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1.
Oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin (beta-Lg)-pectin membranes were produced using a two-stage process. A primary emulsion containing small droplets (d(32) approximately 0.3 microm) was prepared by homogenizing 10 wt % corn oil with 90 wt % aqueous solution (1 wt % beta-Lg, 5 mM imidazole/acetate buffer, pH 3.0) using a high-pressure valve homogenizer. The primary emulsion was then diluted with pectin solutions to produce secondary emulsions with a range of pectin concentrations (5 wt % corn oil, 0.45 wt % beta-Lg, 5 mM imidazole/acetate buffer, 0-0.22 wt % pectin, pH 3.0). The electrical charge on the droplets in the secondary emulsions decreased from +33 +/- 3 to -19 +/- 1 mV as the pectin concentration was increased from 0 to 0.22 wt %, which indicated that pectin adsorbed to the droplet surfaces. The mean particle diameter of the secondary emulsions was small (d(32) < 1 microm) at relatively low pectin concentrations (<0.04 wt %), but increased dramatically at higher pectin concentrations (e.g., d(32) approximately 13 microm at 0.1 wt % pectin), which was attributed to charge neutralization and bridging flocculation effects. Emulsions with relatively small mean particle diameters (d(32) approximately 1.2 microm at 0.1 wt % pectin) could be produced by disrupting flocs formed in secondary emulsions containing highly negatively charged droplets, for example, by sonication, blending, or homogenization. The particles in these emulsions probably consisted of small flocs containing a number of protein-coated droplets bound together by pectin molecules. These emulsions had good stability to further particle aggregation up to relatively high ionic strengths (< or =500 mM NaCl) and low pH (pH 3). The interfacial engineering technology used in this study could lead to the creation of food emulsions with improved physicochemical properties or stability.  相似文献   

2.
Oil-in-water (O/W) emulsions containing small oil droplets (d32 approximately 0.22 microm) stabilized by sodium dodecyl sulfate (SDS)-fish gelatin (FG) membranes were produced by an electrostatic deposition technique. A primary emulsion containing anionic SDS-coated droplets (zeta approximately -40 mV) was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (20 wt % corn oil, 0.46 wt % SDS, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic SDS-FG-coated droplets (zeta approximately +30 mV) was formed by diluting the primary emulsion with an aqueous fish gelatin solution (10 wt % corn oil, 0.23 wt % SDS, 100 mM acetic acid, 2.00 wt % fish gelatin, pH 3.0). The stabilities of primary and secondary emulsions with the same oil concentration to thermal processing, ionic strength, and pH were assessed by measuring particle size distribution, zeta potential, microstructure, destabilized oil, and creaming stability. The droplets in secondary emulsions had good stability to droplet aggregation at holding temperatures from 30 to 90 degrees C for 30 min, [NaCl] < or = 100 mM, and pH values from 3 to 8. This study shows that the ability to generate emulsions containing droplets stabilized by multilayer interfacial membranes comprised of two or more types of emulsifiers, rather than a single interfacial layer comprised of one type of emulsifier, may lead to the development of food products with improved stability to environmental stresses.  相似文献   

3.
Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion containing anionic lecithin-coated droplets was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (5 wt % corn oil, 1 wt % lecithin, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic lecithin-chitosan-coated droplets was formed by diluting the primary emulsion with an aqueous chitosan solution (1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0.036 wt % chitosan). The stabilities of the primary and secondary emulsions with the same oil concentration to thermal processing, freeze-thaw cycling, high calcium chloride concentrations, and lipid oxidation were determined. The results showed that the secondary emulsions had better stability to droplet aggregation during thermal processing (30-90 degrees C for 30 min), freeze-thaw cycling (-10 degrees C for 22 h/30 degrees C for 2 h), and high calcium chloride contents (相似文献   

