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This study aimed to evaluate the effect of incorporating different concentrations (0, 200, 300, and 400 mg L

Methane production of chicken litter in anaerobic digestion (AD) was evaluated with different concentrations of magnetite (Fe3O4) nanoparticles (NPs). The Fe3O4 NPs were synthesized by co-precipitation, where the effect of different concentrations and dissolution temperatures of the passivant and precursors, as well as the sonication time, on NPs size was determined. The best NPs were selected based on the smallest hydrodynamic diameter (79.37 nm) with the highest absolute value of zeta potential (−18.06 mV). These NPs were analyzed in a transmission electron microscope (average size of 4.2 nm) and by X-ray diffraction (to corroborate their structure). These 4.2 nm NPs were used to evaluate their effect on AD of chicken litter under mesophilic conditions. The treatments for AD were the control (only chicken litter) and the addition of different concentrations of Fe3O4 NPs (20, 40 and 60 mg L−1). The treatment with 20 mg L−1 of NPs had the highest methane production rate (2.55 mL CH4∙gvsf−1∙d−1) and the highest cumulative methane yield (137.23 mL CH4∙gvsf−1), the last one with an increase of 73.9% compared to the control, while the concentration of volatile fatty acids was similar in all treatments. In general, NPs had a biostimulating effect on methanogenic activity.

ntroduction: The productivity of current agricultural practices depends largely on the use of fertilizers. A major limitation of conventional fertilizers is their low crop yields, so the development and application of new types of fertilizers using nanotechnology are potentially effective options for increasing agricultural production. Objective: To synthesize and characterize calcium-loaded gelatin nanoparticles, and evaluate their behavior as controlled-release systems. Methodology:The nanoparticles were obtained by spray drying. The physicochemical characteristics of the particles were analyzed by scanning electron microscopy and FTIR spectroscopy, while their behavior as controlled release systems was evaluated by in vitro tests. Results: Calcium-loaded gelatin nanoparticles with average sizes below 700 nm, mainly spherical morphology and smooth microstructure were obtained. FTIR spectra showed the formation of electrostatic interactions between the charge and the gelatin. In vitro tests allowed to assume that the biopolymer matrix acted adequately in the controlled release of calcium ions. Limitations of the study: The physicochemical characteristics of nanomaterials only apply to the processing conditions used. Originality: There are no reports on calcium-loaded biopolymer nanomaterials with potential application in agriculture. Conclusions: Gelatin nanoparticles, with adequate morphology and sizes, which act as controlled calcium release systems were obtained.

Introduction: The drying of nopal offers an alternative for their preservation, storage, handling and consumption. Objective: The effects of microwave drying on the microstructural characteristics of nopal and their thermodynamic properties at the food-water interface were evaluated. Methodology: Nopal cladodes were microwave-dried by applying powers of 75 and 158 kW∙kg-1. Microstructure of the samples was evaluated by Scanning Electron Microscope. Adsorption isotherms were determined at temperatures of 10, 20, 30 and 40 °C. Net isosteric heat (q-st) was calculated using the Clausius-Clapeyron equation and the Peleg model. Results: Samples dehydrated at 75 kW∙kg-1 showed greater preservation of their internal and external structure. When applying a higher power (158 kW∙kg-1), greater damage was observed in the microstructure of the material. Type III adsorption isotherm curves were obtained according to the Brunauer classification. The q-st of the dehydrated nopal was 7.51 kJ∙mol-1 for a moisture content of 0.05 kgH2O∙kg-1. Limitations of the study: The results obtained are valid only for microwave drying by applying powers of 75 and 158 kW∙kg-1. Originality: This work proposes the microwave drying of nopal as an alternative method that reduces drying time and allows the preservation of the material’s structural properties. Conclusions: The power applied in the microwave drying of nopal had a direct impact on the microstructure of the samples. The use of a power of 75 kW∙kg-1 was the best drying condition to preserve the structures constituting the cladodes.

