Polyglycerol Polyricinoleate Concentration Research Articles

Effect of stigmasterol and polyglycerol polyricinoleate concentrations on the preparation and properties of rapeseed oil-based gel emulsions

Emulsion gels mimic the rheological properties of solid and semi-solid fats, offering a viable solution to replace conventional fats in low-fat food formulations. In this study, gel emulsions stabilized with stigmasterol (ST) and polyglycerol polyricinoleate (PGPR) complexes were prepared. Initially, we examined the effect of the ST/PGPR complex on the mechanism of gel emulsion stabilization. Our findings revealed that the gel emulsion formulated with 3% PGPR and ST exhibited a robust structure, effectively stabilizing the entire system and ensuring uniform distribution, and increasing ST concentration led to greater stability of the gel emulsion system. Stability assessments demonstrated that gel emulsions containing 3% PGPR and varying ST concentrations exhibited remarkable thermal stability and effectively delayed oil oxidation. These results underscore the high stability of gel emulsions stabilized with the ST/PGPR complex, highlighting their potential as a margarine substitute.

Double W/O/W emulsion is effective for carrying calcium and vitamin D

A double emulsion is a promising system to facilitate the fortification process of nutrients such as calcium and vitamin D, as it protects vitamin D from oxidation and calcium from interactions with food proteins. The aim of this work was to produce Wi/O/We type double emulsions carrying vitamin D and calcium. The influence of the proportion of aqueous phase Wi/We (10/60, 15/55 and 20/70) and the concentration of polyglycerol polyricinoleate (PGPR) emulsifier (2.0, 2.5 and 3.0% w/w) on the kinetic stability of the emulsions over 13 days of storage was evaluated. For this, the following were analyzed: zeta potential, rheological properties (flow curve and viscoelasticity), entrapment efficiency (EE), and kinetic stability (KS) of calcium localization, microstructure, and macroscopic stability of the W/O/W emulsions, as well as the interfacial tension of the primary emulsions (Wi/O). The highest EE and KS of calcium localization were observed in treatments with smaller proportions of internal aqueous phase, regardless of the PGPR concentration. Therefore, an aqueous phase proportion of 10/60 combined with 2% PGPR is recommended.

Double Emulsions Stabilized by PGPR and Arabic Gum as Capsules: The Surprising Stabilizing Role of Inner Droplets.

The encapsulation efficiency and stability over time of either vitamin B12, a model hydrophilic drug, or an aqueous suspension of Cydia pomonella granulovirus (CpGV), which is a biopesticide, using a water-in-sunflower oil-in-water (W1/O/W2) double emulsion, are studied. Two antagonistic stabilizers are used to prepare the double emulsion: the mainly lipophilic polyglycerol polyricinoleate (PGPR) and the mainly hydrophilic polysaccharide Arabic gum (AG). Combining ultraviolet-visible (UV-visible) titration, rheology, and oil globule size measurement allows assessing drug release, emulsion elasticity, and globule evolution as a function of time. A stability diagram is plotted as a function of two determining parameters: the nonadsorbed PGPR concentration in the oil and the inner water droplet fraction. To understand the presence of the nonstability domains, the influence of the two identified parameters on the outermost interfacial tension is examined. Surprisingly, the inner water drop volume fraction exhibits a stabilizing phenomenon that is discussed in terms of interfacial shielding to PGPR adsorption.

Stabilization mechanism of emulsion containing vitamin B12: Impact of preparation methods and surfactant concentration

The aim of this study was to investigate the effect of the preparation methods and the concentration of polyglycerol polyricinoleate (PGPR) on the stability of the water-in-oil (W/O) emulsion. By comparing two different emulsions preparation methods, high-speed shear (16000 rpm) and high-pressure homogenization. We were found that high-speed shear treatment could reduce the particle size of the emulsion more effectively, thus significantly improving the stability of the emulsion. In addition, the effect of PGPR concentration on the stabilization mechanism of the emulsion was also discussed. The results showed that when the concentration of the PGPR was increased from 2 % to 6 %, it effectively prevented emulsion droplets polymerization and improved the stability of the emulsion. When the PGPR concentration was further increased to 10 %, the physical properties of the emulsion were mainly characterized by an increase in viscosity, which further enhanced the stability of the emulsion. In experiments involving the encapsulation of VB12, the encapsulation efficiency (EE) exceeded 95 %, and the retention efficiency (RE) exceeded 85 % even after 21 days of storage, demonstrating excellent stability. This study provided new insights into the preparation of stable water–oil emulsions, particularly regarding the efficient encapsulation and long-term stability of nutrients, and held significant application value for the food and pharmaceutical industries.

