Emulsion Stability Properties Research Articles

Prosopis alba exudate gum as novel excipient for fish oil encapsulation in polyelectrolyte bead system

In this work, a bottom-up approach based on the study of polyelectrolyte interactions was performed in order to evaluate the effect of Prosopis alba exudate gum as novel excipient for fish oil encapsulation in composed calcium-alginate-chitosan beads. Emulsion and beads properties such as oil distribution, encapsulation efficiency, yield, microstructure and thermo-oxidative protection were evaluated. Alginate and gum exert a synergistic effect on emulsion stability properties, which conducted to better oil distribution in the beads and higher encapsulation efficiencies (98%) and yield (89%). The positive effect of including the gum as wall material was observed in terms of a higher oil retention capacity of the alginate beads, improved oxidative thermal stability and better microstructural features. Present results are promising and allowed considering P. alba gum as a novel non-conventional polyelectrolyte for improving Ca-alginate beads microstructure and stability with the added benefit of taking advantage of an available resource currently untapped.

Characterization of emulsion stabilization properties of quince seed extract as a new source of hydrocolloid

The capability of seed extracts in stabilizing emulsions has particularly received interest in recent years. Upon soaking quince seeds into water, biopolymers inside the seeds are extracted to water, forming mucilage. This study investigates the physical stability, rheology and microstructure of oil (sunflower oil) in water emulsions, stabilized by 2% (w/v) whey protein isolate with varying concentrations of xanthan and quince seed gum. Quince seed gum resulted in emulsions with smaller low-shear viscosities and shear thinning capabilities compared to the same concentrations of xanthan. Quince seed gum emulsions with concentrations≤0.1 (w/v), displayed rapid creaming due to bridging flocculation. Despite the difference in apparent viscosities, for gum concentrations<0.2 (w/v), both gums demonstrated comparable stability with xanthan gum in general yielding marginally more stable emulsions. Gum concentrations>0.3 (w/v) resulted in physically stable emulsions even after 5months. Overall, quince seed gum displayed significant emulsification and stabilization properties.

Impact of dual-enzyme treatment on the octenylsuccinic anhydride esterification of soluble starch nanoparticle

The hypothesis of improving the esterification of sugary maize soluble starch through dual-enzyme pretreatment was investigated. Native starch nanoparticle (NSP) was enzymatically pretreated using β-amylase and transglucosidase (ESP) and then esterified with octenylsuccinic anhydride (OSA). The degree of substitution (DS), reaction efficiency (RE), molecular weight (Mw), molecular density (ρ) and in vitro digestibility were determined. Fourier transform infrared spectroscopy and confocal laser scanning microscopy were used to analyze starch particle and its OS derivatives. The emulsification properties of OS-NSP and OS-ESP were also compared. The results showed that dual-enzyme modification increased the DS and RE of OSA modified starch particle compared with the control. Enzymatic modification had a thinning effect at the surface of starch particle, resulting in lower Mw. The extent of reduction in ρ of OS-ESP was greater than that of OS-NSP. At equivalent DS, OSA modification of EPS was more effective than that of NPS in reducing digestibility. Also, there was brighter fluorescence spheres of OS-ESP in comparison to OS-NSP at equivalent DS, suggesting more OS groups were substituted on the chains near the branch points at less density areas. OS-ESP with higher DS (0.0197) had lower zeta-potential and average particle size for superior emulsion stabilization properties with high stability. The results revealed the OS-starch prepared under dual-enzyme pretreatment was a Pickering particle stabilizer for potential application in encapsulation and delivery of bioactive components.

The major proteins of the seed of the fruit of the date palm (Phoenix dactylifera L.): Characterisation and emulsifying properties

Proteins were extracted from the seeds of the fruit of the date palm. Proteomic analysis and SDS–PAGE electrophoresis of the extracted proteome suggested it is composed predominantly of the storage proteins glycinin and β-conglycinin, although over 300 proteins were detected, 91 of which were identified with confidence. In terms of protein type, the largest numbers of proteins were associated, not unexpectedly, with metabolism and energy functions, which reflected the requirements of the germinating and growing embryonic plant. The emulsifying properties of the extracted proteins were determined. Date seed protein exhibited a lower emulsifying activity than either whey protein concentrate or soy protein isolate, at each of the pH values tested. However, the stability of the emulsions produced with all three proteins was very similar at the different pH values. This combination of large emulsion droplet size and high emulsion stability properties suggested that the date proteins may adsorb as large protein oligomers.

