Droplet Flocculation Research Articles

Molecular mechanisms affecting the stability of high internal phase emulsions of zein-soy isoflavone complexes fabricated with ultrasound-assisted dynamic high-pressure microfluidization

In this study, zein-soy isoflavone complex (ZSI) emulsifiers were fabricated using ultrasound-assisted dynamic high-pressure micro fluidization to stabilise highinternal phase pickering emulsions. Ultrasound-assisted dynamic high-pressure micro-fluidization enhanced surface hydrophobicity, zeta potential, and soy isoflavone binding capacity, while it decreased particle size, especially during ultrasound and subsequent microfluidization. The treated ZSI could produce small droplet clusters and gel-like structures, with excellent viscoelasticity, thixotropy and creaming stability owing to their neutral contact angles. Ultrasound and subsequent micro fluidization treatment of the ZSI complexes were highly effective in preventing droplet flocculation and coalescence after long-term storage or centrifugation due to their higher surface load, thicker multi-layer interfacial structure, and stronger electronic repulsion between the oil droplets. This study provides insights and extends our current knowledge of how non-thermal technology affects the interfacial distribution of plant based particles and the physical stability of emulsions.

Transforming monomeric globulins into pickering particles to stabilize nanoemulsions: Contribution of trehalose

Monomeric globulins have been widely employed in food-grade nanoemulsion preparation owing to their outstanding emulsification performance. However, a limitation to stabilize nanoemulsions during storage exists when using monomeric globulin as sole emulsifier, mainly due to the low structural stability of protein during emulsification and at water-oil interface. In the current work, an efficient strategy to fabricate ultra-stable protein-based nanoemulsions was proposed through the incorporation of trehalose to enhance the structural stability of bovine serum albumin (as a model monomeric globulin) in the aqueous phase. The as-prepared nanoemulsions exhibited a high stability against droplet flocculation and coalescence during emulsification and upon long-term storage. Further analyses indicated that the presence of trehalose could form a “shell” structure around protein particles to protect protein against denaturation, unfolding and aggregation during microfluidization. The globulins in trehalose-rich system could behave as a kind of soft nanoparticles with a strong structural integrity and were unaffected by adsorption at the interface. Moreover, the existence of abundant aggregated trehalose greatly favored protein diffusion and adsorption and contributed to more balanced protein wettability, thus allowing monomeric globulins to stabilize more interfaces with Pickering effect. The findings are of value for providing a strategy to prepare stable nanoemulsion using monomeric globulins as the sole emulsifier by simply transforming monomeric globulins into Pickering nanoparticles with the addition of trehalose.

Coagulation of model infant formulae: Impact on their in vitro dynamic gastric digestion

The rheological properties and the in vitro dynamic gastric digestion behaviours of model infant formulae containing various ratios of casein to whey protein (0:100, 40:60, 60:40 and 80:20) were investigated using a rheometer and an infant human gastric simulator. The pH profiles and the viscoelastic moduli were determined during acidification by glucono-δ-lactone and at different pepsin concentrations (0, 0.3, 1.0, 1.7 and 2.5 U/mL). The infant formula containing whey protein only formed a weak gel at about pH 5. In the presence of pepsin, all casein-containing infant formulae formed gels at pH ∼6.0 and only low pepsin activity (>0.3 U/mL) was required for the gelation. The strength of the gel/coagulum was dependent mainly on the casein content. Coagulation of protein and flocculation of oil droplets, induced by both pepsin proteolysis and the low pH under gastric conditions, were observed in the infant formulae during dynamic digestion in the human gastric simulator. Confocal images showed that the infant formula containing whey protein only formed smaller flocs of aggregated protein and oil droplets, which may have led to their observed faster protein digestion, than the infant formulae containing a combination of casein and whey protein. The casein-dominant infant formulae had greater aggregation than the whey-protein-dominant infant formulae during gastric digestion, which led to their lower rate of casein digestion. These results suggest that the extent of coagulation and the gastric digestion of the proteins in infant formulae can be controlled by the rational selection of the protein components and the ratio of casein to whey protein, such that different nutritional requirements of infants can be met.