Anthocyanin-Rich Butterfly Pea Petal Extract Loaded Double Pickering Emulsion Containing Nanocrystalline Cellulose: Physicochemical Properties, Stability, and Rheology.

Butterfly pea petal extract (BPE)-loaded water-in-oil-in-water (W/O/W) emulsions were fabricated using nanocrystalline cellulose (NCC) as a hydrophilic stabilizer and polyglycerol polyricinoleate (PGPR) as a hydrophobic emulsifier. The impact of different concentrations of NCC and PGPR in different phase proportions on the emulsion formation, rheology, and stability of an anthocyanin-loaded (pH ≈ 7.0) emulsion was investigated. The mean droplet size of the emulsions increased as the NCC concentration increased, while color intensity (greenness) decreased as the PGPR and NCC concentrations increased. A microscopic examination confirmed that the NCC nanoparticles stabilized the inner W1/O phase, whereas the excess concentration of non-adsorbing NCC nanoparticles was suspended in the continuous aqueous phase. The rheological results showed that robust emulsion networks were formed when the NCC concentration increased. A network structure between the droplets and the development of the NCC network during the continuous phase were attributed to a gel-like behavior. Over the course of seven days, the emulsions with a higher proportion of NCC remained stable, as in samples 3%P-%N, 5%P-2%N, and 5%P@1%N, the total anthocyanin content decreased from 89.83% to 76.49%, 89.40% to 79.65, and 86.63% to 71.40%, respectively. These findings have significant implications for the accurate formulation of particle-stabilized double emulsions for anthocyanin delivery with higher stability.

Fabrication and stability of W/O/W emulsions stabilized by gum arabic and polyglycerol polyricinoleate.

In order to study the effect of adsorption of surfactant at the two interfacial layers on emulsion stability, the kinetically stable water-in-oil-in-water (W/O/W) emulsion carriers were prepared using polyglycerol polyricinoleate (PGPR) and gum arabic (GA) as emulsifiers. The relationship between the adsorption of the surfactant and the stability mechanism of the emulsions was elucidated. When the contents of PGPR and GA were low, the interfaces between oil and the inner and outer water phases, respectively, could not be completely covered. However, when the concentration of PGPR was higher than 60 g kg-1 , the excess PGPR was adsorbed on the interface between the oil phase and the outer water phase. When the concentration of GA reached 80 g kg-1 , more GA was adsorbed to the oil-in-water interface. Moreover, the presence of PGPR on the interface could reduce the adsorption capacity of GA. Two types of kinetically stable emulsions were obtained by optimizing the interface composition (60 g kg-1 GA/80 g kg-1 PGPR and 60 g kg-1 PGPR/80 g kg-1 GA). The kinetically stable W/O/W emulsions prepared in this study were successfully used to encapsulate a hydrophilic vitamin (vitamin B12) with an encapsulation efficiency (EE) of 80% and release efficiency (RE) of 95%. The interfacial adsorption GA can accelerate the hydrolysis of fat. Overall, this study provides a new strategy for the preparation of W/O/W emulsions, which might be beneficial for application in food, cosmetic, chemical, and pharmaceutical industries. © 2023 Society of Chemical Industry.

Microstructure, Rheology and Stability of Vegetable Cream-Like Emulsions Prepared with Natural Oils: Effects of Homogenization Speed and Polyglycerol Polyricinoleate Concentration

Microstructure, Rheology and Stability of Vegetable Cream-Like Emulsions Prepared with Natural Oils: Effects of Homogenization Speed and Polyglycerol Polyricinoleate Concentration

