Estimation of Digital Porosity of Electrospun Veils by Image Analysis.

The present work reports on an empirical mathematical expression for predicting the digital porosity (DP) of electrospun nanofiber veils, employing emulsions of poly(vinyl alcohol) (PVOH) and olive and orange oils. The electrospun nanofibers were analyzed by scanning electron microscopy (SEM), observing orientation and digital porosity (DP) in the electrospun veils. To determine the DP of the veils, the SEM micrographs were transformed into a binary system, and then the threshold was established, and the nanofiber solid surfaces were emphasized. The relationship between the experimental results and those obtained with the empirical mathematical expression displayed a correlation coefficient (R2) of 0.97 by employing threshold II. The mathematical expression took into account experimental variables such as the nanofiber humidity and emulsion conductivity prior to electrospinning, in addition to the corresponding operation conditions. The results produced with the proposed expression showed that the prediction of the DP of the electrospun veils was feasible with the considered thresholds.

Production of Cellulosic Microfibers from Coffee Pulp via Alkaline Treatment, Bleaching and Acid Hydrolysis.

The present work deals with the production of cellulosic microfibers (CMFs) from coffee pulp. The experimental development corresponds to an experimental design of three variables (concentration, temperature and time) of alkaline treatment for delignification, finding that concentration, temperature and time were the most representative variables. Higher delignification was achieved by bleaching cellulosic fibers, followed by acid hydrolysis, thus producing cellulosic fibers with an average diameter of 5.2 µm, which was confirmed using scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). An X-ray diffraction (XRD) analysis revealed, via the crystallinity index, the presence of Type I cellulose and removal of lignocellulosic compounds through chemical treatments. The proximate chemical analysis (PChA) of coffee pulp helped to identify 17% of the crude fiber corresponding to the plant cell wall consisting of lignocellulosic compounds. The initial cellulose content of 26.06% increased gradually to 48.74% with the alkaline treatment, to 57.5% with bleaching, and to 64.7% with acid hydrolysis. These results attested to the rich cellulosic content in the coffee pulp.

Artificial Neural Networks for Predicting the Diameter of Electrospun Nanofibers Synthesized from Solutions/Emulsions of Biopolymers and Oils.

In the present work, different configurations of nt iartificial neural networks (ANNs) were analyzed in order to predict the experimental diameter of nanofibers produced by means of the electrospinning process and employing polyvinyl alcohol (PVA), PVA/chitosan (CS) and PVA/aloe vera (Av) solutions. In addition, gelatin type A (GT)/alpha-tocopherol (α-TOC), PVA/olive oil (OO), PVA/orange essential oil (OEO), and PVA/anise oil (AO) emulsions were used. The experimental diameters of the nanofibers electrospun from the different tested systems were obtained using scanning electron microscopy (SEM) and ranged from 93.52 nm to 352.1 nm. Of the three studied ANNs, the one that displayed the best prediction results was the one with three hidden layers with the flow rate, voltage, viscosity, and conductivity variables. The calculation error between the experimental and calculated diameters was 3.79%. Additionally, the correlation coefficient (R2) was identified as a function of the ANN configuration, obtaining values of 0.96, 0.98, and 0.98 for one, two, and three hidden layer(s), respectively. It was found that an ANN configuration having more than three hidden layers did not improve the prediction of the experimental diameter of synthesized nanofibers.

The spatial distribution of ß-carotene impregnated in apple slices determined using image and fractal analysis.

Changes in the concentration profiles of ß-carotene caused by diffusion through parenchymatic dried apple tissue were characterized by image and fractal analysis. Apple slices were dried by convection, and then impregnated with an aqueous ß-carotene solution. Scanning electron microscopy images of dried apple slices were captured and the fractal dimension (FD) values of the textures of the images were obtained (FDSEM). It was observed that the microstructure of the foodstuff being impregnated have an important effect on the impregnation phenomenon, generating irregular concentration profiles of ß-carotene, which are numerically described by the fractal dimension FDPROFILES and are related to the diffusion process during impregnation in dried edible tissue.