The efficiency of nanoparticles covered with type A gel and loaded with KH2PO4, as a source of P, was evaluated on growth, phosphorus concentration and accumulation, and photosynthesis-related parameters in rice plants (Oryza sativa L. ssp. indica) cv. Morelos A-2010, under greenhouse conditions. Plants were treated for 14 days with P concentrations equivalent to 50 and 100% of those established in the Yoshida nutrient solution. Sources of P were KH2PO4, nano-KH2PO4, and nano-KH2PO4 with trypsin; control treatments were distilled water and nanoparticles with type A gel. The solutions were renewed every 7 d. Rice plants exhibited differential P absorption in function of the P source tested. P supplied by KH2PO4 had a higher uptake rate than P supplied by nano-KH2PO4, alone or with trypsin. Nevertheless, nano-KH2PO4 promoted higher physiological efficiency for P in both roots and shoots, which consequently induced higher biomass accumulation in these organs. P concentration in shoots, as well as P accumulation in shoots and roots, were positively correlated with the photosynthetic rate. Also, nano-KH2PO4 increased instant water use efficiency in rice plants.

The authors synthesised nanoparticles (NPs) loaded with P and K from KH(2) PO(4) using gelatin type‐A and type‐B, and sodium alginate as carriers. Using type‐A and type‐B gelatin, quasi‐spherical particles were obtained, with average sizes of 682 and 856 nm, respectively; with sodium alginate, the resulting NPs exhibited spherical shapes and 600 nm particle average size. The authors found an interaction between KH(2) PO(4) and alginate via the hydrogen bonds existent among the carboxylic groups of the carbohydrate and the OH‐groups of the H(2) PO(4) ‐; interactions among gelatin types with the OH‐groups and the H(2) PO(4) ‐ion were also observed. Adding trypsin to the distilled water solutions of the NPs coated with type‐A gelatin increased the concentration of P in the solution by threefold, while increasing that of K increased by 2.6‐fold. Conversely, adding α ‐amylase to the water solutions with sodium alginate increased the P and K concentrations in the solution by nearly 1.3‐ and 1.1‐fold, respectively. Thus, sodium alginate resulted in NPs with smaller sizes and better spherical formations, though with a high polydispersity index and lower release rate of P and K. This low release rate represents an advantage since plants demand nutrients for long periods, and conventional fertilisers display low use efficiency.

Rheological properties of tapioca starch-galactomannan mixtures at different concentrations (0, 0.3, 0.6 and 1.0%, w/w) of guar gum, tara gum and locust bean gum were investigated in visco-analysis, steady and dynamic shear and textural analysis. Galactomannans may influence the pasting temperature and other pasting parameters, the viscosity and pseudoplasticity of the blend systems increased as time-dependence and thixotropy decreased. This can be explained by the phase separation of systems where the galactomannans were placed in the continuous phase and the volume fraction of starch granules increased its concentration in the disperse phase. The addition of guar gum and tara gum could accelerate the formation of new structures and increase the degree of structural recovery until a 50% more than the starch gel pastes. The apparent viscosity (ηa) and dynamic moduli (G' and G″) of the mixed pastes increased with the addition of galactomannans. Changes in textural properties were significant. The gel hardness, gel strength and adhesiveness of gel pastes were higher in the starch-tara gum and starch-locust bean gum systems than in the starch-guar gum system in gum concentrations values of 0.3 and 0.6% w/w. Overall, addition of galactomannans affected the rheological and textural properties of tapioca starch.

Introduction: Biosynthesis has emerged as an option for obtaining nanometric materials due to the need to use more environmentally-friendly synthesis methods. Objective: To synthesize silver nanoparticles (Ag NPs) with aqueous Crataegus gracilior Phipps (tejocote) bark extract as precursor. Methodology: Ag NPs were synthesized with AgNO3 and aqueous Crataegus gracilior bark extracts, and later characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, their size distribution and zeta potential were obtained. Results: The presence of Ag NPs reached maximum values at concentrations of 10 % (w/v). Mostly spherical nanoparticles were found in the range of 20 to 50 nm in size. FTIR confirmed the stabilization of the nanoparticles through their interactions with functional groups of carbohydrates and proteins. XRD and TEM results were explained by their face-centered cubic (FCC) structure with a size of 26 nm, a mean hydrodynamic diameter of 108 nm and polydispersity index of 0.24. The zeta potential values in the dispersions were -21.9 ± 5.11 mV, denoting colloidal stability. Limitations of the study: The characteristics of the nanoparticles obtained are only valid under the following synthesis conditions: 10 % (w/v) solids and pH 10. Originality: A non-reported plant material was used, capable of acting as a reducing and passivating agent of silver nanoparticles. Conclusions: Biosynthesis of Ag NPs with tejocote extract is an efficient, low-cost and environmentally-friendly method.