A Water in Oil Gelled Emulsion as a Topical Release Vehicle for Curcumin

AbstractThe objective of this work is to assess the influence of the concentration of polyglycerol polyricinoleate (PGPR) (at 1%, 1.5%, and 2%) on the physical properties of water in oil gelled emulsions (W/O) and evaluates their efficiency as a delivery vehicle for curcumin. Emulsions are characterized by drop size, centrifugal test, texture, and rheology during 28 days of storage. When the surfactant concentration increases, smaller droplet sizes are obtained (<5 µm), the phase separation (tested by centrifugal force) decreases from 6% to 4% with little variation of the time. The mechanical properties of emulsions show a tendency to decrease as time passed and concentration of PGPR increased. The emulsions increased viscosity as the concentration increased, but the addition of curcumin reduce the viscosity of the emulsions. About controlled release profiles, a low concentration of PGPR shows an increase in the affinity between curcumin and the emulsions, following a pseudo‐Fickian release behavior. At higher concentration of PGPR shows a decrease in the affinity between curcumin and the emulsion, displaying a Fickian release behavior. The authors were able to prepare tailor made curcumin water in oil emulsion systems for the topical release of this compound.

Polyglycerol polyricinoleate stabilised water-in-oil emulsion: structural characteristics and functional performance

In the present work, the relationship between structural characteristics and functional performance in polyglycerol polyricinoleate (PGPR) stabilised water-in-oil (W/O) emulsions was investigated. Novel W/O emulsions with a PGPR concentration of 4%, and oil volume fractions (φO) of 0.7 and 0.8 showed the smallest mean droplet size (~5 μm) and highest emulsification index (~97%). Both W/O emulsions showed shear-thinning and elastic-dominant properties with a weak frequency dependence. Both W/O emulsions possessed superior thixotropic recovery properties with recovery percentages of 131.26% (φO = 0.7) and 114.56% (φO = 0.8). The thermo-responsive properties could be closely related to the PGPR aggregation induced by hydrophobic interaction and interfacial rearrangement. The present work helped to design and develop functional W/O emulsions as alternatives to butter spreads, bio-lubricants, and other thermo-responsive delivery systems.

Novel Water-in-Oil Emulsions for Co-Loading Sialic Acid and Chitosan: Formulation, Characterization, and Stability Evaluation.

This study was designed to co-load sialic acid (SA) and chitosan in a water-in-oil (W/O) emulsion and investigated its characterization and stability. Emulsions were prepared using two different oils (olive oil and maize oil) and polyglycerol polyricinoleate (PGPR) alone or in combination with lecithin (LE) as emulsifiers. The results revealed that the aqueous phase of 5% (w/v) SA and 2% (w/v) chitosan could form a stable complex and make the aqueous phase into a transparent colloidal state. Increasing the concentration of PGPR and LE presented different effects on emulsion formation between olive oil-base and maize oil-base. Two stable W/O emulsions that were olive oil-based with 1.5% (w/v) PGPR+ 0.5% (w/v) LE and maize oil-based with 2% (w/v) PGPR+ 0% (w/v) LE were obtained. Initial droplet size distribution curves of the two stable emulsions displayed unimodal distribution, and the rheological curves displayed the characteristics of shear thinning and low static shear viscosity. Moreover, the storage stability showed that there was no significant change in droplet size distribution and Sauter mean diameter of the emulsions at room temperature (25 °C) for 30 days. These results indicated that the W/O emulsions could effectively co-load and protect sialic acid and chitosan and thus could be a novel method for increasing the stability of these water-soluble bioactive compounds.

Stability and rheological properties of water-in-oil (W/O) emulsions prepared with a soyasaponin-PGPR system

This study aimed to develop an innovative water-in-oil (W/O) emulsion with soyasaponin (Ssa) and polyglycerol polyricinoleate (PGPR) as emulsifiers. The effects of the oil/water ratio and aqueous Ssa concentration on the stability of emulsions was investigated. The analyses performed include evaluations of the overall stability, droplet size, rheological analysis, and interfacial tension. Research indicated that the most stable W/O emulsion corresponded to a water/oil ratio of 30/70, and the stability could be further enhanced by increasing the concentration of Ssa and PGPR. In the case of a 1% (w/w) Ssa emulsifier, results indicate a decreased particle size, increased viscosity, and increased stability of the prepared W/O emulsions. Furthermore, with 1% Ssa, the Turbiscan stability index (TSI) value of the W/O emulsions at 3% PGPR was lower than that of pure 4% PGPR emulsions. The results clearly show that 3% PGPR and 1% Ssa exhibited a synergistic effect on the stability of the emulsion. Overall, this study establishes a method for constructing food-grade W/O emulsions, which has prospects for certain applications in delivering functional components.

