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Öğe Ability of Sodium Dodecyl Sulfate (SDS) Micelles to Increase the Antioxidant Activity of ?-Tocopherol(Amer Chemical Soc, 2021) Inchingolo, Raffaella; Bayram, Ipek; Uluata, Sibel; Kiralan, S. Sezer; Rodriguez-Estrada, Maria T.; McClements, D. Julian; Decker, Eric A.As emulsifiers become saturated on the surface of an emulsion droplet, any additional emulsifier migrates to the aqueous phase. Continuous phase surfactants have been shown to increase alpha-tocopherol efficacy, but it is unclear if this is the result of chemical or physical effects. The addition of alpha-tocopherol to an oil-in-water emulsion after homogenization resulted in a 70% increase of alpha-tocopherol in the continuous phase when sodium dodecyl sulfate (SDS) was at levels that were greater than the SDS critical micelle concentration. Conversely, when alpha-tocopherol was dissolved in the lipid before emulsification, continuous phase SDS concentrations did not increase. When SDS concentration led to an increase in the aqueous phase alpha-tocopherol, the oxidative stability of oil-in-water emulsions increased. Data indicated that the increased antioxidant activity was the result of surfactant micelles being able to decrease the prooxidant activity of alpha-tocopherol. Considering these results, surfactant micelles could be an important tool to increase the effectiveness of alpha-tocopherol.Öğe Comparing DPPP fluorescence and UV based methods to assess oxidation degree of krill oil-in-water emulsions(Elsevier Sci Ltd, 2021) Uluata, Sibel; Durmaz, Gokhan; McClements, D. Julian; Decker, Eric A.In this study, lipid oxidation evaluation methods were compared for a krill-oil-in-water emulsion system. With this aim, thiocyanate and DPPP (diphenyl-1-pyrenylphosphine) fluorescence methods were comparatively examined to determine primary oxidation products. 2-thiobarbituric acid reactive substances (TBARS), hexanal and propanal formation were also monitored as secondary oxidations products. All oxidation experiments were performed via both auto-oxidation at 45 degrees C and light-riboflavin induced photooxidation at 37 degrees C. The results have shown that thiocyanate method was not suitable to measure lipid hydroperoxides by the both in auto- and photo-oxidation systems. On the other hand, fluorescence intensity of samples containing the DPPP probe increased during incubation period which indicates the formation of lipid hydroperoxides could be detected via this method. TBARS, hexanal and propanal concentrations also increased during storage period and the formation kinetics of secondary oxidation products was confirmed that the DPPP fluorescence method was accurate and reliable at different environmental conditions.Öğe How the Multiple Antioxidant Properties of Ascorbic Acid Affect Lipid Oxidation in Oil-in-Water Emulsions(Amer Chemical Soc, 2015) Uluata, Sibel; McClements, D. Julian; Decker, Eric A.Lipid oxidation is a serious problem for oil-containing food products because it negatively affects shelf life and nutritional composition. An antioxidant strategy commonly employed to prevent or delay oxidation in foods is to remove oxygen from the closed food-packaging system. An alternative technique is use of an edible oxygen scavenger to remove oxygen within the food. Ascorbic acid (AA) is a particularly promising antioxidant because of its natural label and multiple antioxidative functions. In this study, AA was tested as an oxygen scavenger in buffer and an oil-in-water (O/W) emulsion. The effects of transition metals on the ability of AA to scavenge oxygen were determined. Headspace oxygen decrease less than 1% in the medium-chain triacylglycerol (MCT) O/W emulsion system (pH 3 and 7). AA was able to almost completely remove dissolved oxygen (DO) in a buffered solution. Transition metals (Fe2+ and Cu+) significantly accelerated the degradation of AA; however, iron and copper only increased DO depletion rates, by 10.6-16.4% from day 1 to 7, compared to the control. AA (2.5-20 mM) decreased DO in a 1% O/W emulsion system 32.0-64.0% and delayed the formation of headspace hexanal in the emulsion from 7 to over 20 days. This research shows that, when AA is used in an O/W emulsion system, oxidation of the emulsion system can be delay by multiple mechanisms.