Jamming to unjamming: Phase transition in cyclodextrin-based emulsions mediated by sodium casein

HypothesisCyclodextrin (CD) can spontaneously build up the solid particle membrane with CD-oil inclusion complexes (ICs) by a self-assembly process. Sodium casein (SC) is expected to preferentially adsorb at the interface to transform the type of interfacial film. The high-pressure homogenization can increase interfacial contact opportunities of the components, which promote the phase transition of the interfacial film. ExperimentsWe added SC by sequential and simultaneous orders to mediate the assembly model of the CD-based films, examined the patterns in which the films adopt phase transitions to retard emulsion flocculation, and studied the physic-chemical properties of the emulsions and films from the structural arrest, interface tension, interfacial rheology, linear rheology, and nonlinear viscoelasticities through Fourier transform (FT)-rheology and Lissajous-Bowditch plots. FindingsThe interfacial and large amplitude oscillatory shear (LAOS) rheological results showed that the films changed from jammed to unjammed. We divide the unjammed films into two types: one is SC dominated liquid-like film, which is fragile and related to droplet coalescence; the other is cohesive SC-CD film, which helps droplet rearrangement and retards droplet flocculation. Our results highlight the potential of mediating phase transformation of interfacial films to improve emulsion stability.

Effects of FeII, tannic acid, and pH on the physicochemical stability of oil body emulsions

This study examined the effects of solution pH (3.0, 5.0, and 7.0), FeII, and tannic acid (TA) on oil body (OB) emulsions and monitored changes in emulsion particle size, zeta potential, appearance, microstructure, and oxidation stability over 14 days of storage at 37 °C. The chelation efficiency, zeta potential, and fourier-transform infrared spectroscopy results showed that the ability of TA to chelate FeII and the absolute charge of TA-Fe complexes increased with the pH. In addition, the distribution of these complexes in the emulsions was influenced by their electrostatic and hydrogen bonding interactions with the OB. At pH 3.0 and 5.0, the TA-Fe and OB emulsion particles attracted each other, resulting in droplet flocculation. At pH 7.0, the TA-Fe and OB emulsion particles carried the same (negative) charge, and had little effect on physical stability of OB emulsions. TA generally inhibited the oxidation of OB emulsions but promoted the concentration of the primary and secondary oxidation products (61.48 mmol/kg and 50.5 μmol/kg, respectively) of FeII-containing emulsions at pH 3.0. The obtained results provide new insights into the efficacy of TA as a natural antioxidant for emulsified foods and thus pave the way to increasing their quality and shelf life.

Nano and micro lupin protein-grape seed extract conjugates stabilizing oil-in-water emulsions

Conjugation of plant proteins with phenolic compounds has been an efficient strategy to improve the limited capacity of this kind of protein to stabilize emulsions. In this sense, the stabilizing capacity of lupin protein-grape seed extract conjugates in the form of nano (NC) or micro (MC) particles was evaluated in oil-in-water emulsions. Covalent binding between lupin protein isolate (LPI) and grape seed extract (GSE) was confirmed by quantification of total free sulfhydryl groups and fluorescence assays in both NC and MC for all GSE concentrations tested (0.04–1.2 wt%). The main differences between MC and NC were the larger size and surface hydrophobicity of the former, reflecting different stabilizing capacities. The droplet size and microstructure of all emulsions after 28 days of storage suggest that NC- and MC-stabilized emulsions were highly stable to coalescence. However, NC produced emulsions with a higher tendency to flocculation. Increasing the GSE concentration in the conjugates attenuated the droplet flocculation, resulting in emulsions with improved kinetic stability. Results indicate that the dominant stabilizing mechanism of the conjugates is Pickering-type, although others may occur simultaneously. Indeed, MC produced emulsions with better stability with no visible creaming and more complex rheological properties. A gel-like behavior (G’>G’’) was observed from oscillatory rheology, which was considered an additional stabilizing mechanism. In contrast, NC produced emulsions with predominantly liquid-like behavior (G’’>G’). Shear resistance was evaluated after homogenization of the emulsions, showing that the 3D network formed in the emulsions was rapidly recovered, including the highly structured MC-stabilized emulsions. Different properties of emulsions stabilized by NC or MC indicate potential varied applications in the food industry. The conjugation of GSE with LPI showed improvements in the overall stability of the emulsions, demonstrating the great potential for usage of these conjugates in the formulation of highly stable emulsion-based systems, even using a protein of limited stabilizing capacity.