Development of a GC-FID method for the quantitative determination of polyglycerol polyricinoleate (PGPR) in foods

ABSTRACT Polyglycerol polyricinoleate (PGPR) is a powerful lipophilic emulsifier used in low-fat spreads and chocolate. It should be used at the lowest level at which the desired technological effect is achieved, not exceeding the specified maxima according to Annexe II to Regulation (EC) No 1333/2008. A gas chromatography–flame ionisation detection (GC-FID) method was developed for quantification of PGPR. This method is based on estimating the content of ricinoleic acid using 12-hydroxyoctadecanoic acid as an internal standard, from which the PGPR concentration was deduced. The method involved saponification, methylation, a two-step solid phase extraction (SPE) separation of the fatty acid methyl esters (FAMEs), silylation, and GC-FID analysis. The limits of detection and quantification of ricinoleic acid were 2.2 and 6.7 μg/mL, respectively, at 0.1 µL injection volume. Considering the average content of ricinoleic acid in PGPR (i.e. 86.63 ± 2.0 wt%) and the amount of food product that is used in the proposed protocol (i.e. 20 mg), this resulted in a LOD and LOQ of 0.76 and 2.32 μg PGPR per mg of food product, respectively. The developed method was validated by determining PGPR recovery from a high oleic sunflower oil (HOSO) solution, from chocolate spiked with a commercially available PGPR, and from commercially available low fat spreads with a known PGPR content. The actual recovery was more than 95% for all matrices, indicating the accuracy of the developed analytical technique. Moreover, the method proved to be very reproducible, with RSD < 4% for concentrations ranging from 0.2 to 5 wt%. The results showed that our proposed GC-FID method enables the reliable and quantitative determination of the PGPR concentration in commercial food products with various fat contents.

Effect of Selected Stabilizers and Processing Aids on the Stability of a Double Emulsion Encapsulating Bitter Gourd Extract

Effect of three variables in differing concentrations [NaCl (3-5%), polyglycerol polyricinoleate (PGPR) (2-4%) and dairy protein-polysaccharide complexes (Whey protein concentrate(WPC-80)-gum Arabic(GA) and sodium caseinate(SC)-gum Arabic in 1:2 ratio)] on the stability of W1/O/W2 emulsion matrix that was used to encapsulate bitter gourd extract was evaluated. The double emulsion matrix was characterized by apparent viscosity, zeta potential, turbidity and sedimentation stability by visual appearance. The physical parameters of the double emulsion matrix were very highly significantly (p &lt; 0.001) affected by all variables such as the concentration of salt, PGPR and complex (WPC-GA and SC-P) as well as their interactions. The double emulsions prepared with WPC-GA became unstable immediately after preparation or after one day of preparation. SC-GA stabilized double emulsions were found more stable than WPC-GA stabilized emulsions. A double emulsion containing 5% NaCl, 2% PGPR and 16.5% SC-GA were found most stable (10 days at 37°C) in comparison to other combinations used.

The Stability, Microstructure, and Microrheological Properties of Monascus Pigment Double Emulsions Stabilized by Polyglycerol Polyricinoleate and Soybean Protein Isolate.

Monascus pigment is a natural food pigment and is commonly used for coloring and as antiseptic of cured meat products, confectionery, cakes, and beverages. However, Monascus pigment is sensitive to environmental conditions. The main aim of this study was to investigate the effect of polyglycerol polyricinoleate (PGPR) and soy protein isolate (SPI) on the particle size, zeta potential, physical stability, microstructure, and microrheological properties of Monascus pigment double emulsions. The effects of ionic strength, heating, and freeze thawing treatment on the stabilities of Monascus pigment double emulsions were also characterized. It was found that the optimum PGPR and SPI concentrations for fabricating Monascus pigment double emulsion were 3.6 and 3.0 wt%, respectively. The fabricated Monascus pigment double emulsion was composed of fine particles with narrow and uniform size distributions. Microrheological property results suggested that the elastic characteristic of the Monascus pigment double emulsion was dominated with increasing PGPR and SPI contents. It was mainly due to the increased collision and interaction between the droplets during the movement resulting in force increasing. Monascus pigment double emulsions with <5 mM CaCl2 prevented calcium to destroy the physical stability of emulsions, while Monascus pigment double emulsions with more than 10 mM CaCl2 formed creaming. After freeze thawing treatment, creaming occurred in Monascus pigment double emulsion. However, it was stable against heating treatment due to heating leading to a dense network structure. It could be contributed to the practical applications of Monascus pigment double emulsions in food products.