Physical characterization of freeze-dried foam prepared from Aloe Vera gel and guar gum / Caracterización de espumas liofilizadas preparadas a partir de gel de Aloe vera y goma guar

Background: Foams are colloidal dispersions of a gas suspended in a dispersing phase, which consisting of a semi-freeze-dried or viscous liquid phase. The physical properties of food foams are the result of the bubble characteristics and their spatial arrangement. Objectives: The aim of this work was to obtain foams of A. vera gel and guar gum and describe the changes in their physical properties and microstructure during freeze-drying using the fractal dimension concept and image analysis techniques. Methods: The porosity, density, and volume expansion factor of the fresh foams that were based on the A. vera foams were determined. The kinetics of foam texture, color, porosity and microstructure of the freeze-dried foams were obtained. The fractal texture dimension of surface (FDSDBC) and microstructure (FDESEM) of the foams were determined as indicators of structural changes after freeze-drying. The guar gum concentrations used to obtain the A. vera prefoam were expressed in w/w as F1 (control sample without gum), F2 (2%), F3 (4%) and F4 (6%). Results: We obtained stable freeze-dried foams of Aloe vera gel and guar gum. The porosity, density and volume expansion factor of the fresh and freeze-dried foams were affected by the addition of the guar gum. Changes in the topology of the freeze-dried foam surface during the drying process resulted in a high rugosity compared with the original smooth surface. The microstructure of the dried foam samples suggested a relationship between the gum concentration of the prefoam A. vera gel mixture and the physical properties before and after freeze-drying, such as an increase in the microstructural alterations and surface roughness during freeze-drying. The roughness of the freeze-dried foam surface, described by the FDSDBC represented the macroscopic physical changes of the samples and correlated with the changes in the foam microstructure, which were described by the fractal dimension of the Environmental Scanning Electron Microscopy ESEM microphotographs (FDESEM). Conclusions: The digital analysis of the structure and porosity of the freeze-dried foam can be used to quantify the effect of gum concentrations on the morphological features and physical properties of foams during freeze-drying.

Antecedentes: Las espumas son dispersiones coloidales de un gas en una fase líquida viscosa. Las propiedades físicas de las espumas alimentarias son el resultado de las características de sus burbujas y su disposición espacial. Objetivos: El objetivo de este trabajo fue obtener espumas de gel de A. vera y goma guar y describir los cambios en sus propiedades físicas y su microestructura durante el secado por liofilización utilizando el concepto de dimensión fractal y las técnicas de análisis de imagen. Métodos: Se determinó la porosidad, densidad, factor de expansión volumétrico de las espumas frescas de A. vera. Así como la cinética de liofilización, textura, isotermas de sorción, color, porosidad y la microestructura las espumas liofilizadas. La dimensión fractal de la textura (FDSDBC) y microestructural (FDESEM) de las espumas de gel de A. vera y goma guar liofilizadas se determinó como un indicador de los cambios estructurales después de la liofilización. Las concentraciones de goma de guar utilizados para obtener la solución de clara de huevo preespuma se expresaron en w/w como F1 (muestra de control sin goma), F2 (2%), F3 (4%) y F4 (6%). Resultados: Fue posible obtener espumas liofilizadas estables de gel de A. vera y goma guar. La porosidad, densidad, factor de expansión volumétrico de las espumas se vieron afectadas con la adición de goma guar. Los cambios en la topología de la superficie de la espuma liofilizada durante todo el proceso de secado dieron lugar a alta rugosidad en comparación con la superficie lisa original. La microestructura de las muestras de espuma secas sugirió una relación entre la concentración de goma de las espumas de A. vera y las propiedades físicas antes y después de la liofilización como un aumento en las alteraciones microestructurales y rugosidad de la superficie durante el secado por congelación. La rugosidad de la superficie de la espuma liofilizada, se describió por la relación FDSDBC que representa los cambios físicos macroscópicos de las muestras y se correlacionó con los cambios en la microestructura de espuma, que fueron descritos por la dimensión fractal de las micrografías ESEM (FDESEM). Conclusiones: El análisis digital de la estructura y la porosidad de la espuma liofilizada se puede utilizar para cuantificar el efecto de las concentraciones de goma guar en las características morfológicas de las espumas durante el secado por congelación.