"Some plants, roots or tubers have been used as possible cereal substitutes in gluten-free cookies. Chayotextle is rich in starch and other compounds that could make it a potential ingredient for products aimed at the celiac population. In this study, we evaluated the effect of different mixtures of rice flour (RF) and Chayotextle flour (CF) on the final properties of cookies and the prebiotic capacity when adding agave fructans (AF). The properties of flour and cookies were determined. CF presented the highest emulsifying, water absorption and oil absorption (27.1 %, 66.22% and 95.93 %, respectively) capacities. Cookies made with CF-AF reached the highest values in diameter (66.82 mm) and humidity (10.64%). By incorporating rice flour to this combination, cookies had the highest thickness (10.04 mm), specific volume (2.07 mL / g), and hardness (201.82 N). CF and the CF-AF formulation presented the ability to promote the growth of both strains studied: Lactobacillus acidophilus LA-3 and Bifidobacterium animalis ssp. Lactis, reaching values of up to 9.82 log10 CFU/mL and 9.85 log10 CFU/mL (CF) respectively, in a period of 24 h. The CF and the addition of FA improved cookies properties, and proved to be a possible prebiotic source."

El cáncer de mama es un problema de salud pública en el mundo, esta enfermedad es la principal causa de muerte por cáncer en las mujeres; por ello, es fundamental sumar esfuerzos para el desarrollo de estrategias que permitan mitigar su impacto social, económico y a la salud. Las moléculas activas derivadas de las plantas (fitofármacos) son una fuente prometedora de soluciones para esta problemática y su mejoramiento con la aplicación de sistemas de liberación de fármacos de base nanotecnológica es sin duda, una estrategia que debe ser evaluada para ofrecer alternativas para el tratamiento de los pacientes oncológicos. La consideración correcta de los factores que impactan en el éxito de estas estrategias es primordial, por ello, en este capítulo se exponen los fundamentos teóricos para la obtención de fitofármacos nanotransportados para el tratamiento del cáncer de mama, así como una breve introducción a esta neoplasia; el concepto de fitofármacos, sus métodos de obtención y las características de calidad que deben cumplir; así mismo, se describen los sistemas nanométricos para el transporte de fármacos contra el cáncer y las características fisicoquímicas y de calidad que estos deben cumplir para su éxito. Finalmente, se exponen algunos avances que este grupo de investigación ha logrado en el desarrollo de fitofármacos nanotransportados para el tratamiento del cáncer de mama.

En este trabajo, se elaboraron nanopartículas cargadas con extractos polifenólicos de Theobroma cacao L. (cacao) y Justicia spicigera (muicle). El contenido de fenoles totales del grano de cacao y el muicle se determinó usando el reactivo Folin-Ciocalteu y la actividad antioxidante se estimó usando los ensayos DPPH (2,2-difenil-2-picrilhidrazilo) y FRAP (reducción férrica / poder antioxidante). El proceso de nanoencapsulación se realizó mediante un nano-secador por aspersión utilizando pectina y aislado de proteína de suero como materiales de pared. Los resultados mostraron que fue posible obtener nanopartículas con morfología esferoidal homogénea y un tamaño promedio de aproximadamente 500 nm. Los experimentos in vitro, en los que se utilizó el método DPPH para evaluar la prevalencia de la capacidad inhibitoria de radicales libres de los extractos nanoencapsulados, indicaron que las eficiencias de carga para las nanopartículas cargadas con ambos extractos fueron aproximadamente del 56.53 % y 41.38 % para muicle y cacao, respectivamente; de la misma manera los resultados de FRAP fueron equivalentes respecto a la capacidad antioxidante.

