Evaluación bioquímica de fracciones proteínicas de piñón Mexicano (Jatropha curcas L.)

J. curcas seed proteins were fractioned according to the Osborne method and some biochemical properties were determined for these fractions. Glutelins (378 g kg–1 protein) and globulins (201 g kg–1 protein) were the main components. Albumins and prolamins were the minor components. Protein digestibility was highest in glutelins and globulins with values of 81 and 80% respectively. Electrophoresis analysis showed that globulins and glutelins exhibited similar polypeptide profiles. Electrophoresis patterns suggested that there could be a structural relationship among 2S, 7S and 11S storage proteins from plant sources. According to the FAO⁄WHO reference, the protein fractions had acceptable levels of most of the essential amino acids, but its globulins and glutelins were low in lysine and tryptophan.Las proteínas de semillas de J. curcas L. se fraccionaron empleando el método de Osborne y posteriormente se determinaron algunas de sus propiedades bioquímicas y nutricionales. Las fracciones mayoritarias resultaron ser glutelinas (378 g kg–1 de proteína) y globulinas (201 g kg–1 de proteína) mientras que las albúminas y prolaminas fueron las fracciones minoritarias. La digestibilidad de la proteína resultó ser más alta en las glutelinas y globulinas, con valores de 81 y 80% respectivamente. El análisis por electroforesis mostró que las globulinas y glutelinas presentaron perfiles similares, los resultados sugieren que podría existir una relación con proteínas de almacenamiento 2S, 7S y 11S de origen vegetal. Asimismo, de acuerdo con la FAO/WHO, las fracciones proteínicas tuvieron niveles aceptables para la mayoría de los aminoácidos esenciales, sin embargo, las globulinas y glutelinas fueron deficientes en Lys y Trp

Biochemical evaluation of protein fractions from physic nut (<i>Jatropha curcas</i> L.)

<i>J. curcas</i> seed proteins were fractioned according to the Osborne method and some biochemical properties were determined for these fractions. Glutelins (378 g kg–1 protein) and globulins (201 g kg^–1 protein) were the main components. Albumins and prolamins were the minor components. Protein digestibility was highest in glutelins and globulins with values of 81 and 80% respectively. Electrophoresis analysis showed that globulins and glutelins exhibited similar polypeptide profiles. Electrophoresis patterns suggested that there could be a structural relationship among ₂S, ₇S and ₁₁S storage proteins from plant sources. According to the FAO⁄WHO reference, the protein fractions had acceptable levels of most of the essential amino acids, but its globulins and glutelins were low in lysine and tryptophan.<br><br>Las proteínas de semillas de <i>J. curcas</i> L. se fraccionaron empleando el método de Osborne y posteriormente se determinaron algunas de sus propiedades bioquímicas y nutricionales. Las fracciones mayoritarias resultaron ser glutelinas (378 g kg^–1 de proteína) y globulinas (201 g kg^–1 de proteína) mientras que las albúminas y prolaminas fueron las fracciones minoritarias. La digestibilidad de la proteína resultó ser más alta en las glutelinas y globulinas, con valores de 81 y 80% respectivamente. El análisis por electroforesis mostró que las globulinas y glutelinas presentaron perfiles similares, los resultados sugieren que podría existir una relación con proteínas de almacenamiento 2S, 7S y 11S de origen vegetal. Asimismo, de acuerdo con la FAO/WHO, las fracciones proteínicas tuvieron niveles aceptables para la mayoría de los aminoácidos esenciales, sin embargo, las globulinas y glutelinas fueron deficientes en Lys y Trp

Nitrogen-carbon graphite-like semiconductor synthesized from uric acid

A new carbon-nitrogen organic semiconductor has been synthesized by pyrolysis of uric acid. This layered carbon-nitrogen material contains imidazole-, pyridine (naphthyridine)- and graphitic-like nitrogen, as evinced by infrared and X-ray photoelectron spectroscopies. Quantum chemistry calculations support that it would consist of a 2D polymeric material held together by hydrogen bonds. Layers are stacked with an interplanar distance between 3.30 and 3.36 Å, as in graphite and coke. Terahertz spectroscopy shows a behavior similar to that of amorphous carbons, such as coke, with non-interacting layers. This material features substantial differences from polymeric carbon nitride, with some characteristics closer to those of nitrogen-doped graphene, in spite of its higher nitrogen content. The direct optical band gap, dependent on the polycondensation temperature, ranges from 2.10 to 2.32 eV. Although in general the degree of crystallinity is low, in the material synthesized at 600 °C some spots with a certain degree of crystallinity can be found