Effect of polyglycerol polyricinoleate concentrations on the adsorption behavior of hydroxyapatite nanoparticles at the oil-water interface of emulsion

The adsorption behavior of hydroxyapatite (HAp) nanoparticles at the oil-water interface is very important for the microstructure of organic-inorganic composite fabricated using HAp nanoparticles stabilized Pickering emulsion as template. Studies on its adsorption behavior have attracted much interest because of the importance for their applications in biomedical field. Emulsions with dichloromethane (CH2Cl2) dissolved poly(l-lactic acid) (PLLA) as the oil phase and hydroxyapatite (HAp) nanoparticles dispersed in deionized water as the aqueous phase were prepared with different polyglycerol polyricinoleate (PGPR) concentrations in order to obtain PLLA/HAp porous composite. The distribution of HAp nanoparticles at the oil-water interface with different PGPR concentrations were characterized by confocal laser scanning microscope, and the adsorption behavior of HAp nanoparticles was also discussed. Transmission electron microscope and cryo-scanning electron microscope were used to characterize the emulsion stabilized by HAp nanoparticles with PGPR concentration of 1.0 w/v%. The results indicated that HAp nanoparticles were dispersed on the surface of emulsion droplets to stabilize emulsion, and some of them were also distributed on the surface of emulsion droplets or adjacent emulsion droplets in the form of agglomerates with lower PGPR concentrations. HAp nanoparticles escaped from the oil-water interface to the oil phase with increasing PGPR concentrations, and PGPR became the main emulsion stabilizer. Pickering emulsion was changed into classical emulsion with increasing PGPR concentration because PGPR turned to be the main stabilizer instead of HAp nanoparticles. Both microspheres and porous materials were fabricated using the as-received emulsion as template. This work would be helpful to study the adsorption behavior of HAp nanoparticles as well as its effect on the emulsion properties.

In-vitro oral digestion of microfluidically produced monodispersed W/O/W food emulsions loaded with concentrated sucrose solution designed to enhance sweetness perception

Monodispersed W1/O/W2 emulsions consisting of sunflower oil droplets containing a single large internal droplet or numerous small internal droplets of concentrated sucrose solution were prepared by microfluidic emulsification. The external droplet interface was stabilized by waxy rice starch, which hydrolyzes during oral processing thereby releasing the encapsulated sucrose solution to the proximity of taste receptors imparting a higher sweetness perception compared to adding the same amount of sugar to the bulk phase. The sucrose release was tracked by adding NaCl to the internal phase as a conductivity tracer. Core/shell droplets containing 50 wt% sucrose and 1.5 wt% NaCl in the internal phase, 1.40–2.86 wt% polyglycerol polyricinoleate (PGPR) in the middle phase, and 4 wt% gelatinized waxy rice starch in the external phase were produced with 100% encapsulation efficiency and showed stability against coalescence for at least two months, because the gelatinized starch acted as a highly efficient Pickering stabilizer. The sucrose release from the inner droplets during in-vitro oral processing at 37 °C for 30 s with 50 U/mL α-amylase increased from 16% to 49% when the PGPR concentration in the oil phase was reduced from 2.86 wt% to 0.7 wt%. Core/shell droplets were less stable during storage when the surface-active molecularly dissolved octenyl succinic anhydride (OSA) modified starch was selected as stabilizer although the oil droplets were smaller due to the lower interfacial tension at the external interface. W1/O/W2 emulsion consisting of numerous internal droplets coalesced during storage in one day and released 91% of sucrose during in-vitro oral processing.

Determination of Formulation Conditions Allowing Double Emulsions Stabilized by PGPR and Sodium Caseinate to Be Used as Capsules.