Actualmente las enfermedades cardiovasculares representan la principal causa de morbimortalidad en el mundo; la aplicación de la nanotecnología es una gran promesa para su prevención y tratamiento. Actualmente se están desarrollando nanodispositivos para la liberación dirigida y controlada de medicamentos en sitios específicos en el organismo, por ejemplo, en células, tejidos, vasos sanguíneos y el corazón, así como para su diagnóstico, detección temprana de enfermedades cardiovasculares y tratamiento individualizado de pacientes. Otra aplicación de los nanodispositivos es la liberación de fármacos para corregir el mal acoplamiento de proteínas defectuosas. Con potentes superefectos, las nanopartículas deben ser capaces de provocar efectos terapéuticos a bajas dosis en periodos prolongados. La fabricación de nanodispositivos y nanoacarreadores deberá llevarse a cabo con un enfoque integral que tome en cuenta las propiedades generales, con la finalidad de evaluar la biocompatibilidad y, en consecuencia, evitar efectos adversos y tóxicos. La investigación intensificada en este campo ayudará a disminuir significativamente la morbimortalidad provocada por las enfermedades cardiovasculares. El presente trabajo incluye una sinopsis que describe algunos de los avances más recientes, relevantes y comunes de la nanomedicina en las ECV.

El interés en el estudio de los polifenoles ha crecido de manera considerable en los últimos años debido a su alta capacidad para atrapar radicales libres asociados con diversas enfermedades. Por este motivo, el objetivo del presente trabajo fue obtener y caracterizar los compuestos fenólicos de Justicia spicigera Schltdl. mediante extracción asistida por ultrasonido. A los extractos, se les determinó el contenido fenólico total (método de Folin-Ciocalteu), actividad antioxidante (potencial antioxidante/reductor del hierro) y actividad secuestradora de radicales libres (método del radical libre 2,2-difenil-2-picrilhidrazil). La metodología de superficie de respuesta (MSR) se empleó para evaluar el efecto del disolvente (agua/etanol) y el tiempo de extracción, en el contenido de fenoles totales y las propiedades antioxidantes. El análisis de varianza (ANOVA) indicó que la concentración de agua en la mezcla del disolvente afectó de manera importante el rendimiento de los compuestos, así como la actividad antioxidante y antiradical. De acuerdo con la MSR, las condiciones óptimas para la extracción son 25% de agua en la mezcla del disolvente y un tiempo de sonicación de 16 minutos.

Nanoparticles of magnetite passivated with gelatin and starch were synthesised using a co-precipitation technique. The nanoparticles were characterised using ultraviolet-visible (UV-vis), dynamic light scattering (DLS), Zeta potential, transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The UV-vis spectra showed characteristic surface plasmon resonance of magnetite nanoparticles. The DLS results showed the nanoparticles to have average hydrodynamic diameters of 138 ± 2 and 283 ± 21 nm for particles passivated with gelatin and starch, respectively. The stability in a colloidal solution was greater in nanoparticles passivated with gelatin than nanoparticles obtained with starch, as can be seen by their Zeta potential value (-31 ± 2 and -16 ± 0.5 mV, respectively). According to the TEM evaluation, the use of gelatin allowed to obtain nanoparticles with a spherical morphology and an average size of 10 ± 2 nm. However, when using starch the nanoparticles exhibited diverse morphologies with an average size of 25 ± 7 nm. The XRD results confirmed the crystalline structure of the samples, which showed crystallite sizes of 14.90 and 24.43 nm for nanoparticles passivated with gelatin and starch, respectively. FTIR analysis proved the establishment of interactions between functional groups of biopolymers and magnetite nanoparticles.

