Effects of emulsifiers on the oxidative stability of soybean oil TAG in emulsions

The effects of two types of commercial emulsifiers, sucrose FA esters and polyglycerol FA esters, on the oxidation of soybean oil TAG-in-water emulsions were studied. Both emulsifiers influenced the oxidative stability of soybean oil TAG in the emulsion, but they had little effect on the oxidation of TAG in bulk phase. When the TAG were dispersed with sucrose esters having the same FA composition, the oxidative stability increased as their hydrophilic-lipophilic balance (HLB) increased. On the other hand, when the HLB was the same, the oxidative stability increased with increasing acyl chain length of the FA esterified on sucrose ester. However, the effect of the polyglycerol ester could not be explained by the relationship with HLB or the acyl composition. When the stability of TAG in emulsion was compared under the same concentrations of TAG, emulsifier, and oxidation inducer, the TAG dispersed with sucrose esters were oxidatively less stable than with polyglycerol esters. Analysis of the emulsion droplet size suggested that the lower oxidative stability of TAG dispersed with sucrose esters was partly due to their relatively smaller droplet sizes.     

Dispersed phase destabilization in table spreads

Commercially available butter, regular-fat margarine, and a fat-reduced margarine (38% fat w/w) were stored between 10 and 35°C for up to 4 d to elaborate on the relationship between droplet size and solid fat content (SFC) that exists in these spreads. At 10°C, the mean volume-weighted droplet size for butter was 4.22±0.40 μm followed by margarine (6.22±0.10 μm) and fat-reduced margarine (12.62±0.28 μm). At higher temperatures, as a result of decreasing SFC, the mean droplet size increased as did the droplet size distribution, leading to eventual coalescence and destabilization in all spreads. In butter, the critical SFC was ∼9%, whereas in margarine notable coalescence occurred at ∼5% SFC. The fat-reduced margarine destabilized at lower temperatures than the other spreads (∼20°C vs. ∼30°C), at an SFC of ∼6.5%. In these spreads, two different mechanisms influenced dispersed phase stability: (i) steric stabilization against coalescence via fat crystals located at the droplet interface, known as Pickering stabilization, and (ii) stabilization against droplet sedimentation (and droplet encounters) due to the presence of the fat crystal network.     

Preparation of monodispersed emulsion with large droplets using microchannel emulsification

Microchannel (MC) emulsification is a novel technique for producing monodispersed emulsions with coefficients of variation of less than 5%. To produce emulsions with large droplets, we designed three MC with large dimensions. The MC structure consists of two parts: a channel and a terrace. Terrace length was defined as the length from the exit of the MC to the end of the terrace. The MC plates used in this study have deeper channels and longer terraces. The size limit of droplets prepared by MC emulsification was studied. Monodispersed emulsions with droplets as large as 100 μm were prepared using an MC with a depth of 16 μm and a terrace length of 240 μm. The average diameter (coefficient of variation) of the emulsion droplets was 98.1 μm (2.5%). Emulsions with larger-diameter droplets were prepared using an MC with a longer terrace. The effect of the applied pressure on emulsification behavior was studied and discussed from the viewpoint of the droplet formation mechanism. At low applied pressures, droplet diameters were independent of the applied pressure, and monodispersed emulsions were produced. The pressure ranges of constant droplet diameter for large-droplet emulsions were narrower than those for the 5 to 30 μm droplet size emulsions because interfacial tension is more significant on a smaller scale compared with the other forces.     

Do antioxidants improve the oxidative stability of oil-in-water emulsions?

Oil-in-water emulsions were prepared with 30% stripped sunflower oil, stabilized by 20 g/L BSA and homogenized under high pressure to obtain a mean droplet size near 0.5 μm. The emulsions were shown to be physically stable during storage in a shaker at 47°C for 5 d. Such a medium was suitable to test the efficiency of different types of antioxidants. Oxidation of control emulsions appeared rapidly without a lag phase, and the contents of conjugated dienes and hexanal reached a plateau after around 20 h. In the presence of EDTA, the oxidation was strongly inhibited, suggesting that some metallic ions present in the oil or the protein solution act as inducers. Ascorbic acid and ascorbyl palmitate were inactive. Isoeugenol was found to be a powerful antioxidant, better than eugenol, α-tocopherol, and Trolox.     

