Antioxidant properties of myricetin and quercetin in oil and emulsions

The effect of quercetin and myricetin on the stability of sunflower oil and oil-in-water emulsions was studied by storage experiments monitored by measurement of peroxide values, conjugated dienes, and headspace volatile analysis. Myricetin showed strong antioxidant activity in oils stored at 60 or 30°C and in oil-in-water emulsions stored at 30°C, whether tocopherols or citric acid were present or not; however, quercetin showed similar antioxidant activity in stripped sunflower oil but no activity in oils that contained tocopherols and citric acid. This showed that myricetin is effective owing to strong radical scavenging and metal-chelating properties, whereas quercetin has weaker radical scavenging activity, although it is also active by metal-chelation. The effects of copper and iron salts on the antioxidant activity of myricetin and quercetin were studied in sunflower oil and oil-in-water emulsions. Quercetin and myricetin enhanced the prooxidant effect of cupric chloride in oil-in-water emulsions (pH 7.4), but this effect was not observed with cupric stearate. The addition of myricetin to emulsions that contained ferric chloride at pH 5.4 also produced a strong prooxidant effect, and small prooxidant effects of flavonols were also detected in the presence of cupric chloride under these conditions. However, myricetin and quercetin reduced the prooxidant effect of ferric palmitate in oils. Myricetin also showed a strong antioxidant effect in oil that contained cupric stearate, although quercetin had no significant effect on the oxidative stability of this system. It therefore appears that flavonols may exert a prooxidant effect in the presence of metal salts, but the nature of the metal salt is important in determining whether a prooxidant effect occurs.     

Influence of Oil Load and Maltodextrin Concentration on Properties of Tuna Oil Microcapsules Encapsulated in Two-Layer Membrane

The two layers of tuna oil-in-water emulsions containing different oil loads (5–10 wt%) and maltodextrin concentrations (10–20 wt%) were stabilized by a lecithin–chitosan membrane. The liquid emulsions were then spray dried at an inlet air temperature of 180 ± 2°C and an outlet air temperature of 85 ± 5°C. The characteristics of liquid emulsion (creaming and mean droplet size) and spray-dried microcapsules (moisture content, water activity, color, morphology, glass transition temperature, and encapsulation efficiency) were measured. The results suggest that two-layer oil-in-water emulsions are an effective system to produce high oil-loaded microcapsules, which may lead to its wide application for use in food products.     

FLOW OF SURFACTANT-STABILIZED OIL-IN-WATER EMULSIONS THROUGH WEDGE METERS AND SEGMENTAL ORIFICE METERS

The flow of surfactant-stabilized oil-in-water emulsions through wedge meters and segmental orifice meters was investigated experimentally. A flow loop consisting of wedge meters and segmental orifice meters of different shapes and sizes was designed and developed. The discharge coefficients were determined for various differently concentrated stable oil-in-water emulsions. The dispersed phase (oilrpar; concentration of emulsions was varied from 0 to 76,14° by volume. At low to moderate values of the dispersed phase concentration, the emulsions were Newtonian in nature. At high oil concentrations of 65.16° and 76.14° by volume, the emulsions were non-Newtonian pseudoplastic in nature. The single phase calibration curves of discharge coefficient versus Reynolds number are found to be applicable to surfactant stabilized oil-in-water emulsions, both Newtonian and non-Newtonian. However, in the latter case. one needs to use the power-law Reynolds number instead of the conventional one. Based on the experimental data obtained in this study, empirical expressions for the wedge and orifice discharge coefficients are given. These expressions can be used to predict the discharge coefficients for the emulsions provided that the emulsions are similar in nature to those investigated in the present work.     

Characterization of enzymatically prepared biosurfactants

Various fatty monoesters of sugars and sugar alcohols were prepared enzymatically in organic solvent. Water produced during esterification was removed by refluxing through a dessicant under reduced pressure. Surface properties of these esters such as surface and interfacial tensions and their ability to stabilize emulsions at 30°C were evaluated: oleate esters of glucose, fructose, and sorbitol show similar behavior in reduction of surface and interfacial tensions, and values for the critical micelle concentration are about 8·10⁻⁵ M. It was also observed with sorbitol esters that the shorter the alkyl chain, the higher the critical micelle concentration. Generally, emulsions prepared with the emulsifier dissolved in the water or in the oil phase lead to oil-in-water or water-in-oil emulsions, respectively. Sorbitol monolaurate significantly increased the stability of oil-in-water emulsions, with only 5% separation of the phases after 48h at 30°C, compared to 10% for chemically prepared sorbitan monolaurate under the same conditions. Sorbitol monoerucate was very efficient in stabilizing water-in-oil emulsions, with only 1% separation of the phases.     