Starch-galactomannan mixtures were elaborated by extrusion using a general factorial statistic design with three variables: galactomannan type (guar gum, tara gum and locust bean gum) at 10% (w/w), citric acid concentration (0‒2.5% w/w) and storage time at 4 °C (0‒7 days). Galactomannan type, citric acid concentration and storage time were factors that affected the physicochemical properties and microstructure of extrudates. Crystallinity of starch-guar gum extruded samples was higher compared with the samples obtained with the addition of the other gums and presented a variation from 3.38 ± 0.16 to 6.68 ± 0.23 when citric acid was added and stored at 4 °C and showed a correlation between long-range order (X-ray diffraction) and short-range order (FTIR). These results demonstrated the influence of the different galactomannans, the addition of citric acid and the storage at 4 oC of the samples, which resulted in an increase in the formation of V-type amorphous structures. The DSC analysis demonstrated the formation of amylose-lipid complexes in which transitions temperatures started at above 90 °C, these structures may slow retrogradation rates of samples. In addition, these complexes can act as a part of resistant starch found in samples, which varies from 4.64 ± 0.15 to 12.13 ± 0.30 g/100 g sample in different extrudates. Overall, galactomannan type, citric acid concentration and storage time were factors that significantly affected the properties and resistant starch content of extruded samples.

One of the main goals in the field of regenerative medicine is the construction of complex 3D scaffolds that can repair damaged tissue. The polymer chosen for this study is poly(vinyl) alcohol (PVA), widely used in tissue engineering [1]. PVA can be tailored for mechanical properties and has high-performance degradation kinetics. Its morphology and shape can be easily manipulated to improve vascular conduction and tissue induction. PVA is an excellent candidate for the manufacture of hydrogels with high tissue repair capacity and low cytotoxicity. We studied the water-polymer interaction of the material using a molecular dynamics (MD) approach for the calculation of solvation free energy and other parameters. For the modeling and data analysis, we used the high-performance computational software, Gromacs. Hydrogels were prepared at 10, 20, and 35 WT PVA. The hydrogel morphology and pore size were analyzed by SEM. Pore diameter tended to be larger when swelling in water than in PBS. The end-to-end distance of the MD simulated 30-mer was found to be larger in pure water than in the presence of ions. The trend can partially explain the experimental results of pore size. We also found an important change in solvation free energy when the polymer changes from an open to a closed conformation in water.

Starch–guar gum mixtures were obtained by extrusion using a three-variable Box–Behnken statistic design. Morphology, expansion index, viscosity, crystallinity and digestion in vitro of the extruded samples were analyzed through response surface methodology (RSM). The extrusion temperature and the moisture content were the factors that significantly affected the physicochemical properties of the samples. Starch–guar gum samples showed expansion index and viscosity up to 1.55 and 1400 mPa s, respectively. The crystallinity of the samples was modified by adding guar gum to the extrudates, showing correlation between long-range order (X-ray diffraction) and short-range order (FTIR spectroscopy). Guar induced microstructural changes and its role in gelatinization–melting processes was significant. The rate of glucose release decreased from 0.47 to 0.43 mM/min when the extrusion temperature decreased. However, adding guar gum to starch had no significant effect on glucose release. Overall, the extrusion temperature and the moisture content were the factors that significantly affected the physicochemical properties of the extruded samples.

In the present research, nanospheres of chitosan (CS), maltodextrin, and sodium tripolyphosphate (STPP), loaded with urea, were synthesized by using an ionic gelation technique. In the nanosphere synthesis was used a central composite experimental design, obtaining nanospheres with an average size of 275 ± 32 nm and 27.5 mV zeta potential. The nanospheres were characterized by their hydrodynamic diameter, polydispersity index, nitrogen content, and thermal properties such as thermal diffusivity (α), effusivity (e), and conductivity (k); also melting temperature was obtained by differential scanning calorimetry. The thermal properties of nanospheres show that the sample with the smallest size has a thermal diffusivity value of (14.4 ± 0.4) × 10−8 m2·s−1 and a thermal conductivity value of (6.4 ± 0.1) × 10−1 W·m−1·K−1, and the obtained melting temperature was 157 °C. Higher concentrations of CS increase the values of these thermal properties, probably because chitosan interacts ionically with STPP forming a reticular network due to the opposite charges of both molecules.

