Effects of Oil Droplet Size and Interfacial Protein Film on the Properties of Fish Myofibrillar Protein-Oil Composite Gels.
ABSTRACT: The effects of oil droplet size and the formation of an interfacial protein film (IPF) on silver carp myofibrillar protein (MP)-oil composite gels were studied. MP- or Tween 80-stabilized camellia seed oil emulsions with different droplet sizes were prepared and added to MPs to prepare composite gels. The oil droplet size of the Tween 80-stabilized emulsion was significantly smaller (p < 0.05) than that of the MP-stabilized emulsion with the same homogenization speed. However, polymerization of Tween 80-stabilized emulsions during the preparation of the composite gels was found. Composite gels with the MP-stabilized emulsions of a small droplet size showed significantly improved water-holding capacity, texture, and dynamic rheological properties. Interfacial shear rheology studies revealed that the storage modulus (G') of the MP-stabilized emulsion composite gels was higher than that of the Tween 80-stabilized gels, and the tan ? of the MP-stabilized oil emulsion composite gels was smaller than that of the Tween 80-stabilized gels, indicating that stronger elastic gel structures were formed. These results suggested that the IPF formed in the MP-stabilized emulsion helped stabilize the oil droplets embedded in the protein gel network, and the smaller the droplet size, the more stable the composite gel. This work provides a better understanding of how oil emulsions interact with protein and affect the properties of MP-oil composite gels.
Project description:Emulsions can be used as delivery systems for bioactive ingredients for their incorporation in food products. Essential oils are natural compounds found in plants that present antioxidant and antimicrobial activity. Therefore, the main goal of this work was to develop emulsions, containing mandarin essential oil stabilized by two food-grade surfactants and guar gum, and to evaluate their physical stability. The initial droplet size of emulsions developed by microfluidization was optimized, obtaining diameters below one micron regardless of the processing conditions. However, the emulsion processed at 25,000 psi and one pass exhibited the lowest mean droplet sizes and polidispersity, and therefore, a higher stability. Different ratios of Tween 80 and Span 80 were assessed as stabilizers. Results obtained indicated that the ratio of surfactants had a significant effect on the mean droplet sizes, physical stability, and rheological properties. Thus, we found that the optimum ratio of surfactants was 75/25 (Tween80/Span80) on account of the lowest droplet mean diameters, lack of coalescence, and a low creaming rate. The rheological characterization of the stable emulsions showed a shear thinning flow behavior, and G? (loss modulus) values higher than G' (storage modulus) values, in all the frequency range. The rheological behavior may be governed by the guar gum, which was confirmed by field emission scanning electron microscopy (FESEM). This research can be considered as the starting point for future applications of mandarin essential oil in emulsions, which can be incorporated in products as food preservatives.
Project description:Tubular liposomes containing a hydrophilic model compound (fluorescein sodium salt, FSS) were entrapped inside the internal aqueous phase (W(1)) of water-in-oil-in-water (W(1)/O/W(2)) double-emulsion globules. Our hypothesis was that the oil membrane of double emulsions can function as a layer of protection to liposomes and their contents and thus better control their release. Liposomes were prepared in bulk, and their release was observed microscopically from individual double-emulsion globules. The liposomes containing FSS were released through external coalescence, and the behavior of this system was monitored visually by capillary video microscopy. Double-emulsion globules were stabilized with Tween 80 as the water-soluble surfactant, with Span 80 as the oil-soluble surfactant, while the oil phase (O) was n-hexadecane. The lipids in the tubular liposomes consist of L-alpha-phosphatidylcholine and Ceramide-VI. Variations of Tween 80 concentration in the external aqueous phase (W(2)) and Span 80 concentration in the O phase controlled the release of liposomes from the W(1) phase to the W(2) phase. The major finding of this work is that the sheer presence of liposomes in the W(1) phase is by itself a stabilizing factor for double-emulsion globules.
Project description:Medium and high internal phase Pickering emulsions stabilized by cellulose nanocrystals (CNCs) have been prepared and the effects of CNC concentration and type of oil phase on the properties of emulsions were studied. The maximum oil phase volume that can be stabilized by CNCs is 87% when the CNC concentration is 0.6?wt.%; this slightly decreases to 83% when the CNC concentration is increased to 1.2?wt.% or higher. In addition, the oil droplets stabilized with 0.6?wt.% CNC suspensions have a larger size than those stabilized with higher concentration CNC suspensions. As evidenced by the change in oil droplet morphology and size, two different emulsion formation mechanisms are proposed. For a CNC concentration of 0.6?wt.%, the extra oil added into the emulsion is accommodated by the expansion of oil droplet size, whereas for CNC concentrations of 1.2?wt.% and higher, the oil is stabilized mainly by the formation of new oil droplets.