ABA low molar mass triblock copolymers in reverse emulsions: A rheological study

The effect of blocks length and molar mass of ABA triblock copolymers on the rheological behavior of water in oil (w/o) emulsions was investigated. Emulsion parameters such as water droplet concentration (and droplet size) of a series of inverted emulsion systems were evaluated. All copolymer/emulsion systems studied showed a non-Newtonian behavior, and the presence of the copolymer in the emulsion system led to an increase of the low shear viscosity when the size of the midblock of the copolymer was in a specific size range. This suggests the formation of a transient network through the interconnection, by the copolymer, of the smaller water droplets present in the emulsion. Consequently, the systems behave as w/o emulsions containing reversibly crosslinked oil-soluble polymers in the continuous phase, resulting in a pronounced shear thinning behavior. For the different emulsions studied, the relative viscosity increased, with few exceptions, with increasing droplet concentration. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Water-in-Diesel Fuel Nanoemulsions Prepared by High Energy: Emulsion Drop Size and Stability, and Emission Characteristics

Water-in-diesel fuel nanoemulsions were prepared with mixed nonionic surfactants. The high energy emulsification method was used to form three emulsions containing different water contents: 5, 10 and 14% (v/v). These nanoemulsions were stabilized with a mixture of 20% sorbitan monooleate, and 80% polyethoxylated (20 EO) sorbitan trioleate, resulting in an HLB of 10 (HLB—hydrophilic-lipophilic balance). The effect of water on the droplet size, emulsion calorific value, and emission gases such as nitrogen oxides, carbon dioxide emissions and exhaust gas temperatures in diesel engines has been studied. It was found that the mean sizes of the droplets formed (between 19.3 and 39 nm) depend on the water content and the concentration of the blend emulsifiers.     

Microencapsulation of a Low-trans Fat in Trehalose as Affected by Emulsifier Type

A low-trans fat blend formulated with high linoleic sunflower seed oil (SFO) and a high melting fraction (HMF) of milk fat was encapsulated by freeze-drying emulsions. The selected emulsifiers were a mixed of the palmitic sucrose esters (SE) P-170 and P-1670, sodium caseinate (NaCas) or a blend of SE and NaCas. The ability to retain the core material with time was studied by storing the powders at different water activities (a _w). Efficiency of encapsulation was strongly dependent on emulsifier type. NaCas formulation was more efficient retaining core material during storage. The formulation with a protein and a small surfactant had the lowest performance. The stabilizer also influenced droplet size distribution and matrix crystallinity. For NaCas-stabilized powder volume weighted mean diameter (D _4,3) remained small for up to 2 months of storage (0.56 ± 0.5 μm) and then grew notably in agreement with matrix collapse. There were no significant differences in D _4,3 with water content. For NaCas/SE-stabilized powder, however, D _4,3 was high at the beginning (100 ± 0.5 μm) and then decreased most likely due to particle break-up. Although particle size distribution showed the same behavior for all a _w, retention was strongly dependent on water content. Retention with time was determined by the counteracting effects of these factors.     

Preparation of water-in-oil and ethanol-in-oil emulsions by membrane emulsification

In this work, water-in-oil emulsions (W/O) and ethanol-in-oil emulsions (E/O) emulsions were prepared successfully by membrane emulsification. The emulsifiers selected were PGPR and MO-750 for the W/O and E/O emulsions, respectively. For W/O emulsions prepared with an oil pre-filled membrane, the dispersed flux was lower and the droplet size sharper than that obtained with a water pre-filled membrane. On the contrary, for E/O emulsions prepared with the membrane pre-filled with oil, the dispersed phase (ethanol) rapidly pushed out the oil from the membrane pores. Therefore, the pre-treatment of the membrane had almost no effect on the dispersed phase flux and on the droplet size. The droplet size distribution of the E/O emulsion was close to that obtained with a classical homogenizer. The dispersed phase fluxes were high and no fouling was observed for our experimental conditions (1.6 l emulsion, 10 wt% ethanol). These results confirm that membrane emulsification could be an interesting alternative for the preparation of E/O emulsions for the purpose of biodiesel fuels, considering the scale-up ability of membranes and their potentiality for industrial processes.     