Introduction. Polyphenols have received significant attention in recent years due to their antioxidant capacity and their significant role in disease prevention. Cocoa is one of the major naturally occurring sources of antioxidants, particularly of polyphenolic compounds. Materials and methods. Gelatin nanoparticles loaded with a cocoa-derived polyphenolic extract were synthesized by nanopreci- pitation. The nanoparticle synthesis was performed using a central composite experimental design that allowed for the assessment of how gelatin concentration and surfactant concentration (Tween 80) affec- ted the hydrodynamic diameter and polydispersity of the particles. The nanoparticles were characterized using dynamic light scattering (DLS), assessments of zeta potential, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Results. The analyses demonstrated that the nano- particles examined exhibited hydrodynamic diameters of (100 to 400) nm, polydispersity indices of less than 0.2 and average zeta potential values of 29-33 mV. SEM images revealed that most nanoparticles were spherical and uniform in morphology, with average sizes less than 250 nm. In vitro experiments in which the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method was used to assess the prevalence of free radical-scavenging ability among these nanoparticles indicated that the loading efficiency for the nano- particles was approximately 77.56%. Conclusion. Nanoparticles loaded with polyphenolic extract were obtained with average sizes ranging from (120 to 250) nm and largely spheroidal morphologies. Polymer and surfactant concentrations significantly influenced the hydrodynamic diameters and polydispersity indices of the particles. The incorporation of the polyphenolic extract into the polymer matrix enabled the preservation of the antiradical activity of the bioactive compound. Mexico / Theobroma cacao / nanotechnology / polyphenols / antioxidants / microencapsulation / gelatin

The aim of this work was to synthesize silver nanoparticles (NPs) through a green synthesis method using starch as a capping agent. The influence of the glucose content, temperature, and pH on the size of the NPs was evaluated by means of a response surface methodology. The obtained nanomaterials were characterized by UV–Vis spectroscopy, XRD, and TEM, and the crystalline structure of the silver was determined by XRD. The optimum synthesis time was after 3 h of reaction time the colloidal solution, did not show any further significant variation in the optical absorption peak (λmax). Response surface results indicate that the reducing agent (glucose) concentration was the most important factor influencing the NPs size, which ranged from 2 to 24 nm. TEM images show that NPs had predominantly spherical shapes, but also polyhedral shapes were present in smaller quantities. Analysis of Raman spectra infers that the glucose initially reduces silver ions to elemental silver. Then the starch undergoes hydrolysis providing primary hydroxyl that contributes to the reduction of silver. The carboxyl and hydroxyl groups of glucose and hydrolyzed starch stabilize the silver NPs by passivating their surface, so that they do not aggregate and remain uniformly distributed.

The end product of low-density polyethylene–starch was manufactured by injection molding process. Four starch concentrations (10, 25, 40, and 50%) were used for blend preparations, which were injected into the mold of a 250 mL commercial cup. A control sample of neat polyethylene (PE) was also included. Square coupons (4 cm × 4 cm) of each blend were buried in the middle of a 50 cm pile of compost. Samples were recovered, washed, dried, and weighed after 25, 50, 75, 100, and 125 days beneath the compost. Scanning electron microscopy (SEM) analysis was performed on the samples to track the biodegradability evolution. A SEM scandium analyzer was used to measure the size and number of pores and the eroded area. Weight loss measurements were conducted to validate the SEM observations. Total biodegradation time was determined by mathematical analysis and graphical extrapolation. SEM analysis revealed the formation of pores, cavities, discontinuities, and cracks resulting from the time beneath the compost. Pore measurements revealed that the specimen composed of 40% starch and submerged for 125 days experienced up to 25% eroded area. Pure PE remained practically unchanged for the 125-day period. Fourier transform infrared spectroscopy studies also demonstrated the biodegradation of PE in PE–starch blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Low density polyethylene (LDPE)–starch blends were prepared by extrusion. Starch content ranged between 0 and 50% under different conditions of temperature and extrusion speed. Each blend was injected into a commercial mold of a 250 mL cup. Cups were cut into 5 cm 5 cm coupons. Biodegradability was assessed placing the coupons in the middle of a 50 cm pile of compost. Samples were recovered, washed, dried, and weighed after 25, 50, 75, 100, and 125 days under compost. Weight loss was determined and structural modifications were evaluated by SEM. Mechanical properties as tensile strength, elongation to break, and yield point were assessed before and after compost treatment. Experimental design and characterization were performed using a central composite design (CCD) and results were modeled with surface response methodology. SEM analysis revealed fractures and pores as a consequence of microorganism degradation. Pure LDPE samples remained unchanged. Mechanical, physical, and thermal properties of LDPE–starch blends are slightly different from that of pure LDPE. Environmental exposure, measured by accelerated intemperism, does not modify blend properties; consequently, they are suitable for the same industrial applications of LDPE.