Dodecenyl succinylated alginate (DSA) as a novel dual-function emulsifier for improved fish oil-in-water emulsions

Alginate was chemically modified with dodecenyl succinic anhydride (SAC12) to produce an innovative emulsifier with antioxidant properties for use in fish oil-in-water emulsions. The modification reaction was conducted in an aqueous reaction system at low temperature and neutral pH. The resulting emulsifier had a degree of succinylation of 33.9 ± 3.5% and the product was structurally verified by Fourier-transformed infrared (FTIR) spectrometric analyses. The surface activity of the DSA was confirmed by contact angle determinations in static drop shape analysis on a non-polar surface. The dodecenyl succinylated alginate (DSA) was applied as stabilizer of 30% fish oil-in-water emulsions. The emulsions' creaming stability was significantly increased compared to emulsions stabilized with native alginate or β-lactoglobulin (BLG). Confocal laser scanning microscopy (CLSM) showed that DSA stabilized emulsions through adsorption to the oil-water interface, while native alginate stabilized emulsions by increasing the viscosity of the aqueous phase. Emulsions stabilized with DSA had a larger negative zeta potential compared to emulsions stabilized with native alginate or BLG, which provided repulsive forces between oil droplets, enhancing the emulsions' physical stability. DSA was found to inhibit lipid oxidation in emulsions, thus lowering the formation of secondary oxidation products by 79% compared to the control with no DSA. In all, this work presents a novel nature-based food emulsifier, which was found to have antioxidant and emulsion-stabilizing properties, thus representing a promising ingredient with application potential for efficient delivery of oxidation-susceptible oils.

Effects of Microfluidized Dietary Fibers on Stability Properties of Emulsions

AbstractThis study aims to determine the stability improving effects of size‐reduced dietary fibers in food emulsions. Orange zest fiber and corn fiber were microfluidized under high pressure (up to 15,000 psi). Model emulsions were prepared by adding 1, 2 and 3% of the fibers into the mixture of 3% whey protein isolate and 20 and 50% oil. These mixtures were homogenized through both colloid mill and microfluidizer to form model emulsions. Rheological properties such as flow and oscillation were measured with frequency scanning rheometer, and emulsion stabilities were measured with dispersion analyzer. Increase in oil amount increased emulsion stabilities independent from fiber content. Likewise, ascending fiber amount also improved stabilities. At constant oil level, 3% fiber containing emulsions had higher elastic and viscous moduli (G' and G'') and viscosity values than those of other groups in same material. In general, addition of dietary fiber into model food emulsions improved stability properties.Practical ApplicationsDietary fiber issue has been widely discussed, and trends in usage of dietary fibers have been increasing for years. Food emulsions and emulsified food products now have a substantial place in basic diet of humans. In practice, widely and daily used products such as mayonnaise, salad dressings, butter, etc., are either emulsions or emulsified products. This article deals with enabling usage of some dietary fibers in emulsions. All products mentioned above are potential applications of this research. Also a novel technology, microfluidization could be effectively used for homogenization process. The results are useful in producing food emulsions with higher emulsion stabilities.

Emulsifying and Emulsion-Stabilizing Properties of Gluten Hydrolysates

Gluten is produced as a coproduct of the wheat starch isolation process. In this study, gluten was hydrolyzed to degrees of hydrolysis (DH) of 3-6-10 and 1-2-3 with alcalase and trypsin, respectively. These peptidases have a clearly distinct substrate specificity. Corn oil-in-water emulsions (10 wt % oil) were prepared by high-pressure homogenization at pH 7.5. Gluten peptides with DH 3 proved to be the most effective in producing peptides displaying emulsifying properties. Higher levels of alcalase hydrolysates (2.0 wt %) than of trypsin hydrolysates (1.0 wt %) were required to produce stable emulsions with small droplet sizes, which is attributed to differences in the nature of the peptides formed. The emulsions had small mean droplet diameters (d32 < 1000 nm). Emulsions produced with trypsin hydrolysates (stable after 9 days at 55 °C) displayed better thermal stability compared to those produced with alcalase hydrolysates (destabilized after 2 days at 37 °C). The hydrolysate-containing emulsions, however, were quickly destabilized by salt addition (≤100 mM NaCl) and when the pH approached the isoelectric point of the coated droplets (pH ~5.5). Microscopic analysis revealed the formation of air-in-oil-in-water emulsions at lower hydrolysate concentrations, whereas at higher concentrations (≥3.0 wt %) extensive flocculation occurred. Both phenomena contributed to creaming of the emulsions. These results may be useful for the utilization of gluten hydrolysates in food and beverage products.

