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Isolated tomato fruit cuticles were subjected to low dose (80 Gy) γ-irradiation, as a potential methodology to prevent harvested fruit and vegetables spoilage. Both irradiated and non-irradiated samples have been morphologically and chemically characterized by scanning electron (SEM), atomic force (AFM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) spectroscopies. Additionally, electrochemical measurements comprising membrane potential and diffusive permeability were carried out to detect modifications in transport properties of the cuticle as the fruit primary protective membrane. It has been found that low dose γ-irradiation causes some textural changes on the surface but no significant chemical modification. Texture modification is found to be due to a partial removal of outermost (epicuticular) waxes which is accompanied by mild changes of electrochemical parameters such as the membrane fixed charge, cation transport number and salt permeability. The modification of such parameters indicates a slight reduction of the barrier properties of the cuticle upon low dose γ-irradiation. © 2012 Elsevier Ireland Ltd.

This study involves the preparation and optimization of polymer inclusion membranes (PIMs) based on the polymer cellulose triacetate and the extractant (carrier) Aliquat 336 (a mixture of quaternary ammonium chlorides) for the transport of inorganic As species (arsenite and arsenate) from their aqueous solutions. The influence of the composition of the membranes on its extraction and transport properties was investigated. Better membrane performance was obtained when the membranes did not contain plasticizer and the concentration of the extractant was high. Under these conditions arsenate (As(V)) could be quantitatively separated from As(III) within 5 h even in the presence of common anions (i.e. chloride, phosphate, nitrate, sulfate and carbonate) often encountered in natural waters and industrial and domestic wastewaters.Electrical impedance spectroscopy measurements allowed the determination of the dielectric constant and conductivity values of the PIMs of interest. These results suggested that the extracted As(V) species was HAsO4 2- which was further transported across the membrane by a hopping mechanism, counter currently to the transport of the chloride anions present at a high concentration in the stripping solution.The overall performance of the proposed PIM in terms of stability, selectivity and permeability compared favorably to those of an Aliquat 336 based supported liquid membrane and a commercial multi-valent anion exchange membrane This work was supported by the Spanish Ministerio de Ciencia e Inovación, through Project (CTM2008-06847-C02 02/TECNO). R. Güell gratefully acknowledges a grant awarded by the University of Girona (Ref. BR06/10)

La adsorción de macromoléculas cargadas sobre la superficie de una membrana en procesos de microfiltración produce la colmatación (o ensuciamiento) de la membrana y, por tanto, una disminución del flujo a través de la membrana. La colmatación puede ser facilmente detectada por la variación de: i) parámetros electroquímicos como la resistencia eléctrica y la permeabilidad salina, directamente relacionados con la porosidad de las membranas; ii) las concentraciones atómicas de los elementos característicos de la superficie de la membrana, determinadas mediante espectroscopía de fotoelectrones de rayos X (XPS). Para membranas comerciales de alúmina (Anopore™, 0.1 µm de tamaño de poro) en contacto con disoluciones que contienen 0.5 g/l de seroalbúmina de bobino (BSA), los parámetros eléctroquímicos indican una disminución en la porosidad de la membrana del 50%, aproximadamente, despues de estar 72 h en contacto con una disolución con proteína. Los resultados de XPS indican: i) que la capa de proteína adsorbida sobre la superficie de la membrana no aumenta linealmente con el tiempo de interacción membrana-proteína, sino que se produce fundamentalmente durante las primeras 24 h.; ii) la no uniformidad de la capa de proteína adsorbida sobre la membrana de alúmina.