Comparative study on properties of edible films based on pinhao (Araucaria angustifolia) starch and flour

The aim of this study was to develop and compare the properties of edible films based on pinhao starch and pinhao flour. Seven formulations were developed by casting methodology: 5% pinhao starch with 0, 1, 1.5, and 2% glycerol, and 5% pinhao flour with 1, 1.5, and 2% glycerol. The films were evaluated and compared to each other for thickness, morphological analysis by Scanning Electronic Microscopy (SEM), glass transition temperature (T-g), apparent porosity (empty set), water vapor permeability (WVP), tensile properties, color, opacity, and Fourier transform infrared analysis (FTIR). In addition, the raw materials were analyzed for moisture content, water activity (Aw), apparent porosity and pasting profile. Pinhao starch and flour did not show differences in moisture content and pinhao starch presented lower Aw, O, but higher peak viscosity than pinhao flour. Films made with pinhao starch exhibited lower thickness, O, WVP and opacity than pinhao flour films, but higher Young's modulus, tensile strength and elongation at break. In addition, films with higher amounts of glycerol exhibited higher WVP and elongation at break, with lower tensile strength and Young's modulus. The pinhao flour films structure presented irregularities and were rougher than pinhao starch films. Differences in glycerol content did not affect Tg values of these films. Flour films were yellowish and also had a higher opacity value. The FTIR spectra of pinhao starch and pinhao flour films showed similar IR absorbance patterns, with no structural change in the presence or absence of glycerol. (C) 2016 Elsevier Ltd. All rights reserved.