4.
The oxidation of fatty acids can be inhibited by engineering the surface of oil-in-water emulsion droplets to decrease interactions between aqueous phase prooxidants and lipids. The objective of this research was to evaluate whether emulsions stabilized by a multilayer emulsifier systems consisting of beta-lactoglobulin and citrus or sugar beet pectin could produce fish oil-in-water emulsions that had good physical and oxidative stability. Sugar beet pectin was compared to citrus pectin because the sugar beet pectin contains the known antioxidant, ferulic acid. A primary Menhaden oil-in-water emulsion was prepared with beta-lactoglobulin upon which the pectins were electrostatically deposited at pH 3.5. Emulsions prepared with 1% oil, 0.05% beta-lactoglobulin, and 0.06% pectins were physically stable for up to 16 days. As determined by monitoring lipid hydroperoxide and headspace propanal formation, emulsions prepared with the multilayer system of beta-lactoglobulin and citrus pectin were more stable than emulsions stabilized with beta-lactoglobulin alone. Emulsions prepared with the multilayer system of beta-lactoglobulin and sugar beet pectin were less stable than emulsions stabilized with beta-lactoglobulin alone despite the presence of ferulic acid in the sugar beet pectin. The lower oxidative stability of the emulsions with the sugar beet pectin could be due to its higher iron and copper concentrations which would produce oxidative stress that would overcome the antioxidant capacity of ferulic acid. These data suggest that the oxidative stability of oil-in-water emulsions containing omega-3 fatty acids could be improved by the use of multilayer emulsion systems containing pectins with low metal concentrations.  相似文献   

5.
Interfacial protein-polysaccharide complexes can be used to improve the physical stability of oil-in-water emulsions. The purpose of this study was to examine the impact of ionic strength on the formation and stability of oil-in-water emulsions containing polysaccharide-protein-coated droplets. Emulsions were prepared that contained 0.1 wt % corn oil, 0.05 wt % beta-lactoglobulin, and 0.02 wt % pectin at pH 7. The emulsions were then adjusted to pH 4 to promote electrostatic deposition of the pectin molecules onto the surfaces of the protein-coated droplets. The salt concentration of the aqueous phase (0 or 50 mM NaCl) was adjusted either before or after deposition of the pectin molecules onto the droplet surfaces. We found that stable emulsions containing polysaccharide-protein-coated droplets could be formed when the salt was added after pectin adsorption but not when it was added before pectin adsorption. This phenomenon was attributed to the ability of NaCl to promote droplet flocculation in the protein-coated droplets so that the pectin molecules adsorbed onto the surfaces of flocs rather than individual droplets when salt was added before pectin adsorption. We also found that polysaccharide-protein-coated droplets had a much improved stability to salt-induced flocculation than protein-coated droplets with the same droplet charge (zeta-potential). Theoretical predictions indicated that this was due to the ability of the adsorbed polysaccharide layer to strongly diminish the van der Waals attraction between the droplets.  相似文献   

6.
Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion was prepared by homogenizing 5 wt % corn oil with 95 wt % aqueous solution (1 wt % lecithin, 100 mM acetic acid, pH 3.0) using a high-pressure valve homogenizer. This emulsion was diluted with aqueous chitosan solutions to form secondary emulsions with varying compositions: 1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0-0.04 wt % chitosan (pH 3.0). The particle size distribution, particle charge, and creaming stability of the primary and secondary emulsions were measured. The electrical charge on the droplets increased from -49 to +54 mV as the chitosan concentration was increased from 0 to 0.04 wt %, which indicated that chitosan adsorbed to the droplet surfaces. The mean particle diameter of the emulsions increased dramatically and the emulsions became unstable to creaming when the chitosan concentration exceeded 0.008 wt %, which was attributed to charge neutralization and bridging flocculation effects. Sonication, blending, or homogenization could be used to disrupt flocs formed in secondary emulsions containing droplets with high positive charges, leading to the production of emulsions with relatively small particle diameters (approximately 1 microm). These emulsions had good stability to droplet aggregation at low pH (< or =5) and ionic strengths (<500 mM). The interfacial engineering technology utilized in this study could lead to the creation of food emulsions with improved stability to environmental stresses.  相似文献   