Öğe Optimization of Nanoemulsion Fabrication Using Microfluidization: Role of Surfactant Concentration on Formation and Stability(Springer, 2016) Uluata, Sibel; Decker, Eric A.; McClements, D. JulianNanoemulsions have some important potential advantages over conventional emulsions for certain commercial applications due to their optical clarity, high physical stability, and ability to increase the bioavailability of lipophilic bioactives. In this study, the factors influencing droplet size and stability in nanoemulsions fabricated from a hydrocarbon oil and an anionic surfactant were examined. Octadecane oil-in-water nanoemulsions were produced by a high pressure homogenizer (microfluidizer) using sodium dodecyl sulfate (SDS) as a model anionic surfactant. The influence of homogenization pressure, number of passes, and surfactant concentration was examined. The droplet size decreased with increasing homogenization pressure, number of passes, and surfactant concentration. Nanoemulsions with low turbidity and small droplet diameters (approximate to 62 nm) could be produced under optimized conditions. Interestingly, nanoemulsions containing relatively high surfactant levels were highly susceptible to creaming when they were only passed through the homogenizer a few times, which was attributed to depletion flocculation. These results show the importance of optimizing surfactant levels to produce small droplets that are also stable to creaming.Öğe Physical Stability, Autoxidation, and Photosensitized Oxidation of ?-3 Oils in Nanoemulsions Prepared with Natural and Synthetic Surfactants(Amer Chemical Soc, 2015) Uluata, Sibel; McClements, D. Julian; Decker, Eric A.The food industry is interested in the utilization of nanoemulsions stabilized by natural emulsifiers, but little research has been conducted to determine the oxidative stability of such emulsions. In this study, two natural (lecithin and quillaja saponin) and two synthetic (Tween 80 and sodium dodecyl sulfate) surfactants were used to fabricate omega-3 nanoemulsion using high pressure homogenization (microfluidization). Initially, all the nanoemulsions contained small (d from 45 to 89 nm) and anionic (zeta-potential from -8 to -65 mV) lipid droplets (pH 7). The effect of pH, ionic strength, and temperature on the physical stability of the nanoemulsion system was examined. Nanoemulsion stabilized with Tween 80, quillaja saponin, or sodium dodecyl sulfate (SDS) exhibited no major changes in particle size or visible creaming in the pH range of 3 to 8. All nanoemulsions were relatively stable to salt addition (0 to 500 mM NaCl, pH 7.0). Nanoemulsions stabilized with SDS and quillaja saponin were stable to heating (30 to 90 degrees C). The impact of surfactant type on lipid oxidation was determined in the presence and absence of the singlet oxygen photosensitizers, riboflavin, and rose bengal. Riboflavin and rose bengal accelerated lipid oxidation when compare to samples without photosensitizers. Lipid hydroperoxide formation followed the order Tween 80 > SDS > lecithin > quillaja saponin, and propanal formation followed the order lecithin > Tween 80 > SDS > quillaja saponin at 37 degrees C for autoxidation. The same order of oxidative stability was observed in the presence of photosensitized oxidation promoted by riboflavin. Quillaja saponin consistently produced the most oxidatively stable emulsions, which could be due to its high free radical scavenging capacity.Öğe Riboflavin-induced oxidation in fish oil-in-water emulsions: Impact of particle size and optical transparency(Elsevier Sci Ltd, 2016) Uluata, Sibel; McClements, D. Julian; Decker, Eric A.The influence of particle size and optical properties on the stability of fish oil-in-water emulsions to riboflavin-induced oxidation by blending different combinations of small (d = 44 nm) and large (d = 216 nm) lipid droplets was examined. Emulsion turbidity increased with increasing mean droplet diameter due to greater light scattering by larger particles. The influence of droplet size on the stability of the emulsions to riboflavin-induced lipid oxidation during storage at 20 or 37 degrees C was measured. At 37 degrees C, the rate of lipid hydroperoxide formation increased with decreasing droplet diameter, but there were no significant differences in propanal concentrations. At 20 degrees C, both peroxide and propanal values indicated that the rate of oxidation increased with decreasing droplet size. These data show that riboflavin was more effective at promoting oxidation in nanoemulsions containing small droplets because light was able to penetrate more easily and generate reactive oxygen species. (C) 2016 Elsevier Ltd. All rights reserved.