Preparing ceramic membranes for oil-in-water emulsions separation with oil-based drilling cutting pyrolysis residues (ODPRs) as raw material

Oil-based drilling cutting pyrolysis residues (ODPRs) are one of the solid wastes from pyrolysis of the oil-based drilling cuttings (OBDCs) that need to be recycled as raw materials to avoid the possible pollution. In this study, a facile low-cost ceramic membrane for oil-in-water emulsions separation was prepared with ODPRs incorporating with fly ash as raw material. CaCO₃ in ODPRs would decompose acting as pore-forming agent, and anorthite was formed in resultant membranes. The obtained membrane with 30 wt% ODPRs and 70 wt% fly ash fired at 1050 °C possessed apparent porosity of 38.2%, mean pore size of 0.4 μm, flexural strength of 13.1 MPa, and Darcy permeability of 1.06 × 10⁻¹³ m². Consequently, commendable filtration performance for oil-in-water emulsions was presented. In addition, the ceramic membrane showed favorable recyclability and corrosion resistance. Leaching test indicated that the membrane is safe for oil-in-water emulsion separation. Hereby, this paper confirmed the availability of ODPRs for preparing ceramic filtration membranes, and provided a new environmental conservation way to treat oil-in-water emulsions that was consistent with the sustainable development goals.     

Pipeline flow behaviour of heavy crude oil emulsions

Pipeline transportation of heavy oils as oil-in-water emulsions has been proposed as an alternative to blending the crude oil with natural gas condensate or other diluent. An 18 m long, 0.02 m I.D. closed loop was constructed to investigate the behaviour of an emulsified Cold Lake crude oil under pipeline flow. Pressure drop was measured as a function of flow rate for freshly produced emulsions to establish correlations of friction factor versus Reynolds number. Stability was observed for long term pipeline flow. The time at which the emulsion breakdown occurred was found to be a function of oil concentration and shear rate. The breakdown of the emulsion was clearly indicated by a simultaneous change in the system variables of pressure drop, temperature and power required to turn the pump at constant speed.     

Homogenization Pressure and Temperature Affect Protein Partitioning and Oxidative Stability of Emulsions

The oxidative stability of 10 % fish oil-in-water emulsions was investigated for emulsions prepared under different homogenization conditions. Homogenization was conducted at two different pressures (5 or 22.5 MPa), and at two different temperatures (22 and 72 °C). Milk proteins were used as the emulsifier. Hence, emulsions were prepared with either a combination of α-lactalbumin and β-lactoglobulin or with a combination of sodium caseinate and β-lactoglobulin. Results showed that an increase in pressure increased the oxidative stability of emulsions with caseinate and β-lactoglobulin, whereas it decreased the oxidative stability of emulsions with α-lactalbumin and β-lactoglobulin. For both types of emulsions the partitioning of proteins between the interface and the aqueous phase appeared to be important for the oxidative stability. The effect of pre-heating the aqueous phase with the milk proteins prior to homogenization did not have any clear effect on lipid oxidation in either of the two types of emulsions.     

一体式陶瓷外膜直接乳化法制备单分散水包油乳液

膜乳化法是靠膜两侧的压差使分散相通过微孔膜,以小液滴的形式分散在连续相中而形成乳状液的方法．与转一定体系、高压均化等传统制乳方法相比,膜乳化法所制得的乳液具有液滴尺寸均一、节能、剪应力小等特点,可应用于食品、医药、聚合物工业等领域．过去的十几年中,尽管在膜乳化方面进行了大量的工作,过程参数对乳滴尺寸的影响并未完全研究清楚．甚至在一些研究中,仅仅把平均乳滴直径作为分布参数．     