7.
The ability of sugar beet pectin to stabilize 20% w/w limonene oil-in-water emulsions has been investigated. The size of the oil droplets as determined by laser diffraction measurements decreased from about 15 mum to about 6 mum when the pectin concentration increased from 0.05% to 2% w/w but leveled off thereafter, suggesting complete coverage of the oil droplets by the polymer at this optimum concentration. Isotherms for the adsorption of pectin, protein, and ferulic acid were constructed. The adsorption capacities at the oil-water interface of approximately 1.4 and approximately 0.2 mg/m (2) for protein and ferulic acid, respectively, compared to approximately 9.5 mg/m (2) for pectin revealed that the adsorbed fractions of the pectin sample were rich in protein (14.7%) and ferulic acid (2.1%) given that there were only 2.7% protein and 1.06% ferulic acid present in the whole pectin sample. Direct measurements on the adsorbed fraction recovered from the oil droplets via desorption with SDS confirmed that it contained 11.1% protein and 2.16% ferulic acid. The results suggest that one or both of these two functional groups adsorb onto the surface of the oil droplets and stabilize the emulsions. High molecular mass fractions adsorbed preferentially onto oil droplets during emulsification. As compared to those made with gum arabic, the emulsion samples made with sugar beet pectin samples exhibited similar (or even slightly higher) stability.  相似文献   

8.
The possibility of producing stable oil-in-water (O/W) emulsions containing oil droplets surrounded by multiple layer interfacial membranes from food grade ingredients has been demonstrated. These emulsions were produced using a three stage process that relies on the adsorption of charged biopolymers to oppositely charged surfaces. Emulsions (0.5 wt % corn oil, 0.1 wt % lecithin, 0.0078 wt % chitosan, 0.02 wt % pectin, and 100 mM acetic acid, pH 3.0) containing oil droplets stabilized by lecithin-chitosan-pectin membranes were formed using this interfacial layer-by-layer deposition process. The droplets in these emulsions had good stability to aggregation over a wide range of pH values and salt concentrations (pH 4-8 at 0 mM NaCl and pH 3-8 at 100 mM NaCl). This technology could be extremely useful to the food industry for the creation of O/W emulsions with improved properties or novel applications, e.g., improved stability to environmental stresses, protection of labile substances, controlled release, and triggered release.  相似文献   

9.
The influence of EDTA on lipid oxidation in sugar beet pectin-stabilized oil-in-water emulsions (pH 6, 15% oil, wet basis), prepared from fish oil (FO) and fish oil-extra virgin olive oil (FO-EVOO) (1:1 w/w), as well as the spray-dried microcapsules (50% oil, dry basis) prepared from these emulsions, was investigated. Under accelerated conditions (80 °C, 5 bar oxygen pressure) the oxidative stability was significantly (P < 0.05) higher for FO and FO-EVOO formulated with EDTA, in comparison to corresponding emulsions and spray-dried microcapsules formulated without EDTA. The EDTA effect was greater in emulsions than in spray-dried microcapsules, with the greatest protective effect obtained in FO-EVOO emulsions. EDTA enhanced the oxidative stability of the spray-dried microcapsules during ambient storage (~25 °C, a(w) = 0.5), as demonstrated by their lower concentration of headspace volatile oxidation products, propanal and hexanal. These results show that the addition of EDTA is an effective strategy to maximize the oxidative stability of both FO emulsions and spray-dried microcapsules in which sugar beet pectin is used as the encapsulant material.  相似文献   