Engineered Hydrophobin for Biomimetic Mineralization of Functional Calcium Carbonate Microparticles

In this study, the modified hydrophobin, engineered for biomimetic mineralization, has been employed as a structure-directing agent for mineralization of calcium carbonate. For the first time amphiphilic calcium carbonate particles have been obtained, using engineered proteins. The mineral microparticles have been characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). While mineralization in the presence of non-modified hydrophobin results in polymorph mineral structures, uniform microspheres with an average particle diameter of one micron are obtained by employing hydrophobin which has been modified with an additional ceramophilic protein sequence. Owing to the tri-functionality of the modified hydrophobin (hydrophilic, hydrophobic and ceramophilic), the obtained mineral microparticles exhibit amphiphilic properties. Potential applications are in the areas of functional fillers and pigments, like biomedical and composite materials. Pickering emulsions have been prepared as a demonstration of the emulsion-stabilizing properties of the obtained amphiphilic mineral microspheres. The structure-directing effects of the studied engineered hydrophobins are compared with those of synthetic polymers (i.e. polycarboxylates) used as crystallization and scaling inhibitors in industrial applications.

Preparation and Properties of Siloxane-Modified Styrene-Acrylate Latex Particles with Core-Shell Structure

Siloxane-modified styrene-acrylate latex particles with core-shell structure were prepared by two-stage semicontinuous emulsion polymerization using a reactive surfactant. Effects of catalyst dosage, weight ratio of γ-methacryloxypropyltrimethoxysilane (MAPS) to hydroxyl silicone oil (HSO) and siloxane content on the grafting degree of siloxane were studied. The chemical components of the copolymer were characterized by Fourier transform infrared spectra. The micromorphology of latex particles was observed by transmission electron microscopy. The stability properties of emulsion were tested by Ca2+, centrifugal, and mechanical stability test. The latex film was studied by water contact angle, water absorption ratio and thermal gravimetric analysis. The results show that siloxane-modified styrene-acrylate latex with core-shell structure can be synthesized using reactive surfactant and the prepared emulsion presents excellent stability. By using hydroxyl silicone oil (HSO) to react with silane coupling agent MAPS during emulsion polymerization, HSO can be located in the side chain of the polymer and endow the latex film with excellent stabilities.

Functional properties of processed Australian wattle (Acacia victoriae Bentham) seed extracts

► Wattle seeds were soaked, heated and roasted, and subsequently extracted with water. ► Most emulsions formed with water extracts from raw and processed wattle seed destabilized by oiling off and flocculation. ► A new wattle protein fraction was isolated which contained >77% protein. ► Wattle protein fraction formed very stable emulsions but had weak foaming and gelling properties. Functional properties of water extracts from processed prickly wattle ( Acacia victoriae Bentham) seed flours were compared to those of raw flours and an ammonium sulphate precipitate (ASP) containing >77% protein. All extracts formed stable 20% and 50% (v/v) oil-in-water emulsions at concentrations between 1% and 5% (w/v) but the emulsions formed from processed flour at low extract concentrations destabilized by oiling off within 7 days at 25 °C. Comparatively, emulsions formed with 5% raw and processed extracts creamed or broke reversibly. Conversely, ASP-stabilized emulsions were very stable at all concentrations and conditions in this study. However, all extracts and ASP had poor foaming capacity and did not gel even at up to 10% solids concentration. The results indicated that processing of wattle seeds for flavour enhancement or destruction of anti-nutrients led to poorer functionality. The excellent emulsifying and emulsion stabilization properties of ASP could potentially be exploited in processed foods.

Interfacial properties of polymethyl alpha-cyanoacrylate and polybutyl alpha-cyanoacrylate.

Several physical properties of two polyalkyl alpha-cyanoacrylates relevant to their use in pharmaceutical dosage forms have been investigated. Formation of polymer films at several oil-water interfaces reveals films of diverse morphology. The retardation of solute transfer across an oil-water interface caused by the presence of polymer films formed in situ from the monomers has revealed that the methyl derivative forms the more effective barrier to the test solute, gentian violet. The emulsion-stabilizing properties of the methyl polymer have been studied, and the film-forming properties of the monomers spread from benzene onto water surfaces have been examined using a surface balance.

