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Abstract: In this work we studied the influence of the drying temperature and relative humidity on the solubility, mechanical properties, water vapor permeability (WVP), and drying time of amaranth flour films plasticized with glycerol or sorbitol. The effect of drying temperature and relative humidity on the mechanical properties of the film is a function of the plasticizer type. In the presence of glycerol, tougher flour films are obtained at a lower drying rate, but an inverse behavior is observed for the films plasticized with sorbitol. The drying conditions do not have a significant effect on WVP compared with sorbitol-plasticized samples, the water sorption isotherm shows that the glycerol-plasticized flour films are able to retain more water at equilibrium at all the studied temperatures. The lower moisture content, WVP and drying time achieved for these films in all the drying conditions indicate better interaction of sorbitol with the starch and protein macromolecules present in the amaranth flour. The optimized drying conditions are 50 °C and 76.2% RH, and 35 °C and 70.3% RH for the films plasticized with glycerol and sorbitol, respectively. [Copyright &y& Elsevier]

Abstract: The optimal formulation for the preparation of amaranth flour films plasticized with glycerol and sorbitol was obtained by a multi-response analysis. The optimization aimed to achieve films with higher resistance to break, moderate elongation and lower solubility in water. The influence of plasticizer concentration (Cg, glycerol or Cs, sorbitol) and process temperature (Tp) on the mechanical properties and solubility of the amaranth flour films was initially studied by response surface methodology (RSM). The optimized conditions obtained were Cg 20.02 g glycerol/100 g flour and Tp 75 °C, and Cs 29.6 g sorbitol/100 g flour and Tp 75 °C. Characterization of the films prepared with these formulations revealed that the optimization methodology employed in this work was satisfactory. Sorbitol was the most suitable plasticizer. It furnished amaranth flour films that were more resistant to break and less permeable to oxygen, due to its greater miscibility with the biopolymers present in the flour and its lower affinity for water. [Copyright &y& Elsevier]