Colloidal silver nanoparticles were synthesized by reducing silver nitrate solutions with glucose, in the presence of gelatin as capping agent. The obtained nanoparticles were characterized by means of UV–Vis spectroscopy, transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The response surface methodology (RSM) was also used to determine the influence of the variables on the size of the nanoparticles. The antifungal activity of the silver nanoparticles was evaluated on the phytopathogen Colletotrichum gloesporioides, which causes anthracnose in a wide range of fruits. The UV–Vis spectra indicated the formation of silver nanoparticles preferably spherical and of relatively small size (

The glass transition temperature (T g) and melting temperature (T m) of gelatin–starch films were determined using differential scanning calorimetry. Also, the microstructure was observed using scanning electron microscopy (SEM) and the crystalline structure by means of X-ray diffraction (XRD). The effect of starch and glycerol concentrations in films on the thermal properties was evaluated through response surface methodology (RSM). The highest values of T m were obtained at starch concentration intervals of (0.26 to 0.54) %w/w and glycerol concentrations lower than 0.5 (%w/w). On the other hand, the T g values diminished as the glycerol concentration increased. Mathematical models for both transitions were fitted to the experimental data. The micrographs obtained by SEM show the influence of glycerol in the microstructure of the films, being more “gummy” as the content of the plasticizer increased. The XRD patterns of the films demonstrate the existence of some pseudo-crystalline regions in the biodegradable materials.

The objective of the present work was to determine the thermal diffusivity and effusivity of biodegradable films by using photothermal techniques. The thermal diffusivity was studied by using the open photoacoustic cell technique. On the other hand the thermal effusivity was obtained by the photopyroelectric technique in a front detection configuration. The films were elaborated from mixtures of low density polyethylene (LDPE) and corn starch. The results showed that at high moisture values, the thermal diffusivity increased as the starch concentration was higher in the film. However at low moisture conditions (

BACKGROUND: Several storage techniques have been developed to extend the post-harvest shelf life of horticultural products. One method involves the use of edible or biodegradable coatings. Such coatings are made of biological materials that are used to coat fresh products, providing a semi-permeable barrier to water vapour and gases, e.g. O2 and CO2. The influence of starch concentration, glycerol content and pH on the carbon dioxide permeability (CO2P) and mechanical properties of gelatine‐starch edible films were evaluated. RESULTS: Results showed that increments in the starch concentration and pH resulted in higher CO2 Pv alues. Film puncture strength increased when the starch concentration decreased and the maximum resistance value (32.6 N) was obtained at pH 6. Deformation was mainly affected by glycerol and starch content. Some films were chosen in order to evaluate their effect, as coatings, in the post-harvest shelf life of avocados (Persea americana Mill c.v. Hass). Fruits were immersed in the coating solutions, air dried and stored at two temperatures. Changes in colour, weight loss and pulp firmness were determined in fruits stored at 6 ◦ C. In addition, respiration rate was measured in avocados kept at 20 ◦ C. CONCLUSION: The application of gelatine‐starch coatings delayed the ripening process of avocados, as indicated by a better pulp firmness and retention of skin colour, and lower weight loss of coated fruits in comparison with control avocados. The coatings also resulted in a delayed respiratory climacteric pattern, by 3days, for coated fruits.  2007 Society of Chemical Industry

