Browsing by Author "Troncoso, Elizabeth"

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    Fabrication, characterization and lipase digestibility of food-grade nanoemulsions
    (ELSEVIER SCI LTD, 2012) Troncoso, Elizabeth; Miguel Aguilera, Jose; McClements, David Julian
    The behavior of nanoemulsion-based delivery systems within the gastrointestinal tract determines their functional performance. In this study, the influence of particle radius (30-85 nm) on the in vitro digestion of nanoemulsions containing non-ionic surfactant stabilized lipid (corn oil) droplets was examined using simulated small intestine conditions. Nanoemulsions were prepared by a combination of high-pressure homogenization and solvent (hexane) displacement. Lipid droplets with different sizes were prepared by varying the oil-to-solvent ratio in the disperse phase prior to homogenization. The fraction of free fatty acids (FFA) released from emulsified triacylglycerols (TG) during digestion was measured by an in vitro model (pH-Stat titration). Nanoemulsions exhibited a lag-period before any FFA were released, which was explained by inhibition of lipase adsorption to the oil-water interface by free surfactant. After the lag-period, the digestion rate increased with decreasing oil droplet diameter (increasing specific surface area). The total amount of FFA released from the emulsions increased from 61% to 71% as the mean droplet radius decreased from 86 nm to 30 nm. The incomplete digestion of the emulsified lipids could be explained by inhibition of lipase activity by the release of fatty acids and/or by interactions between lipase and surfactants molecules. (C) 2011 Elsevier Ltd. All rights reserved.
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    Influence of particle size on the in vitro digestibility of protein-coated lipid nanoparticles
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2012) Troncoso, Elizabeth; Miguel Aguilera, Jose; McClements, David Julian
    The influence of particle size on the in vitro digestion of beta-lactoglobulin (BLG)-coated lipid nanoparticles was examined using simulated small intestine conditions. Nanoemulsions were prepared by high-pressure homogenization and organic solvent (hexane) evaporation. The effect of the initial organic phase composition on the size, microstructure, electrical properties, and digestion of the lipid nanoparticles was evaluated. The radius of the nanoparticles decreased (from 85 to 48 nm) as the solvent concentration in the initial organic phase increased (from 0% to 95%). The lipid digestion rate initially decreased with decreasing particle radius (for r = 85-59 nm), but then it increased (for r = 59-48 nm). This dependence is contrary to the usual assumption that lipid digestion increases with increasing lipid surface area. Our results suggest that the structure of the protein layer coating the lipid nanoparticles has an important effect on lipid digestion. (C) 2012 Elsevier Inc. All rights reserved.
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    Rheological and microstructural characterization of WPI-stabilized O/W emulsions exhibiting time-dependent flow behavior
    (ELSEVIER SCIENCE BV, 2012) Bellalta, Pablo; Troncoso, Elizabeth; Zuniga, Rommy N.; Aguilera, Jose M.
    The theological behavior of oil-in-water (O/W) emulsions stabilized by whey protein isolate (WPI) and its relationship with the microstructural changes caused by shearing was studied. O/W emulsions (50, 55, and 60 g oil/100 g) were made using ultrasound and their theological properties were determined by: flow curve test, constant shear rate test, and hysteresis loop test. Microstructural changes were evaluated in terms of droplet size and droplet size distribution. Emulsions containing 50 and 55 g oil/100 g showed a Newtonian behavior, whereas those with 60 g oil/100 g exhibited shear-thinning behavior. Under constant deformation, the apparent viscosity of the emulsions decreased with time. The hysteresis loop test revealed that increasing oil content increased the degree of thixotropy of the emulsions. Moreover, before and after the constant deformation test droplet size distributions did not show differences, indicating that the decrease in the apparent viscosity may be promoted by breakdown and further deformation and/or reorganization of oil droplets flocs. In turn, experimental data obtained from the constant shear rate test was fitted to a structural kinetic model. The rate constant values showed no particular trend with oil content and shear rate, implying that probably wall slip occurred at high shear rates and high oil contents. (C) 2011 Elsevier Ltd. All rights reserved.