Showing papers by "S. A. Tomás published in 1999"

Estudio de la Influencia del Ca(OH)2 en las Películas de Pericarpio de Maíz Nixtamalizado mediante Técnicas Fototérmicas

Abstract: We present a study of the influence of the Ca(OH) 2 on the thermal and optical properties on pericarp films obtained from nixtamalized corn grains using photothermal techniques. Besides this, we studied the calcium integration and the morphological changes in these biopolymers by using x-ray diffraction analysis and optical microscopy. The nixtamalization process was performed using alkaline solutions with different Ca(OH) 2 concentrations. We obtained that the thermal diffusivity of the pericarp films has a remarkable increase with the Ca(OH) 2 concentration used in the nixtamalization process, which can be explain with our results of a calcium penetration and integration in form of CaCO 3 microcrystals in these biopolymers and mainly the degradation in its layers by the alkali medium action of hemicellulose dissolution, especially the most external layers: cuticle and epidermis. The analysis of optical absorption spectra show the presence of o-glycosides pigments type flavonoids in the pericarp which are sensitive to alkali medium and they are characterized by a remarkable absorption band between 400 and 450 nm which give the characteristic yellow pigmentation in these biopolymers.

Caracterización Óptica de Centros Absorbentes en Películas Biopoliméricas Obtenidas de Pericarpio de Maíz

Abstract: We present a study about the optical caracterization of the absorption centers in corn pericarp biopolymers by means of the Photoacoustic Spectroscopy and Phase Resolved technique. Our results show that the 300-800 nm region of the absorption spectra of these films are constituted by two absorption centers superposition, one of these corresponding to the cellulose of the epidermis (300-350 nm UV region) and the other by pigments present in the hemicellulose of the pericarp (375-450 nm). We demonstrated that these kind of pigments correspond to o-glycosides flavonoids type, which are bound to hemicellulose sugars. We observed a spatial separation of the two absorption centers as a function of the Ca(OH) 2 concentration used in the nixtamalization process and this separation is due to the hemicellulose dissolution in the most external leyers of these biopolymers.

Study of the lime influence on the thermal and optical properties of pericarp films of nixtamalized corn by means of the photoacoustic techniques

Abstract: We present a study of the influence of Ca(OH)2 in the thermal and optical properties on pericarp films obtained from nixtamalized corn grains. The nixtamalization process was performed using alkaline solutions with different Ca(OH)2 concentrations. For this study we have used Photoacoustic techniques and complementary analysis of optical microscopy and x-ray diffraction.