Emulsifying properties of lactose-amines in oil-in-water emulsions

Lactose-amines were synthesized with hexadecyl-amide and lactose via the Maillard reaction and their emulsion stabilization properties were investigated. Lactose-amines were synthesized using two different constant heating (4 and 8 h) and two different heating/cooling cycles (12 and 24 h). Each lactose-amine sample was used as an emulsifier in 20:80 ratio oil-in-water emulsions at four different concentrations (0.01%, 0.05%, 0.1%, and 1%). Emulsion stability was monitored by measuring the oil droplet sizes and the extent of destabilization via clarification over 5 days. At 1% concentrations, emulsions prepared with lactose-amines synthesized for 4, 12, and 24 h were as stable as the whey protein positive control emulsion. The 8 h lactose-amine sample resulted in a less stable emulsion. We assume the difference is related to the amount of heat this sample was exposed to during synthesis, with extensive heat leading to advanced Maillard products, which possessed reduced emulsification properties.

Improvement, by dry-heating, of the emulsion-stabilizing properties of a whey protein concentrate obtained through carboxymethylcellulose complexation

A protein concentrate (WPC) obtained from milk whey by complexation with carboxymethylcellulose (CMC) (protein: 66.2%, CMC: 23.9%) was incubated at 60 °C for time periods of up to 5 weeks and the emulsion-stabilizing ability against creaming and against heat-induced aggregation of the incubated WPC was investigated. Incubation appears to bring about a remarkable improvement in the emulsion-stabilizing properties of the protein concentrate. The results are considered in terms of a conjugate formation during dry-heating between the whey protein and the polysaccharide which, following adsorption to the droplet surfaces, enhances the strength of steric stabilization interaction forces operating between overlapping protein layers adsorbed at the surfaces of neighbouring droplets.

Formation and stabilization of emulsion with A1, A2 and B β-casein genetic variants

The milk protein β-casein (β-CN) is a flexible, approximately random coil protein with a molecular mass of ∼24 kDa. It contains distinct charged and hydrophobic, non-charged regions in the primary structure. The strongly amphiphilic nature of β-casein causes it to concentrate at an interface, which is a prerequisite to form and stabilize emulsions. The emulsifying (particle-size distribution, turbidity measurement) and structural (surface coverage, CD) properties of β-casein genetic variants were studied at pH 6.7 and I = 75 mM (representative pH value for milk). β-Casein B variant produced bigger emulsion droplets than the A1 and A2 variant, having better emulsion-stabilizing properties than A2 and A1 variants. Significant differences were observed in the surface coverage of teflon droplets made with β-casein genetic variants. A relationship between the surface load and emulsion-stabilizing properties was found. An increased content of secondary structure, especially for β-CN B and A1 variants, was found after adsorption onto the hydrophobic surface.

A unique polypeptide from the C-terminus of the exocellular esterase of Acinetobacter venetianus RAG-1 modulates the emulsifying activity of the polymeric bioemulsifier apoemulsan

An exocellular esterase from the oil-degrading Acinetobacter venetianus RAG-1 was previously shown to enhance the emulsification and emulsion stabilization properties of the amphipathic, aminopolysaccharide bioemulsifier, emulsan [Bach H, Berdichevsky Y, Gutnick D (2003) An exocellular protein from the oil-degrading microbe Acinetobacter venetianus RAG-1 enhances the emulsifying activity of the polymeric bioemulsifier emulsan. Appl Environ Microbiol 69:2608-15]. This enhancement was specific for the RAG-1 esterase and was independent of catalytic activity. In this report, fragments from both the N'- and C'-termini were cloned as fusions to the C-terminus of the maltose-binding protein (MBP) and were tested for enhancement activity in the presence of the deproteinated form of emulsan, apoemulsan. The activity could be localized to the C-terminal third of the protein which exhibited the same activity as the intact enzyme. MBP itself was completely inactive and could be cleaved from the fusion without affecting the subsequent emulsification. However, the enhancement completely depended on the presence of a unique C-terminal 20 amino acid peptide not found in any other protein in the databases. In addition, progressive removal of amino acids from the N-terminus of the active MBP polypeptide resulted in a concomitant loss of activity, indicating that enhancement is also proportional to the size of the peptide fragment. The middle third and the C-terminal third of the enzyme each contained a copy of the conserved Cardin-Weintraub consensus sequence for protein binding to heparin. These sequences were not detected in homologous esterases from a closely related strain, Acinetobacter calcoaceticus BD413.