Phase transitions of cassava starch dispersions prepared with glycerol solutions

The aim of this work was to study the glass transition, the glass transition of the maximally freeze-concentrated fractions, the ice melting and the gelatinization phenomenon in dispersions of starch prepared using glycerol- water solutions. The starch concentration was maintained constant at 50 g cassava starch/100 g starch dispersions, but the concentration of the glycerol solutions was variable (C-g= 20, 40, 60, 80 and 100 mass/mass%). The phase transitions of these dispersions were studied by calorimetric methods, using a conventional differential scanning calorimeter (DSC) and a more sensitive equipment (micro-DSC). Apparently, in the glycerol diluted solutions (20 and 40%), the glycerol molecules interacted strongly with the glucose molecules of starch. While in the more concentrated glycerol domains (C-g> 40%), the behaviour was controlled by migration of water molecules from the starch granules, due to a hypertonic character of glycerol, which affected all phase transitions.FAPESP[04/08771-7]FAPESP[05/57781-8]PVAB[05/54688-7]JSF[05/54952-6]CNPqPJA

Properties of Edible Films Based on Oxidized Starch and Zein

The objective of this work was to investigate the effect of zein and film formulation on mechanical and structural properties of native (FNS), and oxidized with 2.5% (FOSA) and 3.5% (FOSB) banana starch. The oxidized starch showed differences from native starch due to the oxidation process, showing a decrease in lipids, proteins, and amylose. The increase of the sodium hypochlorite increased the content of carbonyl and carboxyl groups in the ranges 0.015–0.028% and 0.022–0.031%, respectively. The film obtained from FOSB displayed the highest tensile strength (5.05 MPa) and satisfactory elongation value (27.1%). The zein addition caused a decrease in these mechanical properties, as well as a significant decrease in water vapour permeability (WVP). However, films from FOSA and FOSB showed higher permeability than that of the native starch. The addition of glycerol and the level of oxidation increased the films moisture. Micrographs showed that, during the oxidation process, impurities were largely eliminated from the starch granule, noting more homogeneous structures both in granules and films

Film forming solutions based on gelatin and poly(vinyl alcohol) blends: Thermal and rheological characterizations

The objective of this work was to study the theological and thermal properties of film forming solutions (FFS) based on blends of gelatin and poly(vinyl alcohol) (PVA). The effect of the PVA concentration and plasticizer presence on the flow behavior, and viscoelastic and thermal properties of FFS was studied by steady-shear flow and oscillatory experiments, and also, by microcalorimetry. The FB presented Newtonian behavior at 30 degrees C, and the viscosity was not affected neither by the PVA concentration nor by the plasticizer. All FFS presented a phase transition during tests applying temperature scanning. It was verified that the PVA affected the viscoelastic properties of FFS by dilution of gelatin. This behavior was confirmed by microcalorimetric analysis. The behaviors of the storage (G`) and loss (G ``) moduli as a function of frequency of FFS obtained at 5 degrees C were typical of physical gels; with the G` higher than the G ``. The strength of the gels was affected by the PVA concentration. (C) 2009 Elsevier Ltd. All rights reserved.FAPESP[05/57781-8]PV[05/54952-6]CNPqInstituto Politecnico Nacional in Mexic

Tuning the oxygen reduction activity and stability of Ni(OH)2@Pt/C catalysts through controlling Pt surface composition, strain, and electronic structure.

Nanoparticles of Ni(OH)2 surrounded with ultra-low Pt content and supported on functionalized carbon were prepared by a scalable synthesis method and investigated as electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. The effect of altering the Pt surface composition on the Ni(OH)2 nanoparticle core was investigated as a route to simultaneously increase the ORR activity and stability. Modifying the Pt surface composition resulted in both structural and electronic changes. Decreasing the Pt surface composition resulted in stronger Pt-Pt compressive strain and decrease in the occupancy of d-band vacancies per atom. The correlation of strain and d-vacancies with ORR activity and stability showed a Volcano-type tendency, with the 6 wt. % Pt sample showing the highest activity and stability. The electrochemical results obtained using rotating disk electrode (RDE) tests showed an enhancement of about six times higher surface and mass-normalized activity as well as improved durability compared to commercial Pt/C. These improvements were further corroborated by single cell membrane electrode assembly (MEA) tests where similar trends were observed, showing higher power densities with lower Pt loadings, in comparison with commercial Pt/C. These results show that new electrocatalysts with higher activity and stability can be obtained through precise control of the atomic-level catalyst structure

Effect of moisture content and temperature, on the rheological, microstructural and thermal properties of MASA (dough) from a hybrid corn (Zea Mays sp.) variety [Efecto del contenido de humedad y de la temperatura, en las propiedades reol�gicas, microestructurales y t�rmicas de masa de una variedad de maiz (zea mays sp.) h�brido]