Lauric acid adsorbed cellulose nanocrystals reduced the in vitro gastrointestinal digestion of oil-water pickering emulsions

An in vitro gastrointestinal tract (GIT) fate of beta-carotene-loaded oil-in-water Pickering emulsions stabilized with lauric acid-adsorbed cellulose nanocrystals (CL) was investigated. Different concentrations (0.5, 1.0, 1.5 and 2.0%, w/v) of CL and pure cellulose nanocrystals (CNC) were used. During in vitro digestion, the effects of CL and CNC and their concentrations on the lipid droplet diameter (D 4,3 ), zeta potential, microscopic structure, phase stability (creaming index), degree of lipid digestion (free fatty acid release), and bioaccessibility of loaded beta-carotene were recorded. The Pickering emulsions stabilized with levels of CL above 1.0% (w/v) were stable against lipid droplet flocculation and coalescence and impeded the increase of D 4,3 (p ≤ 0.05) throughout the GIT phases. A significant increase in the D 4,3 was recorded for the emulsion stabilized with CNC due to flocculation and coalescence of lipid droplets. Instead of electrostatic repulsion stabilization, Pickering emulsions stabilized with CL displayed steric stabilization activity at the lower pH of the gastric phase, where the lowest zeta potential of less than +10 mV was found. The Pickering emulsion stabilized with CNC had significantly higher lipid digestion (∼63%) than stabilized with CL (∼52%). Average bioaccessibilities were up to 65% for CL stabilized Pickering emulsions and 70% for CNC-stabilized Pickering emulsions. CL can maintain emulsions phase stability by retaining lipid droplet size, reducing lipid digestibility, and prolonging the release of lipophilic nutrients. Other modifications of CNC may be required to release such nutrients in the small intestine, and in vivo studies are needed to verify in vitro assays. • Modifying nanocellulose with lauric acid improved emulsion stability but delayed the release of beta-carotene for absorption in an in vitro digestion model system. • Other types of chemical modification may be necessary to deliver phytonutrients for absorption in the small intestine.

Stabilization of ginger essential oil Pickering emulsions by pineapple cellulose nanocrystals

Pickering emulsions (PE) are systems made up of two incompatible fluids, these are stabilized by solid organic or inorganic particles located on their interface. Cellulose nanocrystals (CNCs) are sustainable and biocompatible value-added naturally occurring biomolecules which are being investigated as PE stabilizers in the cosmetic, food, and pharmaceutical industries. The objective of this research was to investigate the efficacy of pineapple cellulose nanocrystals as stabilizers for a ginger essential oil-in-water Pickering emulsion. Anionic pineapple cellulose nanocrystals were prepared by acid hydrolysis. Ginger essential oil-in-water emulsions were prepared by ultrasonication. Pineapple CNC produced stable Pickering emulsions with surface average droplet size of 4.3 μm–6.2 μm, high negative zeta potential, high viscosity, and high adsorption at the interface. Pickering emulsions by ultrasonication were stable against droplet coalescence, phase separation, and droplet flocculation for at least 8 weeks at 25 °C or 40 °C at various droplet sizes. The emulsion droplet size and volume density (droplet size distribution) were evaluated by varying the particle concentration (CNC 0.25 g/100 ml or 0.50 g/100 ml) and/or oil fraction (10–20 g/100 ml). At constant oil fraction, the emulsion viscosity increased as the nanocrystal concentration increased. The cellulose nanocrystal-stabilized ginger oil-Pickering emulsions exhibited shear-thinning characteristics of a pseudo-plastic fluid. Pineapple nanocellulose crystal -stabilized ginger oil-Pickering emulsions exhibited high stability with a creaming index of zero. CNC was found to be an effective Pickering stabilizer for oil-in-water emulsions in various food applications.