Emulsion-stabilizing properties of chitosan in the presence of whey protein isolate: Effect of the mixture ratio, ionic strength and pH

The emulsion-stabilizing properties of a chitosan preparation were compared as a function of the whey protein isolate/chitosan mixture ratio (WPI/CNI) and the ionic strength ( μ), at pH 5.5 and 6.0. At both pH conditions, general decreases in emulsion stability towards charge neutralization flocculation and syneresis were observed at WPI/CNI > 5. This was particularly evident at pH 6.0, due to a lower surface net charge (lower electrostatic stabilization). In counterpart, when μ was increased, the higher load of chitosan at pH 6.0 produced higher stabilities (higher steric stabilization), in spite of comparable decreases of surface net charge at both pH conditions. The transition from soluble to insoluble protein–chitosan complex formation in mixtures at pH 6.0 and WPI/CNI > 5.0 was due to an emulsion destabilization towards syneresis, whereas soluble complex formation at pH 5.5 also produced syneresis. It showed that soluble protein–chitosan adsorbing complex formation prior homogenization is not essentially linked to emulsion stabilization.

Functionality of lupin seed protein isolate in relation to its interfacial behaviour

The foaming and emulsifying properties of lupin seed protein isolate (LSPI) were investigated following protein structure modification by heating and/or dithiothreitol (DTT) addition. Heat-treatment of protein solution resulted in an increase of both foamability and foam-stabilization ability while disulfide bond reduction by DTT brought about an improvement in the protein foaming capacity only. Additionally, heat-treated LSPI solutions exhibited markedly improved emulsification and emulsion-stabilization properties. Disulfide bond reduction, on the other hand, brought about an increase in the ability of the protein to stabilize the emulsions against creaming only. The influence of lupin protein structure modification on its solubility and surface-adsorption properties has also been studied in order to elucidate the protein structure/functionality relationship of lupin protein.

Accelerated Stability Testing of a Water-in-Oil Emulsion

Non-optimal or non-predictable stability properties of emulsions can be limiting for the applications of emulsions. Therefore, it is of general interest to predict stability behavior. In the present study, accelerated stability testing employing elevated temperatures with good accuracy predicted long-term stability of a w/o emulsion stabilized with polyglycerol polyricinoleate (PG PR) kept at 4°C. It is argued that elevated temperature testing may successfully be applied to w/o emulsions provided that the phase inversion temperature is not crossed during the accelerated study. Furthermore, some qualitative effects of temperature on chemical stability could be observed. It was found that triglycerol polyricinoleate-6 provided the highest physical stability of four qualities of PG PR. Release characteristics of two entrapped hydrophilic markers, glucose and polyethylene glycol (m.w.4000) showed different sensitivities towards thermal stressing. The high releasing compound, glucose, showed a significant reduction in release rate in contrast to polyethylene glycol.

Dephosphorylation-induced structural changes in β-casein and its amphiphilic fragment in relation to emulsion properties

To promote the understanding of the relationship between emulsifying and molecular properties of proteins/peptides, intact β-casein (βCN) and its amphipathic fragment, i.e., βCN (1–105/107) were dephosphorylated. Dephosphorylation was found not to change significantly their emulsifying properties. Since it is known that the structure of proteins can change upon adsorption onto an interface, the secondary structure of intact β-casein, its amphipathic fragment, and their dephosphorylated forms, both in solution and after adsorption onto a hydrophobic teflon/water interface, were studied by far-UV circular dichroism spectroscopy. An increased content of secondary structure, especially α-helix, was found for all samples after adsorption onto teflon. Dephosphorylation increased the helix-forming propensity, especially for amphipathic fragment of β-casein. No influence of the secondary structure properties on the emulsion-forming and -stabilizing properties was observed, but a relationship between the maximum surface load and the emulsion-stabilizing properties was found.

Beta-lactoglobulin hydrolysis. 1. Peptide composition and functional properties of hydrolysates obtained by the action of plasmin, trypsin, and Staphylococcus aureus V8 protease.

beta-Lactoglobulin (betaLg) was subjected to limited hydrolysis by trypsin, plasmin, and endoproteinase from Staphylococcus aureus V8 (S.aur.V8) to degrees of hydrolysis (DH) of 1, 2, and 4%. The several hydrolysates had different peptide compositions (determined by reversed-phase HPLC and gel-permeation chromatography [GPC]). GPC under nondenaturing, denaturing, and denaturing plus reducing conditions showed that the peptides formed were linked by hydrophobic interactions or by disulfide bonds or were not linked at all. At very low protein concentration, some differences in emulsion-forming properties were observed: only the plasmin hydrolysates could form emulsions with a uniform particle-size distribution. The emulsions formed with S.aur.V8 hydrolysates had poor emulsion-stabilizing properties. Some hydrolysates showed increased foam-forming properties in comparison with the intact protein. All foams formed were stable. Overall, the plasmin hydrolysate (DH4) contained relatively much larger molecules and/or hydrophobic molecules. Many molecules were disulfide-linked peptides. This hydrolysate also had the best functional properties.