Cambios en la textura de la superficie de esferas de melón (Cucumis melo cantalupensis) durante el secado por fluidización / Changes in surface texture of melon (Cucumis melo cantalupensis) spheres during spout fluidized bed drying

Antecedentes: El encogimiento y los cambios morfométricos de las frutas durante el secado son fenómenosdifíciles de evaluar puesto que los alimentos no son tejidos homogéneos y sus propiedades físicasse ven afectadas por su contenido de humedad. Objetivos: El objetivo de este artículo fue describir loscambios morfométricos en la superficie de esferas de melón durante el secado por fluidización, empleandoel análisis de imágenes y la teoría fractal. Métodos: Las imágenes de esferas de melón fueron obtenidascon una videocámara durante el secado por fluidización. Las variables de estudio fueron: velocidad, enniveles de 2, 3 y 4m/s, y temperatura del aire de secado a 70° y 80°C. El encogimiento de las esferas demelón fue definido como A/Ao, donde Ao y A fueron las dimensiones original y final de las esferas duranteel secado, respectivamente. Seis zonas de medición fueron seleccionadas en la superficie de las esferaspara evaluar el contenido de humedad (CHZ). Los cambios morfométricos de la superficie de las esferasdeshidratadas fueron evaluados mediante la dimensión fractal de la textura (DFSDBC) de las imágenesobtenidas durante el secado por fluidización. Resultados: Se observó un decremento irregular del encogimiento(A/Ao) de las esferas vs. Tiempo de secado. Las condiciones de secado que registraron mayorirregularidad en la contracción de la esfera fueron 70°C y 2 m/s, condiciones en las cuales se produjerondistribuciones del contenido de humedad (CHZ) en la superficie de la esfera. La distribución de los CHZcondujo a la aparición de zonas con diferente contenido de humedad durante el secado, produciendouna deshidratación no homogénea de la esfera de melón. Los valores de DFSDBC oscilaron entre 2,22 y2,30. Se observó que los cambios morfométricos en la superficie de la esfera fueron progresivos, comoresultado de la deshidratación...

Shrinkage and morphometric changes of fruit during drying are phenomena difficult to evaluate since foodstuff are not homogeneous material and their physical properties are strongly influenced by its moisture content.Objectives:The aim of this paper was to describe, by means of image analysis and fractal theory the morphometric changes in the surface of melon spheres during spout fluidizedbed drying. Methods: Images of melon spheres during spout fluidized bed drying were obtained with a videocamcorder. The studied variables were the dry airflow, at levels of 2, 3, and 4 m/s; and dry air temperature at 70 and 80ºC. The shrinkage was defined as ratio of areas (A/Ao) of melon spheres, where Ao and A were initial and final dimensions of the spheres during drying, respectively. Six measurement zones were selected on the surface of the spheres to evaluate moisture content (MCZ). Surface morphometricchanges of dehydrated spheres were evaluated by means of fractal dimension of the texture (FDSDBC) of the obtained images during fluidized bed drying.Results: It was observed an irregular decreasing of spheres shrinkage (A/Ao) vs. drying time. The highest irregularity in the contraction of the sphere was obtained at drying conditions of 70ºC, and 2 m/s. At these conditions, a distribution of moisture content zones (MCZ) in the surface of melon spheres were observed. Distribution of MCZ generated the onset of zones with different moisture contents, along the drying on the surface of the spheres, which produced a non-homogeneous dehydration of the melon spheres. FDSDBC values were between 2.22 and2.30. It was observed that morphology changes of surface were progressive because of the dehydration.Conclusions: Morphometric changes on surface of melon spheres were influenced by a distribution of MCZ on the surface, found during spout fluidized bed drying. FD SDBC values of the surface of melon spheres were increased, indicating a rougher surface during.