10.
Polysaccharides are widely used in the food industry to modify the stability of protein-based drinks. However, an in depth knowledge of the interactions occurring in the system is still lacking. In this study, the interactions between sodium caseinate and high methoxyl pectin under acidification conditions were studied nondestructively and without dilution using transmission diffusing wave spectroscopy. Oil-in-water emulsions were prepared with 10% soybean oil and 0.5% sodium caseinate. Various concentrations of pectin (ranging from 0 to 0.2%) were added, and the emulsions were acidified with glucono-delta-lactone. With acidification, a "sol-gel" transition occurred and emulsions containing pectin were more stable at lower pH than those without pectin. Furthermore, the sol-gel transition of the mixtures was more sudden for control emulsions without pectin. While in control samples the final solidlike emulsion after gelation tended to be more inhomogeneous and more dissimilar to the starting emulsion, emulsions with pectin in solution gelled later under acidification. With a sufficient amount of pectin, the emulsions showed no aggregation and the destabilization pH varied depending on the amount of pectin present in the emulsions. At intermediate pH values (pH > 5.5), the emulsions displayed a decrease in particle size, more pronounced in samples containing pectin. The results collected using light scattering in concentrated systems, 10% (v/v) in our case, suggested that pectin stabilizes the emulsion oil droplets forming a network of oil droplets loosely connected by strands of pectin.  相似文献   

11.
Emulsion can be produced with electrostatic layer-by-layer deposition technologies to have cationic, thick multilayer interfacial membranes that are effective at inhibiting the oxidation of omega-3 fatty acids. This study investigated the stability of spray-dried multilayer emulsion upon reconstitution into an aqueous system. The primary (lecithin) and multilayered secondary emulsions (lecithin and chitosan) were spray-dried with corn syrup solids (1-20 wt %). The lecithin-chitosan multilayer interfacial membrane remained intact on the emulsion droplets upon reconstitution into an aqueous system. Reconstituted secondary (lecithin-chitosan) emulsions were more oxidatively stable than reconstituted primary (lecithin) emulsions. A minimum of 5 wt % corn syrup solids was needed to microencapsulate the secondary emulsion droplets. Maximum oxidative stability of both the powder and the reconstituted secondary emulsions was observed in samples with 5% and 20% corn syrup solids. Addition of EDTA (25 microM) inhibited oxidation of reconstituted primary and secondary emulsions. These studies suggest that a microencapsulated multilayered emulsion system could be used as a delivery system for omega-3 fatty acids in functional foods.  相似文献   

12.
Oil-in-water emulsions (4 wt % soy oil) containing 4 wt % whey protein hydrolysate (WPH) (27% degree of hydrolysis) and different levels of calcium, magnesium, or potassium chloride were prepared in a two-stage homogenizer. Other emulsions containing 4 wt % WPH but including 0.35 wt % hydroxylated lecithin and different levels of the above minerals were similarly prepared. The formation and stability of these emulsions were determined by measuring oil droplet size distributions using laser light scattering and by confocal scanning laser microscopy and a gravity creaming test. Both lecithin-free and lecithin-containing emulsions showed no change in droplet size distributions with increasing concentration of potassium in the range 0-37.5 mM. In contrast, the diameter of emulsion droplets increased with increasing calcium or magnesium concentration >12.5 mM. Emulsions containing hydroxylated lecithin were more sensitive to the addition of calcium or magnesium than the lecithin-free emulsions. Storage of emulsions at 20 degrees C for 24 h further increased the diameter of droplets and resulted in extensive creaming in emulsions containing >25 mM calcium or magnesium. It appears that both flocculation and coalescence processes were involved in the destabilization of emulsions induced by the addition of divalent cations.  相似文献   

13.
The influence of chelating agents (disodium ethylenediaminetetraacetate (EDTA) and sodium citrate) on the physicochemical properties of whey protein isolate (WPI)-stabilized oil-in-water emulsions containing calcium chloride was determined. The calcium-binding characteristics of EDTA and citrate at 30 degrees C were characterized in aqueous solutions (20 mM Tris buffer, pH 7.0) by isothermal titration calorimetry (ITC). EDTA and citrate both bound calcium ions in a 1:1 ratio, but EDTA had a much higher binding constant. Oil-in-water emulsions (pH 7.0) were prepared containing 6.94% (w/v) soybean oil, 0.35% (w/v) WPI, 0.02% (w/v) sodium azide, 20 mM Tris buffer, 10 mM CaCl(2), and 0-40 mM chelating agent. The particle size, apparent viscosity, creaming stability, free calcium concentration, and particle surface potential of the emulsions were measured. The chelating agents reduced or prevented droplet aggregation in the emulsions. When they were present above a certain concentration (>3.5 mM EDTA or >5 mM citrate), droplet aggregation was prevented. The reduction of aggregation was indicated by decreases in particle size, shear-thinning behavior, apparent viscosity, and creaming. Emulsions containing chelating agents had lower free calcium concentrations and more negatively charged droplets, indicating that the chelating agents improved emulsion stability by binding calcium ions. EDTA could be used at lower concentrations than citrate because of its higher calcium ion binding constant.  相似文献   