Starch-based biodegradable polymers are obtained by incorporating plant-derived polymers into plastics. This blending allows for a reduction in the polymer's resistance to microbial degradation. Assessing biodegradability is a key step in the characterization of newly designed polymers. Composting has been taken into consideration in waste management strategies as an alternative technology for plastic disposal. This study analyzed the biodegradability of an injection-molded plastic material in which thermoplastic unripe banana flour (TPF) acts as a matrix (70%) and metallocene catalyzed polyethylene acts as a reinforcing filler (30%). This plastic was termed 70 TPF, and the structural, physical, and mechanical changes associated with its degradation were analyzed. The characterization of the microorganism that contributes to 70 TPF biodegradation was also performed. After composting, 70 TPF decreased in tensile strength and the TPF moiety in the blend was lost, greatly affecting the microstructure of the sample. Based on these indicators of degradation, this study identified the fungus Mortierella elongata as the microorganism responsible for the degradation of the plastic, a finding that supports the role of fungal communities in the biodegradation of designed materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42258.

Preparation of cellulose nanowhiskers (CNWs) has grown significantly because they are useful for a wide range of applications. Additional advantage in their design requires that they meet the following characteristics: nontoxicity, abundance, sustainability, renewability, and low cost. To address these requirements, nanowhiskers were prepared fromOpuntia ficus-indica(nopal) cellulose by acid hydrolysis. Monitoring the process of CNWs preparation is necessary to ensure maximum yield and purity of the end product. In this study, the cellulose preparation was monitored by analyzing microscopic morphology by SEM; the purity degree was determined by fluorescence microscopy as a novel and rapid technique, and FTIR spectroscopy was used for confirmation. The additional parameters that monitored the process were the crystallinity index by X-ray diffraction and the size of the particle by dynamic light scattering (DLS). Nopal cellulose was found to be comparable to commercial microcrystalline cellulose. The use ofOpuntia ficus-indicais a viable alternative for the production of highly pure CNWs and the strategy to supervise the preparation process was rapid.

Starch phosphorylation with sodium tripolyphosphate (STP) was performed using a single-screw extrusion process. The extrusion variables studied were temperature (from 99.5°C to 200.4°C), water content (16.3% to 19.7%, w/w), and STP content (0.82% to 4.18%, w/w). The resulting phosphorylated starch was evaluated with respect to expansion, water solubility index (WSI), water absorption index (WAI), degree of substitution (DS), and viscosity. The phosphorylated starch was tested as a stabilizing additive in yogurt formulations, with respect to the syneresis index (SI) and the syneresis susceptibility coefficient (SSC). The results show that the expansion increases with increasing STP content, and decreases with increasing temperature and water content employed in the process. Increasing extrusion temperatures and decreasing water content resulted in increasing WSI and decreasing WAI. The DS was dependent on STP content, increasing as STP content increased, but appeared to be insensitive to changes in water content (between 16% and 20%, w/w). The highest level of yogurt stability, as measured by the syneresis index (SI) and the syneresis susceptibility coefficient (SSC), were obtained when the yogurt was formulated with the starch of the highest DS (0.018), which had been obtained at 150°C, 18% water content, and 4.12% (w/w) of STP.

Water vapor diffusion coefficient (WVDC) and thermal diffusivity (alpha) were determined in gelatin-starch films through photothermal techniques. The effect of different variables in the elaboration of these films, such as starch and glycerol concentrations and pH, were evaluated through the response surface methodology. The results indicated that an increase in the glycerol concentration and pH favored the WVDC of the films. On the other hand, alpha was influenced principally by the starch content and pH of the film-forming solution. The minimum alpha value was 4.5 x 10(-4) cm2/s, which is compared with alpha values reported for commercial synthetic polymers.

We present a microstructural study and thermal diffusivity measurements at room temperature in two different sections of bull dense bone, bull bone and commercial hydroxyapatite, the last two in powder form. A comparison was realised between these measured values and those obtained from metallic samples frequently used in implants, as high purity titanium and 316L stainless steel. Our results show that the porosity and its orientation in the bone are two important factors for the heat flux through the bone. On the other hand, we obtained that the hydroxyapatite, in compact powder form, presents a thermal diffusivity value close to those obtained for the samples of bone which gives a good thermal agreement between these materials. Finally, it was obtained at one order of magnitude difference between the thermal diffusivity values of metallic samples and those corresponding values to bone and hydroxyapatite being this difference greater in titanium than in stainless steel.