Effect of Mucilage Extracted from Corchorus olitorius Leaves on Bovine Serum Albumin (BSA)-Stabilized Oil-in-Water Emulsions.

The present study examined the effect of mucilage extracted from Corchorus olitorius L. leaves on the emulsifying stability of bovine serum albumin (BSA)-stabilized oil-in-water (O/W) emulsions during the storage for seven days. O/W emulsions were prepared with a 90% aqueous phase containing C. olitorius mucilage (0-1.00% w/v) together with 0.5% (w/v) BSA and 10% oil phase. Emulsion properties were analyzed by measuring droplet size, zeta potential, spectroturbidity, backscattering profiles (%BS), and visual observations. The mean droplet size of emulsions prepared with 0.75 and 1.00% mucilage did not show significant changes during storage. The zeta potential of all the emulsions exhibited a negative charge of approximately -40 mV, but electrical repulsion was not the dominant stabilization mechanism in the emulsion. C. olitorius mucilage was able to increase the viscosity of the aqueous phase of the O/W emulsion system, which prevented droplet flocculation and enhanced the emulsion stability against phase separation at higher concentrations. The most stable emulsions during the storage period were those with 1.00% C. olitorius mucilage. In conclusion, C. olitorius mucilage has good potential for the preparation of stable O/W emulsions and can be used as a plant-based natural emulsifying and thickening agent in the food industry.

Tunable oleosome-based oleogels: Influence of polysaccharide type for polymer bridging-based structuring

This research proposes a gelation method using soybean oleosomes as templates in combination with polysaccharides. Two anionic polysaccharides, sodium alginate, and xanthan gum were investigated for their ability to induce bridging flocculation. Bridging flocculation occurs when flexible polysaccharides such as alginate strongly interact with oppositely charged oleosome particles in acidic pH ranges. In contrast, the more rigid xanthan leads to a different flocculation mechanism, which is not driven by strong electrostatic attractive interactions. In microscopy images, xanthan induced microscopic and macroscopic phase separation between oleosome droplets and xanthan, presenting large, irregular-shaped particles. The ratio between alginate chains and oleosome droplets is critical for optimum bridging, where 0.005 g/g (also expressed as an equivalent per droplet surface area 0.4 mg/m2) induced extensive droplet flocculation. It is possible to obtain an interconnected droplet network at this optimum ratio. Upon densification at the optimum ratio, a compact and self-supporting gel of about 46 wt% starting from 5 wt% oleosome is obtained. Oscillatory rheology showed that gels at optimum bridging ratio have higher moduli (G’) than those formed at a different ratio, confirming a highly cross-linked network. Bridging flocculation provides an alternative method to design gels with predictable rheological properties suitable for food and drug design and cosmetic applications.

Pea protein isolates: emulsification properties as affected by preliminary pretreatments

The surface and emulsifying properties of a commercial pea protein isolate in oil-in-water model emulsions and the role of insoluble residues in emulsion stability were investigated. Droplet size distribution, flocculation index, microstructure, and protein coverage of the emulsions were evaluated. The insoluble fraction positively contributed to the pea proteins’ emulsifying properties, allowing the formation of emulsions with higher dispersion degree, especially at low isolate concentration, with an enhancement of the physical stability.