Synthesis of macroporous silica from solid-stabilised emulsion templates

We have investigated the microstructures of the solid residue left behind after the evaporation of solid-stabilised emulsions. The correlation between the microstructure and the properties and preparation conditions of the emulsions will be thoroughly discussed. The type of microstructure is related to the conditions (oil type, oil content, particle type, particle concentration and emulsion type) of the initial emulsion. Solid residues left after evaporation of oil-in-water emulsions containing volatile oils (relative to water) show a “knobbly” microstructure. When oils with similar or lower vapour pressure to that of water were used, “sponge-like” structures were obtained. For emulsions containing volatile oils, the mean drop diameter is similar to the mean pore diameter, whereas when oils with low vapour pressure are used, the pores are much smaller. Finally, this paper will illustrate that stable toluene-in-water emulsions leave porous microstructures, whereas water-in-toluene emulsions and emulsions close to the phase inversion show sheet-like or “knobbly” structure.     

聚偏氟乙烯膜亲水改性及其乳液分离与重金属吸附应用

聚偏氟乙烯（PVDF）膜因其优异的化学和力学稳定性而被广泛应用于水处理领域,但PVDF膜本身的疏水性,容易使其在处理含油废水的过程中被油滴污染,造成膜孔堵塞。以PVDF微滤膜为基底,通过单宁酸（TA）和聚乙烯亚胺（PEI）共沉积形成了TA/PEI黏附层,经戊二醛共价交联和接枝半胱氨酸（Cys）,制备了一种PVDF改性膜（PVDF@TA/PEI-Cys）。改性后的PVDF膜具有良好的亲水性和水下超疏油性,水接触角和水下油接触角分别为22.2°和150.2°。在0.09 MPa下,PVDF@TA/PEI-Cys膜的纯水通量达6328 L/（m²·h）,水包油型乳液分离效率高达99.9%。此外,该改性膜还可同时吸附水中的汞离子,最大吸附量为24.7 mg/g。     

Oxidative stability of stripped and nonstripped borage and evening primrose oils and their emulsions in water

Oxidative stability of stripped and nonstripped borage and evening primrose oils and their emulsions in water was evaluated. The results indicated that column chromatographic techniques provide an effective means for stripping vegetable oils of their minor components. However, some minor components may be retained in the stripped oils. The minor components in borage and evening primrose oils significantly (P<0.05) influenced their oxidative stability in the dark. In contrast, the behavior of endogenous antioxidants in borage and evening primrose oil-in-water emulsions, according to the “polar paradox” theory, was difficult to evaluate. Correlations existed between peroxide value (PV) and conjugated dienes (CD) (P<0.05) as well as 2-thiobarbituric acid-reactive substances (TBARS) and hexanal content (P<0.01) for most oils and emulsion systems. Therefore, CD and TBARS may generally be used to assess the oxidative stability of borage and evening primrose oils and their oil-in-water emulsions in addition to or in place of PV and headspace volatiles, respectively.     

Argan oil-in-water emulsions: Preparation and stabilization

We prepared stable oil-in-water emulsions of argan oil with two different types of mixtures of nonionic emulsifiers. Three different types of oil (Israeli argan oil, Moroccan argan oil, and soybean oil) were emulsified with mixtures of Span 80 and Tween 80. The optimum HLB value for argon oil was 11.0 (±1.0). The argan oil-in-water emulsions were stable for more than 5 mon at 25°C. Synergistic effects were found in enhancing stability of emulsions prepared with sucrose monostearate. The origin of the oil and the internal content of natural emulsifiers, such as monoglycerides and phospholipids, have a profound influence on its interfacial properties and on the stability of the argan oil-in-water emulsions.     

Emulsification using tubular metallic membranes

Tubular metallic membranes with pore diameters of 5 and 10 μm have been used in a cross-flow unit to prepare monodisperse oil-in-water emulsions (O/W) with span values as low as 0.67, significantly lower than for emulsions prepared with a rotor–stator homogenizer. The influence of typical operating parameters (continuous phase flow rate and transmembrane pressure) on droplet size distribution was studied. The smallest droplets were obtained at low transmembrane pressures and high continuous phase flow rates. The droplet production with tubular metallic membranes was higher than with other types of tubular membranes, such as SPG or ceramic.Experimental results were compared with those obtained in a stirred tank unit operating under similar conditions and using flat metallic membranes with the same pore diameter. Droplet size prediction models based on simple force balances were applied to compare theoretical and experimental droplet diameters. The droplet formation regime (dripping, jetting) was also studied for both types of membranes.     

