Browsing by Author "Valenzuela, Loreto M."

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    Design of an antioxidant powder additive based on carvacrol encapsulated into a multilayer chitosan-alginate-maltodextrin emulsion
    (2024) Cardero, Yaniel; Aguirre-Calvo, Tatiana Rocio; Valenzuela, Loreto M.; Matiacevich, Silvia; Santagapita, Patricia Roman
    Carvacrol has demonstrated antioxidant activity; however, its high volatility and low water solubility limit its direct application in food matrices. Then, an effective encapsulation system is required to protect it. This study aimed to design and characterize a carvacrol-based additive encapsulated in a spray-dried multilayer emulsion based on chitosan/sodium alginate/maltodextrin. Spray-drying temperature of 120 degrees C and 3 %(w/w) maltodextrin content maximized both encapsulation efficiency (similar to 97 %) and loading capacity (similar to 53 %). The powder's antioxidant properties were evaluated in two food simulant media: water (SiW) and water-ethanol (SiD). The highest antioxidant activity was observed in SiW for both ABTS(center dot+) (8.2 +/- 0.3mg(EAG)/g) and FRAP (4.1 +/- 0.2mg(EAG)/g) methods because of the reduced release of carvacrol in SiD vs. SiW, as supported by micro- and macrostructural observations by SAXS and microscopy, respectively. An increase from 143 to 157 degrees C attributable to carvacrol protection and T-g = 44.4 degrees C (> ambient) were obtained by TGA and DSC, respectively. FT-IR confirmed intermolecular interactions (e.g. -COO- and -NH3+) as well as H-bonding formation. High water solubility (81 +/- 3 %), low hygroscopicity (8.8 +/- 0.2 %(w/w), poor flowability (CI:45 +/- 4), and high cohesiveness (HR:1.8 +/- 0.1) between particles were achieved, leading to a powdered antioxidant additive with high potential for applications which required avoiding/reducing oxidation on hydrophilic and hydrophobic food products.
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    Eco-Friendly Design of Chitosan-Based Films with Biodegradable Properties as an Alternative to Low-Density Polyethylene Packaging
    (2024) Fiallos-Nunez, Johanna; Cardero, Yaniel; Cabrera-Barjas, Gustavo; Garcia-Herrera, Claudio M.; Inostroza, Matias; Estevez, Miriam; Espana-Sanchez, Beatriz Liliana; Valenzuela, Loreto M.
    Biopolymer-based films are a promising alternative for the food packaging industry, in which petrochemical-based polymers like low-density polyethylene (LDPE) are commanding attention because of their high pollution levels. In this research, a biopolymer-based film made of chitosan (CS), gelatin (GEL), and glycerol (GLY) was designed. A Response Surface Methodology (RSM) analysis was performed to determine the chitosan, gelatin, and glycerol content that improved the mechanical properties selected as response variables (thickness, tensile strength (TS), and elongation at break (EAB). The content of CS (1.1% w/v), GEL (1.1% w/v), and GLY (0.4% w/v) in the film-forming solution guarantees an optimized film (OPT-F) with a 0.046 +/- 0.003 mm thickness, 11.48 +/- 1.42 mPa TS, and 2.6 +/- 0.3% EAB. The OPT-F was characterized in terms of thermal, optical, and biodegradability properties compared to LDPE films. Thermogravimetric analysis (TGA) revealed that the OPT-F was thermally stable at temperatures below 300 degrees C, which is relevant to thermal processes in the food industry of packaging. The reduced water solubility (WS) (24.34 +/- 2.47%) and the improved biodegradability properties (7.1%) compared with LDPE suggests that the biopolymer-based film obtained has potential applications in the food industry as a novel packaging material and can serve as a basis for the design of bioactive packaging.
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    Improving myoblast differentiation on electrospun poly(ε-caprolactone) scaffolds
    (2017) Abarzua-Illanes, Phammela N.; Padilla, Cristina; Ramos, Andrea; Isaacs, Mauricio; Ramos Grez, Jorge; Olguin, Hugo C.; Valenzuela, Loreto M.
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    Multiscale analysis of water uptake and erosion in biodegradable polyarylates
    (ELSEVIER SCI LTD, 2012) Valenzuela, Loreto M.; Zhang, Guojin; Flach, Carol R.; Murthy, N. Sanjeeva; Mendelsohn, Richard; Michniak Kohn, Bozena; Kohn, Joachim
    The role of hydration in degradation and erosion of materials, especially biomaterials used in scaffolds and implants, was investigated by studying the distribution of water at length scales from 0.1 nm to 0.1 mm using Raman spectroscopy, small-angle neutron scattering (SANS). Raman confocal imaging, and scanning electron microscopy (SEM). The measurements were demonstrated using L-tyrosine derived polyarylates. Bound- and free- water were characterized using their respective signatures in the Raman spectra. In the presence of deuterium oxide (D2O), H-D exchange occurred at the amide carbonyl but was not detected at the ester carbonyl. Water appeared to be present in the polymer even in regions where there was little evidence for NH to ND exchange. SANS showed that water is not uniformly dispersed in the polymer matrix. The distribution of water can be described as mass fractals in polymers with low water content (similar to 5 wt%), and surface fractals in polymers with larger water content (15-60 wt%). These fluctuations in the density of water distribution are presumed to be the precursors of the similar to 20 mu m water pockets seen by Raman confocal imaging, and also give rise to the 10-50 mu m porous network seen in SEM. The surfaces of these polymers appeared to resist erosion while the core of the films continued to erode to form a porous structure. This could be due to differences in either the density of the polymer or the solvent environment in the bulk vs. the surface, or a combination of these two factors. There was no correlation between the rate of degradation and the amount of water uptake in these polymers, and this suggests that it is the bound water and not the total amount of water that contributes to hydrolytic degradation. (c) 2011 Elsevier Ltd. All rights reserved.
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    Variability of Water Uptake Studies of Biomedical Polymers
    (WILEY-BLACKWELL, 2011) Valenzuela, Loreto M.; Michniak, Bozena; Kohn, Joachim
    Water uptake influences many properties of polymers and has been widely studied. In the context of polymeric biomaterials, several publications reported an unusual high variability of analytical results, without further investigating the cause for this phenomenon. Using selected polymers from the library of L-tyrosine-derived polyarylates and poly(D,L lactic acid), we showed that nonaged and nonannealed compression molded film samples exhibit the typical large variation in water uptake observed in previous reports. The introduction of an annealing step allows accurate and reproducible water uptake measurements for these polymers. We evaluated the use of 3 H-radiolabeled water for the determination of water uptake, finding that the use of radiolabeled water yields statistically indistinguishable measurements, compared to gravimetric methods, while providing significant advantages in throughput and sensitivity. Using the recommended methods of annealing and (3)H-radiolabled water, the water uptake profiles of 24 polymers of the library of L-tyrosine-derived polyarylates are reported. This article addresses experimental concerns related to water uptake studies and may assist other researchers in improving the accuracy of their water uptake results. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1311-1320, 2011