Emulsifying properties of sugar beet pectin microgels

Particle stabilized (‘Pickering’) oil-in-water (O/W) emulsions were fabricated using sugar beet pectin (SBP) microgel particles (SBPM) that differed in their crosslinking density and therefore elasticity. Droplet size distributions and emulsion microstructures were investigated via light scattering and complimentary imaging techniques: light microscopy, confocal laser scanning microscopy and scanning electron microscopy. Comparisons to emulsions stabilized by native (i.e., non-microgelled) SBP at equivalent overall SBP content were made throughout. The SBPM-stabilized emulsions (20 and 40 vol% oil) were shown to have an improved physical stability compared to those stabilized by SBP. For example, droplet coarsening on prolonged (9 week) storage at ambient temperature (25 °C) and on temperature cycling (75 °C) was substantially reduced for SBPM-stabilized emulsions. This is attributed to the greater steric barrier provided by SBPM particles and their higher energy of displacement. Furthermore, the higher viscoelasticity of the SBPM-stabilized emulsions (particularly at 40 vol% oil) retarded droplet creaming. This higher viscoelasticity could be due to weak flocculation of the SBPM-stabilized droplets or the strong influence of the SBPM on the viscoelasticity of the intervening aqueous phase, even at relatively low SBPM concentrations.

Changes in Emulsifying and Physical Properties of Shrimp Oil/Soybean Oil‐in‐Water Emulsion Stabilized by Fish Myofibrillar Protein during the Storage

AbstractProperties of shrimp oil/soybean oil (30:70)‐in‐water emulsion stabilized using fish myofibrillar protein (FMP) at different concentrations (15, 30, and 45 mg mL−1) are investigated. When FMP concentration increases, emulsion activity index decreases (p < 0.05). Conversely, emulsion stability index, adsorbed protein, and interfacial protein contents are augmented (p < 0.05). During storage of 15 days, emulsion added with FMP at 45 mg mL−1 (FMP‐45) has the highest turbidity, zeta potential, viscosity, and viscoelastic properties (G′ and G″) than the others (p < 0.05). Emulsions show shear‐thinning and non‐Newtonian behavior. The emulsion added with FMP at 15 and 30 mg mL−1 (FMP‐15 and FMP‐30, respectively) has dominant viscous properties (G′ < G″), whereas FMP‐45 shows elastic gel‐like behavior (G′ > G″) (p < 0.05). Lower droplet size (d32 and d43), polydispersity index (PDI), flocculation (Fi), and coalescence (Ci) are observe in FMP‐45 (p < 0.05). Microstructure reveals smaller droplet size and smaller increase in droplet size of FMP‐45 after storage. Overall, all emulsions remain stable with no obvious phase separation throughout the storage. Confocal laser scanning microscopic images show that increase in FMP concentration can yield monodisperse emulsion. Therefore, fish myofibrillar protein exhibits excellent emulsifying property and stability for shrimp/soybean oils‐in‐water emulsion.Practical Applications: Oil from shrimp hepatopancreas, a byproduct from hepatopancreas free whole shrimp, is well known for their health benefits. It can be used to produce functional food emulsion such as mayonnaise. The use of fish myofibrillar protein is proven to be a potential emulsifier, which can improve emulsifying properties. The obtained emulsion is stable without no phase separation during the extended storage. This finding can be beneficial for food industries to produce food emulsion rich in high quality protein and polyunsaturated fatty acid. Also, hepatopancreas can be fully exploited.

Nano-modification of carboxylated polyether for enhanced room temperature demulsification of oil-water emulsions: Synthesis, performance and mechanisms