Project description:The rational formulation of Pickering double emulsions is described using a judicious combination of hydrophilic and hydrophobic block copolymer worms as highly anisotropic emulsifiers. More specifically, RAFT dispersion polymerization was utilized to prepare poly(lauryl methacrylate)-poly(benzyl methacrylate) worms at 20% w/w solids in n-dodecane and poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) worms at 13% w/w solids in water by polymerization-induced self-assembly (PISA). Water-in-oil-in-water (w/o/w) double emulsions can be readily prepared with mean droplet diameters ranging from 30 to 80 μm using a two-stage approach. First, a w/o precursor emulsion comprising 25 μm aqueous droplets is prepared using the hydrophobic worms, followed by encapsulation within oil droplets stabilized by the hydrophilic worms. The double emulsion droplet diameter and number of encapsulated water droplets can be readily varied by adjusting the stirring rate employed during the second stage. For each stage, the droplet volume fraction is relatively high at 0.50. The double emulsion nature of the final formulation was confirmed by optical and fluorescence microscopy studies. Such double emulsions are highly stable to coalescence, with little or no change in droplet diameter being detected over storage at 20 °C for 10 weeks as judged by laser diffraction. Preliminary experiments indicate that the complementary o/w/o emulsions can also be prepared using the same pair of worms by changing the order of homogenization, although somewhat lower droplet volume fractions were required in this case. Finally, we demonstrate that triple and even quadruple emulsions can be formulated using these new highly anisotropic Pickering emulsifiers.
Project description:The Escherichia coli's membrane protein OmpA has been identified as a potential biosurfactant due to their amphiphilic nature, and their capacity to stabilize emulsions of dodecane in water. In this study, the influence of surfactant type, concentration, preservation time and droplet size on the crystallization of n-dodecane and water, in oil-in-water emulsions stabilized with six rationally designed Escherichia coli's OmpA-based peptides was investigated. A differential scanning calorimetry (DSC) protocol was established using emulsions stabilized with Tween 20® and Tween 80®. A relationship between the surfactant concentration and the crystallization temperatures of n-dodecane and water was observed, where the crystallization temperatures seem to be dependent on the preservation time. A deconvolution analysis shows that the peak morphology possibly depends on the interactions at the interface because the enthalpic contributions of each Gaussian peak remained similar in emulsions stabilized with the same peptide. Adsorption results show that the main driver for adsorption and thus stabilization of emulsions is polar interactions (e.g. H-bonding) through the hydrophilic parts of the peptides. Those peptides with a preponderance of polar interaction groups distribution (i.e. NH2, COOH, imidazole) showed the highest interfacial activity under favorable pH conditions. This suggests that custom-made peptides whose hydrophilic/hydrophobic regions can be fine-tuned depending on the application can be easily produced with the additional advantage of their biodegradable nature.
Project description:BACKGROUND:There are a lot of different types of sunscreen products (oils, sticks, gels, creams, lotions) which can be found on the world's market. Sunscreen product that contains active chemical ingredients sometimes has harmful effects on the skin. Sunflower oil contains vitamin E and acts as a natural sunscreen which can absorb UVB light. The average droplet size of nanoemulsion is between 100 and 500 nm and do not show the problems of stability (creaming, flocculation, coalescence, and sedimentation), which are commonly associated with macroemulsions. AIM:The aim of this study was to prepare and evaluate the sunflower oil nanoemulsion as a sunscreen. METHODS:Sunflower oil nanoemulsions were prepared by spontaneous emulsification method with 3 formulas F1 (Tween 80 38%, sorbitol 22%), F2 (Tween 80 36%, sorbitol 24%), F3 (Tween 80 34%, sorbitol 26%) and 5% sunflower oil as a sunscreen substance. The nanoemulsions were evaluated for particle size, physical stability in room temperature (25 ± 2°C), low temperature (4 ± 2°C) and high temperature (40 ± 2°C) during experiment for 12 weeks of storage, centrifugation at 3750 rpm for 5 hours, viscosity, pH, freeze-thaw test and sun protection value (SPF) value by in vitro. RESULTS:The results of nanoemulsion evaluation showed that nanoemulsion formula F1 had the smallest average particle size of 124.47 nm with yellowish colour, clear, transparent, pH value (6.5 ± 0.1), viscosity value (225 ± 25 cP), did not show any separation or creaming in the centrifugation, and stable during experiment for 12 weeks of storage at room temperature, low temperature and high temperature. The SPF value of all nanoemulsion preparations was higher than that of the emulsion. CONCLUSION:The preparation of the sunflower oil nanoemulsion with a ratio of Tween 80 and sorbitol (38: 22) produces a stable nanoemulsion during the experiment for 12 weeks storage at the room, low and high temperature. The nanoemulsion preparation has higher SPF values compared to the emulsion. This nanoemulsion formulation could be considered more effective in sunscreen cosmetic use compare to the emulsion.
