressure applied. According to the polysaccharide used in this work, interactions between SP and polysaccharides apparently favour the foam overrun on untreated mixed systems; this effect was promoted using HPH particularly in the case of E15 at 300 MPa. The effect of SP–E4M was less pronounced from the one observed for E15. Thus, the molecular weight of polysaccharides is a very important factor of interaction with soy protein isolate under these conditions of high-pressure homogenization.

Soy protein–polysaccharides interactions at the air–water interface

This work studies the interfacial behavior of mixed soy protein (SP) + polysaccharide (PS) systems to gain knowledge on the interactions between these biopolymers at the air–water interface under dynamic conditions at neutral pH where a limited incompatibility between macromolecules can occur. The PSs used were: hydroxypropylmethylcellulose (HPMC) as surface-active PS; lambda carrageenan ( λ C ) and locust bean (LB) gum as non-surface-active PSs. Protein and PS concentration in the mixed systems were 2% and 0.25%, respectively. The dynamic surface pressure and rheological properties of films were evaluated with a drop tensiometer at 20 ∘ C , pH 7 and ionic strength 0.05 M. The presence of HPMC and λ C greatly increased the surface pressure, surface dilatational elasticity and relative viscoelasticity on the basis of different mechanisms. HPMC competed for the interface with SP, but due to its unusual strong surface activity it could dominate the surface pressure and improve film viscoelasticity. The modification of surface pressure and rheological properties of adsorbed SP films in the presence of λ C necessarily suggests the participation of λ C + contaminants at the interface. Pure λ C could influence the interface by a complexation mechanism, or indirectly by a depletion mechanism in the vicinity of the interface. In addition surface-active contaminant of λ C if strongly bound to the PS could bring some PS molecules at the interface. LB little affected the surface pressure and rheological properties of SP films even if surface-active contaminants were present in the commercial preparation. Differences in the interaction of λ C and LB gum with the protein should be mainly ascribed to different degrees of incompatibility and to the fact that LB is not charged.

Effect of limited hydrolysis of soy protein on the interactions with polysaccharides at the air–water interface

The objective of the work was to study the effect of limited hydrolysis of soy protein on the interactions with polysaccharides with and without surface activity at the air–water interface at neutral pH where a limited incompatibility between macromolecules can occur. The surface pressure and phase angle as a function of time were evaluated with a drop tensiometer at 20 °C, pH 7 and ionic strength 0.05 M. Hydrolysates of 2% (H1) and 5.4% (H2) degree of hydrolysis (DH) with neutral protease from Aspergillus oryzae were obtained from a commercial soy protein isolate. The polysaccharides used were: hydroxypropylmethylcellulose (HPMC) as surface active polysaccharide; lambda carrageenan ( λC) and locust bean gum (LB) as non-surface active polysaccharides. It was found that increasing DH decreased the surface pressure and increased film viscoelasticity (determined as the phase angle, θ) of soy protein hydrolysates and the nature of protein–polysaccharide interactions was strongly affected by DH. The presence of polysaccharides led to an increase of surface pressure of H1 but when added to H2, HPMC and λC decreased the surface pressure. The less hydrolyzed protein H1 gave rise to a higher surface pressure and film viscoelasticity in combination with the polysaccharides. This result points out that a limited protein hydrolysis was sufficient to improve the surface properties of soy proteins if used in combination with polysaccharides. Polysaccharides used in admixture with hydrolyzed soy proteins could control and improve the stability of foams and emulsions not only by increasing bulk viscosity but also by improving film viscoelasticity.

Competitive adsorption of proteins with methylcellulose and hydroxypropyl methylcellulose

Surface-active polysaccharides are attracting increasing interest for use in a variety of applications. Amongst these, methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC) have been developed, in part, for their foam and emulsion stabilising properties, together with their water holding and viscosity enhancing properties. The aim of this research is to quantify the competitive adsorption between proteins and MC/HPMC, as they are often used together in many applications, and the results of potential effects of competition are unknown. Two proteins were compared; β-lactoglobulin (BLG) and β-casein (BCAS). BLG forms an elastic interface, whereas BCAS does not. Hence, BCAS is displaced by surfactants more easily than BLG. The surface rheology, surface tension and foam stability of the mixed protein:polysaccharide systems were determined to elucidate the mechanism and consequences of competition. In contrast to surfactants, both MC and HPMC formed highly elastic interfaces, more elastic even than BLG. Both HPMC and MC were more surface active than the proteins, therefore at higher MC and HPMC concentrations, the polysaccharides began to dominate the interfacial properties. Whereas surfactants reduce the elasticity of the protein adsorbed layer, the elastic properties of the polysaccharides enhanced the overall strength of the interface, which will potentially result in more stable foams.

Interactions of polysaccharides with β-lactoglobulin adsorbed films at the air–water interface

In the present work we have studied the adsorption (dynamic surface pressure) of β-lactoglobulin (βLG), polysaccharides and their mixtures at the air–water interface at 20 °C and at pH 7. The measurements were performed on a automatic drop tensiometer. As polysaccharides with interfacial activity we have used propylene glycol alginates (PGA). To evaluate the effect of the degree of PGA esterification and viscosity, different commercial samples were studied—Kelcoloid O (KO), Kelcoloid LVF (KLVF) and Manucol ester (MAN). Xanthan gum (XG) and λ-carrageenan (λ-C) were studied as non-surface active polysaccharides. The results reveal a significant effect of surface-active and non-surface-active polysaccharides on dynamic characteristics of β-lactoglobulin adsorbed films. To explain the observed effects on the rates of diffusion, penetration, and rearrangement of these biopolymers at the air–water interface, three phenomena were taken into account: (i) the competitive adsorption; (ii) the complexation, and (iii) the existence of a limited thermodynamic compatibility between protein and polysaccharide at the air–water interface and in the bulk aqueous phase. Surface-active polysaccharides (MAN, KO) are less effective than non-adsorbing polysaccharides (XG) for increasing the surface pressure of protein films, because a competitive behaviour with protein. Highly hydrophilic polysaccharides that do not adsorb by their own at the interface (XG, λ-C) or surface-active polysaccharides with low hydrophobicity (KLVF) show a cooperative behaviour with protein that promotes a significant increase of surface pressure of adsorbed films.

Adsorption of a Hydrophobically Modified Polysaccharide at the Air−Water Interface: Kinetics and Structure

We have used specular neutron reflectivity to study adsorbed layers of a modified polysaccharide bearing lateral cholesterol anchors (cholesterylpullulan, CHP) at the air−water interface. In this system, the otherwise non surface active polysaccharide is attached, at several points along the backbone, to the surface by the hydrophobic cholesterol groups. The properties of these adsorbed polymer layers have been studied for different degrees of cholesterol substitution varying from 0.6 to 1.4 mol % and for different bulk concentrations. Using a parabolic profile to describe the adsorbed layer, it is found that the thickness of the layer decreases with surface concentration. These results are in contrast to those reported for end-attached tethered polymer layers. We attribute this behavior to the associative properties of the polymer as the interacting cholesterol groups are increased in the layer. Furthermore, the amount of polymer adsorbed decreases with the degree of cholesterol substitution. Surface ten...