CARACTERIZACIÓN DE SOLUCIONES FORMADORAS DE PELÍCULAS ELABORADAS CON HARINA Y ALMIDÓN DE CEBADA

Abstract

The use of synthetic polymers to protection, packaging and preservation of products has grown enormously in recent years, however, this increase has created serious environmental problems due to the resistance of these materials to be degraded and integrated by microorganisms present in the nature. Because of this, it is very important to use alternative raw materials, to replace these materials partially or totally to reduce the level of damage produced to the environment. In the present work, starch and flour from barley were used to prepare film-forming solutions; these solutions were characterized in their physicochemical, rheological and digestibility properties. The effect of grain pearled and the concentration of starch, flour and glycerol were studied on the viscosity and surface tension of film-forming solutions; it was applied a response surface methodology and a central composite design. Viscosity was measured in a rheometer AR-1000-TA Instruments at a shear rate sweep from 0.1 to 300 s-1. The surface tension was measured using the Wilhelmy method. For the formulation of the film-forming solutions a central composite design was applied, considering a factorial arrangement 22 (the variables were the starch and glycerol concentrations, and the levels were 2 to 4% (w/w) and 20 to 40% (w/w), respectively) with 3 replicates at the central point, 4 axial points or star, 4 intermediate points, obtaining a total of 11 experiments. The chemical composition of the flour was affected by the process of pearled, during this process the husk and some portions of the grain with different fractions of others components were removed. It was established that the starch and flour were determinants in the viscosity and surface tension of film-forming solutions, and these properties were not affected by the process of pearled neither the glycerol concentration. On the other hand, thermal properties were clearly affected by non-starch components present in the flour; this behavior is attributed to both lipids and proteins, which act as physical barriers that inhibit the process of starch gelatinization. To evaluate its possible application in food preservation, films were produced and characterized by their digestibility, mechanical and barrier properties. Based on some authors and considering that a viscosity close to 0.7 Pa.s is optimal to prevent sedimentation of solid particles dispersed in film-forming solutions, we chose an average strain rate of 1 s-1 and determined the formulation to develop films; this was 3 g of starch and 30% of glycerol with respect to the amount of starch present in the sample. According to the results obtained, pearled process affected directly the mechanical and barrier properties. In digestibility results, the organization of the polymeric structure in the mixture in the film-forming solutions and in the biodegradable films affected enzymatic activity and therefore the rate of digestibility.