Synergistic Influence of pH and Temperature on Rheological Behavior of Adhesive Emulsions Stabilized with Micelle Dispersion of an Anionic Surfactant

The influence of emulsion pH and temperature on the rheological behavior of adhesive oil-in-water (o/w) emulsions stabilized with an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS) was studied. The flow properties of emulsions as a complex fluid were investigated using steady and dynamic rheometry for characterization of non-Newtonian behavior. Emulsion pH was varied from 2 to 12 and temperature was varied from 20 to 50 °C, respectively. The influences of the above-mentioned variables on the rheology of o/w emulsion were studied using steady-shear and dynamic oscillatory experiments. Various viscosity models (2, 3, and 4 parameter rheological model) were used to predict the rheological parameters. An increase in the pH of the emulsion led to an increase in the emulsion stability, viscosity, and viscoelastic properties ( G′ , G″ , η* , and tan δ ), and a decrease in the mean droplet size of the emulsion. A decrease in the temperature yields higher values of steady-shear viscosity and viscoelastic properties upon a decrease in droplet size. Emulsions were characterized as flocculated structured liquid exhibiting a characteristic crossover frequency ( ω* ) within the range of angular frequency studied in oscillatory measurements. Overall, emulsions exhibited non-Newtonian shear-thinning behavior and the synergy of pH and temperature significantly influences the emulsion rheology.     

The Influence of Secondary Emulsifiers on Lipid Oxidation within Sodium Caseinate-Stabilized Oil-in-Water Emulsions

The effect of protein displacement at the interface by a secondary emulsifier on the oxidative stability of sodium caseinate-stabilized tuna oil-in-water emulsion systems was determined. Emulsions were prepared with a selection of anionic and non-ionic emulsifiers and stored at both 25 and 50 °C with no added prooxidant, and at 4 °C in the presence of ferrous sulfate. The progress of oxidation during storage was monitored through solid phase microextraction headspace analysis. Metal ion catalyzed oxidation was enhanced for the emulsions stabilized with an anionic emulsifier in comparison to emulsion systems stabilized with non-ionic emulsifiers and sodium caseinate alone. The increased oxidation observed for the emulsion with the anionic surfactant is due to electrostatic interactions between divalent metal ions and the negatively charged surfactant at the oil-water interface. The sodium caseinate interfacial layer had little prooxidant effect at the droplet surface, most likely due to the ability of free protein molecules in solution to sequester metal ions, which may have provided some protection against oxidative deterioration.     

Thixotropic Behavior of Oil‐in‐Water Emulsions Stabilized with Ethoxylated Amines at Low Shear Rates

Oil‐in‐water (O/W) emulsification is a lubricating pipeline method based on the reduction of the energy frictional loss produced during viscous flow. The flow behavior of heavy O/W emulsions formulated with nonionic surfactants is described. The effects of pH and salinity of the aqueous phase on droplet diameter, stability, and apparent viscosity of O/W emulsions were evaluated. The low‐shear Couette flow of O/W emulsions displayed intense shear‐thinning and thixotropic behavior. Thixotropy was associated to the droplet deformation energy caused by shear rate changes. The droplet deformation and alignment led to the apparent viscosity reduction compared to the fluid at rest. Thixotropic behavior is supposed to balance between the breakdown and recovery of droplet ordered structures. Emulsion formulation parameters were influenced by the aqueous phase pH, enabling to manage the emulsion properties. The droplet mean diameter of < 18 µm resulted in very stable emulsions.     

