Simón Bolívar University

About: Simón Bolívar University is a education organization based out in Caracas, Venezuela. It is known for research contribution in the topics: Population & Crystallization. The organization has 5912 authors who have published 8294 publications receiving 126152 citations.

Identification of gas-producing components in different varieties of Phaseolus vulgaris by in vitro fermentation

Abstract: Phaseolus vulgaris consumption has been limited as part of the occidental diet owing to flatulence production. Raffinose, stachyose and verbascose have been shown to be the main components responsible for flatulence; however, it is thought that soluble fibre could also be involved in this phenomenon. The aim of the present study was to identify the main components of beans influencing flatus. Ten varieties of P vulgaris originating from South America were first analysed for their main nutrient and carbohydrate fractions. Three of the varieties were then fractionated to extract soluble and insoluble fibres. Various combinations of α-galactosides and soluble and insoluble fibre fractions, in similar proportions to those contained in cooked grains, were used as substrates for in vitro fermentation studies using human faecal inoculum to determine the fermentative capacity of each of the three fractions. Considering the white varieties, total gas production and acidification of the medium were correlated with fermented organic matter from soluble fibre (R2 = 1)) and with α-galactosides (R2 = 0.75). On the other hand, tannins present in pigmented varieties did not seem to interfere significantly in fermentation of soluble fibre. The total production of gas per gram of mixed fractions of soluble fibre and α-galactosides in proportions found in cooked grains was lower than that expected from each substrate separately. It can be concluded that soluble fibre and α-galactosides are good substrates for endogenous colonic flora subjected to in vitro fermentation studies and are thus responsible for flatulence induced by legume consumption. © 2001 Society of Chemical Industry

Application of the SSA calorimetric technique to characterize LLDPE grafted with diethyl maleate

Abstract: A linear low density polyethylene (LLDPE) was functionalized with diethyl maleate (DEM) using different amounts of a peroxide as initiator. The modified polymers were characterised by means of FTIR and 1 H NMR spectroscopy and the percentage of grafted DEM was determined. When the initiator concentration is increased from 0.44 to 0.88 g per 100 g of polymer, the degree of functionalization also increases from 0.47 to 0.8 mol-% of grafted DEM per ethylene unit. The results gathered here indicate that in this case, the grafting reaction preferentially occurs on the secondary carbons of LLDPE. Such a result was inferred by the use of the DSC based successive self-nucleation and annealing technique (SSA). The ability of SSA to induce molecular segregation during crystallisation and annealing proved to be very useful to characterise the functionalized polyolefins prepared here. When the amount of initiator was further increased to 1.76 wt.-%, the degree of functionalization only increased marginally to 0.84 mol-%. Combined results by SSA, capillary rheometry and FTIR indicated that secondary reactions occur when only part of the initiator is used in the grafting reactions. Such secondary reactions most probably produce long chain branching in the grafted polymer as indicated by the alterations in the melt flow behaviour of this sample and the modifications of its FTIR spectrum.

Dietary nitrogen as a limiting nutrient in frugivorous birds

Abstract: La pulpa de las frutas es considerada un alimento inadecuado para las aves frugivoras debido a su bajo contenido de proteina. Por lo tanto, se espera que los frugivoros minimicen sus perdidas de nitrogeno como una adaptacion a la frugivoria. En esta revision examinamos las propiedades de las frutas y los rasgos fisiologicos de los frugivoros que afectan su capacidad para subsistir en base a una dieta de frutas. La mayoria de las frutas tropicales y templadas parecen contener suficiente nitrogeno para satisfacer los requerimientos de los pajaros, si su ingesta de alimento estuviera ajustada para compensar el gasto energetico. Los requerimientos, sin embargo, dependen del tamano corporal. Las aves mas grandes deberian requerir alimentos con una relacion de nitrogeno a energia mas elevada que las aves pequenas. No obstante, el nitrogeno digerible puede de hecho ser limitante ya que las pulpas de las frutas parecen contener cantidades considerables de nitrogeno no-proteico y una composicion de aminoacidos diferente a la requerida por las aves. Ambas caracteristicas de las frutas conducen a un aumento de las perdidas de nitrogeno en aves frugivoras al consumir dietas naturales. En terminos de sus adaptaciones fisiologicas, esperariamos que los frugivoros posean una elevada capacidad de extraccion de nitrogeno de la dieta y esbozamos la posibilidad de que las bajas perdidas urinarias de nitrogeno de los frugivoros pudieran estar relacionadas con una baja tasa metabolica. La minimizacion de las perdidas endogenas fecales podria ser la adaptacion mas importante de los frugivoros para subsistir con base en dietas pobres en nitrogeno. No es evidente como los frugivoros especializados pueden tener requerimientos de nitrogeno mas bajos que los esperados en comparacion a aves de otros grupos dietarios. Finalmente, sugerimos varios topicos de investigacion que conducirian a mejorar nuestra comprension de las complejas interacciones involucradas en la regulacion de las necesidades proteicas de las aves frugivoras