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Hermosillo, Mexico

Goycoolea F.M.,Complutense University of Madrid | Goycoolea F.M.,Laboratory of Biopolymers | Goycoolea F.M.,University of Munster | Fernandez-Valle M.E.,Complutense University of Madrid | And 4 more authors.
Macromolecular Chemistry and Physics | Year: 2011

MRI and swelling experiments are used to probe the state of water and infer the microstructure of chitosan hydrogels. SEM reveals a porous open scaffold-type structure for hydrogels that were equilibrated at 2°C before freezing as compared to those equilibrated at 37°C. ADC MRI measurements reveal an anisotropy in the microstructure of these gels. T1 relaxation MRI values were larger as the pH increased from 7.6 to 12.0, the result of a lower rate of exchange between protons of the hydration sphere of the polymer and bulk water. The thermosensitive and pH-sensitive properties of these hydrogels can be utilized in the development of innovative materials for biotechnological and biomedical applications, including criobiocatalysis and bioremediation as well as in programmed drug delivery. Hydrogels obtained from alkali chitin, once neutralized, exhibit negative thermosensitivity in the vicinity of pH=7.6. MRI evidence reveals that these materials also show an anisotropic behavior as the diffusion of water protons along the axial direction (probed by the apparent diffusion coefficient, ADC MRI axial) is greater than that along the radial one (ADC MRI radial). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Martinez-Lopez A.L.,Laboratory of Biopolymers | Carvajal-Millan E.,Laboratory of Biopolymers | Rascon-Chu A.,Research Center for Food and Development | Marquez-Escalantea J.,Laboratory of Biopolymers | Martinez-Robinsona K.,Laboratory of Biopolymers
CYTA - Journal of Food | Year: 2013

The molecular identity, molecular weight distribution, and microstructure of arabinoxylans from nixtamalized (N-MBAX) or nonnixtamalized (MBAX) maize bran were investigated and correlated to their gelling capability and the gels' structural and rheological properties. N-MBAX and MBAX presented Fourier transform infra-red (FT-IR) spectra typical of arabinoxylans. A low-molecular-weight fraction of arabinoxylans was present in MBAX but not in N-MBAX. Scanning electron microscopy (SEM) analysis showed that N-MBAX and MBAX present a rough and smooth surface topography, respectively. N-MBAX and MBAX gels were prepared by laccase oxidative cross-linking. N-MBAX and MBAX gels at 6% (w/v) presented an average pore size of 108 and 134 nm and elasticity values of 328 and 62 Pa, respectively. In SEM images, N-MBAX gels appear as a mix of sheets and rigid plates, while MBAX gels present an irregular honeycomb structure. These results indicate that nixtamalization process modify the molecular weight distribution and microstructure of maize bran arabinoxylans as well as the gels structural and rheological properties. © 2013 Taylor & Francis. Source

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