Double emulsions of water-in-oil-in-water stabilized by α-form fat microcrystals. Part 1: Selection of emulsifiers and fat microcrystalline particles

Double emulsions are commonly stabilized by monomeric and/or polymeric emulsifiers. Pickering stabilization by solid particles such as colloidal microcrystalline cellulose has been mentioned only once as a possible technique to stabilize the external interface of the water-in-oil-in-water emulsion. No further work was carried out exploring this option. The present study shows that solid microcrystalline fat particles of α-form are capable of adsorbing at the water-oil interface and, together with other hydrophobic emulsifiers, can stabilize water-in-oil (W/O) emulsions. The crystals must be submicron in size in order to effectively adsorb and arrange at the interface. Large crystals do not fit and were found to flocculate as free crystals in the continuous oil phase. The α-form crystals can be obtained by flash-cooling saturated triglycerides in vegetable oils in the presence of emulsifiers, such as polyglycerol polyricinoleate (PGPR), that stabilize the dispersion and serve as α-tending crystal structure modifiers. It was assumed that PGPR also serves as a cross-linker or bridge between the crystalline fat particles and the water, and facilitates the anchoring of the fat particles in the oil phase in one direction while dangling itself in the water phase. The double emulsion droplets prepared with these W/O emulsions are relatively large in size (6–18 μm), but stable to coalescence. The marker (NaCl) does not seem to release with time, suggesting that the fat particles form microcapsules on the water interface, totally sealing the water from releasing its addenda. The systems seem to have a significant potential for food emulsions.     

Rheology and stability of phospholipid-stabilized emulsions

Lecithin in cosmetic emulsions produces a unique “skin feel,” which can be related to its rheological properties. In this study, water-in-oil (w/o) and oil-in-water (o/w) emulsions were made from a cosmetic-grade caprylic/capric triglyceride with deoiled lecithin and hydroxylated lecithin. Synthetic surfactants commonly used in commercial cosmetic products were used as controls. Optical light microscope investigation showed significant differences in the structures of the w/o and o/w emulsions made with the lecithins. Freeze/thaw tests were conducted to evaluate emulsion stability. The o/w emulsion (oil/water = 20:80) was stable with 3% hydroxylated lecithin at room temperature. However, 4% hydroxylated lecithin was needed for stabilizing the emulsion with an oil-to-water ratio of 20:80 or 30:70 through the freeze/thaw treatments. With 4% deoiled lecithin, the w/o emulsion showed a water-holding capacity up to 80%, which was also stable through two freeze/thaw cycles. All emulsions in this study exhibited pseudoplastic flow, in which a minimum shearing stress, a yield value, was required before flow became linear. In general, the emulsion viscosity increased as lecithin content increased. Changing the oil-to-water ratio also affected the emulsion viscosity. The deoiled lecithin-based w/o emulsions had higher yield values than hydroxylated lecithin-based o/w emulsions. Therefore, more force was needed to spread the w/o emulsions. In addition, because w/o emulsions had more viscous continuous phases and a greater volume of internal phases, the w/o emulsions were more viscous than the o/w emulsions.     

Stability of Oil-in-Water Emulsions with Sunflower (Helianthus annuus L.) and Chia (Salvia hispanica L.) By-Products

Emulsifiers and stabilizers play an important role in emulsion stability. Optical characterization and droplet size distribution of oil‐in‐water emulsions formulated with different types and concentrations of modified sunflower lecithin [phosphatidylcholine (PC) enriched lecithin and deoiled sunflower lecithin], with or without chia mucilage (0.75 % wt/wt), have been evaluated as a function of storage time at 4 ± 1 °C. Emulsions with PC‐enriched lecithin (without chia mucilage) exhibited the highest stability at the different concentrations because of the high PC/phosphatidylethanolamine ratio in comparison to Control lecithin. The addition of 0.75 % wt/wt mucilage contributed to obtain stable emulsions for all type and concentrations of emulsifiers studied, mainly with PC‐enriched lecithin due to the reduction of the mobility of oil particles by the formation of a tridimensional network.     