The effect of the moisture content (55, 60 and 65% (w/w)) and temperature (30, 40 and 50 �C) on the X-ray diffraction (XDR), microstructural, pasting, thermal and rheological properties of nixtamalized dough (masa) from a corn hybrid variety (Zea mays sp.) is reported here. A complete set of rheological tests including temperature and frequency sweeps, steady shear and transient shear flow was performed in order to get detailed information on the food processing issues. The nixtamalization process affected significantly (P &lt; 0.05) the microstructural and thermal properties of masa. Polarized Light microscopy and X-ray diffraction (XDR) showed that crystallinity in starch granules decreased for the masa; whereas, Scanning Electron Microscopy (SEM), showed swollen granules dispersed into a plasticized surface. Moreover, Differential Scanning Calorimetry (DSC) showed significant (P &lt; 0.05) differences on the gelatinization enthalpy (?Hgel) of masa, where it increased with increasing the moisture content from 6.7 � 0.84 J/g for 55% (w/w) to 10.2 � 0.4 J/g for 60% (w/w). Frequency sweeps showed a predominant elastic behavior where the storage modulus (G?) was higher than the loss modulus (G?) and they were significantly (P &lt; 0.05) affected by the moisture content and temperature into a small range. The steady shear data exhibited a shear-thinning flow behavior and followed a power law equation, where the power law index (n) decreased when the temperature and the moisture content increased. The effect of temperature on the shear-viscosity (?) was well described by the Arrhenius equation, exhibiting energy activation energy (Ea) values in the range from 25.52 to 59.35 KJ/mol. For transient shear test, all masas presented a stress overshoot at high shear rate before reaching a steady state. It was found that the amplitude of this overshoot depends on the shear rate. On the other hand, the stress relaxation test, which gives the main relaxation time (?), showed fast relaxation decay at short times, whereas at long times, a slow relaxation was observed. The ? values ranged from 10.46 to 0.43 s, which decreased with increasing shear rate. The rheological behavior of masa was related to a weak gel-like structure formation, composed by dispersed swollen starch granules into a cross-linked starch network, similar to a biocomposite material

Effect of moisture content and temperature, on the rheological, microstructural and thermal properties of MASA (dough) from a hybrid corn (Zea Mays sp.) variety [Efecto del contenido de humedad y de la temperatura, en las propiedades reológicas, microestructurales y térmicas de masa de una variedad de maiz (zea mays sp.) híbrido]

The effect of the moisture content (55, 60 and 65% (w/w)) and temperature (30, 40 and 50 °C) on the X-ray diffraction (XDR), microstructural, pasting, thermal and rheological properties of nixtamalized dough (masa) from a corn hybrid variety (Zea mays sp.) is reported here. A complete set of rheological tests including temperature and frequency sweeps, steady shear and transient shear flow was performed in order to get detailed information on the food processing issues. The nixtamalization process affected significantly (P &lt; 0.05) the microstructural and thermal properties of masa. Polarized Light microscopy and X-ray diffraction (XDR) showed that crystallinity in starch granules decreased for the masa; whereas, Scanning Electron Microscopy (SEM), showed swollen granules dispersed into a plasticized surface. Moreover, Differential Scanning Calorimetry (DSC) showed significant (P &lt; 0.05) differences on the gelatinization enthalpy (ΔHgel) of masa, where it increased with increasing the moisture content from 6.7 ± 0.84 J/g for 55% (w/w) to 10.2 ± 0.4 J/g for 60% (w/w). Frequency sweeps showed a predominant elastic behavior where the storage modulus (G′) was higher than the loss modulus (G″) and they were significantly (P &lt; 0.05) affected by the moisture content and temperature into a small range. The steady shear data exhibited a shear-thinning flow behavior and followed a power law equation, where the power law index (n) decreased when the temperature and the moisture content increased. The effect of temperature on the shear-viscosity (η) was well described by the Arrhenius equation, exhibiting energy activation energy (Ea) values in the range from 25.52 to 59.35 KJ/mol. For transient shear test, all masas presented a stress overshoot at high shear rate before reaching a steady state. It was found that the amplitude of this overshoot depends on the shear rate. On the other hand, the stress relaxation test, which gives the main relaxation time (τ), showed fast relaxation decay at short times, whereas at long times, a slow relaxation was observed. The τ values ranged from 10.46 to 0.43 s, which decreased with increasing shear rate. The rheological behavior of masa was related to a weak gel-like structure formation, composed by dispersed swollen starch granules into a cross-linked starch network, similar to a biocomposite material