制备单分散含单体O/W乳液的SPG膜乳化过程

采用Shirasu多孔玻璃（SPG）膜乳化法制备了单分散含对苯二甲酰氯（TDC）单体的O/W乳液,系统地研究了SPG膜乳化过程的影响因素.实验结果表明,采用SPG膜乳化法制备单分散O/W乳液时,选择阴离子表面活性剂比考虑亲水亲油平衡（HLB）匹配更重要;增大分散相或连续相的黏度,能够改善乳液的单分散性和稳定性;随着单体浓度增加,乳液的单分散性变差,液滴的平均粒径逐渐变小.当SPG膜孔径大于1.0 μm左右时,可得到单分散的含TDC单体乳液;而当孔径小于1.0 μm左右时,水分子更容易扩散并溶解到油水界面甚至油相内部与TDC生成对苯二甲酸（TPA）,TPA积累到一定程度在油水界面上析出将膜孔堵塞,从而无法制得单分散乳液.随着乳化时间增长,乳液的平均直径逐渐变小、单分散性逐渐变差.     

Study on the Stability of DeoxyArbutin in an Anhydrous Emulsion System

The skin-whitening agent, deoxyArbutin, is a potent tyrosinase inhibitor that is safer than hydroquinone and arbutin. However, it is thermolabile in aqueous solutions, where it decomposes to hydroquinone. Pharmaceutical and cosmetic emulsions are normally oil-in-water (o/w) or water-in-oil (w/o) systems; however, emulsions can be formulated with no aqueous phase to produce an anhydrous emulsion system. An anhydrous emulsion system could offer a stable vehicle for compounds that are sensitive to hydrolysis or oxidation. Therefore, to enhance the stability of deoxyArbutin in formulations, we chose the polyol-in-silicone, anhydrous emulsion system as the basic formulation for investigation. The quantity of deoxyArbutin and the accumulation of hydroquinone in both hydrous and anhydrous emulsions at various temperatures were analyzed through an established high performance liquid chromatographic (HPLC) method. The results indicated that water increased the decomposition of deoxyArbutin in the formulations and that the polyol-in-silicone, oil-based, anhydrous emulsion system provided a relatively stable surrounding for the deoxyArbutin that delayed its degradation at 25 °C and 45 °C. Moreover, the composition of the inner hydrophilic phase, containing different amounts of glycerin and propylene glycol, affected the stability of deoxyArbutin. Thus, these results will be beneficial when using deoxyArbutin in cosmetics and medicines in the future.     

High throughput membrane emulsification using a single-pass annular flow crossflow membrane

Membrane emulsification has the potential to revolutionize the energy-efficient production of uniform emulsions and dispersions, relevant to diverse fields from pharmaceutical active ingredient controlled release particles to Fast Moving Consumer Goods. A novel highly robust single-pass continuous phase crossflow system has been developed providing dispersed phase concentrations up to 40% vol/vol and dispersed phase fluxes up to 5,730 L m⁻² hr⁻¹, from a single 100 mm long membrane tube. Extensive results of two oil-in-water systems (vegetable oil and PolyCaproLactone dissolved in DiChloroMethane) and one water-in-oil system (sodium silicate solution) are reported, using hydrophilic and hydrophobic membranes respectively. Mathematical models are validated enabling comprehensive engineering analysis of processes including predicted droplet size, membrane pressure drops, and energy requirement for dispersion production. Surfactant depletion, pore utilization, and droplet interaction at the membrane surface were investigated to provide a comprehensive analysis of the capabilities of novel annular-flow membrane emulsification for high throughput emulsion generation.     

Edible oil-in-water emulsions stabilized by hydrophile–lipophile balanced sucrose ester

Conventional emulsions are mostly stabilized by surfactants and for stabilization of oil-in-water emulsions the surfactants should be hydrophilic or with HLB numbers larger than seven. In this work, we report that edible oil-in-water emulsions can also be stabilized by surfactants with an HLB value close to seven. With edible sucrose ester C-1807 (HLB no. = 7) as emulsifier and three edible oils (canola oil, olive oil, soybean oil), edible oil-in-water emulsions can be stabilized by C-1807 at concentrations beyond its critical aggregation concentration (CAC). Although monomeric C-1807 behaves as an inferior emulsifier, they assemble to form multilamellar vesicles in water at concentrations higher than the CAC giving a viscoelastic/gel-like aqueous phase which is partly responsible for emulsion stabilization. Specifically, at 2 wt%, high internal phase emulsions (HIPEs) with ϕ_o = 0.75 can be obtained, which are stable against cooling–heating cycles between 5 and 30°C during storage. The vesicles disperse in the aqueous lamellae surrounding the oil droplets, which together with the viscoelastic/gel-like continuous phase prevents them from flocculation and coalescence.     