Project description:Multiwalled carbon nanotubes (MWCNTs) were incorporated into highly concentrated water-in-oil emulsions with the ultimate aim of achieving a uniform and effective dispersion of MWCNTs within the emulsion matrix. The emulsion was formulated in such a way, wherein the internal phase consists of higher than 90 wt %. By keeping the same aqueous-to-oil phase ratio, the amount of MWCNTs in the oil phase was systematically adjusted to investigate their effects on the microstructure development and rheological behavior of the emulsion. The addition of MWCNTs led to a reduced droplet size and also resulted in a narrower distribution of the droplet size. The rheological behavior of nanotube-incorporated emulsions was characterized with varying MWCNT concentrations and also as a function of the emulsification time. The rheological characteristics of the nanotube-incorporated emulsions were identical to those of the neat emulsion and were primarily governed by the variation in the droplet size and droplet-size distribution. However, the yield strain and cross-over strain were independent of the mean droplet size and polydispersity of the emulsion. Emulsions that have smaller droplets exhibited higher storage modulus (G'), yield stress (?Y), and apparent viscosity (?). For all refining times investigated, nanotube-incorporated emulsions have higher G', ?Y, and ? values when compared to the neat emulsion, and these values further increased with the MWCNT concentration. This was primarily due to the decrease in the droplet size with MWCNT addition. Furthermore, our findings suggest that the incorporated MWCNTs did not induce any significant change in the rheological behavior of emulsions with identical droplet sizes, and it remained essentially unchanged with the concentration of MWCNTs. However, the nanotube-incorporated emulsions possessed solidlike behavior up to a higher applied stress when compared to a neat emulsion of identical droplet size.
Project description:Abstract: Never-dried bacterial cellulose (BC) and crosslinked cellulose nanofibers (CNF) were used for the removal of oil from stabilized and non-stabilized oil-in-water emulsions with droplet sizes less than 1 µm. The CNF membranes were exchanged with isopropyl alcohol before drying. The microscopic structure of the prepared membranes was evaluated using scanning electron microscopy (SEM); the water flux and the rejection of oil were evaluated using a dead-end filtration cell. BC harvested after different incubation time periods (2 to 10 days) did not show a change in the width of the nanofibers, but only the thickness of the membranes was increased. Pure water flux was not affected as a result of increasing thicknesses of BC membranes harvested after 4⁻10 days while BC harvested after two days had significantly higher water flux than the others. BC showed a higher flux and efficiency in removing oil from oil emulsions than CNF membranes. Removal of oil by the different membranes from the non-stabilized oil emulsion was more efficient than from the stabilized one.
Project description:Water-in-oil (W/O) emulsions have high potential for several industrial areas as delivery systems of hydrophilic compounds. In general, they are less studied than oil-in-water (O/W) systems, namely in what concerns the so-called fluid systems, partly due to problems of instability. In this context, this work aimed to produce stable W/O emulsions from a natural oil, sweet almond oil, to be further tested as vehicles of natural hydrophilic extracts, here exemplified with an aqueous cinnamon extract. Firstly, a base W/O emulsion using a high-water content (40/60, v/v) was developed by testing different mixtures of emulsifiers, namely Tween 80 combined with Span 80 or Span 85 at different contents. Among the tested systems, the one using a 54/46 (v/v) Span 80/Tween 80 mixture, and subjected to 12 high-pressure homogenizer (HPH) cycles, revealed to be stable up to 6 months, being chosen for the subsequent functionalization tests with cinnamon extract (1.25-5%; w/v; water-basis). The presence of cinnamon extract leaded to changes in the microstructure as well as in the stability. The antimicrobial and antioxidant analysis were evidenced, and a sustained behavior compatible with an extract distribution within the two phases, oil and water, in particular for the higher extract concentration, was observed.
Project description:In this study, two saponins-rich plant extracts, viz. Saponaria officinalis and Quillaja saponaria, were used as surfactants in an oil-in-water (O/W) emulsion based on hempseed oil (HSO). This study focused on a low oil phase content of 2% v/v HSO to investigate stable emulsion systems under minimum oil phase conditions. Emulsion stability was characterized by the emulsification index (EI), centrifugation tests, droplet size distribution as well as microscopic imaging. The smallest droplets recorded by dynamic light scattering (droplets size v. number), one day after the preparation of the emulsion, were around 50-120 nm depending the on use of Saponaria and Quillaja as a surfactant and corresponding to critical micelle concentration (CMC) in the range 0-2 g/L. The surface and interfacial tension of the emulsion components were studied as well. The effect of emulsions on environmental bacteria strains was also investigated. It was observed that emulsions with Saponaria officinalis extract exhibited slight toxic activity (the cell metabolic activity reduced to 80%), in contrast to Quillaja emulsion, which induced Pseudomonas fluorescens ATCC 17400 growth. The highest-stability samples were those with doubled CMC concentration. The presented results demonstrate a possible use of oil emulsions based on plant extract rich in saponins for the food industry, biomedical and cosmetics applications, and nanoemulsion preparations.