Oil-water emulsions separation is frequently required considering the production and environmental issues. Herein, a nano-modification strategy has been proposed for carboxylated poly(propylene oxide)-poly(ethylene oxide) block polyether (mANP) using epoxy-functionalized magnetic nanoparticles (Fe3O4@SiO2-GPTMS), achieving the construction of a highly efficient demulsifier (M-mANP). Bottle tests showed that M-mANP could separate over 98.5% of water from the asphaltene-stabilized water-in-oil (W/O) emulsion at mANP concentration of 150 ppm within 2 min at room temperature. The demulsification efficiency for crude oil-in-water emulsion was nearly 100%. According to interfacial tension and wettability tests, the nano-modification endows M-mANP with good amphiphilicity and high interfacial activity, which enables M-mANP to rapidly adsorb at the oil-water interface. Molecular dynamics simulation shows that abundant oxygen-containing groups (hydroxyl, ether bond, ester and carboxyl groups, Fe−O and Si−O bond) in M-mANP could strengthen the interaction with water, facilitating the replacement of asphaltene molecules at interfacial film. Observation of demulsification process by microscope reveals that the nano-size promotes M-mANP to bridge small dispersed droplets, enhancing the flocculation and coalescence of droplets. The nano-modified carboxylated polyether with outstanding demulsification ability shows a promising application for the treatment of different oil-water emulsions.

The temporal evolution mechanism of structure and function of oxidized soy protein aggregates

The emulsifying activity of soy protein would decrease after long-term storage, which caused huge economic losses to food processing plants. This study explored the temporal evolution mechanism of oxidation on the structure and function of soy protein aggregates, which would improve the application of soy protein in food industry. Decreased α-helix and increased random coil were observed at the initial oxidation stage (0-4h), which induced increases in hydrophobicity and disulfide bond content. In addition, emulsibility increased significantly. However, when the oxidation time extended to 6-12h, the soluble aggregates transformed into insoluble aggregates with large particle size, low solubility, and molecular flexibility. Surface hydrophobicity and emulsifying activity were reduced, resulting in bridging flocculation of emulsion droplets. Mutual transformation between components is affected by factors that include spatial conformation and intermolecular forces, which eventually lead to functional changes in the protein molecules.

Nanoemulsions with sea buckthorn oil and κ-carrageenan

The structure, stability, and rheological properties of nanoemulsions with droplets of sea buckthorn oil stabilized with Tween 80 and Span 80 and κ-carrageenan in the aqueous phase were investigated. The fast flocculation and coalescence of oil droplets occurred in nanoemulsions without κ-carrageenan. The nanoemulsion stability was significantly improved in the presence of the gel network at κ-carrageenan concentrations ≥ 0.5 mass%. TEM analysis showed that oil droplet flocs were trapped in the polymer gel network, so the further floc compaction and creaming were prevented. Nanoemulsions without κ-carrageenan and 0.25 mass% κ-carrageenan displayed the Newtonian-like rheological behavior whereas nanoemulsions with 0.5–5.0 mass% κ-carrageenan demonstrated the non-Newtonian flow of the pseudoplastic type. Oscillatory measurements showed that the values of G′ were higher than the corresponding G″ for nanoemulsions with 0.5 and 2 mass% κ-carrageenan in the investigated range of angular frequencies. However, the G′/G″ crossover was detected for nanoemulsion with 5 mass% κ-carrageenan. The structure relaxation was not observed for this nanoemulsion because the gel in the aqueous phase was irreversibly broken under shear. In nanoemulsions with lower κ-carrageenan concentration, the disintegrated structure was recovered with time after shearing. Apparently, the destruction of the oil droplet flocs under the shear was reversible and the elastic structure of the gel was not destroyed.

Effects of Tea Polyphenol Palmitate Existing in the Oil Phase on the Stability of Myofibrillar Protein O/W Emulsion.

This study aimed to explore the effect of adding different concentrations (0, 0.01%, 0.03%, and 0.05% (w/w)) of tea polyphenol palmitate (TPP) in the oil phase on the emulsifying properties of 5 and 10 mg/mL myofibrillar protein (MP). Particle size results revealed that the flocculation of droplets increased as TPP concentration increased and that droplets in 5 mg/mL MP emulsions (25–34 μm) were larger than in 10 mg/mL MP emulsions (14–22 μm). The emulsifying activity index of 5 mg/mL MP emulsions decreased with increasing TPP concentration. The micrographs showed that the droplets of MP emulsions exhibited extensive flocculation at TPP concentrations >0.03%. Compared with 5 mg/mL MP emulsions, 10 mg/mL MP emulsions showed better physical stability and reduced flocculation degree, which coincided with lower delta backscattering intensity (ΔBS) and Turbiscan stability index values. The flow properties of emulsions can be successfully depicted by Ostwald–de Waele models (R2 > 0.99). The concentrations of TPP and protein affect the K values of emulsions (p < 0.05). Altogether, increased protein concentration in the continuous phase could improve emulsion stability by increasing viscosity, offsetting the adverse effects of TPP to a certain extent. This study is expected to promote the rational application of TPP in protein emulsion products of high quality and acceptability.