Effect of the lupin protein/surfactant ratio on linear viscoelastic properties of oil-in-water emulsions

This work studies the influence of a low-molecular-weight emulsifier/lupin protein ratio on the linear viscoelastic properties of oil-in-water emulsions. With this aim, dynamic viscoelasticity tests, as well as droplet-size distribution measurements, were done. Four types of low-molecular-weight emulsifiers were used. From the results, we conclude that emulsions stabilized by emulsifier blends show, in general, lower values of both the linear viscoelasticity functions and Sauter diameter than those found when lupin protein was used as the only emulsifier. Protein-free emulsions may have similar parameter values when the surfactant induces a structured gel-like continuous phase. Evolution of the linear viscoelastic functions with the composition of the mixed emulsifier has been explained on the basis of changes in interdroplet interactions, rheological behavior of the continuous phase, and surface viscoelasticity of the adsorbed emulsifier layer. However, the above-mentioned behavior cannot be explained from changes in the emulsion droplet-size distribution.     

Characterization of fish oil-in-water emulsions using light-scattering,nuclear magnetic resonance,and gas chromatography-headspace analyses

The effect of the molecular environment on the physical and oxidative properties of homogenized or microfluidized fish oil-in-water emulsions (5% w/w tuna oil in pH 7 phosphate buffer) stabilized by whey protein isolate (WPI, 1 or 5% w/w) or lecithin (2.5% w/w) was examined. Laser light-scattering measurements showed that WPI-stabilized emulsions had smaller particle sizes than lecithin-stabilized emulsions, and that higher pressures reduced the particle size. WPI afforded more protection against oil oxidation than did lecithin, as evidenced by the lower headspace propanal of emulsions as measured by GC-headspace analysis, despite the larger interface in WPI-stabilized emulsions. Reducing the concentration of WPI in emulsions from 5 to 1% decreased the oxidative stability of WPI-stabilized emulsions. The ¹H NMR transverse relaxation times (T ₂) of FA chains in emulsion droplets stabilized by the same surfactants made by homogenization or microfluidization were different and not always related to particle size. The higher mobility (i.e., longer T ₂) of the unsaturated parts of the FA chains within an oil droplet, compared with the saturated parts, suggests that the unsaturated components tended to stay in the core of the oil droplets. This experimental result supports the hypothesis reported in other literature that the more unsaturated FA are buried in the oil core of oil-in-water emulsions. The lack of a universal correlation between particle size and oxidation suggests that the mobility of particles in an emulsion has an influence on the rate of oxidation.     

Antioxidant and Prooxidant Activity Behavior of Phospholipids in Stripped Soybean Oil-in-Water Emulsions

Phospholipids have been reported to inhibit lipid oxidation in bulk oils, but very little is known about their influence on oxidation in oil-in-water emulsions. In the present study, the impact of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) on lipid oxidation was studied in 1% stripped soybean oil-in-water (O/W) emulsions as a function of DOPC concentration and pH (3 and 7). At pH 7.0, DOPC inhibited lipid oxidation in O/W emulsions, while DOPC was prooxidative at pH 3.0. DOPC did not affect emulsion droplet charge or size at either pH 3.0 or 7.0. The antioxidant activity at pH 7.0 was observed in a series of phospholipids (PL) that varied in fatty acid unsaturation level and chain length as well as type of phosphate head group. Overall, phosphatidylcholine with either oleic or palmitic acid were the most effective at inhibiting lipid hydroperoxide and hexanal formation of all of the PL tested. Antioxidant mechanism of PL could not be ascribed to their ability to decompose lipid hydroperoxides. It might be possible that, at pH 7.0, the PL antioxidant activity is related to their ability to form structures within the lipid phase of the emulsions droplets or to chelate metals.