Stabilization of water-in-oil emulsions by submicrocrystalline α-form fat particles

The results presented in this study confirm previous knowledge and stress the need for both hydrophobic emulsifiers and submicronial fat particles to stabilize water-in-vegetable oil emulsions. It was demonstrated that polyglycerol polyricinoleate (PGPR) is superior to glycerol monooleate and/or lecithin, but is incapable of stabilizing these fluid emulsions for sufficient storage periods. Fluid emulsions, unlike margarine, exhibit high droplet mobility and are susceptible to flocculation and coalescence. It was also demonstrated that submicronial α-form crystals of hydrogenated fat can be obtained in the oil phase by the flash-cooling process. The crystals are homogeneously almost mono-dispersed and exhibit insufficient stability against flocculation and phase separation. The use of an emulsifier (PGPR) in the fat crystallization process was very helpful in decreasing the aggregation and flocculation processes. The α-form (mixed with β′-form) submicronial crystals can stabilize water-in-oil emulsions only in the presence of food emulsifiers, provided the concentration of tristearin is limited to 1.0–2.0 wt% (to prevent phase separation and high viscosity) and the PGPR is added at sufficient concentrations (PGPR/tristearin ratio of 2.0 or more). Ideally stable (for over 6–8 wk) fluid emulsions can be formed in systems composed of fat submicrocrystalline hydrophilic particles and food-grade emulsifiers. These water-in-oil emulsions can serve as the basic preparation for any food-grade water-in-oil-in-water double emulsion.     

The Impact of Polyoxyethylene Sorbitan Surfactants in the Microstructure and Rheological Behaviour of Emulsions Made With Melted Fat From Cupuassu (<Emphasis Type="Italic">Theobroma grandiflorum</Emphasis>)

Cupuassu fat is a good candidate for partial substitution of cocoa butter in many products, including emulsions. However, for such use it is necessary to know the characteristics of the products prepared with cupuassu fat. Therefore, the main goal of this work is to characterize emulsions prepared with cupuassu fat using the surfactants Tween^® 60, Tween^® 80 and Tween^® 85 as emulsifiers. The emulsions were prepared at 43 °C with addition of 0.5 or 1.5 % (w/v) of surfactant and compared with an emulsion without surfactant. All emulsions were analysed by conductivity, stability, pH, optical microscopy, rheology and oxidative stability. It was verified that the emulsions prepared with Tween^® 60 and Tween^® 80 have higher stability, smaller droplet size and higher apparent viscosity. Also, these properties are positively influenced by the concentration of the surfactant. On the other hand, emulsions prepared with Tween 85 or without surfactant reached unsatisfactory results. The rheological behaviour of the emulsions was adequately described by both Herschel-Bulkley and Mizhari-Berki models revealing pseudoplastic character. These emulsions also present strong gel behaviour, with storage modulus higher than loss modulus. In conclusion, cupuassu fat can be used as oil phase for emulsions products and this characterization helps to understand their behaviour in order to increase their use in food industry.     

Continuous-phase fat crystals strongly influence water-in-oil emulsion stability

To elucidate the role of continuous-phase fat crystals on emulsion destabilization, water-in-canola oil emulsions prepared with 0–2% (w/w) added solid fat (hydrogenated canola stearine or hydrogenated cottonseed stearine) were examined using pulsed NMR droplet-size analysis, sedimentation, and microscopy. Droplet-size analysis showed that addition of either fat prior to emulsification (precrystallized fat) or fat quench-crystallized in situ following emulsification (postcrystallized fat) decreased the degree of droplet coalescence, based on volume-weighted (d ₃₃) mean droplet diameters, with postcrystallized emulsions being more stable against coalescence. Sedimentation studies corroborated these results, with greatly enhanced stability against sedimentation in postcrystallized emulsions. Precrystallized fat had very little effect on emulsion sedimentation at levels as high as 2% (w/w). Postcrystallized cottonseed stearine produced slightly less resistant emulsions than did canola stearine, even if both were in the β-form. Surface energetics revealed that canola stearine had greater affinity for the oil/water interface and hence a greater displacement energy. The presence of micronsized (Pickering) crystals located directly at the droplet interface, resulting from in situ crystallization or generated by the shearing of precrystallized fats, provided enhanced stability vis-à-vis preformed crystals. These stabilized emulsions via the formation of crystal networks that partially immobilized droplets.     

