Resumen Para la conservación de frutas y hortalizas, se pueden producir y desarrollar películas comestibles (PC). Para producir PC, el almidón es considerado uno de los biopolímeros con mayor potencial mediante diferentes técnicas de procesamiento como la extrusión-casting. El objetivo fue estudiar el efecto de las nanopartículas de carbonato de calcio (NPsCC) y plastificantes [sorbitol-glicerol (80-20%; p/p)] producidas mediante tecnologías combinadas de extrusión (EXT)-casting (CT) para obtener PC con propiedades mecánicas y de barrera mejoradas. La mezcla almidón de maíz-plastificantes fueron procesados en un extrusor de doble tornillo para obtener almidón termoplástico modificado seguido de la adición de NPsCC en el casting para la formación final de la PC. Se utilizó un diseño híbrido (cuatro factores; veintiún tratamientos) de la metodología de superficie de respuesta para el proceso de optimización. Se caracterizó PC óptima acorde a propiedades mecánicas y de barrera, además, de propiedades microestructurales (difracción de rayos X, Microscopía Electrónica de Barrido) para determinar el daño causado en el almidón durante EXT y CT. En conclusión, es posible obtener PC con mayor resistencia a la rotura y deformación, así como, menor permeabilidad al vapor de agua y solubilidad, mediante el uso de NPsCC y plastificantes, utilizando la combinación EXT-CT.

Abstract Edible films (EF) can be produced and developed for preservation of fruits and vegetables. Starch has been considered one of the biopolymers with the greatest potential to produce edible films through different processing techniques, such as extrusion-casting. Our objective was to study the effect of calcium carbonate nanoparticles (NPsCC) and plasticizers (sorbitol-glycerol (80-20%; w/w)) produced by extrusion (EXT)-casting (CT) combination technologies, to obtain EF with improved mechanical and barrier properties. Corn starch-plasticizers were processed in a twin-screw extruder to produce modified thermoplastic starch, followed by the addition of calcium carbonate nanoparticles (CCNP) in casting to EF formation. A hybrid design (four factors; twenty-one treatments) of surface response methodology was used to optimization process. The optimal EF mechanical and barrier properties were characterized according to microstructural properties (X-ray diffraction, Scanning Electron Microscopy) to determine the damage caused in the starch during EXT and CT. In conclusion, it is possible to obtain EF with greater both Breaking Strength and Deformation, as well as, lower Water Vapor Permeability and Solubility (mechanical and barrier properties), through the use of CCNP and plasticizers, using EXT-CT combination processes.

The effect of extrusion variables, such as barrel temperature (100 to 170ºC), feed rate (100 to 500 g/min), feed moisture (20 to 40 g/100 g wet basis), screw speed rate (from 100 to 500 rpm), and slit die rheometer configuration (0.15 and 0.30 cm height) were studied using a co-rotating intermeshing twin-screw extruder coupled to a slit die rheometer on the rheological properties of yellow cornmeal. An increase in feed rate decreased WAI and WSI, but increased the viscosity values. The temperature interacts strongly with screw speed in affecting the WSI. The most important factor in starch degradation was the screw speed. Increasing the screw speed completely modifies the organised structure of starch (crystalline region).