Droplet Dispersion States of Cyclodextrin-Based Emulsions from Nonlinear Rheological Properties.

Polymers are desirable to improve emulsion stability by stuffing them into the continuous phase. How to get information on the droplet dispersion states of the emulsions remains a challenge, as the emulsion characteristics are dictated by two intertwining components, the polymer matrix and the droplets. Herein, we use an amphiphilic polymer, gum arabic (GA), to mediate the droplet flocculation of cyclodextrin (CD)-based emulsions and compare them with our previous studies on the stabilization of CD-based emulsions by a nonamphiphilic polymer, methylcellulose (MC). We characterize the emulsions by using optical microscopy, confocal laser scanning microscopy, and laser particle analysis, explore their rheological behavior through large-amplitude oscillatory shear experiments, and analyze the nonlinear viscoelasticities through Fourier transform (FT)-rheology and Lissajous-Bowditch plots. There is a great difference between GA and MC in the viscosity effect and the arrangement around emulsion droplets. GA is not an effective flocculation inhibitor due to a bridging flocculation mechanism rather than a direct viscosity effect. Our analysis highlights the role of the intrinsic nonlinearity parameter (Q0) extracted by FT analysis in reflecting the droplet dispersion states of the emulsions by decoupling structural contributions from the polymers and the emulsion droplets.

Fabrication, characterization and in vitro digestive behavior of Pickering emulsion incorporated with dextrin

Whey protein-stabilized Pickering emulsion was incorporated with dextrin under different concentrations, and their physicochemical properties and in vitro digestive behavior were examined. The result showed that these emulsions were relatively stable at low dextrin addition (<7.5%), while droplet flocculation appeared at higher concentrations. With progressing dextrin, the apparent shear viscosity significantly increased from 1.7 to 7.3 mPa.s. Further insight into the digestive behaviors of emulsion incorporated with dextrin was determined using a standardized INFOGEST method. Less clump in the oral phase and increasing droplet size in the initial intestine were observed in the emulsion incorporated with dextrin. Based on dextrin incorporation, a significant decrease in the extent of lipid digestion and β-carotene bioaccessibility was presented. This study implies dextrin may be useful in controlling the texture and in vitro digestive behavior of Pickering emulsions, which may be advantageous for the designation of functional foods.

Complexation of pea protein isolate with dextran sulphate and interfacial adsorption behaviour and O/W emulsion stability at acidic conditions

SummaryThis study was aimed at improving the emulsifying property and physical stability of pea protein isolate (PPI) stabilised emulsions at acidic conditions by complexation with dextran sulphate (DS). Soluble and insoluble complexes with different charge and particle size were formed depending on the phase separation behaviour. The surface adsorption of PPI became slower after complexation with DS, but the percentage of adsorbed proteins at the oil–water interface was not affected. The formation of PPI–DS soluble complexes at high content of DS (≥0.4%) significantly improved the negative net charges of PPI, prevented the aggregation of protein, which further improved the emulsifying property of PPI at acidic conditions through the strong electrostatic repulsion and steric hindrance effects. Insoluble complexes with relatively weak net charge and large particles were formed at low DS content (≤0.2%), resulting in the bridging flocculation of oil droplets at pH 5 and 4. Thus, the emulsifying ability of PPI under acidic conditions could be significantly improved by formation of soluble complexes with DS.