Synthesis of sulfonyl fluorinated macro emulsifier for low surface energy emulsion polymerization application

Fluorinated acrylate emulsions have been extensively applied for hydrophobic surface coatings. To obtain fluorinated emulsions of low surface energy, amphiphilic sulfonyl macro emulsifiers consisting of 2‐(perfluorohexyl) ethyl acrylate (PFHEA) and 2‐acrylanmido‐2‐methylpropanesulfonic acid (AMPS) were designed via radical polymerization and subsequently used for the emulsion copolymerization of PFHEA, methyl methacrylate (MMA), and methyl butyl acrylate (MBA). Under optimum synthesis conditions, the emulsifier displayed superior emulsification properties such as high monomer conversion, small particle size, and excellent stability compared with conventional emulsifiers. The corresponding emulsions with sulfonyl macro emulsifiers exhibited extreme low surface energy (9.8 mN/m) and outstanding hydrophobicity due to high contents of fluorinated chains, as well as thimbleful hydrophilic sulfonyl groups, which shows the great potential in water repellent modification application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44921.     

Antioxidant Activity of Raisin Extracts in Bulk Oil,Oil in Water Emulsion,and Sunflower Butter Model Systems

The antioxidant activities of the raisin extract (RE) in stripped corn oil, stripped corn oil emulsions, and sunflower butter stored at 60 °C for up to 15 days was evaluated. Peroxide values and hexanal content were measured on a half day, 2 or 3 day basis for the emulsion, sunflower butter, and bulk oil, respectively. The RE had the best antioxidant activity in the bulk oil system. Statistical contrasts indicated the oxidation of bulk corn oil treated with RE was significantly (p < 0.001 and p = 0.044) lower than bulk oil and bulk oil treated with tertiary-butylhydroquinone (TBHQ), respectively. No differences (p = 0.15) in hexanal concentrations were observed in stored bulk oils treated with RE and TBHQ. However, both these materials inhibited hexanal formation better (p < 0.001) when compared to the control corn oil. In contrast, 200 μg/g TBHQ had better (p = 0.0004) antioxidant activity than 3,000 μg/g RE in the oil in water(o/w) emulsion. No significant differences (p = 0.1637) in hexanal formation were observed in the emulsions treated with RE and TBHQ. However, the data indicated that the RE treated emulsion did undergo more secondary oxidation than the emulsion treated with TBHQ beyond 110 h. The 3,000 μg/g RE had antioxidant activity in sunflower butter, but was less effective than the 200 μg/g TBHQ and a lower RE concentration (200 μg/g). The observations supported the hypothesis that RE has antioxidant activity in the multiple model systems.     

Investigating Factors Affecting Water-In-Diesel Fuel Nanoemulsions

In this work, water-in-diesel fuel nanoemulsions were prepared with mixed nonionic surfactants. Several mixtures of sorbitan monooleate and polyoxyethylene (20) sorbitan monooleate, with different Hydrophilic–Lipophilic Balance (HLB) values (9.6, 9.8, 10, 10.2 and 10.4) were prepared to achieve the optimal HLB value. Three mixed surfactant concentrations were prepared at 6, 8 and 10 wt% to identify the optimum concentration. Five emulsions with different water contents: 5, 6, 7, 8 and 9 % (wt/wt) were prepared using a high energy method under the optimum conditions (HLB = 10 and mixed surfactant concentration = 10 %). The effect of the HLB value, mixed surfactant concentration and water content on the droplet size has been studied. The interfacial tension and thermodynamic properties of the individual and the blended emulsifiers were investigated. Droplet size of the prepared nanoemulsions was determined by dynamic light scattering and the nanoemulsion stability was assessed by measuring the variation of the droplet size as a function of time. From the results obtained, it was found that the mean droplet size was formed between 49.5 and 190 nm depending on the HLB value, surfactant concentration and water content of the blended emulsifiers.