Water-in-oil-in-water (W1/O/W2) double emulsions stabilized by polyglycerol polyricinoleate (PGPR), a lipophilic food grade small polymer, and sodium caseinate, a hydrophilic milk protein, were developed to encapsulate vitamin B12, a model hydrophilic substance easy to titrate. Using rheology, sensitive to drop size evolution and water fluxes, static light scattering, and microscopy both giving the evolution of drops' size and vitamin B12 titration assessing the encapsulation, we were able to detect independently the double emulsion drop size, the encapsulation loss, and the flux of water as a function of time. By differentiating the PGPR required to cover the W1-droplets' surface from PGPR in excess in the oil phase, we built a PGPR-inner droplet volume fraction diagram highlighting the domains where the double emulsion is stable toward encapsulation and/or water fluxes. We demonstrated the key role played by nonadsorbed PGPR concentration in the intermediate sunflower oil phase on the emulsion stability while, surprisingly, the inner droplet volume fraction had no effect on the emulsion stability. At low PGPR concentration, a release of vitamin B12 was observed and the leakage mechanism of coalescence between droplets and oil-water interface of the oily drops (also called globules hereafter), was identified using confocal microscopy. For high enough PGPR content, the emulsions were stable and may therefore serve as efficient capsules without need of an additional gelling, thickening, complexion or interface rigidifying agent. We generalized these results with the encapsulation of an insecticide: Cydia pomonella granulovirus used in organic arboriculture.

Tayloring W/O/W emulsion composition for effective encapsulation: The role of PGPR in water transfer-induced swelling

The role of the lipophilic surfactant, polyglycerol polyricinoleate (PGPR) in water transfer in food-grade double emulsions was investigated, and related to physical emulsion stability. Double (W/O/W) emulsions were prepared with various PGPR concentrations (0.5–5.0 wt%) in the oil phase, at initial osmotic pressure differences of up to 1.1 MPa between the water phases. At high PGPR concentrations (>2 wt%), emulsions showed good physical stability, with encapsulation efficiency close to 100%. It was found that PGPR is involved in water transfer between the water phases through reverse micelle formation by PGPR molecules or hydrated monomers of PGPR, and this allows for controlled swelling. Emulsions that are initially of low viscosity (milk-like emulsions), obtain an apparent viscosity of up to 3 Pa·s, and this effect can be used to tune the emulsion properties to the targeted application, whithout the need to gel either the internal or external phase.

The formation of double emulsions in skim milk using minimal food-grade emulsifiers – A comparison between ultrasonic and high pressure homogenisation efficiencies

Double emulsions of W1/O/W2-type were formed in skim milk. Skim milk (W1) was emulsified within sunflower oil (O) using ultrasonication that was in turn emulsified within an external skim milk phase (W2) using ultrasonication or high pressure homogenisation (HPH). The internalised aqueous phase was stabilised within the oil phase using food-grade surfactants: polyglycerol polyricinoleate (PGPR) and/or lecithin. Encapsulation yields of the W1/O emulsion into the double emulsion were between 30 and 100%, with increased yields achieved with reduced sonication time or HPH pressure, or increased PGPR or lecithin concentration. Ultrasonication was found to form relatively better monodisperse emulsions that showed greater stability to coalescence than those produced by HPH. Ultrasonication and HPH were found to be translatable in the sense that at a similar specific energy density (∼20 J/g) emulsions with similar size distributions in the range 1-10 μm and encapsulation yields (ca 37 wt%) could be achieved.

Effect of protein molecules and MgCl2 in the water phase on the dilational rheology of polyglycerol polyricinoleate molecules adsorbed at the soy oil-water interface

The objective of this study was to investigate the effect of inorganic salt and protein in the aqueous phase on the dilational rheology properties of interfacial film stabilized by the hydrophobic emulsifier polyglycerol polyricinoleate (PGPR). The interfacial behavior was investigated using the oscillating drop method. With increased PGPR concentration, the interfacial tension tended to decrease and reached an equilibrium value of 3.3 mN m−1, at 1.0% (w/w) PGPR. With 0.01% (w/w) PGPR in the oil phase, the presence of whey protein isolate (WPI) increased the dilational elasticity modulus of PGPR, but the addition of bovine serum albumin (BSA) decreased the elasticity modulus. This was likely due to competitive adsorption of BSA and PGPR at the soy oil/water interface, resulting in the desorption of BSA from the interface. At 1.0% (w/w) PGPR, both WPI and BSA increased the interfacial dilational elastic modulus and the reason might be that the presence of protein could suppress the diffusion-exchange process of PGPR between bulk phase and interface. The addition of MgCl2 may enhance the adsorption of PGPR molecules at the interface and therefore increased the dilational modulus.