14.
The effects of lecithin and pectin on riboflavin-photosensitized oxidation of orange oil in a multilayered oil-in-water emulsion are studied by response surface methodology. Lecithin and pectin contents are two variables studied. Mean oil droplet size, viscosity, and ζ-potential are investigated for evaluation of emulsion stability. Headspace oxygen depletion, increase of conjugated diene value, and released amounts of limonene and carvone are used as responses to evaluate the oxidative stability of orange oil in this emulsion. The results show that both lecithin and pectin contents have significant effects (p < 0.05) on the oxidative stability of orange oil in the multilayered emulsion during photosensitized oxidation. No interactive effect (p < 0.05) is found between the lecithin and pectin contents. To achieve optimal oxidative stability, the suggested values in ratio for lecithin and pectin contents are 14.1 ± 0.5 and 19 ± 0.7, respectively.  相似文献   

15.
Soybeans contain oil bodies that are naturally coated by a layer of phospholipids and proteins. In nature, this coating protects the oil bodies from environmental stresses and could be utilized by food manufacturers for the same purpose. However, natural oil bodies are physically unstable to aggregation because of the relatively weak electrostatic repulsion between them, which limits their application in many foods. In this study, oil bodies were extracted from soybean using an aqueous extraction method and then coated by a pectin layer using electrostatic deposition. The influence of NaCl (0-500 mM), pH (2-8), and freeze-thaw cycling (-20 degrees C, 22 h/40 degrees C, 2 h) on the properties and stability of the oil bodies coated by the pectin layer was analyzed using zeta-potential, particle size, and creaming stability measurements. These results suggest that pectin-coated oil bodies have similar or improved stability compared to uncoated oil bodies and may provide a new way of creating functional soy products for use in the food and other industries.  相似文献   

16.
Proteins can be used to produce cationic oil-in-water emulsion droplets at pH 3.0 that have high oxidative stability. This research investigated differences in the physical properties and oxidative stability of corn oil-in-water emulsions stabilized by casein, whey protein isolate (WPI), or soy protein isolate (SPI) at pH 3.0. Emulsions were prepared with 5% corn oil and 0.2-1.5% protein. Physically stable, monomodal emulsions were prepared with 1.5% casein, 1.0 or 1.5% SPI, and > or =0.5% WPI. The oxidative stability of the different protein-stabilized emulsions was in the order of casein > WPI > SPI as determined by monitoring both lipid hydroperoxide and headspace hexanal formation. The degree of positive charge on the protein-stabilized emulsion droplets was not the only factor involved in the inhibition of lipid oxidation because the charge of the emulsion droplets (WPI > casein > or = SPI) did not parallel oxidative stability. Other potential reasons for differences in oxidative stability of the protein-stabilized emulsions include differences in interfacial film thickness, protein chelating properties, and differences in free radical scavenging amino acids. This research shows that differences can be seen in the oxidative stability of protein-stabilized emulsions; however, further research is needed to determine the mechanisms for these differences.  相似文献   

17.
The stability of emulsions prepared with soy protein isolates was investigated as a function of pH in the presence of two negatively charged polysaccharides: high methoxyl pectin (HMP) and soy soluble polysaccharide (SSPS). Both polysaccharides are composed of a backbone which contains galacturonic acid but, when added to soy protein isolate-stabilized emulsions, SSPS showed a different behavior than that of HMP. At neutral pH and above a critical concentration of stabilizer (0.05%), HMP caused flocculation of the emulsion droplets via a depletion mechanism. On the other hand, the emulsions containing a similar amount of SSPS did not show creaming or flocculation. At acidic pH (<4.0) the addition of pectin caused extensive droplet aggregation, while no aggregation was observed with the addition of SSPS. The differences in the stabilization behavior between the two polysaccharides can be attributed to their differences in charge, neutral sugars side chains, and molecular weight.  相似文献   

18.
The potential of utilizing interfacial complexes, formed through the electrostatic interactions of proteins and polysaccharides at oil-water interfaces, to stabilize model beverage cloud emulsions has been examined. These interfacial complexes were formed by mixing charged polysaccharides with oil-in-water emulsions containing oppositely charged protein-coated oil droplets. Model beverage emulsions were prepared that consisted of 0.1 wt % corn oil droplets coated by beta-lactoglobulin (beta-Lg), beta-Lg/alginate, beta-Lg/iota-carrageenan, or beta-Lg/gum arabic interfacial layers (pH 3 or 4). Stable emulsions were formed when the polysaccharide concentration was sufficient to saturate the protein-coated droplets. The emulsions were subjected to variations in pH (from 3 to 7), ionic strength (from 0 to 250 mM NaCl), and thermal processing (from 30 or 90 degrees C), and the influence on their stability was determined. The emulsions containing alginate and carrageenan had the best stability to ionic strength and thermal processing. This study shows that the controlled formation of protein-polysaccharide complexes at droplet surfaces may be used to produce stable beverage emulsions, which may have important implications for industrial applications.  相似文献   

19.
Calcium-induced flocculation of caseinate-stabilized soybean oil-in-water emulsions in conditions of Couette flow was studied. A concentrated emulsion (20% oil, 0.5-2.0% sodium caseinate in 20 mM imidazole, pH 7) was diluted 20 times in buffer containing concentrations of CaCl(2) between 9 and 17 mM and sheared at rates between 335 and 1340 s(-)(1). The average particle size (d(43)), measured by integrated light scattering, increased in a sigmoidal manner with shearing time. An increased shear rate resulted in an increased flocculation rate, because of the increased number of collisions between particles, but a decreased value of the maximum d(43), because higher shear rates increasingly disrupted the flocs. The flocculation rate was increased by increasing the calcium concentration, indicating an increased collision efficiency. The orthokinetic stability of the emulsions was increased with increased protein content, and it is postulated that the increased surface coverage and hydrodynamic thickness of the adsorbed protein layer increased steric repulsion between droplets, so that higher calcium concentrations were necessary to induce sufficient conformational change of the proteins to allow flocculation. At high caseinate concentrations, calcium may also induce precipitation of unadsorbed caseins from the serum to the oil-water interface, thereby increasing steric repulsion and hence increasing orthokinetic stability.  相似文献   

20.
复配亚麻籽油和辅酶Q10乳液的制备及表征   总被引:1,自引:1,他引:0  
亚麻籽油和辅酶Q10都具有水中溶解度低、稳定性差、生物利用度低等缺点。将亚麻籽油和辅酶Q10(coenzyme Q10,CoQ10)同时负载于乳液中,可解决两者的应用瓶颈。使用阿拉伯胶为乳化剂,采用高压均质法制备复配亚麻籽油和CoQ10乳液。采用动态光散射、透射电子显微镜、体外模拟消化、体外释放、稀释稳定性、冻融稳定性、离子强度稳定性、光稳定性和加速氧化稳定性方法对所制备乳液的理化性质进行表征。结果显示,制备的乳液平均粒径为(284±5.6) nm,多分散指数(polydispersity index,PDI)为0.112±0.025,为均匀分散的球形液滴。制备的乳液在模拟小肠液中消化,和亚麻籽油、CoQ10混悬液相比,乳化后亚麻籽油的消化速率和CoQ10的生物可给率明显提高。乳液中CoQ10的释放表现出缓释效果。制备的乳液具有较好的稀释和冻融稳定性。Na^+和Ca^2+会造成乳液Zeta电位的下降,对乳液稳定性影响较大。乳液载体化后CoQ10的光稳定性得到了提高。CoQ10对亚麻籽油具有较好的保护作用。  相似文献   

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